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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
© Brooks/Cole Publishing Company / ITP
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
© Brooks/Cole Publishing Company / ITP
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
© Brooks/Cole Publishing Company / ITP
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.
© Brooks/Cole Publishing Company / ITP
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.
© Brooks/Cole Publishing Company / ITP
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
© Brooks/Cole Publishing Company / ITP
Solar Energy
© Brooks/Cole Publishing Company / ITP
Solar EnergyGenerating high temperature heat and electricity
© Brooks/Cole Publishing Company / ITP
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
© Brooks/Cole Publishing Company / ITP
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