Alternative/Renewable/Sustainable Energy

Alternative EnergiesClean Fuels

◦Create less pollution◦Alcohols, electricity, natural gas &

propaneClean Energy

◦Produced from renewable energy sources

◦Solar, wind, biomass, hydroelectric, geothermal

ElectricityBattery-powered or hybrid gas-

electric vehicles (Prius & Tesla)◦Battery-operated engine kicks in for

acceleration or recharge◦Low-power batteries limit driving

ranges Ranges improving Time to recharge could make this option

viable

Alternative EnergiesWind Energy

◦Wind created by Earth’s atmospheric circulation

◦Green energy creates electricity without consuming natural resources

Wind forms due to pressure difference because of unequal heating at the poles and the equator.

World’s fastest growing source of energy since 1990.

Oklahoma, Kansas, South Dakota, North Dakota, Nebraska, and Texas have enough wind resources to meet the country’s energy needs.

Producing Electricity from Wind

Producing Electricity from Wind

Pros

• unlimited source of energy at favorable sites

• moderate to high net energy yield

• easy to build and expand

• emit no pollutants or greenhouse gases

• land can also be used for agriculture

Cons

• economical only in areas with steady winds

• back–up energy sources are necessary

• mass production takes up a great deal of land space

• noise pollution

• may interfere with migrating birds

Producing Electricity from Wind

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Oregon’s first offshore windfarm

Rotary Windmill

Vertical Blades

Wind Turbine

Power cable

Electricalgenerator

Gearbox

Alternative EnergiesGeothermal Energy

◦Internal heat from the Earth◦Heated groundwater circulates back

to surface

Uses heat stored in the earth◦Heat houses, generate

electricity or use high temp heat for industry

◦Uses the difference in temperature between the surface and underground.

◦Acts as a heat source in the winter and a heat sink in the summer

◦Winter – heat taken from ground and blown through the house ducts

◦Summer – heat is taken from the house and returned to the ground

Geothermal Energy

Very high efficiency

Moderate net energy at accessible sites

Lower CO2 emissions than fossil fuels

Low cost at favorable sites

Low land use

Low land disturbance

Moderate environmental impact

Scarcity of suitable sites

Depleted if used too rapidly

CO2 emissions

Moderate to high local air pollution

Noise and odor (H2S)

Cost too high except at the most concentrated and accessible source

Advantages Disadvantages

Trade-Offs

Geothermal Fuel

Alternative EnergiesOcean Tidal Energy

◦Harnessing of tidal movement

Tidal Power Plant

Alternative EnergiesHydrogen Cells

◦Hydrogen removed from water (electrolysis) stores energy

◦Stored hydrogen atoms release energy when electrolysis reversed

The Solar – Hydrogen Revolution

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The benefits of using hydrogen: Source of hydrogen (water) is plentiful Has no moving parts Twice as efficient as internal combustion engines When burned, hydrogen produces no CO2, but instead water vapor and

nitrogen oxides-elimination of GHG’s Hydrogen Fuel Cell Video

The Solar – Hydrogen Revolution

Problems? Hydrogen is really only a way to store energy; requires

energy source to split hydrogen from water Currently nonrenewable energy sources are used to

produce hydrogen, negating many benefits .

Solutions? Use renewable sources of energy, most notably solar,

to produce hydrogen for combustion Currently it costs more to use solar energy than other

energy sources, but could be phased in over time

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Gas-electric car Fuel cell running on H2

Can be produced from plentiful water

Low environmental impact

Renewable if producedfrom renewable energyresources

No CO2 emissions if produced from water Good substitute for oil Competitive price if environmental and social costs are included incost comparisons Easier to store than electricity Safer than gasoline and natural gas

Nontoxic

High efficiency (65-95%) in fuel cells

Not found in nature

Energy is needed to produce fuel

Negative net energy

CO2 emissions if produced fromcarbon-containing compounds

Nonrenewable if generated byfossil fuels or nuclear power

High costs (but expected to come down)

Will take 25 to 50 years to phase in

Short driving range for current fuel cell cars

No distribution system in place

Excessive H2 leaks may deplete ozone

Advantages Disadvantages

Trade-Offs

Hydrogen

Solar EnergyAmount of solar energy reaching

earth is much greater that worldwide energy demands

Uses Sun’s energy and light to provide heat, light, hot water, electricity & cooling

Photovoltaic reaction – produces voltage when exposed to radiant energy◦Passive or active solar designs

Solar EnergyPassive solar heating

• A passive solar and superinsulated design is the cheapest way to heat a home in regions where sunlight is available more than 60% of daylight hours.

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Solar EnergyPassive Solar

◦Designed to absorb & slowly release sun’s heat South facing windows, construction

materials Can reduce heating bills 50% Cooling through natural ventilation

Solar EnergyPassive solar heating• Sunlight on a U.S. house’s

SOUTH side is captured directly within a structure and converts it into low–temperature heat for space heating.

• Heat is stored in walls and floors made of materials like concrete, brick, stone, or tires and is released slowly throughout the day.

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Solar Energy Passive Solar Heating Solar cookers!

◦ Being used worldwide as an alternative cooking source and to purify water.

◦ Use no gas or firewood in cooking.◦ Reflective surfaces (like cardboard covered

foil) used with black pots and “glazing” (like a cooking bag) which withholds the heat for the greenhouse effect.

◦ Can reach temps over 400 degrees F Decrease deforestation, dangers during

wood collection, climate change, acid rain, smoke inhalation, etc.

Solar EnergyCrystalline Silicon Solar Cells

◦Light-absorbing semi-conductor cell Made of silicon, enriched on side with

phosphorus & the other with boron Arranged in modules, panels and flat arrays Need direct sunlight & must track sunlight

Solar Energy

Active solar heating

• solar collectors absorb solar energy and a fan or pump supplies the building’s space or water heating needs

• Active solar video clip

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Solar Energy

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Solar EnergyGenerating high temperature heat and electricity

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Solar EnergyThin-Wafer Solar Cells

◦Amorphous silicon or polycrystalline Absorb light, are 1 micron thick Cheaper than crystalline silicon Deposited onto coated glass or stainless

steel sheets Staebler-Wronski Effect

Photoconductivity of amorphous silicon can be reduced significantly by prolonged illumination with intense light

Solar EnergyProducing electricity

• Solar energy can be converted directly into electrical energy by photovoltaic cells

• Sunlight striking silicon atoms creates an electrical current

• Electrical energy is stored in batteries for use when the sun is not shining

• Photovoltaic cell video clip

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Solar EnergyHome & building PV installations are

being connected to the electricity grid◦Electricity Grid – electricity transmission and

distribution system, usually supplying power across a wide geographical area

Extra electricity can be sent to the gridNo batteries needed since the grid is

able to meet any extra demandTo be Off the Grid – battery storage is

needed for power at night or diesel generator

Solar Energy

Pros• solar energy is free• net energy yield is high for

passive and moderate for active

• technology is well developed and easily installed

• takes up little land space• does not emit polluting or

greenhouse gases• moderate cost (passive)

Cons• need to secure solar

rights• solar collectors are ugly

to some people• active systems are

costly• need heat storage

system• need to access sun 60%

of the time• active system needs

maintenance and repair

Active and passive solar heating

Solar EnergyDisadvantage – lots of acreage is

needed for the solar panelsAdvantage – renewable,

nonpolluting energy option