renewable energy sources ii: alternatives part i
DESCRIPTION
Renewable Energy Sources II: Alternatives Part I. Lecture #10 HNRS 228 Energy and the Environment. Chapter 5 Summary. Hydroelectric Power Wind Power Ocean Thermal Energy Conversion Biomass as Energy Geothermal Energy Tidal Energy Wave Energy Today’s Focus Hydroelectric Power - PowerPoint PPT PresentationTRANSCRIPT
1
Renewable Energy Sources II Alternatives Part I
Lecture 10HNRS 228Energy and the Environment
2
Chapter 5 Summary
bull Hydroelectric Powerbull Wind Powerbull Ocean Thermal Energy Conversionbull Biomass as Energybull Geothermal Energybull Tidal Energybull Wave Energybull Todayrsquos Focus
ndash Hydroelectric Powerndash Wind Power
3
iClicker Question
bull What is the definition of insolationbull A The effective solar insulation factorbull B The amount of light received by a
horizontal surface averaged over the yearbull C The amount of light received by a unit
area of the atmosphere averaged over the year
bull D There is none it is a mis-spelling of insulation
bull E The amount of insulation that is received from the Sun
4
iClicker Question
bull What is the definition of insolationbull A The effective solar insulation factorbull B The amount of light received by a
horizontal surface averaged over the yearbull C The amount of light received by a unit
area of the atmosphere averaged over the year
bull D There is none it is a mis-spelling of insulation
bull E The amount of insulation that is received from the Sun
5
iClicker Question
bull Roughly what percentage of light from the Sun reaches the groundndash A 10ndash B 20ndash C 30ndash D 40ndash E 50
6
iClicker Question
bull Roughly what percentage of light from the Sun reaches the groundndash A 10ndash B 20ndash C 30ndash D 40ndash E 50
7
iClicker Question
bull What is roughly the maximum efficiency for a photovoltaic cellndash A 10ndash B 15ndash C 30ndash D 40ndash E 50
8
iClicker Question
bull What is roughly the maximum efficiency for a photovoltaic cellndash A 10ndash B 15ndash C 30ndash D 40ndash E 50
9
iClicker Question
bull How much energy does the largest photovoltaic system producendash A 10 MWndash B 20 MWndash C 60 MWndash D 100 MWndash E 200 MW
10
iClicker Question
bull How much energy does the largest photovoltaic system producendash A 10 MWndash B 20 MWndash C 60 MWndash D 100 MWndash E 200 MW
11
iClicker Question
bull What must be done to overcome the setting of the Sun in a solar energy systemndash A Store energy in batteriesndash B Get electrical power from elsewherendash C Donrsquot use electrical power at nightndash D All of the above are alternative
approaches for energy after sunset
12
iClicker Question
bull What must be done to overcome the setting of the Sun in a solar energy systemndash A Store energy in batteriesndash B Get electrical power from elsewherendash C Donrsquot use electrical power at nightndash D All of the above are alternative
approaches for energy after sunset
13
iClicker Question
bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect
bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation
bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation
bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation
bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light
bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation
14
iClicker Question
bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect
bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation
bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation
bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation
bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light
bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation
15
Renewable Resources Discussed in Book
bull Renewable means anything that wonrsquot be permanently destroyed by using itndash sunlight (the sun will rise again tomorrow)ndash biomass (grows again)ndash hydrological cycle (will rain again)ndash wind (sunlight on Earth makes more)ndash ocean currents (driven by Sun)ndash tidal motion (MoonSun keep on producing it)ndash geothermal (heat sources inside Earth not
used up fast)
16
Renewable Energy Consumption
Energy Source
QBtu (1994)
Percent (1994)
QBtu (2003)
Percent (2003)
Hydroelectric 3037 343 2779 283
Geothermal 0357 040 0314 032
Biomass 2852 322 2884 294
Solar Energy 0069 0077 0063 006
Wind 0036 0040 0108 011
Total 6351 718 615 63
17
Another look at available energy flow
bull The flow of radiation (solar and thermal) was covered previouslyndash earth is in an energy balance energy in =
energy outndash 30 reflected 70 thermally re-radiated
bull Some of the incident energy is absorbed but what exactly does this dondash much goes into heating the airlandndash much goes into driving weather (rain wind)ndash some goes into ocean currentsndash some goes into photosynthesis
18
The Renewable Budget
19
Outstanding Points from Fig 51
bull Incident radiation is 1741015 Wndash this is 1370 Wm2 times area facing sun
(R2)bull 30 directly reflected back to space
ndash off clouds air landbull 47 goes into heating air land waterbull 23 goes into evaporating water
precipitation etc (part of weather)bull Adds to 100 so wersquore done
ndash but wait therersquos morehellip
20
Energy Flow continued
bull 021 goes into wind waves convection currentsndash note this is 100 times less than driving the water
cyclendash but this is the ldquootherrdquo aspect of weather
bull 0023 is stored as chemical energy in plants via photosynthesis
ndash total is 401012 W half in ocean (plankton)ndash humans are 6 billion times 100 W = 061012 Wndash this is 15 of bio-energy 000034 of incident
powerbull All of this (bio-activity wind weather etc) ends up
creating heat and re-radiating to spacendash except some small amount of storage in fossil fuels
21
The Hydrologic Cycle
Lots of energy associated with evaporationboth mgh (4 for 10 km lift) and latent heat (96) of water
22
Energetics of the hydrologic cycle
bull It takes energy to evaporate water 2444 J per gramndash this is why ldquoswamp coolersrdquo work evaporation
pulls heat out of environment making it feel cooler
ndash 23 of sunrsquos incident energy goes into evaporation
bull By contrast raising one gram of water to the top of the troposphere (10000 m or 33000 ft) takes
mgh = (0001 kg)(10 ms2)(10000 m) = 100 J
bull So gt 96 of the energy associated with forming clouds is the evaporation lt 4 in lifting against gravity
23
Let it Rain
bull When water condenses in clouds it re-releases this ldquolatent heatrdquo
ndash but this is re-radiated and is of no consequence to hydro-power
bull When it rains the gravitational potential energy is released mostly as kinetic energy and ultimately heat
bull Some tiny bit of gravitational potential energy remains IF the rain falls on terrain (eg higher than sea level where it originated)
ndash hydroelectric plants use this tiny left-over energy itrsquos the energy that drives the flow of streams and rivers
ndash damming up a river concentrates the potential energy in one location for easy exploitation
24
How much of the process do we get to keep
bull According to Figure 51 401015 W of solar power goes into evaporation
ndash this corresponds to 161010 kg per second of evaporated water
ndash this is 35 mm per day off the ocean surface (replenished by rain)
bull The gravitational potential energy given to water vapor (mostly in clouds) in the atmosphere (per second) is thenmgh = (161010 kg)(10 ms2)(2000 m) = 321014 J
bull One can calculate that we gain access to only 25 of the total amount (and use only 125)
ndash based on the 18 land area of the US and the maximum potential of 1477 GW as presented in Table 52
25
iClicker Question
bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical
bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential
energy of precipitationndash E a form of fictitious energy
26
iClicker Question
bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical
bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential
energy of precipitationndash E a form of fictitious energy
27
Power of a hydroelectric dam
bull Most impressive is Grand Coulee in Washington on Columbia River
ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets
rain)ndash each cubic meter of water (1000 kg) has potential
energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ
ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently
28
Importance of Hydroelectricity
29
Hydroelectric potential by region in GW
Region Potential
Developed
Undeveloped
Developed
New England 63 19 44 301
Middle Atlantic 98 49 49 500
East North Central 29 12 17 413
West North Central
62 31 31 500
South Atlantic 139 67 72 482
East South Central 83 59 24 711
West South Central
73 27 46 369
Mountain 286 95 191 332
Pacific 644 382 262 593
Total 1477 741 736 502
30
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
31
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
32
Hydroelectricity in the future
bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale
unitsbull Problems with dams
ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site
ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)
ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers
33
Sorry try againhellip
bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy
bull Though very efficient and seemingly environmentally friendly dams do have their problems
bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future
34
Wind Energy
35
The Power of Wind
bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters
every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is
then the kinetic energy the mass of air defined by a rectangular tube
ndash tube is one square meter by v meters or v m3
ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)
065v3 at sea level
36
Wind Energy proportional to cube of velocity
bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in
continental US (above sea level so air slightly less dense)
bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times
bull A wind of 10 ms (22 mph) has a power density of 610 Wm2
bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2
37
Canrsquot get it all
bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely
bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning
bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy
bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36
38
Practical Efficiencies
bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or
about 30ndash40ndash this figure is the mechanical energy
extracted from the windbull Conversion from mechanical to
electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37
39
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
40
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
41
Achievable efficiencies
42
Typical Windmillsbull A typical windmill might be 15 m in diameter
ndash 176 m2
bull At 10 ms wind 40 efficiency this delivers about 100 kW of power
ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW
bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per
year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2
ndash corresponds to 11ndash57 Wm2 average available power density
bull Note the really high tip speeds bird killers
43
Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2
44
Comparable to solar
bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind
bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area
bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy
bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo
45
Current implementations
bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large
dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years
bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over
California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW
46
Flies in the Ointment
bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it
bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces
substantiallybull If fully developed we could generate an average
power almost equal to our current electrical capacity (764 GW)
ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind
47
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
48
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
- Renewable Energy Sources II Alternatives Part I
- Chapter 5 Summary
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Renewable Resources Discussed in Book
- Renewable Energy Consumption
- Another look at available energy flow
- The Renewable Budget
- Outstanding Points from Fig 51
- Energy Flow continued
- The Hydrologic Cycle
- Energetics of the hydrologic cycle
- Let it Rain
- How much of the process do we get to keep
- iClicker Question
- Slide 26
- Power of a hydroelectric dam
- Importance of Hydroelectricity
- Hydroelectric potential by region in GW
- Slide 30
- Slide 31
- Hydroelectricity in the future
- Sorry try againhellip
- Wind Energy
- The Power of Wind
- Wind Energy proportional to cube of velocity
- Canrsquot get it all
- Practical Efficiencies
- Slide 39
- Slide 40
- Achievable efficiencies
- Typical Windmills
- Average available wind power
- Comparable to solar
- Current implementations
- Flies in the Ointment
- Slide 47
- Slide 48
-
2
Chapter 5 Summary
bull Hydroelectric Powerbull Wind Powerbull Ocean Thermal Energy Conversionbull Biomass as Energybull Geothermal Energybull Tidal Energybull Wave Energybull Todayrsquos Focus
ndash Hydroelectric Powerndash Wind Power
3
iClicker Question
bull What is the definition of insolationbull A The effective solar insulation factorbull B The amount of light received by a
horizontal surface averaged over the yearbull C The amount of light received by a unit
area of the atmosphere averaged over the year
bull D There is none it is a mis-spelling of insulation
bull E The amount of insulation that is received from the Sun
4
iClicker Question
bull What is the definition of insolationbull A The effective solar insulation factorbull B The amount of light received by a
horizontal surface averaged over the yearbull C The amount of light received by a unit
area of the atmosphere averaged over the year
bull D There is none it is a mis-spelling of insulation
bull E The amount of insulation that is received from the Sun
5
iClicker Question
bull Roughly what percentage of light from the Sun reaches the groundndash A 10ndash B 20ndash C 30ndash D 40ndash E 50
6
iClicker Question
bull Roughly what percentage of light from the Sun reaches the groundndash A 10ndash B 20ndash C 30ndash D 40ndash E 50
7
iClicker Question
bull What is roughly the maximum efficiency for a photovoltaic cellndash A 10ndash B 15ndash C 30ndash D 40ndash E 50
8
iClicker Question
bull What is roughly the maximum efficiency for a photovoltaic cellndash A 10ndash B 15ndash C 30ndash D 40ndash E 50
9
iClicker Question
bull How much energy does the largest photovoltaic system producendash A 10 MWndash B 20 MWndash C 60 MWndash D 100 MWndash E 200 MW
10
iClicker Question
bull How much energy does the largest photovoltaic system producendash A 10 MWndash B 20 MWndash C 60 MWndash D 100 MWndash E 200 MW
11
iClicker Question
bull What must be done to overcome the setting of the Sun in a solar energy systemndash A Store energy in batteriesndash B Get electrical power from elsewherendash C Donrsquot use electrical power at nightndash D All of the above are alternative
approaches for energy after sunset
12
iClicker Question
bull What must be done to overcome the setting of the Sun in a solar energy systemndash A Store energy in batteriesndash B Get electrical power from elsewherendash C Donrsquot use electrical power at nightndash D All of the above are alternative
approaches for energy after sunset
13
iClicker Question
bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect
bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation
bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation
bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation
bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light
bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation
14
iClicker Question
bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect
bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation
bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation
bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation
bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light
bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation
15
Renewable Resources Discussed in Book
bull Renewable means anything that wonrsquot be permanently destroyed by using itndash sunlight (the sun will rise again tomorrow)ndash biomass (grows again)ndash hydrological cycle (will rain again)ndash wind (sunlight on Earth makes more)ndash ocean currents (driven by Sun)ndash tidal motion (MoonSun keep on producing it)ndash geothermal (heat sources inside Earth not
used up fast)
16
Renewable Energy Consumption
Energy Source
QBtu (1994)
Percent (1994)
QBtu (2003)
Percent (2003)
Hydroelectric 3037 343 2779 283
Geothermal 0357 040 0314 032
Biomass 2852 322 2884 294
Solar Energy 0069 0077 0063 006
Wind 0036 0040 0108 011
Total 6351 718 615 63
17
Another look at available energy flow
bull The flow of radiation (solar and thermal) was covered previouslyndash earth is in an energy balance energy in =
energy outndash 30 reflected 70 thermally re-radiated
bull Some of the incident energy is absorbed but what exactly does this dondash much goes into heating the airlandndash much goes into driving weather (rain wind)ndash some goes into ocean currentsndash some goes into photosynthesis
18
The Renewable Budget
19
Outstanding Points from Fig 51
bull Incident radiation is 1741015 Wndash this is 1370 Wm2 times area facing sun
(R2)bull 30 directly reflected back to space
ndash off clouds air landbull 47 goes into heating air land waterbull 23 goes into evaporating water
precipitation etc (part of weather)bull Adds to 100 so wersquore done
ndash but wait therersquos morehellip
20
Energy Flow continued
bull 021 goes into wind waves convection currentsndash note this is 100 times less than driving the water
cyclendash but this is the ldquootherrdquo aspect of weather
bull 0023 is stored as chemical energy in plants via photosynthesis
ndash total is 401012 W half in ocean (plankton)ndash humans are 6 billion times 100 W = 061012 Wndash this is 15 of bio-energy 000034 of incident
powerbull All of this (bio-activity wind weather etc) ends up
creating heat and re-radiating to spacendash except some small amount of storage in fossil fuels
21
The Hydrologic Cycle
Lots of energy associated with evaporationboth mgh (4 for 10 km lift) and latent heat (96) of water
22
Energetics of the hydrologic cycle
bull It takes energy to evaporate water 2444 J per gramndash this is why ldquoswamp coolersrdquo work evaporation
pulls heat out of environment making it feel cooler
ndash 23 of sunrsquos incident energy goes into evaporation
bull By contrast raising one gram of water to the top of the troposphere (10000 m or 33000 ft) takes
mgh = (0001 kg)(10 ms2)(10000 m) = 100 J
bull So gt 96 of the energy associated with forming clouds is the evaporation lt 4 in lifting against gravity
23
Let it Rain
bull When water condenses in clouds it re-releases this ldquolatent heatrdquo
ndash but this is re-radiated and is of no consequence to hydro-power
bull When it rains the gravitational potential energy is released mostly as kinetic energy and ultimately heat
bull Some tiny bit of gravitational potential energy remains IF the rain falls on terrain (eg higher than sea level where it originated)
ndash hydroelectric plants use this tiny left-over energy itrsquos the energy that drives the flow of streams and rivers
ndash damming up a river concentrates the potential energy in one location for easy exploitation
24
How much of the process do we get to keep
bull According to Figure 51 401015 W of solar power goes into evaporation
ndash this corresponds to 161010 kg per second of evaporated water
ndash this is 35 mm per day off the ocean surface (replenished by rain)
bull The gravitational potential energy given to water vapor (mostly in clouds) in the atmosphere (per second) is thenmgh = (161010 kg)(10 ms2)(2000 m) = 321014 J
bull One can calculate that we gain access to only 25 of the total amount (and use only 125)
ndash based on the 18 land area of the US and the maximum potential of 1477 GW as presented in Table 52
25
iClicker Question
bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical
bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential
energy of precipitationndash E a form of fictitious energy
26
iClicker Question
bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical
bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential
energy of precipitationndash E a form of fictitious energy
27
Power of a hydroelectric dam
bull Most impressive is Grand Coulee in Washington on Columbia River
ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets
rain)ndash each cubic meter of water (1000 kg) has potential
energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ
ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently
28
Importance of Hydroelectricity
29
Hydroelectric potential by region in GW
Region Potential
Developed
Undeveloped
Developed
New England 63 19 44 301
Middle Atlantic 98 49 49 500
East North Central 29 12 17 413
West North Central
62 31 31 500
South Atlantic 139 67 72 482
East South Central 83 59 24 711
West South Central
73 27 46 369
Mountain 286 95 191 332
Pacific 644 382 262 593
Total 1477 741 736 502
30
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
31
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
32
Hydroelectricity in the future
bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale
unitsbull Problems with dams
ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site
ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)
ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers
33
Sorry try againhellip
bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy
bull Though very efficient and seemingly environmentally friendly dams do have their problems
bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future
34
Wind Energy
35
The Power of Wind
bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters
every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is
then the kinetic energy the mass of air defined by a rectangular tube
ndash tube is one square meter by v meters or v m3
ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)
065v3 at sea level
36
Wind Energy proportional to cube of velocity
bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in
continental US (above sea level so air slightly less dense)
bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times
bull A wind of 10 ms (22 mph) has a power density of 610 Wm2
bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2
37
Canrsquot get it all
bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely
bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning
bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy
bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36
38
Practical Efficiencies
bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or
about 30ndash40ndash this figure is the mechanical energy
extracted from the windbull Conversion from mechanical to
electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37
39
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
40
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
41
Achievable efficiencies
42
Typical Windmillsbull A typical windmill might be 15 m in diameter
ndash 176 m2
bull At 10 ms wind 40 efficiency this delivers about 100 kW of power
ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW
bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per
year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2
ndash corresponds to 11ndash57 Wm2 average available power density
bull Note the really high tip speeds bird killers
43
Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2
44
Comparable to solar
bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind
bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area
bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy
bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo
45
Current implementations
bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large
dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years
bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over
California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW
46
Flies in the Ointment
bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it
bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces
substantiallybull If fully developed we could generate an average
power almost equal to our current electrical capacity (764 GW)
ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind
47
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
48
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
- Renewable Energy Sources II Alternatives Part I
- Chapter 5 Summary
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Renewable Resources Discussed in Book
- Renewable Energy Consumption
- Another look at available energy flow
- The Renewable Budget
- Outstanding Points from Fig 51
- Energy Flow continued
- The Hydrologic Cycle
- Energetics of the hydrologic cycle
- Let it Rain
- How much of the process do we get to keep
- iClicker Question
- Slide 26
- Power of a hydroelectric dam
- Importance of Hydroelectricity
- Hydroelectric potential by region in GW
- Slide 30
- Slide 31
- Hydroelectricity in the future
- Sorry try againhellip
- Wind Energy
- The Power of Wind
- Wind Energy proportional to cube of velocity
- Canrsquot get it all
- Practical Efficiencies
- Slide 39
- Slide 40
- Achievable efficiencies
- Typical Windmills
- Average available wind power
- Comparable to solar
- Current implementations
- Flies in the Ointment
- Slide 47
- Slide 48
-
3
iClicker Question
bull What is the definition of insolationbull A The effective solar insulation factorbull B The amount of light received by a
horizontal surface averaged over the yearbull C The amount of light received by a unit
area of the atmosphere averaged over the year
bull D There is none it is a mis-spelling of insulation
bull E The amount of insulation that is received from the Sun
4
iClicker Question
bull What is the definition of insolationbull A The effective solar insulation factorbull B The amount of light received by a
horizontal surface averaged over the yearbull C The amount of light received by a unit
area of the atmosphere averaged over the year
bull D There is none it is a mis-spelling of insulation
bull E The amount of insulation that is received from the Sun
5
iClicker Question
bull Roughly what percentage of light from the Sun reaches the groundndash A 10ndash B 20ndash C 30ndash D 40ndash E 50
6
iClicker Question
bull Roughly what percentage of light from the Sun reaches the groundndash A 10ndash B 20ndash C 30ndash D 40ndash E 50
7
iClicker Question
bull What is roughly the maximum efficiency for a photovoltaic cellndash A 10ndash B 15ndash C 30ndash D 40ndash E 50
8
iClicker Question
bull What is roughly the maximum efficiency for a photovoltaic cellndash A 10ndash B 15ndash C 30ndash D 40ndash E 50
9
iClicker Question
bull How much energy does the largest photovoltaic system producendash A 10 MWndash B 20 MWndash C 60 MWndash D 100 MWndash E 200 MW
10
iClicker Question
bull How much energy does the largest photovoltaic system producendash A 10 MWndash B 20 MWndash C 60 MWndash D 100 MWndash E 200 MW
11
iClicker Question
bull What must be done to overcome the setting of the Sun in a solar energy systemndash A Store energy in batteriesndash B Get electrical power from elsewherendash C Donrsquot use electrical power at nightndash D All of the above are alternative
approaches for energy after sunset
12
iClicker Question
bull What must be done to overcome the setting of the Sun in a solar energy systemndash A Store energy in batteriesndash B Get electrical power from elsewherendash C Donrsquot use electrical power at nightndash D All of the above are alternative
approaches for energy after sunset
13
iClicker Question
bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect
bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation
bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation
bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation
bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light
bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation
14
iClicker Question
bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect
bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation
bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation
bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation
bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light
bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation
15
Renewable Resources Discussed in Book
bull Renewable means anything that wonrsquot be permanently destroyed by using itndash sunlight (the sun will rise again tomorrow)ndash biomass (grows again)ndash hydrological cycle (will rain again)ndash wind (sunlight on Earth makes more)ndash ocean currents (driven by Sun)ndash tidal motion (MoonSun keep on producing it)ndash geothermal (heat sources inside Earth not
used up fast)
16
Renewable Energy Consumption
Energy Source
QBtu (1994)
Percent (1994)
QBtu (2003)
Percent (2003)
Hydroelectric 3037 343 2779 283
Geothermal 0357 040 0314 032
Biomass 2852 322 2884 294
Solar Energy 0069 0077 0063 006
Wind 0036 0040 0108 011
Total 6351 718 615 63
17
Another look at available energy flow
bull The flow of radiation (solar and thermal) was covered previouslyndash earth is in an energy balance energy in =
energy outndash 30 reflected 70 thermally re-radiated
bull Some of the incident energy is absorbed but what exactly does this dondash much goes into heating the airlandndash much goes into driving weather (rain wind)ndash some goes into ocean currentsndash some goes into photosynthesis
18
The Renewable Budget
19
Outstanding Points from Fig 51
bull Incident radiation is 1741015 Wndash this is 1370 Wm2 times area facing sun
(R2)bull 30 directly reflected back to space
ndash off clouds air landbull 47 goes into heating air land waterbull 23 goes into evaporating water
precipitation etc (part of weather)bull Adds to 100 so wersquore done
ndash but wait therersquos morehellip
20
Energy Flow continued
bull 021 goes into wind waves convection currentsndash note this is 100 times less than driving the water
cyclendash but this is the ldquootherrdquo aspect of weather
bull 0023 is stored as chemical energy in plants via photosynthesis
ndash total is 401012 W half in ocean (plankton)ndash humans are 6 billion times 100 W = 061012 Wndash this is 15 of bio-energy 000034 of incident
powerbull All of this (bio-activity wind weather etc) ends up
creating heat and re-radiating to spacendash except some small amount of storage in fossil fuels
21
The Hydrologic Cycle
Lots of energy associated with evaporationboth mgh (4 for 10 km lift) and latent heat (96) of water
22
Energetics of the hydrologic cycle
bull It takes energy to evaporate water 2444 J per gramndash this is why ldquoswamp coolersrdquo work evaporation
pulls heat out of environment making it feel cooler
ndash 23 of sunrsquos incident energy goes into evaporation
bull By contrast raising one gram of water to the top of the troposphere (10000 m or 33000 ft) takes
mgh = (0001 kg)(10 ms2)(10000 m) = 100 J
bull So gt 96 of the energy associated with forming clouds is the evaporation lt 4 in lifting against gravity
23
Let it Rain
bull When water condenses in clouds it re-releases this ldquolatent heatrdquo
ndash but this is re-radiated and is of no consequence to hydro-power
bull When it rains the gravitational potential energy is released mostly as kinetic energy and ultimately heat
bull Some tiny bit of gravitational potential energy remains IF the rain falls on terrain (eg higher than sea level where it originated)
ndash hydroelectric plants use this tiny left-over energy itrsquos the energy that drives the flow of streams and rivers
ndash damming up a river concentrates the potential energy in one location for easy exploitation
24
How much of the process do we get to keep
bull According to Figure 51 401015 W of solar power goes into evaporation
ndash this corresponds to 161010 kg per second of evaporated water
ndash this is 35 mm per day off the ocean surface (replenished by rain)
bull The gravitational potential energy given to water vapor (mostly in clouds) in the atmosphere (per second) is thenmgh = (161010 kg)(10 ms2)(2000 m) = 321014 J
bull One can calculate that we gain access to only 25 of the total amount (and use only 125)
ndash based on the 18 land area of the US and the maximum potential of 1477 GW as presented in Table 52
25
iClicker Question
bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical
bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential
energy of precipitationndash E a form of fictitious energy
26
iClicker Question
bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical
bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential
energy of precipitationndash E a form of fictitious energy
27
Power of a hydroelectric dam
bull Most impressive is Grand Coulee in Washington on Columbia River
ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets
rain)ndash each cubic meter of water (1000 kg) has potential
energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ
ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently
28
Importance of Hydroelectricity
29
Hydroelectric potential by region in GW
Region Potential
Developed
Undeveloped
Developed
New England 63 19 44 301
Middle Atlantic 98 49 49 500
East North Central 29 12 17 413
West North Central
62 31 31 500
South Atlantic 139 67 72 482
East South Central 83 59 24 711
West South Central
73 27 46 369
Mountain 286 95 191 332
Pacific 644 382 262 593
Total 1477 741 736 502
30
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
31
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
32
Hydroelectricity in the future
bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale
unitsbull Problems with dams
ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site
ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)
ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers
33
Sorry try againhellip
bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy
bull Though very efficient and seemingly environmentally friendly dams do have their problems
bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future
34
Wind Energy
35
The Power of Wind
bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters
every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is
then the kinetic energy the mass of air defined by a rectangular tube
ndash tube is one square meter by v meters or v m3
ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)
065v3 at sea level
36
Wind Energy proportional to cube of velocity
bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in
continental US (above sea level so air slightly less dense)
bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times
bull A wind of 10 ms (22 mph) has a power density of 610 Wm2
bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2
37
Canrsquot get it all
bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely
bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning
bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy
bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36
38
Practical Efficiencies
bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or
about 30ndash40ndash this figure is the mechanical energy
extracted from the windbull Conversion from mechanical to
electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37
39
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
40
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
41
Achievable efficiencies
42
Typical Windmillsbull A typical windmill might be 15 m in diameter
ndash 176 m2
bull At 10 ms wind 40 efficiency this delivers about 100 kW of power
ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW
bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per
year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2
ndash corresponds to 11ndash57 Wm2 average available power density
bull Note the really high tip speeds bird killers
43
Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2
44
Comparable to solar
bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind
bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area
bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy
bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo
45
Current implementations
bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large
dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years
bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over
California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW
46
Flies in the Ointment
bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it
bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces
substantiallybull If fully developed we could generate an average
power almost equal to our current electrical capacity (764 GW)
ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind
47
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
48
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
- Renewable Energy Sources II Alternatives Part I
- Chapter 5 Summary
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Renewable Resources Discussed in Book
- Renewable Energy Consumption
- Another look at available energy flow
- The Renewable Budget
- Outstanding Points from Fig 51
- Energy Flow continued
- The Hydrologic Cycle
- Energetics of the hydrologic cycle
- Let it Rain
- How much of the process do we get to keep
- iClicker Question
- Slide 26
- Power of a hydroelectric dam
- Importance of Hydroelectricity
- Hydroelectric potential by region in GW
- Slide 30
- Slide 31
- Hydroelectricity in the future
- Sorry try againhellip
- Wind Energy
- The Power of Wind
- Wind Energy proportional to cube of velocity
- Canrsquot get it all
- Practical Efficiencies
- Slide 39
- Slide 40
- Achievable efficiencies
- Typical Windmills
- Average available wind power
- Comparable to solar
- Current implementations
- Flies in the Ointment
- Slide 47
- Slide 48
-
4
iClicker Question
bull What is the definition of insolationbull A The effective solar insulation factorbull B The amount of light received by a
horizontal surface averaged over the yearbull C The amount of light received by a unit
area of the atmosphere averaged over the year
bull D There is none it is a mis-spelling of insulation
bull E The amount of insulation that is received from the Sun
5
iClicker Question
bull Roughly what percentage of light from the Sun reaches the groundndash A 10ndash B 20ndash C 30ndash D 40ndash E 50
6
iClicker Question
bull Roughly what percentage of light from the Sun reaches the groundndash A 10ndash B 20ndash C 30ndash D 40ndash E 50
7
iClicker Question
bull What is roughly the maximum efficiency for a photovoltaic cellndash A 10ndash B 15ndash C 30ndash D 40ndash E 50
8
iClicker Question
bull What is roughly the maximum efficiency for a photovoltaic cellndash A 10ndash B 15ndash C 30ndash D 40ndash E 50
9
iClicker Question
bull How much energy does the largest photovoltaic system producendash A 10 MWndash B 20 MWndash C 60 MWndash D 100 MWndash E 200 MW
10
iClicker Question
bull How much energy does the largest photovoltaic system producendash A 10 MWndash B 20 MWndash C 60 MWndash D 100 MWndash E 200 MW
11
iClicker Question
bull What must be done to overcome the setting of the Sun in a solar energy systemndash A Store energy in batteriesndash B Get electrical power from elsewherendash C Donrsquot use electrical power at nightndash D All of the above are alternative
approaches for energy after sunset
12
iClicker Question
bull What must be done to overcome the setting of the Sun in a solar energy systemndash A Store energy in batteriesndash B Get electrical power from elsewherendash C Donrsquot use electrical power at nightndash D All of the above are alternative
approaches for energy after sunset
13
iClicker Question
bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect
bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation
bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation
bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation
bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light
bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation
14
iClicker Question
bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect
bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation
bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation
bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation
bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light
bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation
15
Renewable Resources Discussed in Book
bull Renewable means anything that wonrsquot be permanently destroyed by using itndash sunlight (the sun will rise again tomorrow)ndash biomass (grows again)ndash hydrological cycle (will rain again)ndash wind (sunlight on Earth makes more)ndash ocean currents (driven by Sun)ndash tidal motion (MoonSun keep on producing it)ndash geothermal (heat sources inside Earth not
used up fast)
16
Renewable Energy Consumption
Energy Source
QBtu (1994)
Percent (1994)
QBtu (2003)
Percent (2003)
Hydroelectric 3037 343 2779 283
Geothermal 0357 040 0314 032
Biomass 2852 322 2884 294
Solar Energy 0069 0077 0063 006
Wind 0036 0040 0108 011
Total 6351 718 615 63
17
Another look at available energy flow
bull The flow of radiation (solar and thermal) was covered previouslyndash earth is in an energy balance energy in =
energy outndash 30 reflected 70 thermally re-radiated
bull Some of the incident energy is absorbed but what exactly does this dondash much goes into heating the airlandndash much goes into driving weather (rain wind)ndash some goes into ocean currentsndash some goes into photosynthesis
18
The Renewable Budget
19
Outstanding Points from Fig 51
bull Incident radiation is 1741015 Wndash this is 1370 Wm2 times area facing sun
(R2)bull 30 directly reflected back to space
ndash off clouds air landbull 47 goes into heating air land waterbull 23 goes into evaporating water
precipitation etc (part of weather)bull Adds to 100 so wersquore done
ndash but wait therersquos morehellip
20
Energy Flow continued
bull 021 goes into wind waves convection currentsndash note this is 100 times less than driving the water
cyclendash but this is the ldquootherrdquo aspect of weather
bull 0023 is stored as chemical energy in plants via photosynthesis
ndash total is 401012 W half in ocean (plankton)ndash humans are 6 billion times 100 W = 061012 Wndash this is 15 of bio-energy 000034 of incident
powerbull All of this (bio-activity wind weather etc) ends up
creating heat and re-radiating to spacendash except some small amount of storage in fossil fuels
21
The Hydrologic Cycle
Lots of energy associated with evaporationboth mgh (4 for 10 km lift) and latent heat (96) of water
22
Energetics of the hydrologic cycle
bull It takes energy to evaporate water 2444 J per gramndash this is why ldquoswamp coolersrdquo work evaporation
pulls heat out of environment making it feel cooler
ndash 23 of sunrsquos incident energy goes into evaporation
bull By contrast raising one gram of water to the top of the troposphere (10000 m or 33000 ft) takes
mgh = (0001 kg)(10 ms2)(10000 m) = 100 J
bull So gt 96 of the energy associated with forming clouds is the evaporation lt 4 in lifting against gravity
23
Let it Rain
bull When water condenses in clouds it re-releases this ldquolatent heatrdquo
ndash but this is re-radiated and is of no consequence to hydro-power
bull When it rains the gravitational potential energy is released mostly as kinetic energy and ultimately heat
bull Some tiny bit of gravitational potential energy remains IF the rain falls on terrain (eg higher than sea level where it originated)
ndash hydroelectric plants use this tiny left-over energy itrsquos the energy that drives the flow of streams and rivers
ndash damming up a river concentrates the potential energy in one location for easy exploitation
24
How much of the process do we get to keep
bull According to Figure 51 401015 W of solar power goes into evaporation
ndash this corresponds to 161010 kg per second of evaporated water
ndash this is 35 mm per day off the ocean surface (replenished by rain)
bull The gravitational potential energy given to water vapor (mostly in clouds) in the atmosphere (per second) is thenmgh = (161010 kg)(10 ms2)(2000 m) = 321014 J
bull One can calculate that we gain access to only 25 of the total amount (and use only 125)
ndash based on the 18 land area of the US and the maximum potential of 1477 GW as presented in Table 52
25
iClicker Question
bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical
bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential
energy of precipitationndash E a form of fictitious energy
26
iClicker Question
bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical
bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential
energy of precipitationndash E a form of fictitious energy
27
Power of a hydroelectric dam
bull Most impressive is Grand Coulee in Washington on Columbia River
ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets
rain)ndash each cubic meter of water (1000 kg) has potential
energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ
ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently
28
Importance of Hydroelectricity
29
Hydroelectric potential by region in GW
Region Potential
Developed
Undeveloped
Developed
New England 63 19 44 301
Middle Atlantic 98 49 49 500
East North Central 29 12 17 413
West North Central
62 31 31 500
South Atlantic 139 67 72 482
East South Central 83 59 24 711
West South Central
73 27 46 369
Mountain 286 95 191 332
Pacific 644 382 262 593
Total 1477 741 736 502
30
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
31
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
32
Hydroelectricity in the future
bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale
unitsbull Problems with dams
ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site
ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)
ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers
33
Sorry try againhellip
bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy
bull Though very efficient and seemingly environmentally friendly dams do have their problems
bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future
34
Wind Energy
35
The Power of Wind
bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters
every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is
then the kinetic energy the mass of air defined by a rectangular tube
ndash tube is one square meter by v meters or v m3
ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)
065v3 at sea level
36
Wind Energy proportional to cube of velocity
bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in
continental US (above sea level so air slightly less dense)
bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times
bull A wind of 10 ms (22 mph) has a power density of 610 Wm2
bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2
37
Canrsquot get it all
bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely
bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning
bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy
bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36
38
Practical Efficiencies
bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or
about 30ndash40ndash this figure is the mechanical energy
extracted from the windbull Conversion from mechanical to
electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37
39
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
40
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
41
Achievable efficiencies
42
Typical Windmillsbull A typical windmill might be 15 m in diameter
ndash 176 m2
bull At 10 ms wind 40 efficiency this delivers about 100 kW of power
ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW
bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per
year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2
ndash corresponds to 11ndash57 Wm2 average available power density
bull Note the really high tip speeds bird killers
43
Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2
44
Comparable to solar
bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind
bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area
bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy
bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo
45
Current implementations
bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large
dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years
bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over
California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW
46
Flies in the Ointment
bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it
bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces
substantiallybull If fully developed we could generate an average
power almost equal to our current electrical capacity (764 GW)
ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind
47
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
48
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
- Renewable Energy Sources II Alternatives Part I
- Chapter 5 Summary
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Renewable Resources Discussed in Book
- Renewable Energy Consumption
- Another look at available energy flow
- The Renewable Budget
- Outstanding Points from Fig 51
- Energy Flow continued
- The Hydrologic Cycle
- Energetics of the hydrologic cycle
- Let it Rain
- How much of the process do we get to keep
- iClicker Question
- Slide 26
- Power of a hydroelectric dam
- Importance of Hydroelectricity
- Hydroelectric potential by region in GW
- Slide 30
- Slide 31
- Hydroelectricity in the future
- Sorry try againhellip
- Wind Energy
- The Power of Wind
- Wind Energy proportional to cube of velocity
- Canrsquot get it all
- Practical Efficiencies
- Slide 39
- Slide 40
- Achievable efficiencies
- Typical Windmills
- Average available wind power
- Comparable to solar
- Current implementations
- Flies in the Ointment
- Slide 47
- Slide 48
-
5
iClicker Question
bull Roughly what percentage of light from the Sun reaches the groundndash A 10ndash B 20ndash C 30ndash D 40ndash E 50
6
iClicker Question
bull Roughly what percentage of light from the Sun reaches the groundndash A 10ndash B 20ndash C 30ndash D 40ndash E 50
7
iClicker Question
bull What is roughly the maximum efficiency for a photovoltaic cellndash A 10ndash B 15ndash C 30ndash D 40ndash E 50
8
iClicker Question
bull What is roughly the maximum efficiency for a photovoltaic cellndash A 10ndash B 15ndash C 30ndash D 40ndash E 50
9
iClicker Question
bull How much energy does the largest photovoltaic system producendash A 10 MWndash B 20 MWndash C 60 MWndash D 100 MWndash E 200 MW
10
iClicker Question
bull How much energy does the largest photovoltaic system producendash A 10 MWndash B 20 MWndash C 60 MWndash D 100 MWndash E 200 MW
11
iClicker Question
bull What must be done to overcome the setting of the Sun in a solar energy systemndash A Store energy in batteriesndash B Get electrical power from elsewherendash C Donrsquot use electrical power at nightndash D All of the above are alternative
approaches for energy after sunset
12
iClicker Question
bull What must be done to overcome the setting of the Sun in a solar energy systemndash A Store energy in batteriesndash B Get electrical power from elsewherendash C Donrsquot use electrical power at nightndash D All of the above are alternative
approaches for energy after sunset
13
iClicker Question
bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect
bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation
bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation
bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation
bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light
bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation
14
iClicker Question
bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect
bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation
bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation
bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation
bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light
bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation
15
Renewable Resources Discussed in Book
bull Renewable means anything that wonrsquot be permanently destroyed by using itndash sunlight (the sun will rise again tomorrow)ndash biomass (grows again)ndash hydrological cycle (will rain again)ndash wind (sunlight on Earth makes more)ndash ocean currents (driven by Sun)ndash tidal motion (MoonSun keep on producing it)ndash geothermal (heat sources inside Earth not
used up fast)
16
Renewable Energy Consumption
Energy Source
QBtu (1994)
Percent (1994)
QBtu (2003)
Percent (2003)
Hydroelectric 3037 343 2779 283
Geothermal 0357 040 0314 032
Biomass 2852 322 2884 294
Solar Energy 0069 0077 0063 006
Wind 0036 0040 0108 011
Total 6351 718 615 63
17
Another look at available energy flow
bull The flow of radiation (solar and thermal) was covered previouslyndash earth is in an energy balance energy in =
energy outndash 30 reflected 70 thermally re-radiated
bull Some of the incident energy is absorbed but what exactly does this dondash much goes into heating the airlandndash much goes into driving weather (rain wind)ndash some goes into ocean currentsndash some goes into photosynthesis
18
The Renewable Budget
19
Outstanding Points from Fig 51
bull Incident radiation is 1741015 Wndash this is 1370 Wm2 times area facing sun
(R2)bull 30 directly reflected back to space
ndash off clouds air landbull 47 goes into heating air land waterbull 23 goes into evaporating water
precipitation etc (part of weather)bull Adds to 100 so wersquore done
ndash but wait therersquos morehellip
20
Energy Flow continued
bull 021 goes into wind waves convection currentsndash note this is 100 times less than driving the water
cyclendash but this is the ldquootherrdquo aspect of weather
bull 0023 is stored as chemical energy in plants via photosynthesis
ndash total is 401012 W half in ocean (plankton)ndash humans are 6 billion times 100 W = 061012 Wndash this is 15 of bio-energy 000034 of incident
powerbull All of this (bio-activity wind weather etc) ends up
creating heat and re-radiating to spacendash except some small amount of storage in fossil fuels
21
The Hydrologic Cycle
Lots of energy associated with evaporationboth mgh (4 for 10 km lift) and latent heat (96) of water
22
Energetics of the hydrologic cycle
bull It takes energy to evaporate water 2444 J per gramndash this is why ldquoswamp coolersrdquo work evaporation
pulls heat out of environment making it feel cooler
ndash 23 of sunrsquos incident energy goes into evaporation
bull By contrast raising one gram of water to the top of the troposphere (10000 m or 33000 ft) takes
mgh = (0001 kg)(10 ms2)(10000 m) = 100 J
bull So gt 96 of the energy associated with forming clouds is the evaporation lt 4 in lifting against gravity
23
Let it Rain
bull When water condenses in clouds it re-releases this ldquolatent heatrdquo
ndash but this is re-radiated and is of no consequence to hydro-power
bull When it rains the gravitational potential energy is released mostly as kinetic energy and ultimately heat
bull Some tiny bit of gravitational potential energy remains IF the rain falls on terrain (eg higher than sea level where it originated)
ndash hydroelectric plants use this tiny left-over energy itrsquos the energy that drives the flow of streams and rivers
ndash damming up a river concentrates the potential energy in one location for easy exploitation
24
How much of the process do we get to keep
bull According to Figure 51 401015 W of solar power goes into evaporation
ndash this corresponds to 161010 kg per second of evaporated water
ndash this is 35 mm per day off the ocean surface (replenished by rain)
bull The gravitational potential energy given to water vapor (mostly in clouds) in the atmosphere (per second) is thenmgh = (161010 kg)(10 ms2)(2000 m) = 321014 J
bull One can calculate that we gain access to only 25 of the total amount (and use only 125)
ndash based on the 18 land area of the US and the maximum potential of 1477 GW as presented in Table 52
25
iClicker Question
bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical
bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential
energy of precipitationndash E a form of fictitious energy
26
iClicker Question
bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical
bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential
energy of precipitationndash E a form of fictitious energy
27
Power of a hydroelectric dam
bull Most impressive is Grand Coulee in Washington on Columbia River
ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets
rain)ndash each cubic meter of water (1000 kg) has potential
energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ
ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently
28
Importance of Hydroelectricity
29
Hydroelectric potential by region in GW
Region Potential
Developed
Undeveloped
Developed
New England 63 19 44 301
Middle Atlantic 98 49 49 500
East North Central 29 12 17 413
West North Central
62 31 31 500
South Atlantic 139 67 72 482
East South Central 83 59 24 711
West South Central
73 27 46 369
Mountain 286 95 191 332
Pacific 644 382 262 593
Total 1477 741 736 502
30
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
31
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
32
Hydroelectricity in the future
bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale
unitsbull Problems with dams
ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site
ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)
ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers
33
Sorry try againhellip
bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy
bull Though very efficient and seemingly environmentally friendly dams do have their problems
bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future
34
Wind Energy
35
The Power of Wind
bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters
every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is
then the kinetic energy the mass of air defined by a rectangular tube
ndash tube is one square meter by v meters or v m3
ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)
065v3 at sea level
36
Wind Energy proportional to cube of velocity
bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in
continental US (above sea level so air slightly less dense)
bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times
bull A wind of 10 ms (22 mph) has a power density of 610 Wm2
bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2
37
Canrsquot get it all
bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely
bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning
bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy
bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36
38
Practical Efficiencies
bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or
about 30ndash40ndash this figure is the mechanical energy
extracted from the windbull Conversion from mechanical to
electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37
39
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
40
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
41
Achievable efficiencies
42
Typical Windmillsbull A typical windmill might be 15 m in diameter
ndash 176 m2
bull At 10 ms wind 40 efficiency this delivers about 100 kW of power
ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW
bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per
year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2
ndash corresponds to 11ndash57 Wm2 average available power density
bull Note the really high tip speeds bird killers
43
Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2
44
Comparable to solar
bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind
bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area
bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy
bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo
45
Current implementations
bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large
dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years
bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over
California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW
46
Flies in the Ointment
bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it
bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces
substantiallybull If fully developed we could generate an average
power almost equal to our current electrical capacity (764 GW)
ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind
47
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
48
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
- Renewable Energy Sources II Alternatives Part I
- Chapter 5 Summary
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Renewable Resources Discussed in Book
- Renewable Energy Consumption
- Another look at available energy flow
- The Renewable Budget
- Outstanding Points from Fig 51
- Energy Flow continued
- The Hydrologic Cycle
- Energetics of the hydrologic cycle
- Let it Rain
- How much of the process do we get to keep
- iClicker Question
- Slide 26
- Power of a hydroelectric dam
- Importance of Hydroelectricity
- Hydroelectric potential by region in GW
- Slide 30
- Slide 31
- Hydroelectricity in the future
- Sorry try againhellip
- Wind Energy
- The Power of Wind
- Wind Energy proportional to cube of velocity
- Canrsquot get it all
- Practical Efficiencies
- Slide 39
- Slide 40
- Achievable efficiencies
- Typical Windmills
- Average available wind power
- Comparable to solar
- Current implementations
- Flies in the Ointment
- Slide 47
- Slide 48
-
6
iClicker Question
bull Roughly what percentage of light from the Sun reaches the groundndash A 10ndash B 20ndash C 30ndash D 40ndash E 50
7
iClicker Question
bull What is roughly the maximum efficiency for a photovoltaic cellndash A 10ndash B 15ndash C 30ndash D 40ndash E 50
8
iClicker Question
bull What is roughly the maximum efficiency for a photovoltaic cellndash A 10ndash B 15ndash C 30ndash D 40ndash E 50
9
iClicker Question
bull How much energy does the largest photovoltaic system producendash A 10 MWndash B 20 MWndash C 60 MWndash D 100 MWndash E 200 MW
10
iClicker Question
bull How much energy does the largest photovoltaic system producendash A 10 MWndash B 20 MWndash C 60 MWndash D 100 MWndash E 200 MW
11
iClicker Question
bull What must be done to overcome the setting of the Sun in a solar energy systemndash A Store energy in batteriesndash B Get electrical power from elsewherendash C Donrsquot use electrical power at nightndash D All of the above are alternative
approaches for energy after sunset
12
iClicker Question
bull What must be done to overcome the setting of the Sun in a solar energy systemndash A Store energy in batteriesndash B Get electrical power from elsewherendash C Donrsquot use electrical power at nightndash D All of the above are alternative
approaches for energy after sunset
13
iClicker Question
bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect
bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation
bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation
bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation
bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light
bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation
14
iClicker Question
bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect
bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation
bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation
bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation
bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light
bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation
15
Renewable Resources Discussed in Book
bull Renewable means anything that wonrsquot be permanently destroyed by using itndash sunlight (the sun will rise again tomorrow)ndash biomass (grows again)ndash hydrological cycle (will rain again)ndash wind (sunlight on Earth makes more)ndash ocean currents (driven by Sun)ndash tidal motion (MoonSun keep on producing it)ndash geothermal (heat sources inside Earth not
used up fast)
16
Renewable Energy Consumption
Energy Source
QBtu (1994)
Percent (1994)
QBtu (2003)
Percent (2003)
Hydroelectric 3037 343 2779 283
Geothermal 0357 040 0314 032
Biomass 2852 322 2884 294
Solar Energy 0069 0077 0063 006
Wind 0036 0040 0108 011
Total 6351 718 615 63
17
Another look at available energy flow
bull The flow of radiation (solar and thermal) was covered previouslyndash earth is in an energy balance energy in =
energy outndash 30 reflected 70 thermally re-radiated
bull Some of the incident energy is absorbed but what exactly does this dondash much goes into heating the airlandndash much goes into driving weather (rain wind)ndash some goes into ocean currentsndash some goes into photosynthesis
18
The Renewable Budget
19
Outstanding Points from Fig 51
bull Incident radiation is 1741015 Wndash this is 1370 Wm2 times area facing sun
(R2)bull 30 directly reflected back to space
ndash off clouds air landbull 47 goes into heating air land waterbull 23 goes into evaporating water
precipitation etc (part of weather)bull Adds to 100 so wersquore done
ndash but wait therersquos morehellip
20
Energy Flow continued
bull 021 goes into wind waves convection currentsndash note this is 100 times less than driving the water
cyclendash but this is the ldquootherrdquo aspect of weather
bull 0023 is stored as chemical energy in plants via photosynthesis
ndash total is 401012 W half in ocean (plankton)ndash humans are 6 billion times 100 W = 061012 Wndash this is 15 of bio-energy 000034 of incident
powerbull All of this (bio-activity wind weather etc) ends up
creating heat and re-radiating to spacendash except some small amount of storage in fossil fuels
21
The Hydrologic Cycle
Lots of energy associated with evaporationboth mgh (4 for 10 km lift) and latent heat (96) of water
22
Energetics of the hydrologic cycle
bull It takes energy to evaporate water 2444 J per gramndash this is why ldquoswamp coolersrdquo work evaporation
pulls heat out of environment making it feel cooler
ndash 23 of sunrsquos incident energy goes into evaporation
bull By contrast raising one gram of water to the top of the troposphere (10000 m or 33000 ft) takes
mgh = (0001 kg)(10 ms2)(10000 m) = 100 J
bull So gt 96 of the energy associated with forming clouds is the evaporation lt 4 in lifting against gravity
23
Let it Rain
bull When water condenses in clouds it re-releases this ldquolatent heatrdquo
ndash but this is re-radiated and is of no consequence to hydro-power
bull When it rains the gravitational potential energy is released mostly as kinetic energy and ultimately heat
bull Some tiny bit of gravitational potential energy remains IF the rain falls on terrain (eg higher than sea level where it originated)
ndash hydroelectric plants use this tiny left-over energy itrsquos the energy that drives the flow of streams and rivers
ndash damming up a river concentrates the potential energy in one location for easy exploitation
24
How much of the process do we get to keep
bull According to Figure 51 401015 W of solar power goes into evaporation
ndash this corresponds to 161010 kg per second of evaporated water
ndash this is 35 mm per day off the ocean surface (replenished by rain)
bull The gravitational potential energy given to water vapor (mostly in clouds) in the atmosphere (per second) is thenmgh = (161010 kg)(10 ms2)(2000 m) = 321014 J
bull One can calculate that we gain access to only 25 of the total amount (and use only 125)
ndash based on the 18 land area of the US and the maximum potential of 1477 GW as presented in Table 52
25
iClicker Question
bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical
bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential
energy of precipitationndash E a form of fictitious energy
26
iClicker Question
bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical
bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential
energy of precipitationndash E a form of fictitious energy
27
Power of a hydroelectric dam
bull Most impressive is Grand Coulee in Washington on Columbia River
ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets
rain)ndash each cubic meter of water (1000 kg) has potential
energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ
ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently
28
Importance of Hydroelectricity
29
Hydroelectric potential by region in GW
Region Potential
Developed
Undeveloped
Developed
New England 63 19 44 301
Middle Atlantic 98 49 49 500
East North Central 29 12 17 413
West North Central
62 31 31 500
South Atlantic 139 67 72 482
East South Central 83 59 24 711
West South Central
73 27 46 369
Mountain 286 95 191 332
Pacific 644 382 262 593
Total 1477 741 736 502
30
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
31
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
32
Hydroelectricity in the future
bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale
unitsbull Problems with dams
ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site
ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)
ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers
33
Sorry try againhellip
bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy
bull Though very efficient and seemingly environmentally friendly dams do have their problems
bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future
34
Wind Energy
35
The Power of Wind
bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters
every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is
then the kinetic energy the mass of air defined by a rectangular tube
ndash tube is one square meter by v meters or v m3
ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)
065v3 at sea level
36
Wind Energy proportional to cube of velocity
bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in
continental US (above sea level so air slightly less dense)
bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times
bull A wind of 10 ms (22 mph) has a power density of 610 Wm2
bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2
37
Canrsquot get it all
bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely
bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning
bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy
bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36
38
Practical Efficiencies
bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or
about 30ndash40ndash this figure is the mechanical energy
extracted from the windbull Conversion from mechanical to
electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37
39
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
40
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
41
Achievable efficiencies
42
Typical Windmillsbull A typical windmill might be 15 m in diameter
ndash 176 m2
bull At 10 ms wind 40 efficiency this delivers about 100 kW of power
ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW
bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per
year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2
ndash corresponds to 11ndash57 Wm2 average available power density
bull Note the really high tip speeds bird killers
43
Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2
44
Comparable to solar
bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind
bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area
bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy
bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo
45
Current implementations
bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large
dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years
bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over
California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW
46
Flies in the Ointment
bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it
bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces
substantiallybull If fully developed we could generate an average
power almost equal to our current electrical capacity (764 GW)
ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind
47
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
48
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
- Renewable Energy Sources II Alternatives Part I
- Chapter 5 Summary
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Renewable Resources Discussed in Book
- Renewable Energy Consumption
- Another look at available energy flow
- The Renewable Budget
- Outstanding Points from Fig 51
- Energy Flow continued
- The Hydrologic Cycle
- Energetics of the hydrologic cycle
- Let it Rain
- How much of the process do we get to keep
- iClicker Question
- Slide 26
- Power of a hydroelectric dam
- Importance of Hydroelectricity
- Hydroelectric potential by region in GW
- Slide 30
- Slide 31
- Hydroelectricity in the future
- Sorry try againhellip
- Wind Energy
- The Power of Wind
- Wind Energy proportional to cube of velocity
- Canrsquot get it all
- Practical Efficiencies
- Slide 39
- Slide 40
- Achievable efficiencies
- Typical Windmills
- Average available wind power
- Comparable to solar
- Current implementations
- Flies in the Ointment
- Slide 47
- Slide 48
-
7
iClicker Question
bull What is roughly the maximum efficiency for a photovoltaic cellndash A 10ndash B 15ndash C 30ndash D 40ndash E 50
8
iClicker Question
bull What is roughly the maximum efficiency for a photovoltaic cellndash A 10ndash B 15ndash C 30ndash D 40ndash E 50
9
iClicker Question
bull How much energy does the largest photovoltaic system producendash A 10 MWndash B 20 MWndash C 60 MWndash D 100 MWndash E 200 MW
10
iClicker Question
bull How much energy does the largest photovoltaic system producendash A 10 MWndash B 20 MWndash C 60 MWndash D 100 MWndash E 200 MW
11
iClicker Question
bull What must be done to overcome the setting of the Sun in a solar energy systemndash A Store energy in batteriesndash B Get electrical power from elsewherendash C Donrsquot use electrical power at nightndash D All of the above are alternative
approaches for energy after sunset
12
iClicker Question
bull What must be done to overcome the setting of the Sun in a solar energy systemndash A Store energy in batteriesndash B Get electrical power from elsewherendash C Donrsquot use electrical power at nightndash D All of the above are alternative
approaches for energy after sunset
13
iClicker Question
bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect
bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation
bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation
bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation
bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light
bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation
14
iClicker Question
bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect
bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation
bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation
bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation
bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light
bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation
15
Renewable Resources Discussed in Book
bull Renewable means anything that wonrsquot be permanently destroyed by using itndash sunlight (the sun will rise again tomorrow)ndash biomass (grows again)ndash hydrological cycle (will rain again)ndash wind (sunlight on Earth makes more)ndash ocean currents (driven by Sun)ndash tidal motion (MoonSun keep on producing it)ndash geothermal (heat sources inside Earth not
used up fast)
16
Renewable Energy Consumption
Energy Source
QBtu (1994)
Percent (1994)
QBtu (2003)
Percent (2003)
Hydroelectric 3037 343 2779 283
Geothermal 0357 040 0314 032
Biomass 2852 322 2884 294
Solar Energy 0069 0077 0063 006
Wind 0036 0040 0108 011
Total 6351 718 615 63
17
Another look at available energy flow
bull The flow of radiation (solar and thermal) was covered previouslyndash earth is in an energy balance energy in =
energy outndash 30 reflected 70 thermally re-radiated
bull Some of the incident energy is absorbed but what exactly does this dondash much goes into heating the airlandndash much goes into driving weather (rain wind)ndash some goes into ocean currentsndash some goes into photosynthesis
18
The Renewable Budget
19
Outstanding Points from Fig 51
bull Incident radiation is 1741015 Wndash this is 1370 Wm2 times area facing sun
(R2)bull 30 directly reflected back to space
ndash off clouds air landbull 47 goes into heating air land waterbull 23 goes into evaporating water
precipitation etc (part of weather)bull Adds to 100 so wersquore done
ndash but wait therersquos morehellip
20
Energy Flow continued
bull 021 goes into wind waves convection currentsndash note this is 100 times less than driving the water
cyclendash but this is the ldquootherrdquo aspect of weather
bull 0023 is stored as chemical energy in plants via photosynthesis
ndash total is 401012 W half in ocean (plankton)ndash humans are 6 billion times 100 W = 061012 Wndash this is 15 of bio-energy 000034 of incident
powerbull All of this (bio-activity wind weather etc) ends up
creating heat and re-radiating to spacendash except some small amount of storage in fossil fuels
21
The Hydrologic Cycle
Lots of energy associated with evaporationboth mgh (4 for 10 km lift) and latent heat (96) of water
22
Energetics of the hydrologic cycle
bull It takes energy to evaporate water 2444 J per gramndash this is why ldquoswamp coolersrdquo work evaporation
pulls heat out of environment making it feel cooler
ndash 23 of sunrsquos incident energy goes into evaporation
bull By contrast raising one gram of water to the top of the troposphere (10000 m or 33000 ft) takes
mgh = (0001 kg)(10 ms2)(10000 m) = 100 J
bull So gt 96 of the energy associated with forming clouds is the evaporation lt 4 in lifting against gravity
23
Let it Rain
bull When water condenses in clouds it re-releases this ldquolatent heatrdquo
ndash but this is re-radiated and is of no consequence to hydro-power
bull When it rains the gravitational potential energy is released mostly as kinetic energy and ultimately heat
bull Some tiny bit of gravitational potential energy remains IF the rain falls on terrain (eg higher than sea level where it originated)
ndash hydroelectric plants use this tiny left-over energy itrsquos the energy that drives the flow of streams and rivers
ndash damming up a river concentrates the potential energy in one location for easy exploitation
24
How much of the process do we get to keep
bull According to Figure 51 401015 W of solar power goes into evaporation
ndash this corresponds to 161010 kg per second of evaporated water
ndash this is 35 mm per day off the ocean surface (replenished by rain)
bull The gravitational potential energy given to water vapor (mostly in clouds) in the atmosphere (per second) is thenmgh = (161010 kg)(10 ms2)(2000 m) = 321014 J
bull One can calculate that we gain access to only 25 of the total amount (and use only 125)
ndash based on the 18 land area of the US and the maximum potential of 1477 GW as presented in Table 52
25
iClicker Question
bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical
bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential
energy of precipitationndash E a form of fictitious energy
26
iClicker Question
bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical
bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential
energy of precipitationndash E a form of fictitious energy
27
Power of a hydroelectric dam
bull Most impressive is Grand Coulee in Washington on Columbia River
ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets
rain)ndash each cubic meter of water (1000 kg) has potential
energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ
ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently
28
Importance of Hydroelectricity
29
Hydroelectric potential by region in GW
Region Potential
Developed
Undeveloped
Developed
New England 63 19 44 301
Middle Atlantic 98 49 49 500
East North Central 29 12 17 413
West North Central
62 31 31 500
South Atlantic 139 67 72 482
East South Central 83 59 24 711
West South Central
73 27 46 369
Mountain 286 95 191 332
Pacific 644 382 262 593
Total 1477 741 736 502
30
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
31
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
32
Hydroelectricity in the future
bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale
unitsbull Problems with dams
ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site
ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)
ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers
33
Sorry try againhellip
bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy
bull Though very efficient and seemingly environmentally friendly dams do have their problems
bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future
34
Wind Energy
35
The Power of Wind
bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters
every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is
then the kinetic energy the mass of air defined by a rectangular tube
ndash tube is one square meter by v meters or v m3
ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)
065v3 at sea level
36
Wind Energy proportional to cube of velocity
bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in
continental US (above sea level so air slightly less dense)
bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times
bull A wind of 10 ms (22 mph) has a power density of 610 Wm2
bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2
37
Canrsquot get it all
bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely
bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning
bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy
bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36
38
Practical Efficiencies
bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or
about 30ndash40ndash this figure is the mechanical energy
extracted from the windbull Conversion from mechanical to
electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37
39
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
40
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
41
Achievable efficiencies
42
Typical Windmillsbull A typical windmill might be 15 m in diameter
ndash 176 m2
bull At 10 ms wind 40 efficiency this delivers about 100 kW of power
ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW
bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per
year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2
ndash corresponds to 11ndash57 Wm2 average available power density
bull Note the really high tip speeds bird killers
43
Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2
44
Comparable to solar
bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind
bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area
bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy
bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo
45
Current implementations
bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large
dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years
bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over
California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW
46
Flies in the Ointment
bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it
bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces
substantiallybull If fully developed we could generate an average
power almost equal to our current electrical capacity (764 GW)
ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind
47
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
48
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
- Renewable Energy Sources II Alternatives Part I
- Chapter 5 Summary
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Renewable Resources Discussed in Book
- Renewable Energy Consumption
- Another look at available energy flow
- The Renewable Budget
- Outstanding Points from Fig 51
- Energy Flow continued
- The Hydrologic Cycle
- Energetics of the hydrologic cycle
- Let it Rain
- How much of the process do we get to keep
- iClicker Question
- Slide 26
- Power of a hydroelectric dam
- Importance of Hydroelectricity
- Hydroelectric potential by region in GW
- Slide 30
- Slide 31
- Hydroelectricity in the future
- Sorry try againhellip
- Wind Energy
- The Power of Wind
- Wind Energy proportional to cube of velocity
- Canrsquot get it all
- Practical Efficiencies
- Slide 39
- Slide 40
- Achievable efficiencies
- Typical Windmills
- Average available wind power
- Comparable to solar
- Current implementations
- Flies in the Ointment
- Slide 47
- Slide 48
-
8
iClicker Question
bull What is roughly the maximum efficiency for a photovoltaic cellndash A 10ndash B 15ndash C 30ndash D 40ndash E 50
9
iClicker Question
bull How much energy does the largest photovoltaic system producendash A 10 MWndash B 20 MWndash C 60 MWndash D 100 MWndash E 200 MW
10
iClicker Question
bull How much energy does the largest photovoltaic system producendash A 10 MWndash B 20 MWndash C 60 MWndash D 100 MWndash E 200 MW
11
iClicker Question
bull What must be done to overcome the setting of the Sun in a solar energy systemndash A Store energy in batteriesndash B Get electrical power from elsewherendash C Donrsquot use electrical power at nightndash D All of the above are alternative
approaches for energy after sunset
12
iClicker Question
bull What must be done to overcome the setting of the Sun in a solar energy systemndash A Store energy in batteriesndash B Get electrical power from elsewherendash C Donrsquot use electrical power at nightndash D All of the above are alternative
approaches for energy after sunset
13
iClicker Question
bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect
bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation
bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation
bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation
bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light
bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation
14
iClicker Question
bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect
bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation
bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation
bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation
bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light
bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation
15
Renewable Resources Discussed in Book
bull Renewable means anything that wonrsquot be permanently destroyed by using itndash sunlight (the sun will rise again tomorrow)ndash biomass (grows again)ndash hydrological cycle (will rain again)ndash wind (sunlight on Earth makes more)ndash ocean currents (driven by Sun)ndash tidal motion (MoonSun keep on producing it)ndash geothermal (heat sources inside Earth not
used up fast)
16
Renewable Energy Consumption
Energy Source
QBtu (1994)
Percent (1994)
QBtu (2003)
Percent (2003)
Hydroelectric 3037 343 2779 283
Geothermal 0357 040 0314 032
Biomass 2852 322 2884 294
Solar Energy 0069 0077 0063 006
Wind 0036 0040 0108 011
Total 6351 718 615 63
17
Another look at available energy flow
bull The flow of radiation (solar and thermal) was covered previouslyndash earth is in an energy balance energy in =
energy outndash 30 reflected 70 thermally re-radiated
bull Some of the incident energy is absorbed but what exactly does this dondash much goes into heating the airlandndash much goes into driving weather (rain wind)ndash some goes into ocean currentsndash some goes into photosynthesis
18
The Renewable Budget
19
Outstanding Points from Fig 51
bull Incident radiation is 1741015 Wndash this is 1370 Wm2 times area facing sun
(R2)bull 30 directly reflected back to space
ndash off clouds air landbull 47 goes into heating air land waterbull 23 goes into evaporating water
precipitation etc (part of weather)bull Adds to 100 so wersquore done
ndash but wait therersquos morehellip
20
Energy Flow continued
bull 021 goes into wind waves convection currentsndash note this is 100 times less than driving the water
cyclendash but this is the ldquootherrdquo aspect of weather
bull 0023 is stored as chemical energy in plants via photosynthesis
ndash total is 401012 W half in ocean (plankton)ndash humans are 6 billion times 100 W = 061012 Wndash this is 15 of bio-energy 000034 of incident
powerbull All of this (bio-activity wind weather etc) ends up
creating heat and re-radiating to spacendash except some small amount of storage in fossil fuels
21
The Hydrologic Cycle
Lots of energy associated with evaporationboth mgh (4 for 10 km lift) and latent heat (96) of water
22
Energetics of the hydrologic cycle
bull It takes energy to evaporate water 2444 J per gramndash this is why ldquoswamp coolersrdquo work evaporation
pulls heat out of environment making it feel cooler
ndash 23 of sunrsquos incident energy goes into evaporation
bull By contrast raising one gram of water to the top of the troposphere (10000 m or 33000 ft) takes
mgh = (0001 kg)(10 ms2)(10000 m) = 100 J
bull So gt 96 of the energy associated with forming clouds is the evaporation lt 4 in lifting against gravity
23
Let it Rain
bull When water condenses in clouds it re-releases this ldquolatent heatrdquo
ndash but this is re-radiated and is of no consequence to hydro-power
bull When it rains the gravitational potential energy is released mostly as kinetic energy and ultimately heat
bull Some tiny bit of gravitational potential energy remains IF the rain falls on terrain (eg higher than sea level where it originated)
ndash hydroelectric plants use this tiny left-over energy itrsquos the energy that drives the flow of streams and rivers
ndash damming up a river concentrates the potential energy in one location for easy exploitation
24
How much of the process do we get to keep
bull According to Figure 51 401015 W of solar power goes into evaporation
ndash this corresponds to 161010 kg per second of evaporated water
ndash this is 35 mm per day off the ocean surface (replenished by rain)
bull The gravitational potential energy given to water vapor (mostly in clouds) in the atmosphere (per second) is thenmgh = (161010 kg)(10 ms2)(2000 m) = 321014 J
bull One can calculate that we gain access to only 25 of the total amount (and use only 125)
ndash based on the 18 land area of the US and the maximum potential of 1477 GW as presented in Table 52
25
iClicker Question
bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical
bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential
energy of precipitationndash E a form of fictitious energy
26
iClicker Question
bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical
bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential
energy of precipitationndash E a form of fictitious energy
27
Power of a hydroelectric dam
bull Most impressive is Grand Coulee in Washington on Columbia River
ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets
rain)ndash each cubic meter of water (1000 kg) has potential
energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ
ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently
28
Importance of Hydroelectricity
29
Hydroelectric potential by region in GW
Region Potential
Developed
Undeveloped
Developed
New England 63 19 44 301
Middle Atlantic 98 49 49 500
East North Central 29 12 17 413
West North Central
62 31 31 500
South Atlantic 139 67 72 482
East South Central 83 59 24 711
West South Central
73 27 46 369
Mountain 286 95 191 332
Pacific 644 382 262 593
Total 1477 741 736 502
30
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
31
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
32
Hydroelectricity in the future
bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale
unitsbull Problems with dams
ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site
ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)
ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers
33
Sorry try againhellip
bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy
bull Though very efficient and seemingly environmentally friendly dams do have their problems
bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future
34
Wind Energy
35
The Power of Wind
bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters
every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is
then the kinetic energy the mass of air defined by a rectangular tube
ndash tube is one square meter by v meters or v m3
ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)
065v3 at sea level
36
Wind Energy proportional to cube of velocity
bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in
continental US (above sea level so air slightly less dense)
bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times
bull A wind of 10 ms (22 mph) has a power density of 610 Wm2
bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2
37
Canrsquot get it all
bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely
bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning
bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy
bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36
38
Practical Efficiencies
bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or
about 30ndash40ndash this figure is the mechanical energy
extracted from the windbull Conversion from mechanical to
electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37
39
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
40
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
41
Achievable efficiencies
42
Typical Windmillsbull A typical windmill might be 15 m in diameter
ndash 176 m2
bull At 10 ms wind 40 efficiency this delivers about 100 kW of power
ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW
bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per
year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2
ndash corresponds to 11ndash57 Wm2 average available power density
bull Note the really high tip speeds bird killers
43
Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2
44
Comparable to solar
bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind
bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area
bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy
bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo
45
Current implementations
bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large
dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years
bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over
California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW
46
Flies in the Ointment
bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it
bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces
substantiallybull If fully developed we could generate an average
power almost equal to our current electrical capacity (764 GW)
ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind
47
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
48
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
- Renewable Energy Sources II Alternatives Part I
- Chapter 5 Summary
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Renewable Resources Discussed in Book
- Renewable Energy Consumption
- Another look at available energy flow
- The Renewable Budget
- Outstanding Points from Fig 51
- Energy Flow continued
- The Hydrologic Cycle
- Energetics of the hydrologic cycle
- Let it Rain
- How much of the process do we get to keep
- iClicker Question
- Slide 26
- Power of a hydroelectric dam
- Importance of Hydroelectricity
- Hydroelectric potential by region in GW
- Slide 30
- Slide 31
- Hydroelectricity in the future
- Sorry try againhellip
- Wind Energy
- The Power of Wind
- Wind Energy proportional to cube of velocity
- Canrsquot get it all
- Practical Efficiencies
- Slide 39
- Slide 40
- Achievable efficiencies
- Typical Windmills
- Average available wind power
- Comparable to solar
- Current implementations
- Flies in the Ointment
- Slide 47
- Slide 48
-
9
iClicker Question
bull How much energy does the largest photovoltaic system producendash A 10 MWndash B 20 MWndash C 60 MWndash D 100 MWndash E 200 MW
10
iClicker Question
bull How much energy does the largest photovoltaic system producendash A 10 MWndash B 20 MWndash C 60 MWndash D 100 MWndash E 200 MW
11
iClicker Question
bull What must be done to overcome the setting of the Sun in a solar energy systemndash A Store energy in batteriesndash B Get electrical power from elsewherendash C Donrsquot use electrical power at nightndash D All of the above are alternative
approaches for energy after sunset
12
iClicker Question
bull What must be done to overcome the setting of the Sun in a solar energy systemndash A Store energy in batteriesndash B Get electrical power from elsewherendash C Donrsquot use electrical power at nightndash D All of the above are alternative
approaches for energy after sunset
13
iClicker Question
bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect
bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation
bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation
bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation
bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light
bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation
14
iClicker Question
bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect
bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation
bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation
bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation
bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light
bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation
15
Renewable Resources Discussed in Book
bull Renewable means anything that wonrsquot be permanently destroyed by using itndash sunlight (the sun will rise again tomorrow)ndash biomass (grows again)ndash hydrological cycle (will rain again)ndash wind (sunlight on Earth makes more)ndash ocean currents (driven by Sun)ndash tidal motion (MoonSun keep on producing it)ndash geothermal (heat sources inside Earth not
used up fast)
16
Renewable Energy Consumption
Energy Source
QBtu (1994)
Percent (1994)
QBtu (2003)
Percent (2003)
Hydroelectric 3037 343 2779 283
Geothermal 0357 040 0314 032
Biomass 2852 322 2884 294
Solar Energy 0069 0077 0063 006
Wind 0036 0040 0108 011
Total 6351 718 615 63
17
Another look at available energy flow
bull The flow of radiation (solar and thermal) was covered previouslyndash earth is in an energy balance energy in =
energy outndash 30 reflected 70 thermally re-radiated
bull Some of the incident energy is absorbed but what exactly does this dondash much goes into heating the airlandndash much goes into driving weather (rain wind)ndash some goes into ocean currentsndash some goes into photosynthesis
18
The Renewable Budget
19
Outstanding Points from Fig 51
bull Incident radiation is 1741015 Wndash this is 1370 Wm2 times area facing sun
(R2)bull 30 directly reflected back to space
ndash off clouds air landbull 47 goes into heating air land waterbull 23 goes into evaporating water
precipitation etc (part of weather)bull Adds to 100 so wersquore done
ndash but wait therersquos morehellip
20
Energy Flow continued
bull 021 goes into wind waves convection currentsndash note this is 100 times less than driving the water
cyclendash but this is the ldquootherrdquo aspect of weather
bull 0023 is stored as chemical energy in plants via photosynthesis
ndash total is 401012 W half in ocean (plankton)ndash humans are 6 billion times 100 W = 061012 Wndash this is 15 of bio-energy 000034 of incident
powerbull All of this (bio-activity wind weather etc) ends up
creating heat and re-radiating to spacendash except some small amount of storage in fossil fuels
21
The Hydrologic Cycle
Lots of energy associated with evaporationboth mgh (4 for 10 km lift) and latent heat (96) of water
22
Energetics of the hydrologic cycle
bull It takes energy to evaporate water 2444 J per gramndash this is why ldquoswamp coolersrdquo work evaporation
pulls heat out of environment making it feel cooler
ndash 23 of sunrsquos incident energy goes into evaporation
bull By contrast raising one gram of water to the top of the troposphere (10000 m or 33000 ft) takes
mgh = (0001 kg)(10 ms2)(10000 m) = 100 J
bull So gt 96 of the energy associated with forming clouds is the evaporation lt 4 in lifting against gravity
23
Let it Rain
bull When water condenses in clouds it re-releases this ldquolatent heatrdquo
ndash but this is re-radiated and is of no consequence to hydro-power
bull When it rains the gravitational potential energy is released mostly as kinetic energy and ultimately heat
bull Some tiny bit of gravitational potential energy remains IF the rain falls on terrain (eg higher than sea level where it originated)
ndash hydroelectric plants use this tiny left-over energy itrsquos the energy that drives the flow of streams and rivers
ndash damming up a river concentrates the potential energy in one location for easy exploitation
24
How much of the process do we get to keep
bull According to Figure 51 401015 W of solar power goes into evaporation
ndash this corresponds to 161010 kg per second of evaporated water
ndash this is 35 mm per day off the ocean surface (replenished by rain)
bull The gravitational potential energy given to water vapor (mostly in clouds) in the atmosphere (per second) is thenmgh = (161010 kg)(10 ms2)(2000 m) = 321014 J
bull One can calculate that we gain access to only 25 of the total amount (and use only 125)
ndash based on the 18 land area of the US and the maximum potential of 1477 GW as presented in Table 52
25
iClicker Question
bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical
bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential
energy of precipitationndash E a form of fictitious energy
26
iClicker Question
bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical
bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential
energy of precipitationndash E a form of fictitious energy
27
Power of a hydroelectric dam
bull Most impressive is Grand Coulee in Washington on Columbia River
ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets
rain)ndash each cubic meter of water (1000 kg) has potential
energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ
ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently
28
Importance of Hydroelectricity
29
Hydroelectric potential by region in GW
Region Potential
Developed
Undeveloped
Developed
New England 63 19 44 301
Middle Atlantic 98 49 49 500
East North Central 29 12 17 413
West North Central
62 31 31 500
South Atlantic 139 67 72 482
East South Central 83 59 24 711
West South Central
73 27 46 369
Mountain 286 95 191 332
Pacific 644 382 262 593
Total 1477 741 736 502
30
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
31
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
32
Hydroelectricity in the future
bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale
unitsbull Problems with dams
ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site
ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)
ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers
33
Sorry try againhellip
bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy
bull Though very efficient and seemingly environmentally friendly dams do have their problems
bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future
34
Wind Energy
35
The Power of Wind
bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters
every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is
then the kinetic energy the mass of air defined by a rectangular tube
ndash tube is one square meter by v meters or v m3
ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)
065v3 at sea level
36
Wind Energy proportional to cube of velocity
bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in
continental US (above sea level so air slightly less dense)
bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times
bull A wind of 10 ms (22 mph) has a power density of 610 Wm2
bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2
37
Canrsquot get it all
bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely
bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning
bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy
bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36
38
Practical Efficiencies
bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or
about 30ndash40ndash this figure is the mechanical energy
extracted from the windbull Conversion from mechanical to
electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37
39
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
40
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
41
Achievable efficiencies
42
Typical Windmillsbull A typical windmill might be 15 m in diameter
ndash 176 m2
bull At 10 ms wind 40 efficiency this delivers about 100 kW of power
ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW
bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per
year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2
ndash corresponds to 11ndash57 Wm2 average available power density
bull Note the really high tip speeds bird killers
43
Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2
44
Comparable to solar
bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind
bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area
bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy
bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo
45
Current implementations
bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large
dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years
bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over
California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW
46
Flies in the Ointment
bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it
bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces
substantiallybull If fully developed we could generate an average
power almost equal to our current electrical capacity (764 GW)
ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind
47
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
48
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
- Renewable Energy Sources II Alternatives Part I
- Chapter 5 Summary
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Renewable Resources Discussed in Book
- Renewable Energy Consumption
- Another look at available energy flow
- The Renewable Budget
- Outstanding Points from Fig 51
- Energy Flow continued
- The Hydrologic Cycle
- Energetics of the hydrologic cycle
- Let it Rain
- How much of the process do we get to keep
- iClicker Question
- Slide 26
- Power of a hydroelectric dam
- Importance of Hydroelectricity
- Hydroelectric potential by region in GW
- Slide 30
- Slide 31
- Hydroelectricity in the future
- Sorry try againhellip
- Wind Energy
- The Power of Wind
- Wind Energy proportional to cube of velocity
- Canrsquot get it all
- Practical Efficiencies
- Slide 39
- Slide 40
- Achievable efficiencies
- Typical Windmills
- Average available wind power
- Comparable to solar
- Current implementations
- Flies in the Ointment
- Slide 47
- Slide 48
-
10
iClicker Question
bull How much energy does the largest photovoltaic system producendash A 10 MWndash B 20 MWndash C 60 MWndash D 100 MWndash E 200 MW
11
iClicker Question
bull What must be done to overcome the setting of the Sun in a solar energy systemndash A Store energy in batteriesndash B Get electrical power from elsewherendash C Donrsquot use electrical power at nightndash D All of the above are alternative
approaches for energy after sunset
12
iClicker Question
bull What must be done to overcome the setting of the Sun in a solar energy systemndash A Store energy in batteriesndash B Get electrical power from elsewherendash C Donrsquot use electrical power at nightndash D All of the above are alternative
approaches for energy after sunset
13
iClicker Question
bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect
bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation
bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation
bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation
bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light
bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation
14
iClicker Question
bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect
bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation
bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation
bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation
bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light
bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation
15
Renewable Resources Discussed in Book
bull Renewable means anything that wonrsquot be permanently destroyed by using itndash sunlight (the sun will rise again tomorrow)ndash biomass (grows again)ndash hydrological cycle (will rain again)ndash wind (sunlight on Earth makes more)ndash ocean currents (driven by Sun)ndash tidal motion (MoonSun keep on producing it)ndash geothermal (heat sources inside Earth not
used up fast)
16
Renewable Energy Consumption
Energy Source
QBtu (1994)
Percent (1994)
QBtu (2003)
Percent (2003)
Hydroelectric 3037 343 2779 283
Geothermal 0357 040 0314 032
Biomass 2852 322 2884 294
Solar Energy 0069 0077 0063 006
Wind 0036 0040 0108 011
Total 6351 718 615 63
17
Another look at available energy flow
bull The flow of radiation (solar and thermal) was covered previouslyndash earth is in an energy balance energy in =
energy outndash 30 reflected 70 thermally re-radiated
bull Some of the incident energy is absorbed but what exactly does this dondash much goes into heating the airlandndash much goes into driving weather (rain wind)ndash some goes into ocean currentsndash some goes into photosynthesis
18
The Renewable Budget
19
Outstanding Points from Fig 51
bull Incident radiation is 1741015 Wndash this is 1370 Wm2 times area facing sun
(R2)bull 30 directly reflected back to space
ndash off clouds air landbull 47 goes into heating air land waterbull 23 goes into evaporating water
precipitation etc (part of weather)bull Adds to 100 so wersquore done
ndash but wait therersquos morehellip
20
Energy Flow continued
bull 021 goes into wind waves convection currentsndash note this is 100 times less than driving the water
cyclendash but this is the ldquootherrdquo aspect of weather
bull 0023 is stored as chemical energy in plants via photosynthesis
ndash total is 401012 W half in ocean (plankton)ndash humans are 6 billion times 100 W = 061012 Wndash this is 15 of bio-energy 000034 of incident
powerbull All of this (bio-activity wind weather etc) ends up
creating heat and re-radiating to spacendash except some small amount of storage in fossil fuels
21
The Hydrologic Cycle
Lots of energy associated with evaporationboth mgh (4 for 10 km lift) and latent heat (96) of water
22
Energetics of the hydrologic cycle
bull It takes energy to evaporate water 2444 J per gramndash this is why ldquoswamp coolersrdquo work evaporation
pulls heat out of environment making it feel cooler
ndash 23 of sunrsquos incident energy goes into evaporation
bull By contrast raising one gram of water to the top of the troposphere (10000 m or 33000 ft) takes
mgh = (0001 kg)(10 ms2)(10000 m) = 100 J
bull So gt 96 of the energy associated with forming clouds is the evaporation lt 4 in lifting against gravity
23
Let it Rain
bull When water condenses in clouds it re-releases this ldquolatent heatrdquo
ndash but this is re-radiated and is of no consequence to hydro-power
bull When it rains the gravitational potential energy is released mostly as kinetic energy and ultimately heat
bull Some tiny bit of gravitational potential energy remains IF the rain falls on terrain (eg higher than sea level where it originated)
ndash hydroelectric plants use this tiny left-over energy itrsquos the energy that drives the flow of streams and rivers
ndash damming up a river concentrates the potential energy in one location for easy exploitation
24
How much of the process do we get to keep
bull According to Figure 51 401015 W of solar power goes into evaporation
ndash this corresponds to 161010 kg per second of evaporated water
ndash this is 35 mm per day off the ocean surface (replenished by rain)
bull The gravitational potential energy given to water vapor (mostly in clouds) in the atmosphere (per second) is thenmgh = (161010 kg)(10 ms2)(2000 m) = 321014 J
bull One can calculate that we gain access to only 25 of the total amount (and use only 125)
ndash based on the 18 land area of the US and the maximum potential of 1477 GW as presented in Table 52
25
iClicker Question
bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical
bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential
energy of precipitationndash E a form of fictitious energy
26
iClicker Question
bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical
bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential
energy of precipitationndash E a form of fictitious energy
27
Power of a hydroelectric dam
bull Most impressive is Grand Coulee in Washington on Columbia River
ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets
rain)ndash each cubic meter of water (1000 kg) has potential
energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ
ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently
28
Importance of Hydroelectricity
29
Hydroelectric potential by region in GW
Region Potential
Developed
Undeveloped
Developed
New England 63 19 44 301
Middle Atlantic 98 49 49 500
East North Central 29 12 17 413
West North Central
62 31 31 500
South Atlantic 139 67 72 482
East South Central 83 59 24 711
West South Central
73 27 46 369
Mountain 286 95 191 332
Pacific 644 382 262 593
Total 1477 741 736 502
30
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
31
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
32
Hydroelectricity in the future
bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale
unitsbull Problems with dams
ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site
ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)
ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers
33
Sorry try againhellip
bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy
bull Though very efficient and seemingly environmentally friendly dams do have their problems
bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future
34
Wind Energy
35
The Power of Wind
bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters
every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is
then the kinetic energy the mass of air defined by a rectangular tube
ndash tube is one square meter by v meters or v m3
ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)
065v3 at sea level
36
Wind Energy proportional to cube of velocity
bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in
continental US (above sea level so air slightly less dense)
bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times
bull A wind of 10 ms (22 mph) has a power density of 610 Wm2
bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2
37
Canrsquot get it all
bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely
bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning
bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy
bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36
38
Practical Efficiencies
bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or
about 30ndash40ndash this figure is the mechanical energy
extracted from the windbull Conversion from mechanical to
electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37
39
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
40
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
41
Achievable efficiencies
42
Typical Windmillsbull A typical windmill might be 15 m in diameter
ndash 176 m2
bull At 10 ms wind 40 efficiency this delivers about 100 kW of power
ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW
bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per
year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2
ndash corresponds to 11ndash57 Wm2 average available power density
bull Note the really high tip speeds bird killers
43
Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2
44
Comparable to solar
bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind
bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area
bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy
bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo
45
Current implementations
bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large
dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years
bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over
California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW
46
Flies in the Ointment
bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it
bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces
substantiallybull If fully developed we could generate an average
power almost equal to our current electrical capacity (764 GW)
ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind
47
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
48
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
- Renewable Energy Sources II Alternatives Part I
- Chapter 5 Summary
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Renewable Resources Discussed in Book
- Renewable Energy Consumption
- Another look at available energy flow
- The Renewable Budget
- Outstanding Points from Fig 51
- Energy Flow continued
- The Hydrologic Cycle
- Energetics of the hydrologic cycle
- Let it Rain
- How much of the process do we get to keep
- iClicker Question
- Slide 26
- Power of a hydroelectric dam
- Importance of Hydroelectricity
- Hydroelectric potential by region in GW
- Slide 30
- Slide 31
- Hydroelectricity in the future
- Sorry try againhellip
- Wind Energy
- The Power of Wind
- Wind Energy proportional to cube of velocity
- Canrsquot get it all
- Practical Efficiencies
- Slide 39
- Slide 40
- Achievable efficiencies
- Typical Windmills
- Average available wind power
- Comparable to solar
- Current implementations
- Flies in the Ointment
- Slide 47
- Slide 48
-
11
iClicker Question
bull What must be done to overcome the setting of the Sun in a solar energy systemndash A Store energy in batteriesndash B Get electrical power from elsewherendash C Donrsquot use electrical power at nightndash D All of the above are alternative
approaches for energy after sunset
12
iClicker Question
bull What must be done to overcome the setting of the Sun in a solar energy systemndash A Store energy in batteriesndash B Get electrical power from elsewherendash C Donrsquot use electrical power at nightndash D All of the above are alternative
approaches for energy after sunset
13
iClicker Question
bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect
bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation
bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation
bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation
bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light
bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation
14
iClicker Question
bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect
bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation
bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation
bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation
bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light
bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation
15
Renewable Resources Discussed in Book
bull Renewable means anything that wonrsquot be permanently destroyed by using itndash sunlight (the sun will rise again tomorrow)ndash biomass (grows again)ndash hydrological cycle (will rain again)ndash wind (sunlight on Earth makes more)ndash ocean currents (driven by Sun)ndash tidal motion (MoonSun keep on producing it)ndash geothermal (heat sources inside Earth not
used up fast)
16
Renewable Energy Consumption
Energy Source
QBtu (1994)
Percent (1994)
QBtu (2003)
Percent (2003)
Hydroelectric 3037 343 2779 283
Geothermal 0357 040 0314 032
Biomass 2852 322 2884 294
Solar Energy 0069 0077 0063 006
Wind 0036 0040 0108 011
Total 6351 718 615 63
17
Another look at available energy flow
bull The flow of radiation (solar and thermal) was covered previouslyndash earth is in an energy balance energy in =
energy outndash 30 reflected 70 thermally re-radiated
bull Some of the incident energy is absorbed but what exactly does this dondash much goes into heating the airlandndash much goes into driving weather (rain wind)ndash some goes into ocean currentsndash some goes into photosynthesis
18
The Renewable Budget
19
Outstanding Points from Fig 51
bull Incident radiation is 1741015 Wndash this is 1370 Wm2 times area facing sun
(R2)bull 30 directly reflected back to space
ndash off clouds air landbull 47 goes into heating air land waterbull 23 goes into evaporating water
precipitation etc (part of weather)bull Adds to 100 so wersquore done
ndash but wait therersquos morehellip
20
Energy Flow continued
bull 021 goes into wind waves convection currentsndash note this is 100 times less than driving the water
cyclendash but this is the ldquootherrdquo aspect of weather
bull 0023 is stored as chemical energy in plants via photosynthesis
ndash total is 401012 W half in ocean (plankton)ndash humans are 6 billion times 100 W = 061012 Wndash this is 15 of bio-energy 000034 of incident
powerbull All of this (bio-activity wind weather etc) ends up
creating heat and re-radiating to spacendash except some small amount of storage in fossil fuels
21
The Hydrologic Cycle
Lots of energy associated with evaporationboth mgh (4 for 10 km lift) and latent heat (96) of water
22
Energetics of the hydrologic cycle
bull It takes energy to evaporate water 2444 J per gramndash this is why ldquoswamp coolersrdquo work evaporation
pulls heat out of environment making it feel cooler
ndash 23 of sunrsquos incident energy goes into evaporation
bull By contrast raising one gram of water to the top of the troposphere (10000 m or 33000 ft) takes
mgh = (0001 kg)(10 ms2)(10000 m) = 100 J
bull So gt 96 of the energy associated with forming clouds is the evaporation lt 4 in lifting against gravity
23
Let it Rain
bull When water condenses in clouds it re-releases this ldquolatent heatrdquo
ndash but this is re-radiated and is of no consequence to hydro-power
bull When it rains the gravitational potential energy is released mostly as kinetic energy and ultimately heat
bull Some tiny bit of gravitational potential energy remains IF the rain falls on terrain (eg higher than sea level where it originated)
ndash hydroelectric plants use this tiny left-over energy itrsquos the energy that drives the flow of streams and rivers
ndash damming up a river concentrates the potential energy in one location for easy exploitation
24
How much of the process do we get to keep
bull According to Figure 51 401015 W of solar power goes into evaporation
ndash this corresponds to 161010 kg per second of evaporated water
ndash this is 35 mm per day off the ocean surface (replenished by rain)
bull The gravitational potential energy given to water vapor (mostly in clouds) in the atmosphere (per second) is thenmgh = (161010 kg)(10 ms2)(2000 m) = 321014 J
bull One can calculate that we gain access to only 25 of the total amount (and use only 125)
ndash based on the 18 land area of the US and the maximum potential of 1477 GW as presented in Table 52
25
iClicker Question
bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical
bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential
energy of precipitationndash E a form of fictitious energy
26
iClicker Question
bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical
bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential
energy of precipitationndash E a form of fictitious energy
27
Power of a hydroelectric dam
bull Most impressive is Grand Coulee in Washington on Columbia River
ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets
rain)ndash each cubic meter of water (1000 kg) has potential
energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ
ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently
28
Importance of Hydroelectricity
29
Hydroelectric potential by region in GW
Region Potential
Developed
Undeveloped
Developed
New England 63 19 44 301
Middle Atlantic 98 49 49 500
East North Central 29 12 17 413
West North Central
62 31 31 500
South Atlantic 139 67 72 482
East South Central 83 59 24 711
West South Central
73 27 46 369
Mountain 286 95 191 332
Pacific 644 382 262 593
Total 1477 741 736 502
30
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
31
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
32
Hydroelectricity in the future
bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale
unitsbull Problems with dams
ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site
ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)
ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers
33
Sorry try againhellip
bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy
bull Though very efficient and seemingly environmentally friendly dams do have their problems
bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future
34
Wind Energy
35
The Power of Wind
bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters
every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is
then the kinetic energy the mass of air defined by a rectangular tube
ndash tube is one square meter by v meters or v m3
ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)
065v3 at sea level
36
Wind Energy proportional to cube of velocity
bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in
continental US (above sea level so air slightly less dense)
bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times
bull A wind of 10 ms (22 mph) has a power density of 610 Wm2
bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2
37
Canrsquot get it all
bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely
bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning
bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy
bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36
38
Practical Efficiencies
bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or
about 30ndash40ndash this figure is the mechanical energy
extracted from the windbull Conversion from mechanical to
electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37
39
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
40
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
41
Achievable efficiencies
42
Typical Windmillsbull A typical windmill might be 15 m in diameter
ndash 176 m2
bull At 10 ms wind 40 efficiency this delivers about 100 kW of power
ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW
bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per
year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2
ndash corresponds to 11ndash57 Wm2 average available power density
bull Note the really high tip speeds bird killers
43
Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2
44
Comparable to solar
bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind
bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area
bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy
bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo
45
Current implementations
bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large
dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years
bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over
California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW
46
Flies in the Ointment
bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it
bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces
substantiallybull If fully developed we could generate an average
power almost equal to our current electrical capacity (764 GW)
ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind
47
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
48
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
- Renewable Energy Sources II Alternatives Part I
- Chapter 5 Summary
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Renewable Resources Discussed in Book
- Renewable Energy Consumption
- Another look at available energy flow
- The Renewable Budget
- Outstanding Points from Fig 51
- Energy Flow continued
- The Hydrologic Cycle
- Energetics of the hydrologic cycle
- Let it Rain
- How much of the process do we get to keep
- iClicker Question
- Slide 26
- Power of a hydroelectric dam
- Importance of Hydroelectricity
- Hydroelectric potential by region in GW
- Slide 30
- Slide 31
- Hydroelectricity in the future
- Sorry try againhellip
- Wind Energy
- The Power of Wind
- Wind Energy proportional to cube of velocity
- Canrsquot get it all
- Practical Efficiencies
- Slide 39
- Slide 40
- Achievable efficiencies
- Typical Windmills
- Average available wind power
- Comparable to solar
- Current implementations
- Flies in the Ointment
- Slide 47
- Slide 48
-
12
iClicker Question
bull What must be done to overcome the setting of the Sun in a solar energy systemndash A Store energy in batteriesndash B Get electrical power from elsewherendash C Donrsquot use electrical power at nightndash D All of the above are alternative
approaches for energy after sunset
13
iClicker Question
bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect
bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation
bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation
bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation
bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light
bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation
14
iClicker Question
bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect
bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation
bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation
bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation
bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light
bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation
15
Renewable Resources Discussed in Book
bull Renewable means anything that wonrsquot be permanently destroyed by using itndash sunlight (the sun will rise again tomorrow)ndash biomass (grows again)ndash hydrological cycle (will rain again)ndash wind (sunlight on Earth makes more)ndash ocean currents (driven by Sun)ndash tidal motion (MoonSun keep on producing it)ndash geothermal (heat sources inside Earth not
used up fast)
16
Renewable Energy Consumption
Energy Source
QBtu (1994)
Percent (1994)
QBtu (2003)
Percent (2003)
Hydroelectric 3037 343 2779 283
Geothermal 0357 040 0314 032
Biomass 2852 322 2884 294
Solar Energy 0069 0077 0063 006
Wind 0036 0040 0108 011
Total 6351 718 615 63
17
Another look at available energy flow
bull The flow of radiation (solar and thermal) was covered previouslyndash earth is in an energy balance energy in =
energy outndash 30 reflected 70 thermally re-radiated
bull Some of the incident energy is absorbed but what exactly does this dondash much goes into heating the airlandndash much goes into driving weather (rain wind)ndash some goes into ocean currentsndash some goes into photosynthesis
18
The Renewable Budget
19
Outstanding Points from Fig 51
bull Incident radiation is 1741015 Wndash this is 1370 Wm2 times area facing sun
(R2)bull 30 directly reflected back to space
ndash off clouds air landbull 47 goes into heating air land waterbull 23 goes into evaporating water
precipitation etc (part of weather)bull Adds to 100 so wersquore done
ndash but wait therersquos morehellip
20
Energy Flow continued
bull 021 goes into wind waves convection currentsndash note this is 100 times less than driving the water
cyclendash but this is the ldquootherrdquo aspect of weather
bull 0023 is stored as chemical energy in plants via photosynthesis
ndash total is 401012 W half in ocean (plankton)ndash humans are 6 billion times 100 W = 061012 Wndash this is 15 of bio-energy 000034 of incident
powerbull All of this (bio-activity wind weather etc) ends up
creating heat and re-radiating to spacendash except some small amount of storage in fossil fuels
21
The Hydrologic Cycle
Lots of energy associated with evaporationboth mgh (4 for 10 km lift) and latent heat (96) of water
22
Energetics of the hydrologic cycle
bull It takes energy to evaporate water 2444 J per gramndash this is why ldquoswamp coolersrdquo work evaporation
pulls heat out of environment making it feel cooler
ndash 23 of sunrsquos incident energy goes into evaporation
bull By contrast raising one gram of water to the top of the troposphere (10000 m or 33000 ft) takes
mgh = (0001 kg)(10 ms2)(10000 m) = 100 J
bull So gt 96 of the energy associated with forming clouds is the evaporation lt 4 in lifting against gravity
23
Let it Rain
bull When water condenses in clouds it re-releases this ldquolatent heatrdquo
ndash but this is re-radiated and is of no consequence to hydro-power
bull When it rains the gravitational potential energy is released mostly as kinetic energy and ultimately heat
bull Some tiny bit of gravitational potential energy remains IF the rain falls on terrain (eg higher than sea level where it originated)
ndash hydroelectric plants use this tiny left-over energy itrsquos the energy that drives the flow of streams and rivers
ndash damming up a river concentrates the potential energy in one location for easy exploitation
24
How much of the process do we get to keep
bull According to Figure 51 401015 W of solar power goes into evaporation
ndash this corresponds to 161010 kg per second of evaporated water
ndash this is 35 mm per day off the ocean surface (replenished by rain)
bull The gravitational potential energy given to water vapor (mostly in clouds) in the atmosphere (per second) is thenmgh = (161010 kg)(10 ms2)(2000 m) = 321014 J
bull One can calculate that we gain access to only 25 of the total amount (and use only 125)
ndash based on the 18 land area of the US and the maximum potential of 1477 GW as presented in Table 52
25
iClicker Question
bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical
bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential
energy of precipitationndash E a form of fictitious energy
26
iClicker Question
bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical
bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential
energy of precipitationndash E a form of fictitious energy
27
Power of a hydroelectric dam
bull Most impressive is Grand Coulee in Washington on Columbia River
ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets
rain)ndash each cubic meter of water (1000 kg) has potential
energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ
ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently
28
Importance of Hydroelectricity
29
Hydroelectric potential by region in GW
Region Potential
Developed
Undeveloped
Developed
New England 63 19 44 301
Middle Atlantic 98 49 49 500
East North Central 29 12 17 413
West North Central
62 31 31 500
South Atlantic 139 67 72 482
East South Central 83 59 24 711
West South Central
73 27 46 369
Mountain 286 95 191 332
Pacific 644 382 262 593
Total 1477 741 736 502
30
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
31
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
32
Hydroelectricity in the future
bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale
unitsbull Problems with dams
ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site
ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)
ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers
33
Sorry try againhellip
bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy
bull Though very efficient and seemingly environmentally friendly dams do have their problems
bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future
34
Wind Energy
35
The Power of Wind
bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters
every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is
then the kinetic energy the mass of air defined by a rectangular tube
ndash tube is one square meter by v meters or v m3
ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)
065v3 at sea level
36
Wind Energy proportional to cube of velocity
bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in
continental US (above sea level so air slightly less dense)
bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times
bull A wind of 10 ms (22 mph) has a power density of 610 Wm2
bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2
37
Canrsquot get it all
bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely
bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning
bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy
bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36
38
Practical Efficiencies
bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or
about 30ndash40ndash this figure is the mechanical energy
extracted from the windbull Conversion from mechanical to
electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37
39
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
40
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
41
Achievable efficiencies
42
Typical Windmillsbull A typical windmill might be 15 m in diameter
ndash 176 m2
bull At 10 ms wind 40 efficiency this delivers about 100 kW of power
ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW
bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per
year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2
ndash corresponds to 11ndash57 Wm2 average available power density
bull Note the really high tip speeds bird killers
43
Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2
44
Comparable to solar
bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind
bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area
bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy
bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo
45
Current implementations
bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large
dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years
bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over
California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW
46
Flies in the Ointment
bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it
bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces
substantiallybull If fully developed we could generate an average
power almost equal to our current electrical capacity (764 GW)
ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind
47
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
48
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
- Renewable Energy Sources II Alternatives Part I
- Chapter 5 Summary
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Renewable Resources Discussed in Book
- Renewable Energy Consumption
- Another look at available energy flow
- The Renewable Budget
- Outstanding Points from Fig 51
- Energy Flow continued
- The Hydrologic Cycle
- Energetics of the hydrologic cycle
- Let it Rain
- How much of the process do we get to keep
- iClicker Question
- Slide 26
- Power of a hydroelectric dam
- Importance of Hydroelectricity
- Hydroelectric potential by region in GW
- Slide 30
- Slide 31
- Hydroelectricity in the future
- Sorry try againhellip
- Wind Energy
- The Power of Wind
- Wind Energy proportional to cube of velocity
- Canrsquot get it all
- Practical Efficiencies
- Slide 39
- Slide 40
- Achievable efficiencies
- Typical Windmills
- Average available wind power
- Comparable to solar
- Current implementations
- Flies in the Ointment
- Slide 47
- Slide 48
-
13
iClicker Question
bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect
bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation
bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation
bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation
bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light
bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation
14
iClicker Question
bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect
bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation
bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation
bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation
bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light
bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation
15
Renewable Resources Discussed in Book
bull Renewable means anything that wonrsquot be permanently destroyed by using itndash sunlight (the sun will rise again tomorrow)ndash biomass (grows again)ndash hydrological cycle (will rain again)ndash wind (sunlight on Earth makes more)ndash ocean currents (driven by Sun)ndash tidal motion (MoonSun keep on producing it)ndash geothermal (heat sources inside Earth not
used up fast)
16
Renewable Energy Consumption
Energy Source
QBtu (1994)
Percent (1994)
QBtu (2003)
Percent (2003)
Hydroelectric 3037 343 2779 283
Geothermal 0357 040 0314 032
Biomass 2852 322 2884 294
Solar Energy 0069 0077 0063 006
Wind 0036 0040 0108 011
Total 6351 718 615 63
17
Another look at available energy flow
bull The flow of radiation (solar and thermal) was covered previouslyndash earth is in an energy balance energy in =
energy outndash 30 reflected 70 thermally re-radiated
bull Some of the incident energy is absorbed but what exactly does this dondash much goes into heating the airlandndash much goes into driving weather (rain wind)ndash some goes into ocean currentsndash some goes into photosynthesis
18
The Renewable Budget
19
Outstanding Points from Fig 51
bull Incident radiation is 1741015 Wndash this is 1370 Wm2 times area facing sun
(R2)bull 30 directly reflected back to space
ndash off clouds air landbull 47 goes into heating air land waterbull 23 goes into evaporating water
precipitation etc (part of weather)bull Adds to 100 so wersquore done
ndash but wait therersquos morehellip
20
Energy Flow continued
bull 021 goes into wind waves convection currentsndash note this is 100 times less than driving the water
cyclendash but this is the ldquootherrdquo aspect of weather
bull 0023 is stored as chemical energy in plants via photosynthesis
ndash total is 401012 W half in ocean (plankton)ndash humans are 6 billion times 100 W = 061012 Wndash this is 15 of bio-energy 000034 of incident
powerbull All of this (bio-activity wind weather etc) ends up
creating heat and re-radiating to spacendash except some small amount of storage in fossil fuels
21
The Hydrologic Cycle
Lots of energy associated with evaporationboth mgh (4 for 10 km lift) and latent heat (96) of water
22
Energetics of the hydrologic cycle
bull It takes energy to evaporate water 2444 J per gramndash this is why ldquoswamp coolersrdquo work evaporation
pulls heat out of environment making it feel cooler
ndash 23 of sunrsquos incident energy goes into evaporation
bull By contrast raising one gram of water to the top of the troposphere (10000 m or 33000 ft) takes
mgh = (0001 kg)(10 ms2)(10000 m) = 100 J
bull So gt 96 of the energy associated with forming clouds is the evaporation lt 4 in lifting against gravity
23
Let it Rain
bull When water condenses in clouds it re-releases this ldquolatent heatrdquo
ndash but this is re-radiated and is of no consequence to hydro-power
bull When it rains the gravitational potential energy is released mostly as kinetic energy and ultimately heat
bull Some tiny bit of gravitational potential energy remains IF the rain falls on terrain (eg higher than sea level where it originated)
ndash hydroelectric plants use this tiny left-over energy itrsquos the energy that drives the flow of streams and rivers
ndash damming up a river concentrates the potential energy in one location for easy exploitation
24
How much of the process do we get to keep
bull According to Figure 51 401015 W of solar power goes into evaporation
ndash this corresponds to 161010 kg per second of evaporated water
ndash this is 35 mm per day off the ocean surface (replenished by rain)
bull The gravitational potential energy given to water vapor (mostly in clouds) in the atmosphere (per second) is thenmgh = (161010 kg)(10 ms2)(2000 m) = 321014 J
bull One can calculate that we gain access to only 25 of the total amount (and use only 125)
ndash based on the 18 land area of the US and the maximum potential of 1477 GW as presented in Table 52
25
iClicker Question
bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical
bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential
energy of precipitationndash E a form of fictitious energy
26
iClicker Question
bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical
bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential
energy of precipitationndash E a form of fictitious energy
27
Power of a hydroelectric dam
bull Most impressive is Grand Coulee in Washington on Columbia River
ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets
rain)ndash each cubic meter of water (1000 kg) has potential
energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ
ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently
28
Importance of Hydroelectricity
29
Hydroelectric potential by region in GW
Region Potential
Developed
Undeveloped
Developed
New England 63 19 44 301
Middle Atlantic 98 49 49 500
East North Central 29 12 17 413
West North Central
62 31 31 500
South Atlantic 139 67 72 482
East South Central 83 59 24 711
West South Central
73 27 46 369
Mountain 286 95 191 332
Pacific 644 382 262 593
Total 1477 741 736 502
30
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
31
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
32
Hydroelectricity in the future
bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale
unitsbull Problems with dams
ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site
ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)
ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers
33
Sorry try againhellip
bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy
bull Though very efficient and seemingly environmentally friendly dams do have their problems
bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future
34
Wind Energy
35
The Power of Wind
bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters
every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is
then the kinetic energy the mass of air defined by a rectangular tube
ndash tube is one square meter by v meters or v m3
ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)
065v3 at sea level
36
Wind Energy proportional to cube of velocity
bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in
continental US (above sea level so air slightly less dense)
bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times
bull A wind of 10 ms (22 mph) has a power density of 610 Wm2
bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2
37
Canrsquot get it all
bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely
bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning
bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy
bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36
38
Practical Efficiencies
bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or
about 30ndash40ndash this figure is the mechanical energy
extracted from the windbull Conversion from mechanical to
electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37
39
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
40
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
41
Achievable efficiencies
42
Typical Windmillsbull A typical windmill might be 15 m in diameter
ndash 176 m2
bull At 10 ms wind 40 efficiency this delivers about 100 kW of power
ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW
bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per
year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2
ndash corresponds to 11ndash57 Wm2 average available power density
bull Note the really high tip speeds bird killers
43
Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2
44
Comparable to solar
bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind
bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area
bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy
bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo
45
Current implementations
bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large
dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years
bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over
California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW
46
Flies in the Ointment
bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it
bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces
substantiallybull If fully developed we could generate an average
power almost equal to our current electrical capacity (764 GW)
ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind
47
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
48
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
- Renewable Energy Sources II Alternatives Part I
- Chapter 5 Summary
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Renewable Resources Discussed in Book
- Renewable Energy Consumption
- Another look at available energy flow
- The Renewable Budget
- Outstanding Points from Fig 51
- Energy Flow continued
- The Hydrologic Cycle
- Energetics of the hydrologic cycle
- Let it Rain
- How much of the process do we get to keep
- iClicker Question
- Slide 26
- Power of a hydroelectric dam
- Importance of Hydroelectricity
- Hydroelectric potential by region in GW
- Slide 30
- Slide 31
- Hydroelectricity in the future
- Sorry try againhellip
- Wind Energy
- The Power of Wind
- Wind Energy proportional to cube of velocity
- Canrsquot get it all
- Practical Efficiencies
- Slide 39
- Slide 40
- Achievable efficiencies
- Typical Windmills
- Average available wind power
- Comparable to solar
- Current implementations
- Flies in the Ointment
- Slide 47
- Slide 48
-
14
iClicker Question
bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect
bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation
bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation
bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation
bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light
bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation
15
Renewable Resources Discussed in Book
bull Renewable means anything that wonrsquot be permanently destroyed by using itndash sunlight (the sun will rise again tomorrow)ndash biomass (grows again)ndash hydrological cycle (will rain again)ndash wind (sunlight on Earth makes more)ndash ocean currents (driven by Sun)ndash tidal motion (MoonSun keep on producing it)ndash geothermal (heat sources inside Earth not
used up fast)
16
Renewable Energy Consumption
Energy Source
QBtu (1994)
Percent (1994)
QBtu (2003)
Percent (2003)
Hydroelectric 3037 343 2779 283
Geothermal 0357 040 0314 032
Biomass 2852 322 2884 294
Solar Energy 0069 0077 0063 006
Wind 0036 0040 0108 011
Total 6351 718 615 63
17
Another look at available energy flow
bull The flow of radiation (solar and thermal) was covered previouslyndash earth is in an energy balance energy in =
energy outndash 30 reflected 70 thermally re-radiated
bull Some of the incident energy is absorbed but what exactly does this dondash much goes into heating the airlandndash much goes into driving weather (rain wind)ndash some goes into ocean currentsndash some goes into photosynthesis
18
The Renewable Budget
19
Outstanding Points from Fig 51
bull Incident radiation is 1741015 Wndash this is 1370 Wm2 times area facing sun
(R2)bull 30 directly reflected back to space
ndash off clouds air landbull 47 goes into heating air land waterbull 23 goes into evaporating water
precipitation etc (part of weather)bull Adds to 100 so wersquore done
ndash but wait therersquos morehellip
20
Energy Flow continued
bull 021 goes into wind waves convection currentsndash note this is 100 times less than driving the water
cyclendash but this is the ldquootherrdquo aspect of weather
bull 0023 is stored as chemical energy in plants via photosynthesis
ndash total is 401012 W half in ocean (plankton)ndash humans are 6 billion times 100 W = 061012 Wndash this is 15 of bio-energy 000034 of incident
powerbull All of this (bio-activity wind weather etc) ends up
creating heat and re-radiating to spacendash except some small amount of storage in fossil fuels
21
The Hydrologic Cycle
Lots of energy associated with evaporationboth mgh (4 for 10 km lift) and latent heat (96) of water
22
Energetics of the hydrologic cycle
bull It takes energy to evaporate water 2444 J per gramndash this is why ldquoswamp coolersrdquo work evaporation
pulls heat out of environment making it feel cooler
ndash 23 of sunrsquos incident energy goes into evaporation
bull By contrast raising one gram of water to the top of the troposphere (10000 m or 33000 ft) takes
mgh = (0001 kg)(10 ms2)(10000 m) = 100 J
bull So gt 96 of the energy associated with forming clouds is the evaporation lt 4 in lifting against gravity
23
Let it Rain
bull When water condenses in clouds it re-releases this ldquolatent heatrdquo
ndash but this is re-radiated and is of no consequence to hydro-power
bull When it rains the gravitational potential energy is released mostly as kinetic energy and ultimately heat
bull Some tiny bit of gravitational potential energy remains IF the rain falls on terrain (eg higher than sea level where it originated)
ndash hydroelectric plants use this tiny left-over energy itrsquos the energy that drives the flow of streams and rivers
ndash damming up a river concentrates the potential energy in one location for easy exploitation
24
How much of the process do we get to keep
bull According to Figure 51 401015 W of solar power goes into evaporation
ndash this corresponds to 161010 kg per second of evaporated water
ndash this is 35 mm per day off the ocean surface (replenished by rain)
bull The gravitational potential energy given to water vapor (mostly in clouds) in the atmosphere (per second) is thenmgh = (161010 kg)(10 ms2)(2000 m) = 321014 J
bull One can calculate that we gain access to only 25 of the total amount (and use only 125)
ndash based on the 18 land area of the US and the maximum potential of 1477 GW as presented in Table 52
25
iClicker Question
bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical
bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential
energy of precipitationndash E a form of fictitious energy
26
iClicker Question
bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical
bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential
energy of precipitationndash E a form of fictitious energy
27
Power of a hydroelectric dam
bull Most impressive is Grand Coulee in Washington on Columbia River
ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets
rain)ndash each cubic meter of water (1000 kg) has potential
energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ
ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently
28
Importance of Hydroelectricity
29
Hydroelectric potential by region in GW
Region Potential
Developed
Undeveloped
Developed
New England 63 19 44 301
Middle Atlantic 98 49 49 500
East North Central 29 12 17 413
West North Central
62 31 31 500
South Atlantic 139 67 72 482
East South Central 83 59 24 711
West South Central
73 27 46 369
Mountain 286 95 191 332
Pacific 644 382 262 593
Total 1477 741 736 502
30
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
31
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
32
Hydroelectricity in the future
bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale
unitsbull Problems with dams
ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site
ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)
ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers
33
Sorry try againhellip
bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy
bull Though very efficient and seemingly environmentally friendly dams do have their problems
bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future
34
Wind Energy
35
The Power of Wind
bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters
every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is
then the kinetic energy the mass of air defined by a rectangular tube
ndash tube is one square meter by v meters or v m3
ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)
065v3 at sea level
36
Wind Energy proportional to cube of velocity
bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in
continental US (above sea level so air slightly less dense)
bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times
bull A wind of 10 ms (22 mph) has a power density of 610 Wm2
bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2
37
Canrsquot get it all
bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely
bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning
bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy
bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36
38
Practical Efficiencies
bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or
about 30ndash40ndash this figure is the mechanical energy
extracted from the windbull Conversion from mechanical to
electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37
39
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
40
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
41
Achievable efficiencies
42
Typical Windmillsbull A typical windmill might be 15 m in diameter
ndash 176 m2
bull At 10 ms wind 40 efficiency this delivers about 100 kW of power
ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW
bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per
year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2
ndash corresponds to 11ndash57 Wm2 average available power density
bull Note the really high tip speeds bird killers
43
Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2
44
Comparable to solar
bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind
bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area
bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy
bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo
45
Current implementations
bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large
dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years
bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over
California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW
46
Flies in the Ointment
bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it
bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces
substantiallybull If fully developed we could generate an average
power almost equal to our current electrical capacity (764 GW)
ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind
47
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
48
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
- Renewable Energy Sources II Alternatives Part I
- Chapter 5 Summary
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Renewable Resources Discussed in Book
- Renewable Energy Consumption
- Another look at available energy flow
- The Renewable Budget
- Outstanding Points from Fig 51
- Energy Flow continued
- The Hydrologic Cycle
- Energetics of the hydrologic cycle
- Let it Rain
- How much of the process do we get to keep
- iClicker Question
- Slide 26
- Power of a hydroelectric dam
- Importance of Hydroelectricity
- Hydroelectric potential by region in GW
- Slide 30
- Slide 31
- Hydroelectricity in the future
- Sorry try againhellip
- Wind Energy
- The Power of Wind
- Wind Energy proportional to cube of velocity
- Canrsquot get it all
- Practical Efficiencies
- Slide 39
- Slide 40
- Achievable efficiencies
- Typical Windmills
- Average available wind power
- Comparable to solar
- Current implementations
- Flies in the Ointment
- Slide 47
- Slide 48
-
15
Renewable Resources Discussed in Book
bull Renewable means anything that wonrsquot be permanently destroyed by using itndash sunlight (the sun will rise again tomorrow)ndash biomass (grows again)ndash hydrological cycle (will rain again)ndash wind (sunlight on Earth makes more)ndash ocean currents (driven by Sun)ndash tidal motion (MoonSun keep on producing it)ndash geothermal (heat sources inside Earth not
used up fast)
16
Renewable Energy Consumption
Energy Source
QBtu (1994)
Percent (1994)
QBtu (2003)
Percent (2003)
Hydroelectric 3037 343 2779 283
Geothermal 0357 040 0314 032
Biomass 2852 322 2884 294
Solar Energy 0069 0077 0063 006
Wind 0036 0040 0108 011
Total 6351 718 615 63
17
Another look at available energy flow
bull The flow of radiation (solar and thermal) was covered previouslyndash earth is in an energy balance energy in =
energy outndash 30 reflected 70 thermally re-radiated
bull Some of the incident energy is absorbed but what exactly does this dondash much goes into heating the airlandndash much goes into driving weather (rain wind)ndash some goes into ocean currentsndash some goes into photosynthesis
18
The Renewable Budget
19
Outstanding Points from Fig 51
bull Incident radiation is 1741015 Wndash this is 1370 Wm2 times area facing sun
(R2)bull 30 directly reflected back to space
ndash off clouds air landbull 47 goes into heating air land waterbull 23 goes into evaporating water
precipitation etc (part of weather)bull Adds to 100 so wersquore done
ndash but wait therersquos morehellip
20
Energy Flow continued
bull 021 goes into wind waves convection currentsndash note this is 100 times less than driving the water
cyclendash but this is the ldquootherrdquo aspect of weather
bull 0023 is stored as chemical energy in plants via photosynthesis
ndash total is 401012 W half in ocean (plankton)ndash humans are 6 billion times 100 W = 061012 Wndash this is 15 of bio-energy 000034 of incident
powerbull All of this (bio-activity wind weather etc) ends up
creating heat and re-radiating to spacendash except some small amount of storage in fossil fuels
21
The Hydrologic Cycle
Lots of energy associated with evaporationboth mgh (4 for 10 km lift) and latent heat (96) of water
22
Energetics of the hydrologic cycle
bull It takes energy to evaporate water 2444 J per gramndash this is why ldquoswamp coolersrdquo work evaporation
pulls heat out of environment making it feel cooler
ndash 23 of sunrsquos incident energy goes into evaporation
bull By contrast raising one gram of water to the top of the troposphere (10000 m or 33000 ft) takes
mgh = (0001 kg)(10 ms2)(10000 m) = 100 J
bull So gt 96 of the energy associated with forming clouds is the evaporation lt 4 in lifting against gravity
23
Let it Rain
bull When water condenses in clouds it re-releases this ldquolatent heatrdquo
ndash but this is re-radiated and is of no consequence to hydro-power
bull When it rains the gravitational potential energy is released mostly as kinetic energy and ultimately heat
bull Some tiny bit of gravitational potential energy remains IF the rain falls on terrain (eg higher than sea level where it originated)
ndash hydroelectric plants use this tiny left-over energy itrsquos the energy that drives the flow of streams and rivers
ndash damming up a river concentrates the potential energy in one location for easy exploitation
24
How much of the process do we get to keep
bull According to Figure 51 401015 W of solar power goes into evaporation
ndash this corresponds to 161010 kg per second of evaporated water
ndash this is 35 mm per day off the ocean surface (replenished by rain)
bull The gravitational potential energy given to water vapor (mostly in clouds) in the atmosphere (per second) is thenmgh = (161010 kg)(10 ms2)(2000 m) = 321014 J
bull One can calculate that we gain access to only 25 of the total amount (and use only 125)
ndash based on the 18 land area of the US and the maximum potential of 1477 GW as presented in Table 52
25
iClicker Question
bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical
bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential
energy of precipitationndash E a form of fictitious energy
26
iClicker Question
bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical
bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential
energy of precipitationndash E a form of fictitious energy
27
Power of a hydroelectric dam
bull Most impressive is Grand Coulee in Washington on Columbia River
ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets
rain)ndash each cubic meter of water (1000 kg) has potential
energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ
ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently
28
Importance of Hydroelectricity
29
Hydroelectric potential by region in GW
Region Potential
Developed
Undeveloped
Developed
New England 63 19 44 301
Middle Atlantic 98 49 49 500
East North Central 29 12 17 413
West North Central
62 31 31 500
South Atlantic 139 67 72 482
East South Central 83 59 24 711
West South Central
73 27 46 369
Mountain 286 95 191 332
Pacific 644 382 262 593
Total 1477 741 736 502
30
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
31
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
32
Hydroelectricity in the future
bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale
unitsbull Problems with dams
ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site
ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)
ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers
33
Sorry try againhellip
bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy
bull Though very efficient and seemingly environmentally friendly dams do have their problems
bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future
34
Wind Energy
35
The Power of Wind
bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters
every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is
then the kinetic energy the mass of air defined by a rectangular tube
ndash tube is one square meter by v meters or v m3
ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)
065v3 at sea level
36
Wind Energy proportional to cube of velocity
bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in
continental US (above sea level so air slightly less dense)
bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times
bull A wind of 10 ms (22 mph) has a power density of 610 Wm2
bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2
37
Canrsquot get it all
bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely
bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning
bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy
bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36
38
Practical Efficiencies
bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or
about 30ndash40ndash this figure is the mechanical energy
extracted from the windbull Conversion from mechanical to
electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37
39
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
40
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
41
Achievable efficiencies
42
Typical Windmillsbull A typical windmill might be 15 m in diameter
ndash 176 m2
bull At 10 ms wind 40 efficiency this delivers about 100 kW of power
ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW
bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per
year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2
ndash corresponds to 11ndash57 Wm2 average available power density
bull Note the really high tip speeds bird killers
43
Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2
44
Comparable to solar
bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind
bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area
bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy
bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo
45
Current implementations
bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large
dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years
bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over
California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW
46
Flies in the Ointment
bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it
bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces
substantiallybull If fully developed we could generate an average
power almost equal to our current electrical capacity (764 GW)
ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind
47
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
48
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
- Renewable Energy Sources II Alternatives Part I
- Chapter 5 Summary
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Renewable Resources Discussed in Book
- Renewable Energy Consumption
- Another look at available energy flow
- The Renewable Budget
- Outstanding Points from Fig 51
- Energy Flow continued
- The Hydrologic Cycle
- Energetics of the hydrologic cycle
- Let it Rain
- How much of the process do we get to keep
- iClicker Question
- Slide 26
- Power of a hydroelectric dam
- Importance of Hydroelectricity
- Hydroelectric potential by region in GW
- Slide 30
- Slide 31
- Hydroelectricity in the future
- Sorry try againhellip
- Wind Energy
- The Power of Wind
- Wind Energy proportional to cube of velocity
- Canrsquot get it all
- Practical Efficiencies
- Slide 39
- Slide 40
- Achievable efficiencies
- Typical Windmills
- Average available wind power
- Comparable to solar
- Current implementations
- Flies in the Ointment
- Slide 47
- Slide 48
-
16
Renewable Energy Consumption
Energy Source
QBtu (1994)
Percent (1994)
QBtu (2003)
Percent (2003)
Hydroelectric 3037 343 2779 283
Geothermal 0357 040 0314 032
Biomass 2852 322 2884 294
Solar Energy 0069 0077 0063 006
Wind 0036 0040 0108 011
Total 6351 718 615 63
17
Another look at available energy flow
bull The flow of radiation (solar and thermal) was covered previouslyndash earth is in an energy balance energy in =
energy outndash 30 reflected 70 thermally re-radiated
bull Some of the incident energy is absorbed but what exactly does this dondash much goes into heating the airlandndash much goes into driving weather (rain wind)ndash some goes into ocean currentsndash some goes into photosynthesis
18
The Renewable Budget
19
Outstanding Points from Fig 51
bull Incident radiation is 1741015 Wndash this is 1370 Wm2 times area facing sun
(R2)bull 30 directly reflected back to space
ndash off clouds air landbull 47 goes into heating air land waterbull 23 goes into evaporating water
precipitation etc (part of weather)bull Adds to 100 so wersquore done
ndash but wait therersquos morehellip
20
Energy Flow continued
bull 021 goes into wind waves convection currentsndash note this is 100 times less than driving the water
cyclendash but this is the ldquootherrdquo aspect of weather
bull 0023 is stored as chemical energy in plants via photosynthesis
ndash total is 401012 W half in ocean (plankton)ndash humans are 6 billion times 100 W = 061012 Wndash this is 15 of bio-energy 000034 of incident
powerbull All of this (bio-activity wind weather etc) ends up
creating heat and re-radiating to spacendash except some small amount of storage in fossil fuels
21
The Hydrologic Cycle
Lots of energy associated with evaporationboth mgh (4 for 10 km lift) and latent heat (96) of water
22
Energetics of the hydrologic cycle
bull It takes energy to evaporate water 2444 J per gramndash this is why ldquoswamp coolersrdquo work evaporation
pulls heat out of environment making it feel cooler
ndash 23 of sunrsquos incident energy goes into evaporation
bull By contrast raising one gram of water to the top of the troposphere (10000 m or 33000 ft) takes
mgh = (0001 kg)(10 ms2)(10000 m) = 100 J
bull So gt 96 of the energy associated with forming clouds is the evaporation lt 4 in lifting against gravity
23
Let it Rain
bull When water condenses in clouds it re-releases this ldquolatent heatrdquo
ndash but this is re-radiated and is of no consequence to hydro-power
bull When it rains the gravitational potential energy is released mostly as kinetic energy and ultimately heat
bull Some tiny bit of gravitational potential energy remains IF the rain falls on terrain (eg higher than sea level where it originated)
ndash hydroelectric plants use this tiny left-over energy itrsquos the energy that drives the flow of streams and rivers
ndash damming up a river concentrates the potential energy in one location for easy exploitation
24
How much of the process do we get to keep
bull According to Figure 51 401015 W of solar power goes into evaporation
ndash this corresponds to 161010 kg per second of evaporated water
ndash this is 35 mm per day off the ocean surface (replenished by rain)
bull The gravitational potential energy given to water vapor (mostly in clouds) in the atmosphere (per second) is thenmgh = (161010 kg)(10 ms2)(2000 m) = 321014 J
bull One can calculate that we gain access to only 25 of the total amount (and use only 125)
ndash based on the 18 land area of the US and the maximum potential of 1477 GW as presented in Table 52
25
iClicker Question
bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical
bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential
energy of precipitationndash E a form of fictitious energy
26
iClicker Question
bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical
bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential
energy of precipitationndash E a form of fictitious energy
27
Power of a hydroelectric dam
bull Most impressive is Grand Coulee in Washington on Columbia River
ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets
rain)ndash each cubic meter of water (1000 kg) has potential
energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ
ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently
28
Importance of Hydroelectricity
29
Hydroelectric potential by region in GW
Region Potential
Developed
Undeveloped
Developed
New England 63 19 44 301
Middle Atlantic 98 49 49 500
East North Central 29 12 17 413
West North Central
62 31 31 500
South Atlantic 139 67 72 482
East South Central 83 59 24 711
West South Central
73 27 46 369
Mountain 286 95 191 332
Pacific 644 382 262 593
Total 1477 741 736 502
30
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
31
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
32
Hydroelectricity in the future
bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale
unitsbull Problems with dams
ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site
ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)
ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers
33
Sorry try againhellip
bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy
bull Though very efficient and seemingly environmentally friendly dams do have their problems
bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future
34
Wind Energy
35
The Power of Wind
bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters
every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is
then the kinetic energy the mass of air defined by a rectangular tube
ndash tube is one square meter by v meters or v m3
ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)
065v3 at sea level
36
Wind Energy proportional to cube of velocity
bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in
continental US (above sea level so air slightly less dense)
bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times
bull A wind of 10 ms (22 mph) has a power density of 610 Wm2
bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2
37
Canrsquot get it all
bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely
bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning
bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy
bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36
38
Practical Efficiencies
bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or
about 30ndash40ndash this figure is the mechanical energy
extracted from the windbull Conversion from mechanical to
electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37
39
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
40
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
41
Achievable efficiencies
42
Typical Windmillsbull A typical windmill might be 15 m in diameter
ndash 176 m2
bull At 10 ms wind 40 efficiency this delivers about 100 kW of power
ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW
bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per
year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2
ndash corresponds to 11ndash57 Wm2 average available power density
bull Note the really high tip speeds bird killers
43
Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2
44
Comparable to solar
bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind
bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area
bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy
bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo
45
Current implementations
bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large
dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years
bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over
California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW
46
Flies in the Ointment
bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it
bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces
substantiallybull If fully developed we could generate an average
power almost equal to our current electrical capacity (764 GW)
ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind
47
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
48
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
- Renewable Energy Sources II Alternatives Part I
- Chapter 5 Summary
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Renewable Resources Discussed in Book
- Renewable Energy Consumption
- Another look at available energy flow
- The Renewable Budget
- Outstanding Points from Fig 51
- Energy Flow continued
- The Hydrologic Cycle
- Energetics of the hydrologic cycle
- Let it Rain
- How much of the process do we get to keep
- iClicker Question
- Slide 26
- Power of a hydroelectric dam
- Importance of Hydroelectricity
- Hydroelectric potential by region in GW
- Slide 30
- Slide 31
- Hydroelectricity in the future
- Sorry try againhellip
- Wind Energy
- The Power of Wind
- Wind Energy proportional to cube of velocity
- Canrsquot get it all
- Practical Efficiencies
- Slide 39
- Slide 40
- Achievable efficiencies
- Typical Windmills
- Average available wind power
- Comparable to solar
- Current implementations
- Flies in the Ointment
- Slide 47
- Slide 48
-
17
Another look at available energy flow
bull The flow of radiation (solar and thermal) was covered previouslyndash earth is in an energy balance energy in =
energy outndash 30 reflected 70 thermally re-radiated
bull Some of the incident energy is absorbed but what exactly does this dondash much goes into heating the airlandndash much goes into driving weather (rain wind)ndash some goes into ocean currentsndash some goes into photosynthesis
18
The Renewable Budget
19
Outstanding Points from Fig 51
bull Incident radiation is 1741015 Wndash this is 1370 Wm2 times area facing sun
(R2)bull 30 directly reflected back to space
ndash off clouds air landbull 47 goes into heating air land waterbull 23 goes into evaporating water
precipitation etc (part of weather)bull Adds to 100 so wersquore done
ndash but wait therersquos morehellip
20
Energy Flow continued
bull 021 goes into wind waves convection currentsndash note this is 100 times less than driving the water
cyclendash but this is the ldquootherrdquo aspect of weather
bull 0023 is stored as chemical energy in plants via photosynthesis
ndash total is 401012 W half in ocean (plankton)ndash humans are 6 billion times 100 W = 061012 Wndash this is 15 of bio-energy 000034 of incident
powerbull All of this (bio-activity wind weather etc) ends up
creating heat and re-radiating to spacendash except some small amount of storage in fossil fuels
21
The Hydrologic Cycle
Lots of energy associated with evaporationboth mgh (4 for 10 km lift) and latent heat (96) of water
22
Energetics of the hydrologic cycle
bull It takes energy to evaporate water 2444 J per gramndash this is why ldquoswamp coolersrdquo work evaporation
pulls heat out of environment making it feel cooler
ndash 23 of sunrsquos incident energy goes into evaporation
bull By contrast raising one gram of water to the top of the troposphere (10000 m or 33000 ft) takes
mgh = (0001 kg)(10 ms2)(10000 m) = 100 J
bull So gt 96 of the energy associated with forming clouds is the evaporation lt 4 in lifting against gravity
23
Let it Rain
bull When water condenses in clouds it re-releases this ldquolatent heatrdquo
ndash but this is re-radiated and is of no consequence to hydro-power
bull When it rains the gravitational potential energy is released mostly as kinetic energy and ultimately heat
bull Some tiny bit of gravitational potential energy remains IF the rain falls on terrain (eg higher than sea level where it originated)
ndash hydroelectric plants use this tiny left-over energy itrsquos the energy that drives the flow of streams and rivers
ndash damming up a river concentrates the potential energy in one location for easy exploitation
24
How much of the process do we get to keep
bull According to Figure 51 401015 W of solar power goes into evaporation
ndash this corresponds to 161010 kg per second of evaporated water
ndash this is 35 mm per day off the ocean surface (replenished by rain)
bull The gravitational potential energy given to water vapor (mostly in clouds) in the atmosphere (per second) is thenmgh = (161010 kg)(10 ms2)(2000 m) = 321014 J
bull One can calculate that we gain access to only 25 of the total amount (and use only 125)
ndash based on the 18 land area of the US and the maximum potential of 1477 GW as presented in Table 52
25
iClicker Question
bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical
bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential
energy of precipitationndash E a form of fictitious energy
26
iClicker Question
bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical
bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential
energy of precipitationndash E a form of fictitious energy
27
Power of a hydroelectric dam
bull Most impressive is Grand Coulee in Washington on Columbia River
ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets
rain)ndash each cubic meter of water (1000 kg) has potential
energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ
ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently
28
Importance of Hydroelectricity
29
Hydroelectric potential by region in GW
Region Potential
Developed
Undeveloped
Developed
New England 63 19 44 301
Middle Atlantic 98 49 49 500
East North Central 29 12 17 413
West North Central
62 31 31 500
South Atlantic 139 67 72 482
East South Central 83 59 24 711
West South Central
73 27 46 369
Mountain 286 95 191 332
Pacific 644 382 262 593
Total 1477 741 736 502
30
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
31
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
32
Hydroelectricity in the future
bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale
unitsbull Problems with dams
ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site
ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)
ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers
33
Sorry try againhellip
bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy
bull Though very efficient and seemingly environmentally friendly dams do have their problems
bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future
34
Wind Energy
35
The Power of Wind
bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters
every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is
then the kinetic energy the mass of air defined by a rectangular tube
ndash tube is one square meter by v meters or v m3
ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)
065v3 at sea level
36
Wind Energy proportional to cube of velocity
bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in
continental US (above sea level so air slightly less dense)
bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times
bull A wind of 10 ms (22 mph) has a power density of 610 Wm2
bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2
37
Canrsquot get it all
bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely
bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning
bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy
bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36
38
Practical Efficiencies
bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or
about 30ndash40ndash this figure is the mechanical energy
extracted from the windbull Conversion from mechanical to
electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37
39
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
40
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
41
Achievable efficiencies
42
Typical Windmillsbull A typical windmill might be 15 m in diameter
ndash 176 m2
bull At 10 ms wind 40 efficiency this delivers about 100 kW of power
ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW
bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per
year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2
ndash corresponds to 11ndash57 Wm2 average available power density
bull Note the really high tip speeds bird killers
43
Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2
44
Comparable to solar
bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind
bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area
bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy
bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo
45
Current implementations
bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large
dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years
bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over
California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW
46
Flies in the Ointment
bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it
bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces
substantiallybull If fully developed we could generate an average
power almost equal to our current electrical capacity (764 GW)
ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind
47
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
48
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
- Renewable Energy Sources II Alternatives Part I
- Chapter 5 Summary
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Renewable Resources Discussed in Book
- Renewable Energy Consumption
- Another look at available energy flow
- The Renewable Budget
- Outstanding Points from Fig 51
- Energy Flow continued
- The Hydrologic Cycle
- Energetics of the hydrologic cycle
- Let it Rain
- How much of the process do we get to keep
- iClicker Question
- Slide 26
- Power of a hydroelectric dam
- Importance of Hydroelectricity
- Hydroelectric potential by region in GW
- Slide 30
- Slide 31
- Hydroelectricity in the future
- Sorry try againhellip
- Wind Energy
- The Power of Wind
- Wind Energy proportional to cube of velocity
- Canrsquot get it all
- Practical Efficiencies
- Slide 39
- Slide 40
- Achievable efficiencies
- Typical Windmills
- Average available wind power
- Comparable to solar
- Current implementations
- Flies in the Ointment
- Slide 47
- Slide 48
-
18
The Renewable Budget
19
Outstanding Points from Fig 51
bull Incident radiation is 1741015 Wndash this is 1370 Wm2 times area facing sun
(R2)bull 30 directly reflected back to space
ndash off clouds air landbull 47 goes into heating air land waterbull 23 goes into evaporating water
precipitation etc (part of weather)bull Adds to 100 so wersquore done
ndash but wait therersquos morehellip
20
Energy Flow continued
bull 021 goes into wind waves convection currentsndash note this is 100 times less than driving the water
cyclendash but this is the ldquootherrdquo aspect of weather
bull 0023 is stored as chemical energy in plants via photosynthesis
ndash total is 401012 W half in ocean (plankton)ndash humans are 6 billion times 100 W = 061012 Wndash this is 15 of bio-energy 000034 of incident
powerbull All of this (bio-activity wind weather etc) ends up
creating heat and re-radiating to spacendash except some small amount of storage in fossil fuels
21
The Hydrologic Cycle
Lots of energy associated with evaporationboth mgh (4 for 10 km lift) and latent heat (96) of water
22
Energetics of the hydrologic cycle
bull It takes energy to evaporate water 2444 J per gramndash this is why ldquoswamp coolersrdquo work evaporation
pulls heat out of environment making it feel cooler
ndash 23 of sunrsquos incident energy goes into evaporation
bull By contrast raising one gram of water to the top of the troposphere (10000 m or 33000 ft) takes
mgh = (0001 kg)(10 ms2)(10000 m) = 100 J
bull So gt 96 of the energy associated with forming clouds is the evaporation lt 4 in lifting against gravity
23
Let it Rain
bull When water condenses in clouds it re-releases this ldquolatent heatrdquo
ndash but this is re-radiated and is of no consequence to hydro-power
bull When it rains the gravitational potential energy is released mostly as kinetic energy and ultimately heat
bull Some tiny bit of gravitational potential energy remains IF the rain falls on terrain (eg higher than sea level where it originated)
ndash hydroelectric plants use this tiny left-over energy itrsquos the energy that drives the flow of streams and rivers
ndash damming up a river concentrates the potential energy in one location for easy exploitation
24
How much of the process do we get to keep
bull According to Figure 51 401015 W of solar power goes into evaporation
ndash this corresponds to 161010 kg per second of evaporated water
ndash this is 35 mm per day off the ocean surface (replenished by rain)
bull The gravitational potential energy given to water vapor (mostly in clouds) in the atmosphere (per second) is thenmgh = (161010 kg)(10 ms2)(2000 m) = 321014 J
bull One can calculate that we gain access to only 25 of the total amount (and use only 125)
ndash based on the 18 land area of the US and the maximum potential of 1477 GW as presented in Table 52
25
iClicker Question
bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical
bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential
energy of precipitationndash E a form of fictitious energy
26
iClicker Question
bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical
bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential
energy of precipitationndash E a form of fictitious energy
27
Power of a hydroelectric dam
bull Most impressive is Grand Coulee in Washington on Columbia River
ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets
rain)ndash each cubic meter of water (1000 kg) has potential
energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ
ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently
28
Importance of Hydroelectricity
29
Hydroelectric potential by region in GW
Region Potential
Developed
Undeveloped
Developed
New England 63 19 44 301
Middle Atlantic 98 49 49 500
East North Central 29 12 17 413
West North Central
62 31 31 500
South Atlantic 139 67 72 482
East South Central 83 59 24 711
West South Central
73 27 46 369
Mountain 286 95 191 332
Pacific 644 382 262 593
Total 1477 741 736 502
30
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
31
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
32
Hydroelectricity in the future
bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale
unitsbull Problems with dams
ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site
ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)
ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers
33
Sorry try againhellip
bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy
bull Though very efficient and seemingly environmentally friendly dams do have their problems
bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future
34
Wind Energy
35
The Power of Wind
bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters
every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is
then the kinetic energy the mass of air defined by a rectangular tube
ndash tube is one square meter by v meters or v m3
ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)
065v3 at sea level
36
Wind Energy proportional to cube of velocity
bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in
continental US (above sea level so air slightly less dense)
bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times
bull A wind of 10 ms (22 mph) has a power density of 610 Wm2
bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2
37
Canrsquot get it all
bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely
bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning
bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy
bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36
38
Practical Efficiencies
bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or
about 30ndash40ndash this figure is the mechanical energy
extracted from the windbull Conversion from mechanical to
electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37
39
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
40
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
41
Achievable efficiencies
42
Typical Windmillsbull A typical windmill might be 15 m in diameter
ndash 176 m2
bull At 10 ms wind 40 efficiency this delivers about 100 kW of power
ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW
bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per
year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2
ndash corresponds to 11ndash57 Wm2 average available power density
bull Note the really high tip speeds bird killers
43
Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2
44
Comparable to solar
bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind
bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area
bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy
bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo
45
Current implementations
bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large
dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years
bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over
California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW
46
Flies in the Ointment
bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it
bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces
substantiallybull If fully developed we could generate an average
power almost equal to our current electrical capacity (764 GW)
ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind
47
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
48
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
- Renewable Energy Sources II Alternatives Part I
- Chapter 5 Summary
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Renewable Resources Discussed in Book
- Renewable Energy Consumption
- Another look at available energy flow
- The Renewable Budget
- Outstanding Points from Fig 51
- Energy Flow continued
- The Hydrologic Cycle
- Energetics of the hydrologic cycle
- Let it Rain
- How much of the process do we get to keep
- iClicker Question
- Slide 26
- Power of a hydroelectric dam
- Importance of Hydroelectricity
- Hydroelectric potential by region in GW
- Slide 30
- Slide 31
- Hydroelectricity in the future
- Sorry try againhellip
- Wind Energy
- The Power of Wind
- Wind Energy proportional to cube of velocity
- Canrsquot get it all
- Practical Efficiencies
- Slide 39
- Slide 40
- Achievable efficiencies
- Typical Windmills
- Average available wind power
- Comparable to solar
- Current implementations
- Flies in the Ointment
- Slide 47
- Slide 48
-
19
Outstanding Points from Fig 51
bull Incident radiation is 1741015 Wndash this is 1370 Wm2 times area facing sun
(R2)bull 30 directly reflected back to space
ndash off clouds air landbull 47 goes into heating air land waterbull 23 goes into evaporating water
precipitation etc (part of weather)bull Adds to 100 so wersquore done
ndash but wait therersquos morehellip
20
Energy Flow continued
bull 021 goes into wind waves convection currentsndash note this is 100 times less than driving the water
cyclendash but this is the ldquootherrdquo aspect of weather
bull 0023 is stored as chemical energy in plants via photosynthesis
ndash total is 401012 W half in ocean (plankton)ndash humans are 6 billion times 100 W = 061012 Wndash this is 15 of bio-energy 000034 of incident
powerbull All of this (bio-activity wind weather etc) ends up
creating heat and re-radiating to spacendash except some small amount of storage in fossil fuels
21
The Hydrologic Cycle
Lots of energy associated with evaporationboth mgh (4 for 10 km lift) and latent heat (96) of water
22
Energetics of the hydrologic cycle
bull It takes energy to evaporate water 2444 J per gramndash this is why ldquoswamp coolersrdquo work evaporation
pulls heat out of environment making it feel cooler
ndash 23 of sunrsquos incident energy goes into evaporation
bull By contrast raising one gram of water to the top of the troposphere (10000 m or 33000 ft) takes
mgh = (0001 kg)(10 ms2)(10000 m) = 100 J
bull So gt 96 of the energy associated with forming clouds is the evaporation lt 4 in lifting against gravity
23
Let it Rain
bull When water condenses in clouds it re-releases this ldquolatent heatrdquo
ndash but this is re-radiated and is of no consequence to hydro-power
bull When it rains the gravitational potential energy is released mostly as kinetic energy and ultimately heat
bull Some tiny bit of gravitational potential energy remains IF the rain falls on terrain (eg higher than sea level where it originated)
ndash hydroelectric plants use this tiny left-over energy itrsquos the energy that drives the flow of streams and rivers
ndash damming up a river concentrates the potential energy in one location for easy exploitation
24
How much of the process do we get to keep
bull According to Figure 51 401015 W of solar power goes into evaporation
ndash this corresponds to 161010 kg per second of evaporated water
ndash this is 35 mm per day off the ocean surface (replenished by rain)
bull The gravitational potential energy given to water vapor (mostly in clouds) in the atmosphere (per second) is thenmgh = (161010 kg)(10 ms2)(2000 m) = 321014 J
bull One can calculate that we gain access to only 25 of the total amount (and use only 125)
ndash based on the 18 land area of the US and the maximum potential of 1477 GW as presented in Table 52
25
iClicker Question
bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical
bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential
energy of precipitationndash E a form of fictitious energy
26
iClicker Question
bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical
bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential
energy of precipitationndash E a form of fictitious energy
27
Power of a hydroelectric dam
bull Most impressive is Grand Coulee in Washington on Columbia River
ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets
rain)ndash each cubic meter of water (1000 kg) has potential
energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ
ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently
28
Importance of Hydroelectricity
29
Hydroelectric potential by region in GW
Region Potential
Developed
Undeveloped
Developed
New England 63 19 44 301
Middle Atlantic 98 49 49 500
East North Central 29 12 17 413
West North Central
62 31 31 500
South Atlantic 139 67 72 482
East South Central 83 59 24 711
West South Central
73 27 46 369
Mountain 286 95 191 332
Pacific 644 382 262 593
Total 1477 741 736 502
30
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
31
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
32
Hydroelectricity in the future
bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale
unitsbull Problems with dams
ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site
ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)
ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers
33
Sorry try againhellip
bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy
bull Though very efficient and seemingly environmentally friendly dams do have their problems
bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future
34
Wind Energy
35
The Power of Wind
bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters
every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is
then the kinetic energy the mass of air defined by a rectangular tube
ndash tube is one square meter by v meters or v m3
ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)
065v3 at sea level
36
Wind Energy proportional to cube of velocity
bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in
continental US (above sea level so air slightly less dense)
bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times
bull A wind of 10 ms (22 mph) has a power density of 610 Wm2
bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2
37
Canrsquot get it all
bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely
bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning
bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy
bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36
38
Practical Efficiencies
bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or
about 30ndash40ndash this figure is the mechanical energy
extracted from the windbull Conversion from mechanical to
electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37
39
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
40
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
41
Achievable efficiencies
42
Typical Windmillsbull A typical windmill might be 15 m in diameter
ndash 176 m2
bull At 10 ms wind 40 efficiency this delivers about 100 kW of power
ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW
bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per
year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2
ndash corresponds to 11ndash57 Wm2 average available power density
bull Note the really high tip speeds bird killers
43
Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2
44
Comparable to solar
bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind
bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area
bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy
bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo
45
Current implementations
bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large
dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years
bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over
California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW
46
Flies in the Ointment
bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it
bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces
substantiallybull If fully developed we could generate an average
power almost equal to our current electrical capacity (764 GW)
ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind
47
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
48
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
- Renewable Energy Sources II Alternatives Part I
- Chapter 5 Summary
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Renewable Resources Discussed in Book
- Renewable Energy Consumption
- Another look at available energy flow
- The Renewable Budget
- Outstanding Points from Fig 51
- Energy Flow continued
- The Hydrologic Cycle
- Energetics of the hydrologic cycle
- Let it Rain
- How much of the process do we get to keep
- iClicker Question
- Slide 26
- Power of a hydroelectric dam
- Importance of Hydroelectricity
- Hydroelectric potential by region in GW
- Slide 30
- Slide 31
- Hydroelectricity in the future
- Sorry try againhellip
- Wind Energy
- The Power of Wind
- Wind Energy proportional to cube of velocity
- Canrsquot get it all
- Practical Efficiencies
- Slide 39
- Slide 40
- Achievable efficiencies
- Typical Windmills
- Average available wind power
- Comparable to solar
- Current implementations
- Flies in the Ointment
- Slide 47
- Slide 48
-
20
Energy Flow continued
bull 021 goes into wind waves convection currentsndash note this is 100 times less than driving the water
cyclendash but this is the ldquootherrdquo aspect of weather
bull 0023 is stored as chemical energy in plants via photosynthesis
ndash total is 401012 W half in ocean (plankton)ndash humans are 6 billion times 100 W = 061012 Wndash this is 15 of bio-energy 000034 of incident
powerbull All of this (bio-activity wind weather etc) ends up
creating heat and re-radiating to spacendash except some small amount of storage in fossil fuels
21
The Hydrologic Cycle
Lots of energy associated with evaporationboth mgh (4 for 10 km lift) and latent heat (96) of water
22
Energetics of the hydrologic cycle
bull It takes energy to evaporate water 2444 J per gramndash this is why ldquoswamp coolersrdquo work evaporation
pulls heat out of environment making it feel cooler
ndash 23 of sunrsquos incident energy goes into evaporation
bull By contrast raising one gram of water to the top of the troposphere (10000 m or 33000 ft) takes
mgh = (0001 kg)(10 ms2)(10000 m) = 100 J
bull So gt 96 of the energy associated with forming clouds is the evaporation lt 4 in lifting against gravity
23
Let it Rain
bull When water condenses in clouds it re-releases this ldquolatent heatrdquo
ndash but this is re-radiated and is of no consequence to hydro-power
bull When it rains the gravitational potential energy is released mostly as kinetic energy and ultimately heat
bull Some tiny bit of gravitational potential energy remains IF the rain falls on terrain (eg higher than sea level where it originated)
ndash hydroelectric plants use this tiny left-over energy itrsquos the energy that drives the flow of streams and rivers
ndash damming up a river concentrates the potential energy in one location for easy exploitation
24
How much of the process do we get to keep
bull According to Figure 51 401015 W of solar power goes into evaporation
ndash this corresponds to 161010 kg per second of evaporated water
ndash this is 35 mm per day off the ocean surface (replenished by rain)
bull The gravitational potential energy given to water vapor (mostly in clouds) in the atmosphere (per second) is thenmgh = (161010 kg)(10 ms2)(2000 m) = 321014 J
bull One can calculate that we gain access to only 25 of the total amount (and use only 125)
ndash based on the 18 land area of the US and the maximum potential of 1477 GW as presented in Table 52
25
iClicker Question
bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical
bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential
energy of precipitationndash E a form of fictitious energy
26
iClicker Question
bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical
bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential
energy of precipitationndash E a form of fictitious energy
27
Power of a hydroelectric dam
bull Most impressive is Grand Coulee in Washington on Columbia River
ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets
rain)ndash each cubic meter of water (1000 kg) has potential
energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ
ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently
28
Importance of Hydroelectricity
29
Hydroelectric potential by region in GW
Region Potential
Developed
Undeveloped
Developed
New England 63 19 44 301
Middle Atlantic 98 49 49 500
East North Central 29 12 17 413
West North Central
62 31 31 500
South Atlantic 139 67 72 482
East South Central 83 59 24 711
West South Central
73 27 46 369
Mountain 286 95 191 332
Pacific 644 382 262 593
Total 1477 741 736 502
30
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
31
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
32
Hydroelectricity in the future
bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale
unitsbull Problems with dams
ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site
ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)
ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers
33
Sorry try againhellip
bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy
bull Though very efficient and seemingly environmentally friendly dams do have their problems
bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future
34
Wind Energy
35
The Power of Wind
bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters
every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is
then the kinetic energy the mass of air defined by a rectangular tube
ndash tube is one square meter by v meters or v m3
ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)
065v3 at sea level
36
Wind Energy proportional to cube of velocity
bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in
continental US (above sea level so air slightly less dense)
bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times
bull A wind of 10 ms (22 mph) has a power density of 610 Wm2
bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2
37
Canrsquot get it all
bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely
bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning
bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy
bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36
38
Practical Efficiencies
bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or
about 30ndash40ndash this figure is the mechanical energy
extracted from the windbull Conversion from mechanical to
electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37
39
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
40
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
41
Achievable efficiencies
42
Typical Windmillsbull A typical windmill might be 15 m in diameter
ndash 176 m2
bull At 10 ms wind 40 efficiency this delivers about 100 kW of power
ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW
bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per
year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2
ndash corresponds to 11ndash57 Wm2 average available power density
bull Note the really high tip speeds bird killers
43
Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2
44
Comparable to solar
bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind
bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area
bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy
bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo
45
Current implementations
bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large
dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years
bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over
California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW
46
Flies in the Ointment
bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it
bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces
substantiallybull If fully developed we could generate an average
power almost equal to our current electrical capacity (764 GW)
ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind
47
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
48
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
- Renewable Energy Sources II Alternatives Part I
- Chapter 5 Summary
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Renewable Resources Discussed in Book
- Renewable Energy Consumption
- Another look at available energy flow
- The Renewable Budget
- Outstanding Points from Fig 51
- Energy Flow continued
- The Hydrologic Cycle
- Energetics of the hydrologic cycle
- Let it Rain
- How much of the process do we get to keep
- iClicker Question
- Slide 26
- Power of a hydroelectric dam
- Importance of Hydroelectricity
- Hydroelectric potential by region in GW
- Slide 30
- Slide 31
- Hydroelectricity in the future
- Sorry try againhellip
- Wind Energy
- The Power of Wind
- Wind Energy proportional to cube of velocity
- Canrsquot get it all
- Practical Efficiencies
- Slide 39
- Slide 40
- Achievable efficiencies
- Typical Windmills
- Average available wind power
- Comparable to solar
- Current implementations
- Flies in the Ointment
- Slide 47
- Slide 48
-
21
The Hydrologic Cycle
Lots of energy associated with evaporationboth mgh (4 for 10 km lift) and latent heat (96) of water
22
Energetics of the hydrologic cycle
bull It takes energy to evaporate water 2444 J per gramndash this is why ldquoswamp coolersrdquo work evaporation
pulls heat out of environment making it feel cooler
ndash 23 of sunrsquos incident energy goes into evaporation
bull By contrast raising one gram of water to the top of the troposphere (10000 m or 33000 ft) takes
mgh = (0001 kg)(10 ms2)(10000 m) = 100 J
bull So gt 96 of the energy associated with forming clouds is the evaporation lt 4 in lifting against gravity
23
Let it Rain
bull When water condenses in clouds it re-releases this ldquolatent heatrdquo
ndash but this is re-radiated and is of no consequence to hydro-power
bull When it rains the gravitational potential energy is released mostly as kinetic energy and ultimately heat
bull Some tiny bit of gravitational potential energy remains IF the rain falls on terrain (eg higher than sea level where it originated)
ndash hydroelectric plants use this tiny left-over energy itrsquos the energy that drives the flow of streams and rivers
ndash damming up a river concentrates the potential energy in one location for easy exploitation
24
How much of the process do we get to keep
bull According to Figure 51 401015 W of solar power goes into evaporation
ndash this corresponds to 161010 kg per second of evaporated water
ndash this is 35 mm per day off the ocean surface (replenished by rain)
bull The gravitational potential energy given to water vapor (mostly in clouds) in the atmosphere (per second) is thenmgh = (161010 kg)(10 ms2)(2000 m) = 321014 J
bull One can calculate that we gain access to only 25 of the total amount (and use only 125)
ndash based on the 18 land area of the US and the maximum potential of 1477 GW as presented in Table 52
25
iClicker Question
bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical
bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential
energy of precipitationndash E a form of fictitious energy
26
iClicker Question
bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical
bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential
energy of precipitationndash E a form of fictitious energy
27
Power of a hydroelectric dam
bull Most impressive is Grand Coulee in Washington on Columbia River
ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets
rain)ndash each cubic meter of water (1000 kg) has potential
energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ
ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently
28
Importance of Hydroelectricity
29
Hydroelectric potential by region in GW
Region Potential
Developed
Undeveloped
Developed
New England 63 19 44 301
Middle Atlantic 98 49 49 500
East North Central 29 12 17 413
West North Central
62 31 31 500
South Atlantic 139 67 72 482
East South Central 83 59 24 711
West South Central
73 27 46 369
Mountain 286 95 191 332
Pacific 644 382 262 593
Total 1477 741 736 502
30
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
31
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
32
Hydroelectricity in the future
bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale
unitsbull Problems with dams
ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site
ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)
ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers
33
Sorry try againhellip
bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy
bull Though very efficient and seemingly environmentally friendly dams do have their problems
bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future
34
Wind Energy
35
The Power of Wind
bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters
every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is
then the kinetic energy the mass of air defined by a rectangular tube
ndash tube is one square meter by v meters or v m3
ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)
065v3 at sea level
36
Wind Energy proportional to cube of velocity
bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in
continental US (above sea level so air slightly less dense)
bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times
bull A wind of 10 ms (22 mph) has a power density of 610 Wm2
bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2
37
Canrsquot get it all
bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely
bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning
bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy
bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36
38
Practical Efficiencies
bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or
about 30ndash40ndash this figure is the mechanical energy
extracted from the windbull Conversion from mechanical to
electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37
39
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
40
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
41
Achievable efficiencies
42
Typical Windmillsbull A typical windmill might be 15 m in diameter
ndash 176 m2
bull At 10 ms wind 40 efficiency this delivers about 100 kW of power
ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW
bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per
year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2
ndash corresponds to 11ndash57 Wm2 average available power density
bull Note the really high tip speeds bird killers
43
Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2
44
Comparable to solar
bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind
bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area
bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy
bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo
45
Current implementations
bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large
dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years
bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over
California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW
46
Flies in the Ointment
bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it
bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces
substantiallybull If fully developed we could generate an average
power almost equal to our current electrical capacity (764 GW)
ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind
47
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
48
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
- Renewable Energy Sources II Alternatives Part I
- Chapter 5 Summary
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Renewable Resources Discussed in Book
- Renewable Energy Consumption
- Another look at available energy flow
- The Renewable Budget
- Outstanding Points from Fig 51
- Energy Flow continued
- The Hydrologic Cycle
- Energetics of the hydrologic cycle
- Let it Rain
- How much of the process do we get to keep
- iClicker Question
- Slide 26
- Power of a hydroelectric dam
- Importance of Hydroelectricity
- Hydroelectric potential by region in GW
- Slide 30
- Slide 31
- Hydroelectricity in the future
- Sorry try againhellip
- Wind Energy
- The Power of Wind
- Wind Energy proportional to cube of velocity
- Canrsquot get it all
- Practical Efficiencies
- Slide 39
- Slide 40
- Achievable efficiencies
- Typical Windmills
- Average available wind power
- Comparable to solar
- Current implementations
- Flies in the Ointment
- Slide 47
- Slide 48
-
22
Energetics of the hydrologic cycle
bull It takes energy to evaporate water 2444 J per gramndash this is why ldquoswamp coolersrdquo work evaporation
pulls heat out of environment making it feel cooler
ndash 23 of sunrsquos incident energy goes into evaporation
bull By contrast raising one gram of water to the top of the troposphere (10000 m or 33000 ft) takes
mgh = (0001 kg)(10 ms2)(10000 m) = 100 J
bull So gt 96 of the energy associated with forming clouds is the evaporation lt 4 in lifting against gravity
23
Let it Rain
bull When water condenses in clouds it re-releases this ldquolatent heatrdquo
ndash but this is re-radiated and is of no consequence to hydro-power
bull When it rains the gravitational potential energy is released mostly as kinetic energy and ultimately heat
bull Some tiny bit of gravitational potential energy remains IF the rain falls on terrain (eg higher than sea level where it originated)
ndash hydroelectric plants use this tiny left-over energy itrsquos the energy that drives the flow of streams and rivers
ndash damming up a river concentrates the potential energy in one location for easy exploitation
24
How much of the process do we get to keep
bull According to Figure 51 401015 W of solar power goes into evaporation
ndash this corresponds to 161010 kg per second of evaporated water
ndash this is 35 mm per day off the ocean surface (replenished by rain)
bull The gravitational potential energy given to water vapor (mostly in clouds) in the atmosphere (per second) is thenmgh = (161010 kg)(10 ms2)(2000 m) = 321014 J
bull One can calculate that we gain access to only 25 of the total amount (and use only 125)
ndash based on the 18 land area of the US and the maximum potential of 1477 GW as presented in Table 52
25
iClicker Question
bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical
bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential
energy of precipitationndash E a form of fictitious energy
26
iClicker Question
bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical
bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential
energy of precipitationndash E a form of fictitious energy
27
Power of a hydroelectric dam
bull Most impressive is Grand Coulee in Washington on Columbia River
ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets
rain)ndash each cubic meter of water (1000 kg) has potential
energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ
ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently
28
Importance of Hydroelectricity
29
Hydroelectric potential by region in GW
Region Potential
Developed
Undeveloped
Developed
New England 63 19 44 301
Middle Atlantic 98 49 49 500
East North Central 29 12 17 413
West North Central
62 31 31 500
South Atlantic 139 67 72 482
East South Central 83 59 24 711
West South Central
73 27 46 369
Mountain 286 95 191 332
Pacific 644 382 262 593
Total 1477 741 736 502
30
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
31
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
32
Hydroelectricity in the future
bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale
unitsbull Problems with dams
ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site
ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)
ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers
33
Sorry try againhellip
bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy
bull Though very efficient and seemingly environmentally friendly dams do have their problems
bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future
34
Wind Energy
35
The Power of Wind
bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters
every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is
then the kinetic energy the mass of air defined by a rectangular tube
ndash tube is one square meter by v meters or v m3
ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)
065v3 at sea level
36
Wind Energy proportional to cube of velocity
bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in
continental US (above sea level so air slightly less dense)
bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times
bull A wind of 10 ms (22 mph) has a power density of 610 Wm2
bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2
37
Canrsquot get it all
bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely
bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning
bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy
bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36
38
Practical Efficiencies
bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or
about 30ndash40ndash this figure is the mechanical energy
extracted from the windbull Conversion from mechanical to
electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37
39
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
40
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
41
Achievable efficiencies
42
Typical Windmillsbull A typical windmill might be 15 m in diameter
ndash 176 m2
bull At 10 ms wind 40 efficiency this delivers about 100 kW of power
ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW
bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per
year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2
ndash corresponds to 11ndash57 Wm2 average available power density
bull Note the really high tip speeds bird killers
43
Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2
44
Comparable to solar
bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind
bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area
bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy
bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo
45
Current implementations
bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large
dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years
bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over
California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW
46
Flies in the Ointment
bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it
bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces
substantiallybull If fully developed we could generate an average
power almost equal to our current electrical capacity (764 GW)
ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind
47
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
48
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
- Renewable Energy Sources II Alternatives Part I
- Chapter 5 Summary
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Renewable Resources Discussed in Book
- Renewable Energy Consumption
- Another look at available energy flow
- The Renewable Budget
- Outstanding Points from Fig 51
- Energy Flow continued
- The Hydrologic Cycle
- Energetics of the hydrologic cycle
- Let it Rain
- How much of the process do we get to keep
- iClicker Question
- Slide 26
- Power of a hydroelectric dam
- Importance of Hydroelectricity
- Hydroelectric potential by region in GW
- Slide 30
- Slide 31
- Hydroelectricity in the future
- Sorry try againhellip
- Wind Energy
- The Power of Wind
- Wind Energy proportional to cube of velocity
- Canrsquot get it all
- Practical Efficiencies
- Slide 39
- Slide 40
- Achievable efficiencies
- Typical Windmills
- Average available wind power
- Comparable to solar
- Current implementations
- Flies in the Ointment
- Slide 47
- Slide 48
-
23
Let it Rain
bull When water condenses in clouds it re-releases this ldquolatent heatrdquo
ndash but this is re-radiated and is of no consequence to hydro-power
bull When it rains the gravitational potential energy is released mostly as kinetic energy and ultimately heat
bull Some tiny bit of gravitational potential energy remains IF the rain falls on terrain (eg higher than sea level where it originated)
ndash hydroelectric plants use this tiny left-over energy itrsquos the energy that drives the flow of streams and rivers
ndash damming up a river concentrates the potential energy in one location for easy exploitation
24
How much of the process do we get to keep
bull According to Figure 51 401015 W of solar power goes into evaporation
ndash this corresponds to 161010 kg per second of evaporated water
ndash this is 35 mm per day off the ocean surface (replenished by rain)
bull The gravitational potential energy given to water vapor (mostly in clouds) in the atmosphere (per second) is thenmgh = (161010 kg)(10 ms2)(2000 m) = 321014 J
bull One can calculate that we gain access to only 25 of the total amount (and use only 125)
ndash based on the 18 land area of the US and the maximum potential of 1477 GW as presented in Table 52
25
iClicker Question
bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical
bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential
energy of precipitationndash E a form of fictitious energy
26
iClicker Question
bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical
bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential
energy of precipitationndash E a form of fictitious energy
27
Power of a hydroelectric dam
bull Most impressive is Grand Coulee in Washington on Columbia River
ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets
rain)ndash each cubic meter of water (1000 kg) has potential
energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ
ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently
28
Importance of Hydroelectricity
29
Hydroelectric potential by region in GW
Region Potential
Developed
Undeveloped
Developed
New England 63 19 44 301
Middle Atlantic 98 49 49 500
East North Central 29 12 17 413
West North Central
62 31 31 500
South Atlantic 139 67 72 482
East South Central 83 59 24 711
West South Central
73 27 46 369
Mountain 286 95 191 332
Pacific 644 382 262 593
Total 1477 741 736 502
30
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
31
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
32
Hydroelectricity in the future
bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale
unitsbull Problems with dams
ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site
ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)
ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers
33
Sorry try againhellip
bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy
bull Though very efficient and seemingly environmentally friendly dams do have their problems
bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future
34
Wind Energy
35
The Power of Wind
bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters
every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is
then the kinetic energy the mass of air defined by a rectangular tube
ndash tube is one square meter by v meters or v m3
ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)
065v3 at sea level
36
Wind Energy proportional to cube of velocity
bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in
continental US (above sea level so air slightly less dense)
bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times
bull A wind of 10 ms (22 mph) has a power density of 610 Wm2
bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2
37
Canrsquot get it all
bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely
bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning
bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy
bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36
38
Practical Efficiencies
bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or
about 30ndash40ndash this figure is the mechanical energy
extracted from the windbull Conversion from mechanical to
electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37
39
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
40
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
41
Achievable efficiencies
42
Typical Windmillsbull A typical windmill might be 15 m in diameter
ndash 176 m2
bull At 10 ms wind 40 efficiency this delivers about 100 kW of power
ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW
bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per
year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2
ndash corresponds to 11ndash57 Wm2 average available power density
bull Note the really high tip speeds bird killers
43
Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2
44
Comparable to solar
bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind
bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area
bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy
bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo
45
Current implementations
bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large
dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years
bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over
California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW
46
Flies in the Ointment
bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it
bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces
substantiallybull If fully developed we could generate an average
power almost equal to our current electrical capacity (764 GW)
ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind
47
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
48
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
- Renewable Energy Sources II Alternatives Part I
- Chapter 5 Summary
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Renewable Resources Discussed in Book
- Renewable Energy Consumption
- Another look at available energy flow
- The Renewable Budget
- Outstanding Points from Fig 51
- Energy Flow continued
- The Hydrologic Cycle
- Energetics of the hydrologic cycle
- Let it Rain
- How much of the process do we get to keep
- iClicker Question
- Slide 26
- Power of a hydroelectric dam
- Importance of Hydroelectricity
- Hydroelectric potential by region in GW
- Slide 30
- Slide 31
- Hydroelectricity in the future
- Sorry try againhellip
- Wind Energy
- The Power of Wind
- Wind Energy proportional to cube of velocity
- Canrsquot get it all
- Practical Efficiencies
- Slide 39
- Slide 40
- Achievable efficiencies
- Typical Windmills
- Average available wind power
- Comparable to solar
- Current implementations
- Flies in the Ointment
- Slide 47
- Slide 48
-
24
How much of the process do we get to keep
bull According to Figure 51 401015 W of solar power goes into evaporation
ndash this corresponds to 161010 kg per second of evaporated water
ndash this is 35 mm per day off the ocean surface (replenished by rain)
bull The gravitational potential energy given to water vapor (mostly in clouds) in the atmosphere (per second) is thenmgh = (161010 kg)(10 ms2)(2000 m) = 321014 J
bull One can calculate that we gain access to only 25 of the total amount (and use only 125)
ndash based on the 18 land area of the US and the maximum potential of 1477 GW as presented in Table 52
25
iClicker Question
bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical
bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential
energy of precipitationndash E a form of fictitious energy
26
iClicker Question
bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical
bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential
energy of precipitationndash E a form of fictitious energy
27
Power of a hydroelectric dam
bull Most impressive is Grand Coulee in Washington on Columbia River
ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets
rain)ndash each cubic meter of water (1000 kg) has potential
energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ
ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently
28
Importance of Hydroelectricity
29
Hydroelectric potential by region in GW
Region Potential
Developed
Undeveloped
Developed
New England 63 19 44 301
Middle Atlantic 98 49 49 500
East North Central 29 12 17 413
West North Central
62 31 31 500
South Atlantic 139 67 72 482
East South Central 83 59 24 711
West South Central
73 27 46 369
Mountain 286 95 191 332
Pacific 644 382 262 593
Total 1477 741 736 502
30
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
31
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
32
Hydroelectricity in the future
bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale
unitsbull Problems with dams
ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site
ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)
ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers
33
Sorry try againhellip
bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy
bull Though very efficient and seemingly environmentally friendly dams do have their problems
bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future
34
Wind Energy
35
The Power of Wind
bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters
every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is
then the kinetic energy the mass of air defined by a rectangular tube
ndash tube is one square meter by v meters or v m3
ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)
065v3 at sea level
36
Wind Energy proportional to cube of velocity
bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in
continental US (above sea level so air slightly less dense)
bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times
bull A wind of 10 ms (22 mph) has a power density of 610 Wm2
bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2
37
Canrsquot get it all
bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely
bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning
bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy
bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36
38
Practical Efficiencies
bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or
about 30ndash40ndash this figure is the mechanical energy
extracted from the windbull Conversion from mechanical to
electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37
39
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
40
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
41
Achievable efficiencies
42
Typical Windmillsbull A typical windmill might be 15 m in diameter
ndash 176 m2
bull At 10 ms wind 40 efficiency this delivers about 100 kW of power
ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW
bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per
year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2
ndash corresponds to 11ndash57 Wm2 average available power density
bull Note the really high tip speeds bird killers
43
Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2
44
Comparable to solar
bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind
bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area
bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy
bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo
45
Current implementations
bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large
dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years
bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over
California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW
46
Flies in the Ointment
bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it
bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces
substantiallybull If fully developed we could generate an average
power almost equal to our current electrical capacity (764 GW)
ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind
47
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
48
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
- Renewable Energy Sources II Alternatives Part I
- Chapter 5 Summary
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Renewable Resources Discussed in Book
- Renewable Energy Consumption
- Another look at available energy flow
- The Renewable Budget
- Outstanding Points from Fig 51
- Energy Flow continued
- The Hydrologic Cycle
- Energetics of the hydrologic cycle
- Let it Rain
- How much of the process do we get to keep
- iClicker Question
- Slide 26
- Power of a hydroelectric dam
- Importance of Hydroelectricity
- Hydroelectric potential by region in GW
- Slide 30
- Slide 31
- Hydroelectricity in the future
- Sorry try againhellip
- Wind Energy
- The Power of Wind
- Wind Energy proportional to cube of velocity
- Canrsquot get it all
- Practical Efficiencies
- Slide 39
- Slide 40
- Achievable efficiencies
- Typical Windmills
- Average available wind power
- Comparable to solar
- Current implementations
- Flies in the Ointment
- Slide 47
- Slide 48
-
25
iClicker Question
bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical
bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential
energy of precipitationndash E a form of fictitious energy
26
iClicker Question
bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical
bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential
energy of precipitationndash E a form of fictitious energy
27
Power of a hydroelectric dam
bull Most impressive is Grand Coulee in Washington on Columbia River
ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets
rain)ndash each cubic meter of water (1000 kg) has potential
energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ
ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently
28
Importance of Hydroelectricity
29
Hydroelectric potential by region in GW
Region Potential
Developed
Undeveloped
Developed
New England 63 19 44 301
Middle Atlantic 98 49 49 500
East North Central 29 12 17 413
West North Central
62 31 31 500
South Atlantic 139 67 72 482
East South Central 83 59 24 711
West South Central
73 27 46 369
Mountain 286 95 191 332
Pacific 644 382 262 593
Total 1477 741 736 502
30
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
31
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
32
Hydroelectricity in the future
bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale
unitsbull Problems with dams
ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site
ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)
ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers
33
Sorry try againhellip
bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy
bull Though very efficient and seemingly environmentally friendly dams do have their problems
bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future
34
Wind Energy
35
The Power of Wind
bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters
every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is
then the kinetic energy the mass of air defined by a rectangular tube
ndash tube is one square meter by v meters or v m3
ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)
065v3 at sea level
36
Wind Energy proportional to cube of velocity
bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in
continental US (above sea level so air slightly less dense)
bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times
bull A wind of 10 ms (22 mph) has a power density of 610 Wm2
bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2
37
Canrsquot get it all
bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely
bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning
bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy
bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36
38
Practical Efficiencies
bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or
about 30ndash40ndash this figure is the mechanical energy
extracted from the windbull Conversion from mechanical to
electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37
39
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
40
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
41
Achievable efficiencies
42
Typical Windmillsbull A typical windmill might be 15 m in diameter
ndash 176 m2
bull At 10 ms wind 40 efficiency this delivers about 100 kW of power
ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW
bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per
year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2
ndash corresponds to 11ndash57 Wm2 average available power density
bull Note the really high tip speeds bird killers
43
Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2
44
Comparable to solar
bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind
bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area
bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy
bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo
45
Current implementations
bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large
dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years
bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over
California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW
46
Flies in the Ointment
bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it
bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces
substantiallybull If fully developed we could generate an average
power almost equal to our current electrical capacity (764 GW)
ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind
47
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
48
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
- Renewable Energy Sources II Alternatives Part I
- Chapter 5 Summary
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Renewable Resources Discussed in Book
- Renewable Energy Consumption
- Another look at available energy flow
- The Renewable Budget
- Outstanding Points from Fig 51
- Energy Flow continued
- The Hydrologic Cycle
- Energetics of the hydrologic cycle
- Let it Rain
- How much of the process do we get to keep
- iClicker Question
- Slide 26
- Power of a hydroelectric dam
- Importance of Hydroelectricity
- Hydroelectric potential by region in GW
- Slide 30
- Slide 31
- Hydroelectricity in the future
- Sorry try againhellip
- Wind Energy
- The Power of Wind
- Wind Energy proportional to cube of velocity
- Canrsquot get it all
- Practical Efficiencies
- Slide 39
- Slide 40
- Achievable efficiencies
- Typical Windmills
- Average available wind power
- Comparable to solar
- Current implementations
- Flies in the Ointment
- Slide 47
- Slide 48
-
26
iClicker Question
bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical
bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential
energy of precipitationndash E a form of fictitious energy
27
Power of a hydroelectric dam
bull Most impressive is Grand Coulee in Washington on Columbia River
ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets
rain)ndash each cubic meter of water (1000 kg) has potential
energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ
ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently
28
Importance of Hydroelectricity
29
Hydroelectric potential by region in GW
Region Potential
Developed
Undeveloped
Developed
New England 63 19 44 301
Middle Atlantic 98 49 49 500
East North Central 29 12 17 413
West North Central
62 31 31 500
South Atlantic 139 67 72 482
East South Central 83 59 24 711
West South Central
73 27 46 369
Mountain 286 95 191 332
Pacific 644 382 262 593
Total 1477 741 736 502
30
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
31
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
32
Hydroelectricity in the future
bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale
unitsbull Problems with dams
ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site
ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)
ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers
33
Sorry try againhellip
bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy
bull Though very efficient and seemingly environmentally friendly dams do have their problems
bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future
34
Wind Energy
35
The Power of Wind
bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters
every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is
then the kinetic energy the mass of air defined by a rectangular tube
ndash tube is one square meter by v meters or v m3
ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)
065v3 at sea level
36
Wind Energy proportional to cube of velocity
bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in
continental US (above sea level so air slightly less dense)
bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times
bull A wind of 10 ms (22 mph) has a power density of 610 Wm2
bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2
37
Canrsquot get it all
bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely
bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning
bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy
bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36
38
Practical Efficiencies
bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or
about 30ndash40ndash this figure is the mechanical energy
extracted from the windbull Conversion from mechanical to
electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37
39
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
40
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
41
Achievable efficiencies
42
Typical Windmillsbull A typical windmill might be 15 m in diameter
ndash 176 m2
bull At 10 ms wind 40 efficiency this delivers about 100 kW of power
ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW
bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per
year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2
ndash corresponds to 11ndash57 Wm2 average available power density
bull Note the really high tip speeds bird killers
43
Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2
44
Comparable to solar
bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind
bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area
bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy
bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo
45
Current implementations
bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large
dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years
bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over
California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW
46
Flies in the Ointment
bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it
bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces
substantiallybull If fully developed we could generate an average
power almost equal to our current electrical capacity (764 GW)
ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind
47
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
48
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
- Renewable Energy Sources II Alternatives Part I
- Chapter 5 Summary
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Renewable Resources Discussed in Book
- Renewable Energy Consumption
- Another look at available energy flow
- The Renewable Budget
- Outstanding Points from Fig 51
- Energy Flow continued
- The Hydrologic Cycle
- Energetics of the hydrologic cycle
- Let it Rain
- How much of the process do we get to keep
- iClicker Question
- Slide 26
- Power of a hydroelectric dam
- Importance of Hydroelectricity
- Hydroelectric potential by region in GW
- Slide 30
- Slide 31
- Hydroelectricity in the future
- Sorry try againhellip
- Wind Energy
- The Power of Wind
- Wind Energy proportional to cube of velocity
- Canrsquot get it all
- Practical Efficiencies
- Slide 39
- Slide 40
- Achievable efficiencies
- Typical Windmills
- Average available wind power
- Comparable to solar
- Current implementations
- Flies in the Ointment
- Slide 47
- Slide 48
-
27
Power of a hydroelectric dam
bull Most impressive is Grand Coulee in Washington on Columbia River
ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets
rain)ndash each cubic meter of water (1000 kg) has potential
energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ
ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently
28
Importance of Hydroelectricity
29
Hydroelectric potential by region in GW
Region Potential
Developed
Undeveloped
Developed
New England 63 19 44 301
Middle Atlantic 98 49 49 500
East North Central 29 12 17 413
West North Central
62 31 31 500
South Atlantic 139 67 72 482
East South Central 83 59 24 711
West South Central
73 27 46 369
Mountain 286 95 191 332
Pacific 644 382 262 593
Total 1477 741 736 502
30
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
31
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
32
Hydroelectricity in the future
bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale
unitsbull Problems with dams
ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site
ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)
ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers
33
Sorry try againhellip
bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy
bull Though very efficient and seemingly environmentally friendly dams do have their problems
bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future
34
Wind Energy
35
The Power of Wind
bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters
every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is
then the kinetic energy the mass of air defined by a rectangular tube
ndash tube is one square meter by v meters or v m3
ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)
065v3 at sea level
36
Wind Energy proportional to cube of velocity
bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in
continental US (above sea level so air slightly less dense)
bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times
bull A wind of 10 ms (22 mph) has a power density of 610 Wm2
bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2
37
Canrsquot get it all
bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely
bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning
bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy
bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36
38
Practical Efficiencies
bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or
about 30ndash40ndash this figure is the mechanical energy
extracted from the windbull Conversion from mechanical to
electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37
39
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
40
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
41
Achievable efficiencies
42
Typical Windmillsbull A typical windmill might be 15 m in diameter
ndash 176 m2
bull At 10 ms wind 40 efficiency this delivers about 100 kW of power
ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW
bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per
year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2
ndash corresponds to 11ndash57 Wm2 average available power density
bull Note the really high tip speeds bird killers
43
Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2
44
Comparable to solar
bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind
bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area
bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy
bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo
45
Current implementations
bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large
dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years
bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over
California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW
46
Flies in the Ointment
bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it
bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces
substantiallybull If fully developed we could generate an average
power almost equal to our current electrical capacity (764 GW)
ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind
47
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
48
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
- Renewable Energy Sources II Alternatives Part I
- Chapter 5 Summary
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Renewable Resources Discussed in Book
- Renewable Energy Consumption
- Another look at available energy flow
- The Renewable Budget
- Outstanding Points from Fig 51
- Energy Flow continued
- The Hydrologic Cycle
- Energetics of the hydrologic cycle
- Let it Rain
- How much of the process do we get to keep
- iClicker Question
- Slide 26
- Power of a hydroelectric dam
- Importance of Hydroelectricity
- Hydroelectric potential by region in GW
- Slide 30
- Slide 31
- Hydroelectricity in the future
- Sorry try againhellip
- Wind Energy
- The Power of Wind
- Wind Energy proportional to cube of velocity
- Canrsquot get it all
- Practical Efficiencies
- Slide 39
- Slide 40
- Achievable efficiencies
- Typical Windmills
- Average available wind power
- Comparable to solar
- Current implementations
- Flies in the Ointment
- Slide 47
- Slide 48
-
28
Importance of Hydroelectricity
29
Hydroelectric potential by region in GW
Region Potential
Developed
Undeveloped
Developed
New England 63 19 44 301
Middle Atlantic 98 49 49 500
East North Central 29 12 17 413
West North Central
62 31 31 500
South Atlantic 139 67 72 482
East South Central 83 59 24 711
West South Central
73 27 46 369
Mountain 286 95 191 332
Pacific 644 382 262 593
Total 1477 741 736 502
30
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
31
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
32
Hydroelectricity in the future
bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale
unitsbull Problems with dams
ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site
ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)
ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers
33
Sorry try againhellip
bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy
bull Though very efficient and seemingly environmentally friendly dams do have their problems
bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future
34
Wind Energy
35
The Power of Wind
bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters
every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is
then the kinetic energy the mass of air defined by a rectangular tube
ndash tube is one square meter by v meters or v m3
ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)
065v3 at sea level
36
Wind Energy proportional to cube of velocity
bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in
continental US (above sea level so air slightly less dense)
bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times
bull A wind of 10 ms (22 mph) has a power density of 610 Wm2
bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2
37
Canrsquot get it all
bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely
bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning
bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy
bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36
38
Practical Efficiencies
bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or
about 30ndash40ndash this figure is the mechanical energy
extracted from the windbull Conversion from mechanical to
electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37
39
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
40
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
41
Achievable efficiencies
42
Typical Windmillsbull A typical windmill might be 15 m in diameter
ndash 176 m2
bull At 10 ms wind 40 efficiency this delivers about 100 kW of power
ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW
bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per
year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2
ndash corresponds to 11ndash57 Wm2 average available power density
bull Note the really high tip speeds bird killers
43
Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2
44
Comparable to solar
bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind
bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area
bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy
bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo
45
Current implementations
bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large
dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years
bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over
California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW
46
Flies in the Ointment
bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it
bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces
substantiallybull If fully developed we could generate an average
power almost equal to our current electrical capacity (764 GW)
ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind
47
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
48
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
- Renewable Energy Sources II Alternatives Part I
- Chapter 5 Summary
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Renewable Resources Discussed in Book
- Renewable Energy Consumption
- Another look at available energy flow
- The Renewable Budget
- Outstanding Points from Fig 51
- Energy Flow continued
- The Hydrologic Cycle
- Energetics of the hydrologic cycle
- Let it Rain
- How much of the process do we get to keep
- iClicker Question
- Slide 26
- Power of a hydroelectric dam
- Importance of Hydroelectricity
- Hydroelectric potential by region in GW
- Slide 30
- Slide 31
- Hydroelectricity in the future
- Sorry try againhellip
- Wind Energy
- The Power of Wind
- Wind Energy proportional to cube of velocity
- Canrsquot get it all
- Practical Efficiencies
- Slide 39
- Slide 40
- Achievable efficiencies
- Typical Windmills
- Average available wind power
- Comparable to solar
- Current implementations
- Flies in the Ointment
- Slide 47
- Slide 48
-
29
Hydroelectric potential by region in GW
Region Potential
Developed
Undeveloped
Developed
New England 63 19 44 301
Middle Atlantic 98 49 49 500
East North Central 29 12 17 413
West North Central
62 31 31 500
South Atlantic 139 67 72 482
East South Central 83 59 24 711
West South Central
73 27 46 369
Mountain 286 95 191 332
Pacific 644 382 262 593
Total 1477 741 736 502
30
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
31
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
32
Hydroelectricity in the future
bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale
unitsbull Problems with dams
ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site
ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)
ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers
33
Sorry try againhellip
bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy
bull Though very efficient and seemingly environmentally friendly dams do have their problems
bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future
34
Wind Energy
35
The Power of Wind
bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters
every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is
then the kinetic energy the mass of air defined by a rectangular tube
ndash tube is one square meter by v meters or v m3
ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)
065v3 at sea level
36
Wind Energy proportional to cube of velocity
bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in
continental US (above sea level so air slightly less dense)
bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times
bull A wind of 10 ms (22 mph) has a power density of 610 Wm2
bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2
37
Canrsquot get it all
bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely
bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning
bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy
bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36
38
Practical Efficiencies
bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or
about 30ndash40ndash this figure is the mechanical energy
extracted from the windbull Conversion from mechanical to
electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37
39
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
40
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
41
Achievable efficiencies
42
Typical Windmillsbull A typical windmill might be 15 m in diameter
ndash 176 m2
bull At 10 ms wind 40 efficiency this delivers about 100 kW of power
ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW
bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per
year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2
ndash corresponds to 11ndash57 Wm2 average available power density
bull Note the really high tip speeds bird killers
43
Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2
44
Comparable to solar
bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind
bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area
bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy
bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo
45
Current implementations
bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large
dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years
bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over
California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW
46
Flies in the Ointment
bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it
bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces
substantiallybull If fully developed we could generate an average
power almost equal to our current electrical capacity (764 GW)
ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind
47
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
48
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
- Renewable Energy Sources II Alternatives Part I
- Chapter 5 Summary
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Renewable Resources Discussed in Book
- Renewable Energy Consumption
- Another look at available energy flow
- The Renewable Budget
- Outstanding Points from Fig 51
- Energy Flow continued
- The Hydrologic Cycle
- Energetics of the hydrologic cycle
- Let it Rain
- How much of the process do we get to keep
- iClicker Question
- Slide 26
- Power of a hydroelectric dam
- Importance of Hydroelectricity
- Hydroelectric potential by region in GW
- Slide 30
- Slide 31
- Hydroelectricity in the future
- Sorry try againhellip
- Wind Energy
- The Power of Wind
- Wind Energy proportional to cube of velocity
- Canrsquot get it all
- Practical Efficiencies
- Slide 39
- Slide 40
- Achievable efficiencies
- Typical Windmills
- Average available wind power
- Comparable to solar
- Current implementations
- Flies in the Ointment
- Slide 47
- Slide 48
-
30
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
31
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
32
Hydroelectricity in the future
bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale
unitsbull Problems with dams
ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site
ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)
ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers
33
Sorry try againhellip
bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy
bull Though very efficient and seemingly environmentally friendly dams do have their problems
bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future
34
Wind Energy
35
The Power of Wind
bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters
every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is
then the kinetic energy the mass of air defined by a rectangular tube
ndash tube is one square meter by v meters or v m3
ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)
065v3 at sea level
36
Wind Energy proportional to cube of velocity
bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in
continental US (above sea level so air slightly less dense)
bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times
bull A wind of 10 ms (22 mph) has a power density of 610 Wm2
bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2
37
Canrsquot get it all
bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely
bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning
bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy
bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36
38
Practical Efficiencies
bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or
about 30ndash40ndash this figure is the mechanical energy
extracted from the windbull Conversion from mechanical to
electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37
39
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
40
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
41
Achievable efficiencies
42
Typical Windmillsbull A typical windmill might be 15 m in diameter
ndash 176 m2
bull At 10 ms wind 40 efficiency this delivers about 100 kW of power
ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW
bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per
year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2
ndash corresponds to 11ndash57 Wm2 average available power density
bull Note the really high tip speeds bird killers
43
Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2
44
Comparable to solar
bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind
bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area
bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy
bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo
45
Current implementations
bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large
dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years
bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over
California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW
46
Flies in the Ointment
bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it
bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces
substantiallybull If fully developed we could generate an average
power almost equal to our current electrical capacity (764 GW)
ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind
47
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
48
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
- Renewable Energy Sources II Alternatives Part I
- Chapter 5 Summary
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Renewable Resources Discussed in Book
- Renewable Energy Consumption
- Another look at available energy flow
- The Renewable Budget
- Outstanding Points from Fig 51
- Energy Flow continued
- The Hydrologic Cycle
- Energetics of the hydrologic cycle
- Let it Rain
- How much of the process do we get to keep
- iClicker Question
- Slide 26
- Power of a hydroelectric dam
- Importance of Hydroelectricity
- Hydroelectric potential by region in GW
- Slide 30
- Slide 31
- Hydroelectricity in the future
- Sorry try againhellip
- Wind Energy
- The Power of Wind
- Wind Energy proportional to cube of velocity
- Canrsquot get it all
- Practical Efficiencies
- Slide 39
- Slide 40
- Achievable efficiencies
- Typical Windmills
- Average available wind power
- Comparable to solar
- Current implementations
- Flies in the Ointment
- Slide 47
- Slide 48
-
31
iClicker Question
bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total
MW produced but is now at a peakndash D It has both increased and decreased in
total MW producedndash E The percentage of electric power
produced by hydroelectric plants has generally increased over time
32
Hydroelectricity in the future
bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale
unitsbull Problems with dams
ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site
ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)
ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers
33
Sorry try againhellip
bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy
bull Though very efficient and seemingly environmentally friendly dams do have their problems
bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future
34
Wind Energy
35
The Power of Wind
bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters
every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is
then the kinetic energy the mass of air defined by a rectangular tube
ndash tube is one square meter by v meters or v m3
ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)
065v3 at sea level
36
Wind Energy proportional to cube of velocity
bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in
continental US (above sea level so air slightly less dense)
bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times
bull A wind of 10 ms (22 mph) has a power density of 610 Wm2
bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2
37
Canrsquot get it all
bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely
bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning
bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy
bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36
38
Practical Efficiencies
bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or
about 30ndash40ndash this figure is the mechanical energy
extracted from the windbull Conversion from mechanical to
electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37
39
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
40
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
41
Achievable efficiencies
42
Typical Windmillsbull A typical windmill might be 15 m in diameter
ndash 176 m2
bull At 10 ms wind 40 efficiency this delivers about 100 kW of power
ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW
bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per
year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2
ndash corresponds to 11ndash57 Wm2 average available power density
bull Note the really high tip speeds bird killers
43
Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2
44
Comparable to solar
bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind
bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area
bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy
bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo
45
Current implementations
bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large
dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years
bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over
California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW
46
Flies in the Ointment
bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it
bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces
substantiallybull If fully developed we could generate an average
power almost equal to our current electrical capacity (764 GW)
ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind
47
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
48
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
- Renewable Energy Sources II Alternatives Part I
- Chapter 5 Summary
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Renewable Resources Discussed in Book
- Renewable Energy Consumption
- Another look at available energy flow
- The Renewable Budget
- Outstanding Points from Fig 51
- Energy Flow continued
- The Hydrologic Cycle
- Energetics of the hydrologic cycle
- Let it Rain
- How much of the process do we get to keep
- iClicker Question
- Slide 26
- Power of a hydroelectric dam
- Importance of Hydroelectricity
- Hydroelectric potential by region in GW
- Slide 30
- Slide 31
- Hydroelectricity in the future
- Sorry try againhellip
- Wind Energy
- The Power of Wind
- Wind Energy proportional to cube of velocity
- Canrsquot get it all
- Practical Efficiencies
- Slide 39
- Slide 40
- Achievable efficiencies
- Typical Windmills
- Average available wind power
- Comparable to solar
- Current implementations
- Flies in the Ointment
- Slide 47
- Slide 48
-
32
Hydroelectricity in the future
bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale
unitsbull Problems with dams
ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site
ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)
ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers
33
Sorry try againhellip
bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy
bull Though very efficient and seemingly environmentally friendly dams do have their problems
bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future
34
Wind Energy
35
The Power of Wind
bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters
every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is
then the kinetic energy the mass of air defined by a rectangular tube
ndash tube is one square meter by v meters or v m3
ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)
065v3 at sea level
36
Wind Energy proportional to cube of velocity
bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in
continental US (above sea level so air slightly less dense)
bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times
bull A wind of 10 ms (22 mph) has a power density of 610 Wm2
bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2
37
Canrsquot get it all
bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely
bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning
bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy
bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36
38
Practical Efficiencies
bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or
about 30ndash40ndash this figure is the mechanical energy
extracted from the windbull Conversion from mechanical to
electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37
39
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
40
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
41
Achievable efficiencies
42
Typical Windmillsbull A typical windmill might be 15 m in diameter
ndash 176 m2
bull At 10 ms wind 40 efficiency this delivers about 100 kW of power
ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW
bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per
year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2
ndash corresponds to 11ndash57 Wm2 average available power density
bull Note the really high tip speeds bird killers
43
Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2
44
Comparable to solar
bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind
bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area
bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy
bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo
45
Current implementations
bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large
dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years
bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over
California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW
46
Flies in the Ointment
bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it
bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces
substantiallybull If fully developed we could generate an average
power almost equal to our current electrical capacity (764 GW)
ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind
47
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
48
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
- Renewable Energy Sources II Alternatives Part I
- Chapter 5 Summary
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Renewable Resources Discussed in Book
- Renewable Energy Consumption
- Another look at available energy flow
- The Renewable Budget
- Outstanding Points from Fig 51
- Energy Flow continued
- The Hydrologic Cycle
- Energetics of the hydrologic cycle
- Let it Rain
- How much of the process do we get to keep
- iClicker Question
- Slide 26
- Power of a hydroelectric dam
- Importance of Hydroelectricity
- Hydroelectric potential by region in GW
- Slide 30
- Slide 31
- Hydroelectricity in the future
- Sorry try againhellip
- Wind Energy
- The Power of Wind
- Wind Energy proportional to cube of velocity
- Canrsquot get it all
- Practical Efficiencies
- Slide 39
- Slide 40
- Achievable efficiencies
- Typical Windmills
- Average available wind power
- Comparable to solar
- Current implementations
- Flies in the Ointment
- Slide 47
- Slide 48
-
33
Sorry try againhellip
bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy
bull Though very efficient and seemingly environmentally friendly dams do have their problems
bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future
34
Wind Energy
35
The Power of Wind
bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters
every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is
then the kinetic energy the mass of air defined by a rectangular tube
ndash tube is one square meter by v meters or v m3
ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)
065v3 at sea level
36
Wind Energy proportional to cube of velocity
bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in
continental US (above sea level so air slightly less dense)
bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times
bull A wind of 10 ms (22 mph) has a power density of 610 Wm2
bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2
37
Canrsquot get it all
bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely
bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning
bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy
bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36
38
Practical Efficiencies
bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or
about 30ndash40ndash this figure is the mechanical energy
extracted from the windbull Conversion from mechanical to
electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37
39
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
40
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
41
Achievable efficiencies
42
Typical Windmillsbull A typical windmill might be 15 m in diameter
ndash 176 m2
bull At 10 ms wind 40 efficiency this delivers about 100 kW of power
ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW
bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per
year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2
ndash corresponds to 11ndash57 Wm2 average available power density
bull Note the really high tip speeds bird killers
43
Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2
44
Comparable to solar
bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind
bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area
bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy
bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo
45
Current implementations
bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large
dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years
bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over
California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW
46
Flies in the Ointment
bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it
bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces
substantiallybull If fully developed we could generate an average
power almost equal to our current electrical capacity (764 GW)
ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind
47
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
48
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
- Renewable Energy Sources II Alternatives Part I
- Chapter 5 Summary
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Renewable Resources Discussed in Book
- Renewable Energy Consumption
- Another look at available energy flow
- The Renewable Budget
- Outstanding Points from Fig 51
- Energy Flow continued
- The Hydrologic Cycle
- Energetics of the hydrologic cycle
- Let it Rain
- How much of the process do we get to keep
- iClicker Question
- Slide 26
- Power of a hydroelectric dam
- Importance of Hydroelectricity
- Hydroelectric potential by region in GW
- Slide 30
- Slide 31
- Hydroelectricity in the future
- Sorry try againhellip
- Wind Energy
- The Power of Wind
- Wind Energy proportional to cube of velocity
- Canrsquot get it all
- Practical Efficiencies
- Slide 39
- Slide 40
- Achievable efficiencies
- Typical Windmills
- Average available wind power
- Comparable to solar
- Current implementations
- Flies in the Ointment
- Slide 47
- Slide 48
-
34
Wind Energy
35
The Power of Wind
bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters
every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is
then the kinetic energy the mass of air defined by a rectangular tube
ndash tube is one square meter by v meters or v m3
ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)
065v3 at sea level
36
Wind Energy proportional to cube of velocity
bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in
continental US (above sea level so air slightly less dense)
bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times
bull A wind of 10 ms (22 mph) has a power density of 610 Wm2
bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2
37
Canrsquot get it all
bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely
bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning
bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy
bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36
38
Practical Efficiencies
bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or
about 30ndash40ndash this figure is the mechanical energy
extracted from the windbull Conversion from mechanical to
electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37
39
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
40
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
41
Achievable efficiencies
42
Typical Windmillsbull A typical windmill might be 15 m in diameter
ndash 176 m2
bull At 10 ms wind 40 efficiency this delivers about 100 kW of power
ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW
bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per
year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2
ndash corresponds to 11ndash57 Wm2 average available power density
bull Note the really high tip speeds bird killers
43
Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2
44
Comparable to solar
bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind
bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area
bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy
bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo
45
Current implementations
bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large
dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years
bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over
California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW
46
Flies in the Ointment
bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it
bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces
substantiallybull If fully developed we could generate an average
power almost equal to our current electrical capacity (764 GW)
ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind
47
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
48
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
- Renewable Energy Sources II Alternatives Part I
- Chapter 5 Summary
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Renewable Resources Discussed in Book
- Renewable Energy Consumption
- Another look at available energy flow
- The Renewable Budget
- Outstanding Points from Fig 51
- Energy Flow continued
- The Hydrologic Cycle
- Energetics of the hydrologic cycle
- Let it Rain
- How much of the process do we get to keep
- iClicker Question
- Slide 26
- Power of a hydroelectric dam
- Importance of Hydroelectricity
- Hydroelectric potential by region in GW
- Slide 30
- Slide 31
- Hydroelectricity in the future
- Sorry try againhellip
- Wind Energy
- The Power of Wind
- Wind Energy proportional to cube of velocity
- Canrsquot get it all
- Practical Efficiencies
- Slide 39
- Slide 40
- Achievable efficiencies
- Typical Windmills
- Average available wind power
- Comparable to solar
- Current implementations
- Flies in the Ointment
- Slide 47
- Slide 48
-
35
The Power of Wind
bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters
every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is
then the kinetic energy the mass of air defined by a rectangular tube
ndash tube is one square meter by v meters or v m3
ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)
065v3 at sea level
36
Wind Energy proportional to cube of velocity
bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in
continental US (above sea level so air slightly less dense)
bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times
bull A wind of 10 ms (22 mph) has a power density of 610 Wm2
bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2
37
Canrsquot get it all
bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely
bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning
bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy
bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36
38
Practical Efficiencies
bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or
about 30ndash40ndash this figure is the mechanical energy
extracted from the windbull Conversion from mechanical to
electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37
39
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
40
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
41
Achievable efficiencies
42
Typical Windmillsbull A typical windmill might be 15 m in diameter
ndash 176 m2
bull At 10 ms wind 40 efficiency this delivers about 100 kW of power
ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW
bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per
year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2
ndash corresponds to 11ndash57 Wm2 average available power density
bull Note the really high tip speeds bird killers
43
Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2
44
Comparable to solar
bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind
bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area
bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy
bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo
45
Current implementations
bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large
dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years
bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over
California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW
46
Flies in the Ointment
bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it
bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces
substantiallybull If fully developed we could generate an average
power almost equal to our current electrical capacity (764 GW)
ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind
47
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
48
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
- Renewable Energy Sources II Alternatives Part I
- Chapter 5 Summary
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Renewable Resources Discussed in Book
- Renewable Energy Consumption
- Another look at available energy flow
- The Renewable Budget
- Outstanding Points from Fig 51
- Energy Flow continued
- The Hydrologic Cycle
- Energetics of the hydrologic cycle
- Let it Rain
- How much of the process do we get to keep
- iClicker Question
- Slide 26
- Power of a hydroelectric dam
- Importance of Hydroelectricity
- Hydroelectric potential by region in GW
- Slide 30
- Slide 31
- Hydroelectricity in the future
- Sorry try againhellip
- Wind Energy
- The Power of Wind
- Wind Energy proportional to cube of velocity
- Canrsquot get it all
- Practical Efficiencies
- Slide 39
- Slide 40
- Achievable efficiencies
- Typical Windmills
- Average available wind power
- Comparable to solar
- Current implementations
- Flies in the Ointment
- Slide 47
- Slide 48
-
36
Wind Energy proportional to cube of velocity
bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in
continental US (above sea level so air slightly less dense)
bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times
bull A wind of 10 ms (22 mph) has a power density of 610 Wm2
bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2
37
Canrsquot get it all
bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely
bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning
bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy
bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36
38
Practical Efficiencies
bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or
about 30ndash40ndash this figure is the mechanical energy
extracted from the windbull Conversion from mechanical to
electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37
39
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
40
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
41
Achievable efficiencies
42
Typical Windmillsbull A typical windmill might be 15 m in diameter
ndash 176 m2
bull At 10 ms wind 40 efficiency this delivers about 100 kW of power
ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW
bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per
year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2
ndash corresponds to 11ndash57 Wm2 average available power density
bull Note the really high tip speeds bird killers
43
Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2
44
Comparable to solar
bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind
bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area
bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy
bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo
45
Current implementations
bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large
dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years
bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over
California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW
46
Flies in the Ointment
bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it
bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces
substantiallybull If fully developed we could generate an average
power almost equal to our current electrical capacity (764 GW)
ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind
47
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
48
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
- Renewable Energy Sources II Alternatives Part I
- Chapter 5 Summary
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Renewable Resources Discussed in Book
- Renewable Energy Consumption
- Another look at available energy flow
- The Renewable Budget
- Outstanding Points from Fig 51
- Energy Flow continued
- The Hydrologic Cycle
- Energetics of the hydrologic cycle
- Let it Rain
- How much of the process do we get to keep
- iClicker Question
- Slide 26
- Power of a hydroelectric dam
- Importance of Hydroelectricity
- Hydroelectric potential by region in GW
- Slide 30
- Slide 31
- Hydroelectricity in the future
- Sorry try againhellip
- Wind Energy
- The Power of Wind
- Wind Energy proportional to cube of velocity
- Canrsquot get it all
- Practical Efficiencies
- Slide 39
- Slide 40
- Achievable efficiencies
- Typical Windmills
- Average available wind power
- Comparable to solar
- Current implementations
- Flies in the Ointment
- Slide 47
- Slide 48
-
37
Canrsquot get it all
bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely
bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning
bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy
bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36
38
Practical Efficiencies
bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or
about 30ndash40ndash this figure is the mechanical energy
extracted from the windbull Conversion from mechanical to
electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37
39
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
40
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
41
Achievable efficiencies
42
Typical Windmillsbull A typical windmill might be 15 m in diameter
ndash 176 m2
bull At 10 ms wind 40 efficiency this delivers about 100 kW of power
ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW
bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per
year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2
ndash corresponds to 11ndash57 Wm2 average available power density
bull Note the really high tip speeds bird killers
43
Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2
44
Comparable to solar
bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind
bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area
bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy
bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo
45
Current implementations
bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large
dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years
bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over
California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW
46
Flies in the Ointment
bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it
bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces
substantiallybull If fully developed we could generate an average
power almost equal to our current electrical capacity (764 GW)
ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind
47
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
48
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
- Renewable Energy Sources II Alternatives Part I
- Chapter 5 Summary
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Renewable Resources Discussed in Book
- Renewable Energy Consumption
- Another look at available energy flow
- The Renewable Budget
- Outstanding Points from Fig 51
- Energy Flow continued
- The Hydrologic Cycle
- Energetics of the hydrologic cycle
- Let it Rain
- How much of the process do we get to keep
- iClicker Question
- Slide 26
- Power of a hydroelectric dam
- Importance of Hydroelectricity
- Hydroelectric potential by region in GW
- Slide 30
- Slide 31
- Hydroelectricity in the future
- Sorry try againhellip
- Wind Energy
- The Power of Wind
- Wind Energy proportional to cube of velocity
- Canrsquot get it all
- Practical Efficiencies
- Slide 39
- Slide 40
- Achievable efficiencies
- Typical Windmills
- Average available wind power
- Comparable to solar
- Current implementations
- Flies in the Ointment
- Slide 47
- Slide 48
-
38
Practical Efficiencies
bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or
about 30ndash40ndash this figure is the mechanical energy
extracted from the windbull Conversion from mechanical to
electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37
39
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
40
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
41
Achievable efficiencies
42
Typical Windmillsbull A typical windmill might be 15 m in diameter
ndash 176 m2
bull At 10 ms wind 40 efficiency this delivers about 100 kW of power
ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW
bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per
year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2
ndash corresponds to 11ndash57 Wm2 average available power density
bull Note the really high tip speeds bird killers
43
Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2
44
Comparable to solar
bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind
bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area
bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy
bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo
45
Current implementations
bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large
dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years
bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over
California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW
46
Flies in the Ointment
bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it
bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces
substantiallybull If fully developed we could generate an average
power almost equal to our current electrical capacity (764 GW)
ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind
47
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
48
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
- Renewable Energy Sources II Alternatives Part I
- Chapter 5 Summary
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Renewable Resources Discussed in Book
- Renewable Energy Consumption
- Another look at available energy flow
- The Renewable Budget
- Outstanding Points from Fig 51
- Energy Flow continued
- The Hydrologic Cycle
- Energetics of the hydrologic cycle
- Let it Rain
- How much of the process do we get to keep
- iClicker Question
- Slide 26
- Power of a hydroelectric dam
- Importance of Hydroelectricity
- Hydroelectric potential by region in GW
- Slide 30
- Slide 31
- Hydroelectricity in the future
- Sorry try againhellip
- Wind Energy
- The Power of Wind
- Wind Energy proportional to cube of velocity
- Canrsquot get it all
- Practical Efficiencies
- Slide 39
- Slide 40
- Achievable efficiencies
- Typical Windmills
- Average available wind power
- Comparable to solar
- Current implementations
- Flies in the Ointment
- Slide 47
- Slide 48
-
39
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
40
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
41
Achievable efficiencies
42
Typical Windmillsbull A typical windmill might be 15 m in diameter
ndash 176 m2
bull At 10 ms wind 40 efficiency this delivers about 100 kW of power
ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW
bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per
year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2
ndash corresponds to 11ndash57 Wm2 average available power density
bull Note the really high tip speeds bird killers
43
Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2
44
Comparable to solar
bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind
bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area
bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy
bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo
45
Current implementations
bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large
dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years
bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over
California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW
46
Flies in the Ointment
bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it
bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces
substantiallybull If fully developed we could generate an average
power almost equal to our current electrical capacity (764 GW)
ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind
47
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
48
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
- Renewable Energy Sources II Alternatives Part I
- Chapter 5 Summary
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Renewable Resources Discussed in Book
- Renewable Energy Consumption
- Another look at available energy flow
- The Renewable Budget
- Outstanding Points from Fig 51
- Energy Flow continued
- The Hydrologic Cycle
- Energetics of the hydrologic cycle
- Let it Rain
- How much of the process do we get to keep
- iClicker Question
- Slide 26
- Power of a hydroelectric dam
- Importance of Hydroelectricity
- Hydroelectric potential by region in GW
- Slide 30
- Slide 31
- Hydroelectricity in the future
- Sorry try againhellip
- Wind Energy
- The Power of Wind
- Wind Energy proportional to cube of velocity
- Canrsquot get it all
- Practical Efficiencies
- Slide 39
- Slide 40
- Achievable efficiencies
- Typical Windmills
- Average available wind power
- Comparable to solar
- Current implementations
- Flies in the Ointment
- Slide 47
- Slide 48
-
40
iClicker Question
bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100
41
Achievable efficiencies
42
Typical Windmillsbull A typical windmill might be 15 m in diameter
ndash 176 m2
bull At 10 ms wind 40 efficiency this delivers about 100 kW of power
ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW
bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per
year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2
ndash corresponds to 11ndash57 Wm2 average available power density
bull Note the really high tip speeds bird killers
43
Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2
44
Comparable to solar
bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind
bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area
bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy
bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo
45
Current implementations
bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large
dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years
bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over
California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW
46
Flies in the Ointment
bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it
bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces
substantiallybull If fully developed we could generate an average
power almost equal to our current electrical capacity (764 GW)
ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind
47
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
48
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
- Renewable Energy Sources II Alternatives Part I
- Chapter 5 Summary
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Renewable Resources Discussed in Book
- Renewable Energy Consumption
- Another look at available energy flow
- The Renewable Budget
- Outstanding Points from Fig 51
- Energy Flow continued
- The Hydrologic Cycle
- Energetics of the hydrologic cycle
- Let it Rain
- How much of the process do we get to keep
- iClicker Question
- Slide 26
- Power of a hydroelectric dam
- Importance of Hydroelectricity
- Hydroelectric potential by region in GW
- Slide 30
- Slide 31
- Hydroelectricity in the future
- Sorry try againhellip
- Wind Energy
- The Power of Wind
- Wind Energy proportional to cube of velocity
- Canrsquot get it all
- Practical Efficiencies
- Slide 39
- Slide 40
- Achievable efficiencies
- Typical Windmills
- Average available wind power
- Comparable to solar
- Current implementations
- Flies in the Ointment
- Slide 47
- Slide 48
-
41
Achievable efficiencies
42
Typical Windmillsbull A typical windmill might be 15 m in diameter
ndash 176 m2
bull At 10 ms wind 40 efficiency this delivers about 100 kW of power
ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW
bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per
year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2
ndash corresponds to 11ndash57 Wm2 average available power density
bull Note the really high tip speeds bird killers
43
Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2
44
Comparable to solar
bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind
bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area
bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy
bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo
45
Current implementations
bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large
dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years
bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over
California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW
46
Flies in the Ointment
bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it
bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces
substantiallybull If fully developed we could generate an average
power almost equal to our current electrical capacity (764 GW)
ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind
47
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
48
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
- Renewable Energy Sources II Alternatives Part I
- Chapter 5 Summary
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Renewable Resources Discussed in Book
- Renewable Energy Consumption
- Another look at available energy flow
- The Renewable Budget
- Outstanding Points from Fig 51
- Energy Flow continued
- The Hydrologic Cycle
- Energetics of the hydrologic cycle
- Let it Rain
- How much of the process do we get to keep
- iClicker Question
- Slide 26
- Power of a hydroelectric dam
- Importance of Hydroelectricity
- Hydroelectric potential by region in GW
- Slide 30
- Slide 31
- Hydroelectricity in the future
- Sorry try againhellip
- Wind Energy
- The Power of Wind
- Wind Energy proportional to cube of velocity
- Canrsquot get it all
- Practical Efficiencies
- Slide 39
- Slide 40
- Achievable efficiencies
- Typical Windmills
- Average available wind power
- Comparable to solar
- Current implementations
- Flies in the Ointment
- Slide 47
- Slide 48
-
42
Typical Windmillsbull A typical windmill might be 15 m in diameter
ndash 176 m2
bull At 10 ms wind 40 efficiency this delivers about 100 kW of power
ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW
bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per
year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2
ndash corresponds to 11ndash57 Wm2 average available power density
bull Note the really high tip speeds bird killers
43
Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2
44
Comparable to solar
bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind
bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area
bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy
bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo
45
Current implementations
bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large
dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years
bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over
California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW
46
Flies in the Ointment
bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it
bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces
substantiallybull If fully developed we could generate an average
power almost equal to our current electrical capacity (764 GW)
ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind
47
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
48
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
- Renewable Energy Sources II Alternatives Part I
- Chapter 5 Summary
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Renewable Resources Discussed in Book
- Renewable Energy Consumption
- Another look at available energy flow
- The Renewable Budget
- Outstanding Points from Fig 51
- Energy Flow continued
- The Hydrologic Cycle
- Energetics of the hydrologic cycle
- Let it Rain
- How much of the process do we get to keep
- iClicker Question
- Slide 26
- Power of a hydroelectric dam
- Importance of Hydroelectricity
- Hydroelectric potential by region in GW
- Slide 30
- Slide 31
- Hydroelectricity in the future
- Sorry try againhellip
- Wind Energy
- The Power of Wind
- Wind Energy proportional to cube of velocity
- Canrsquot get it all
- Practical Efficiencies
- Slide 39
- Slide 40
- Achievable efficiencies
- Typical Windmills
- Average available wind power
- Comparable to solar
- Current implementations
- Flies in the Ointment
- Slide 47
- Slide 48
-
43
Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2
44
Comparable to solar
bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind
bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area
bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy
bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo
45
Current implementations
bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large
dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years
bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over
California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW
46
Flies in the Ointment
bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it
bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces
substantiallybull If fully developed we could generate an average
power almost equal to our current electrical capacity (764 GW)
ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind
47
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
48
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
- Renewable Energy Sources II Alternatives Part I
- Chapter 5 Summary
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Renewable Resources Discussed in Book
- Renewable Energy Consumption
- Another look at available energy flow
- The Renewable Budget
- Outstanding Points from Fig 51
- Energy Flow continued
- The Hydrologic Cycle
- Energetics of the hydrologic cycle
- Let it Rain
- How much of the process do we get to keep
- iClicker Question
- Slide 26
- Power of a hydroelectric dam
- Importance of Hydroelectricity
- Hydroelectric potential by region in GW
- Slide 30
- Slide 31
- Hydroelectricity in the future
- Sorry try againhellip
- Wind Energy
- The Power of Wind
- Wind Energy proportional to cube of velocity
- Canrsquot get it all
- Practical Efficiencies
- Slide 39
- Slide 40
- Achievable efficiencies
- Typical Windmills
- Average available wind power
- Comparable to solar
- Current implementations
- Flies in the Ointment
- Slide 47
- Slide 48
-
44
Comparable to solar
bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind
bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area
bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy
bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo
45
Current implementations
bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large
dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years
bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over
California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW
46
Flies in the Ointment
bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it
bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces
substantiallybull If fully developed we could generate an average
power almost equal to our current electrical capacity (764 GW)
ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind
47
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
48
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
- Renewable Energy Sources II Alternatives Part I
- Chapter 5 Summary
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Renewable Resources Discussed in Book
- Renewable Energy Consumption
- Another look at available energy flow
- The Renewable Budget
- Outstanding Points from Fig 51
- Energy Flow continued
- The Hydrologic Cycle
- Energetics of the hydrologic cycle
- Let it Rain
- How much of the process do we get to keep
- iClicker Question
- Slide 26
- Power of a hydroelectric dam
- Importance of Hydroelectricity
- Hydroelectric potential by region in GW
- Slide 30
- Slide 31
- Hydroelectricity in the future
- Sorry try againhellip
- Wind Energy
- The Power of Wind
- Wind Energy proportional to cube of velocity
- Canrsquot get it all
- Practical Efficiencies
- Slide 39
- Slide 40
- Achievable efficiencies
- Typical Windmills
- Average available wind power
- Comparable to solar
- Current implementations
- Flies in the Ointment
- Slide 47
- Slide 48
-
45
Current implementations
bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large
dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years
bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over
California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW
46
Flies in the Ointment
bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it
bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces
substantiallybull If fully developed we could generate an average
power almost equal to our current electrical capacity (764 GW)
ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind
47
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
48
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
- Renewable Energy Sources II Alternatives Part I
- Chapter 5 Summary
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Renewable Resources Discussed in Book
- Renewable Energy Consumption
- Another look at available energy flow
- The Renewable Budget
- Outstanding Points from Fig 51
- Energy Flow continued
- The Hydrologic Cycle
- Energetics of the hydrologic cycle
- Let it Rain
- How much of the process do we get to keep
- iClicker Question
- Slide 26
- Power of a hydroelectric dam
- Importance of Hydroelectricity
- Hydroelectric potential by region in GW
- Slide 30
- Slide 31
- Hydroelectricity in the future
- Sorry try againhellip
- Wind Energy
- The Power of Wind
- Wind Energy proportional to cube of velocity
- Canrsquot get it all
- Practical Efficiencies
- Slide 39
- Slide 40
- Achievable efficiencies
- Typical Windmills
- Average available wind power
- Comparable to solar
- Current implementations
- Flies in the Ointment
- Slide 47
- Slide 48
-
46
Flies in the Ointment
bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it
bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces
substantiallybull If fully developed we could generate an average
power almost equal to our current electrical capacity (764 GW)
ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind
47
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
48
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
- Renewable Energy Sources II Alternatives Part I
- Chapter 5 Summary
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Renewable Resources Discussed in Book
- Renewable Energy Consumption
- Another look at available energy flow
- The Renewable Budget
- Outstanding Points from Fig 51
- Energy Flow continued
- The Hydrologic Cycle
- Energetics of the hydrologic cycle
- Let it Rain
- How much of the process do we get to keep
- iClicker Question
- Slide 26
- Power of a hydroelectric dam
- Importance of Hydroelectricity
- Hydroelectric potential by region in GW
- Slide 30
- Slide 31
- Hydroelectricity in the future
- Sorry try againhellip
- Wind Energy
- The Power of Wind
- Wind Energy proportional to cube of velocity
- Canrsquot get it all
- Practical Efficiencies
- Slide 39
- Slide 40
- Achievable efficiencies
- Typical Windmills
- Average available wind power
- Comparable to solar
- Current implementations
- Flies in the Ointment
- Slide 47
- Slide 48
-
47
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
48
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
- Renewable Energy Sources II Alternatives Part I
- Chapter 5 Summary
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Renewable Resources Discussed in Book
- Renewable Energy Consumption
- Another look at available energy flow
- The Renewable Budget
- Outstanding Points from Fig 51
- Energy Flow continued
- The Hydrologic Cycle
- Energetics of the hydrologic cycle
- Let it Rain
- How much of the process do we get to keep
- iClicker Question
- Slide 26
- Power of a hydroelectric dam
- Importance of Hydroelectricity
- Hydroelectric potential by region in GW
- Slide 30
- Slide 31
- Hydroelectricity in the future
- Sorry try againhellip
- Wind Energy
- The Power of Wind
- Wind Energy proportional to cube of velocity
- Canrsquot get it all
- Practical Efficiencies
- Slide 39
- Slide 40
- Achievable efficiencies
- Typical Windmills
- Average available wind power
- Comparable to solar
- Current implementations
- Flies in the Ointment
- Slide 47
- Slide 48
-
48
iClicker Question
bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas
- Renewable Energy Sources II Alternatives Part I
- Chapter 5 Summary
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Renewable Resources Discussed in Book
- Renewable Energy Consumption
- Another look at available energy flow
- The Renewable Budget
- Outstanding Points from Fig 51
- Energy Flow continued
- The Hydrologic Cycle
- Energetics of the hydrologic cycle
- Let it Rain
- How much of the process do we get to keep
- iClicker Question
- Slide 26
- Power of a hydroelectric dam
- Importance of Hydroelectricity
- Hydroelectric potential by region in GW
- Slide 30
- Slide 31
- Hydroelectricity in the future
- Sorry try againhellip
- Wind Energy
- The Power of Wind
- Wind Energy proportional to cube of velocity
- Canrsquot get it all
- Practical Efficiencies
- Slide 39
- Slide 40
- Achievable efficiencies
- Typical Windmills
- Average available wind power
- Comparable to solar
- Current implementations
- Flies in the Ointment
- Slide 47
- Slide 48
-