cities and energy, winter 2006, "what is energy?" what is energy?
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Cities and Energy, Winter 2006, "What is energy?"
What is Energy?
Cities and Energy, Winter 2006, "What is energy?"
Defining Energy and Its Importance in DescribingHuman Activity
Outline
molecules Forms of Energy
1st Law of Thermodynamics
$$$ - A Broader Definition of Energy$$$ - A Broader Definition of Energy
Cities and Energy, Winter 2006, "What is energy?"
Outline
2nd Law of Thermodynamics
To engine
Earth oil
Principle of Maximum Energy FlowThrough for Survival
Principle of Maximum Energy FlowThrough for Survival
Energy and Its Implications for CitiesEnergy and Its Implications for Cities
Cities and Energy, Winter 2006, "What is energy?"
Forms of Energy
Energy in Transition …Moving in and out of systems
windkineticenergy
electrical energy out
Energy Associated with Mass
Cities and Energy, Winter 2006, "What is energy?"
Total Energy Associated With Mass
i. Potential energy (mgz) g
ii. Kinetic energy (1/2 mV2) Velocity
iii. Internal energy
Forms of Energy
Cities and Energy, Winter 2006, "What is energy?"
Rotational
molecules
Total Energy Associated With Mass- Internal Energy
Forms of Energy
Translational KE
molecule electron
Vibrational Kinetic Energy
molecules
Molecular/Chemical Bonds Nuclear Energy
Cities and Energy, Winter 2006, "What is energy?"
Heat Transfer
Energy in Transition
Forms of Energy
Acoustic transmission, electromagnetic radiation
Work – Work due to deformation of a
solid
Dx
F=kdxF=kdx
x
W = Force x distance
Cities and Energy, Winter 2006, "What is energy?"
“Energy can be defined and measured as the ability to generate heat.”
Odum and Odum, p. 27
I disagree! Heat or thermal energy is the consequence of our energy inefficiencies.
In the industrialized world, the overall efficiency of how we employ energy to enable human processes is about 3.5% efficient, which means that 96.5% of the energy we use doesn’t do anything but transfer to our environment as heat!
It seems better to define energy in terms of what is usefulto human / biological processes.
Work
Defining Energy and Its Importance in DescribingHuman Activity
Cities and Energy, Winter 2006, "What is energy?"
Work = Force x Distance
(Newton – meter)(Joule)(Pound – foot)
Defining Energy and Its Importance in DescribingHuman Activity
Cities and Energy, Winter 2006, "What is energy?"
da Vinci
Cengel and Boles, Thermodynamics
Defining Energy and Its Importance in DescribingHuman Activity
Cities and Energy, Winter 2006, "What is energy?"
Cengel and Boles, Thermodynamics
Defining Energy and Its Importance in DescribingHuman Activity
Cities and Energy, Winter 2006, "What is energy?"
To fuel cell/motor
Solar energy
Solar photovoltaic panel
electricalenergyproduced
water
hydrogen
Heat
Heat
Work out Heat
Cities and Energy, Winter 2006, "What is energy?"
Broader Perspective of “Work”
“Energy is a measure of everything. It measures the amountof stored capability for future processes and the rate at which processes go. The total amount of an accomplished process ismeasured by the enery used.”
Odum and Odum, p. 23
Exaggeration?
Defining Energy and Its Importance in DescribingHuman Activity
Cities and Energy, Winter 2006, "What is energy?"
Process Energy UsedEducate 10 students
Educate 1,000,000,000 students
Feed 1,000 people in the 3rd world
Feed 1,000 people in the industrialized world
Provide sewage service to 10,000,000 people in a city
Enable 1,000 people to attend the local opera
Defining Energy and Its Importance in DescribingHuman Activity
Cities and Energy, Winter 2006, "What is energy?"
From a broader perspective, then:
Defining Energy and Its Importance in DescribingHuman Activity
“Work” can also be:•the ($$$) produced from the use of energy, thus permitting thepurchase of additional energy•the human processes made possible from the use of energy•the products produced by the use of energy
Cities and Energy, Winter 2006, "What is energy?"
Energy is conserved
1st Law of Thermodynamics -
Cities and Energy, Winter 2006, "What is energy?"
To fuel cell/motor
Solar energy
Solar photovoltaic panel
electricalenergyproduced
water
hydrogen
Heat
Heat
Work out
Heat
Cities and Energy, Winter 2006, "What is energy?"
Solar energy
Solar photovoltaic panel
electricalenergyproduced
water
hydrogen
Heat
Heat
Sales $$$$
1st Law from a BroaderPerspective
Cities and Energy, Winter 2006, "What is energy?"
To engine
Earth oil
Energy “quality” diminishes with each process
2nd Law of Thermodynamics -
Cities and Energy, Winter 2006, "What is energy?"
• Where the oil, natural gas, and coal came from
Photosynthesis
GeologicalActivity +
MUCH time
Power plant
9000 J 8 J
heat 8992 J heat 4 J
fossil fuel
4 J 1 J
Fossil fuels representhighly concentrated energy!
Fossil fuels representhighly concentrated energy!
Odum and Odum, 1976
Energy “quality” diminishes with each process
2nd Law of Thermodynamics -
Cities and Energy, Winter 2006, "What is energy?"
Energy “Cascades” from high entropy (concentration) to low entropy (concentration)
Quality of E
nergy on E
arth
Solar
Oil
Coal
High Temperature
Mass
Mass at Atmospheric Temperature
There is MUCH moreTotal Energy Here,
But Not UsefulReason: Energy Efficiency
There is MUCH moreTotal Energy Here,
But Not UsefulReason: Energy Efficiency
Energy “quality” diminishes with each process
2nd Law of Thermodynamics -
Cities and Energy, Winter 2006, "What is energy?"
Energy Efficiency = Useful energy output / energy input that costs
Typical B
estE
nergy E
fficiency
Solar
Fossil fuel / power plant
Fossil fuel / I.C. auto
50%
~40%
~20%
0%
Mass at Atmospheric Temperature
Pre-industrial revolution
<0.1%
Energy “quality” diminishes with each process
2nd Law of Thermodynamics -
Cities and Energy, Winter 2006, "What is energy?"
Quality of E
nergy
Materials are also associated with quality of energy
2nd Law of Thermodynamics -
$$$$$
Cities and Energy, Winter 2006, "What is energy?"
gasoline
Sales $$$$
2nd Law from a BroaderPerspective
What does the 2nd
Law tell us about the Quality of the energy madeavail. with the $$$ generated?
Earth oil
refinery
Cities and Energy, Winter 2006, "What is energy?"
Relevance of 2nd Law to a City?
Cities and Energy, Winter 2006, "What is energy?"
EnergySource(s)
“Interaction process” (production)
Storage of high quality energy
Production of higher qualityenergy
Heat dissipated in production
Feedback workloop
depreciation
Principle of Maximizing Energy Throughput for Survival
Cities and Energy, Winter 2006, "What is energy?"
Fossil fuels enabled the formation of cities and the mass migration from Farm to city.
Solar Energy Income: 700 Watts/square meter
Pre-industrial (oil/coal) age effic.: 0.1 %
Human energy needs: 100 Watts
Land needed to support family of 6 (for crops/meat) ~2-5 acres required to feed family
Pre-industrial
Coal, then oil and natural gas, became the drivers for the city. Could transportfood and trade goods.Provided alternative career paths; all needing energy.
Energy: Implications to the City
Cities and Energy, Winter 2006, "What is energy?"
MIT, Sustainable Energy Course
Energy: Implications to the City
Cities and Energy, Winter 2006, "What is energy?"
MaterialVirgin
MJ/kgRecycled
MJ/kg
Aluminum 196 27
Polyethylene 98 56
PVC 65 29
Steel 40 18
Glass 30 13
Nylon 120.2 32.1
Wood 0.1-2
CSIRO
Energy for humansupport for 1 year = 2500 MJ
Car = 2000 kg= 80,000 MJ
Skyscraper = 1x1010 MJ (energy needed by1 million peopleper year)
Energy: Implications to the City
Cities and Energy, Winter 2006, "What is energy?"
http://www.eia.doe.gov/emeu/aer/eh/frame.html
Energy: Implications to the City
Cities and Energy, Winter 2006, "What is energy?"
http://www.hubbertpeak.com/curves.htm
1997
2004
M. King Hubbert
His prediction in 1956 that U.S.oil production would
peak in about 1970 and decline thereafter was
scoffed at then but his analysis has since proved
to be remarkably accurate.”
Energy: Implications to the City