CHAPTER 16 Renewable Energy © 2011 Pearson Education, Inc.
An introduction to renewable energy • Coastal locations are known for constant, cooling wind • Drawing tourists and residents • Vacationers increase the population and stress the energy infrastructure • A proposed wind farm off Nantucket Sound could supply 75% of the area’s electricity • There would be 130 turbines, each 417 feet tall • People opposed to the wind farm filed lawsuits • Visual pollution • Threats to tourism, navigation, fishing, and birds © 2011 Pearson Education, Inc.
Wind farms are controversial • Proponents of wind farms view concerns as a case of NIMBY (Not In My Backyard) • Opinion polls show strong support for wind farms • Every state and federal agency has approved • The wind farm may be operable by 2011 • Wind farms are appearing all over the U. S. and other countries • In 2008, wind power provided energy to 6. 5 million U. S. homes © 2011 Pearson Education, Inc.
Solar, too • Solar energy provides hot water and electricity globally • Building design, insulation, and solar collection devices can reduce energy bills by 75% • “Farms” with trough-shaped mirrors boil water or synthetic oil and drive turbogenerators • A renewable-energy future is absolutely essential • It can replace limited, polluting fossil fuels and nuclear • Solar and wind energy are becoming cost competitive • Renewables provide 6. 7% of U. S. and 18% of world energy © 2011 Pearson Education, Inc.
Rooftop hot water © 2011 Pearson Education, Inc.
Solar thermal power in southern California © 2011 Pearson Education, Inc.
Renewable-energy use in the United States © 2011 Pearson Education, Inc.
Putting solar energy to work • Solar energy originates from the Sun’s thermonuclear fusion • Solar constant: radiant (solar) energy reaching Earth • Energy ranges from ultraviolet to visible to infrared (heat) • 50% of the energy makes it to Earth, 30% is reflected, 20% is absorbed by the atmosphere • The amount of sunlight reaching Earth is almost unbelievable • Full sunlight delivers 700 watts/m 2 to Earth’s surface • 700 MW of power (equals a large power plant) delivered to 390 mi 2 • The Sun delivers 10, 000 times the energy used by humans © 2011 Pearson Education, Inc.
The solar-energy spectrum © 2011 Pearson Education, Inc.
Using solar energy • Using solar energy does not change the biosphere’s energy balance • Energy absorbed by water or land, in photosynthesis, or used by humans is ultimately lost as heat • Solar energy is abundant but diffuse • Varies with season, latitude, and atmospheric conditions • Using solar energy requires turning a diffuse, intermittent source into a form (fuel, electricity) that can be used • Collection, conversion, and storage of solar energy are difficult and must be cost effective © 2011 Pearson Education, Inc.
Solar heating of water • Flat-plate collector: a thin, broad box • The black bottom absorbs sunlight and heats up • Water in tubes absorbs the heat • The glass top prevents heat loss • Active systems: use pumps to move the heated water • Passive systems: use gravity and convection to move water • The collector is lower than the tank • Heated water from the collector rises through convection © 2011 Pearson Education, Inc.
The principle of a flat-plate solar collector © 2011 Pearson Education, Inc.
Solar energy is used worldwide • The U. S. has over 1 million residential and 200, 000 commercial solar hot-water systems • This is only a small fraction of hot-water heaters • The initial cost is 5– 10 times higher than gas or electric heaters • Over time, the solar system is cheaper to use • In the U. S. , solar thermal collection systems heat pools • China leads the world in using solar thermal systems • 10% of people get hot water from these systems © 2011 Pearson Education, Inc.
Solar space heating • Flat-plate collectors can be used for space heating • They are less expensive and can be homemade • It is necessary only to have air circulate through the collector box • Efficiency is gained if collectors are mounted to allow convection to circulate the heated air into areas to be heated © 2011 Pearson Education, Inc.
Passive hot-air solar heating © 2011 Pearson Education, Inc.
Building = collector • A building can act as a collector for solar space heating • Windows should face the Sun • Insulated drapes or shades can trap heat inside • The building should have appropriate insulation, doors, and windows to store heat • Tanks of water or rocks do not store heat economically • Awnings or shades shield windows from summer heat • Deciduous vegetation blocks summer but not winter heat • Evergreen hedges on the shady side protect from the cold © 2011 Pearson Education, Inc.
Solar building siting © 2011 Pearson Education, Inc.
Earth-sheltered housing • Combines insulation and solar heating • Earth insulates the building • The building is oriented for passive solar energy • Earth (berms) can be built up against a conventional house • Or the building can be covered with earth • The building has south-facing windows • Walls and floors store heat during the day • Release it during the night to warm the house • Moisture must be controlled with dehumidifiers © 2011 Pearson Education, Inc.
Earth hall © 2011 Pearson Education, Inc.
Energy Stars • A well-designed solar-energy building can reduce bills • With added construction costs of only 5– 10% • 25% of our energy use is for space and water heating • Solar design can save oil, natural gas, and coal • In 2001, the EPA extended its Energy Star Program to buildings using at least 40% less energy and meeting other criteria • By 2008, 4, 100 buildings had saved $1. 5 billion/yr © 2011 Pearson Education, Inc.
Criticizing solar heating misses the point • Solar heating is criticized for needing a backup heating system • Good insulation minimizes this need • Backup can come from a small wood stove or gas heater • This criticism misses the point: • The objective of solar heating is to reduce dependency on conventional fuels • Fuel demand is reduced, and the economic and environmental costs are also reduced © 2011 Pearson Education, Inc.
Solar production of electricity • Solar energy can produce electrical power • Providing an alternative to coal and nuclear power • Photovoltaic (PV) cells: a wafer of material • One wire is attached to the top, one to the bottom • Sunlight striking the wafer puts out 1 watt of power • 40 linked PV cells produce enough energy to light a lightbulb • PV cells are highly sophisticated • Light hitting the wafer causes an electron to go from the lower layer to the upper layer © 2011 Pearson Education, Inc.
Photovoltaic cell © 2011 Pearson Education, Inc.
Solar cells do not wear out • Solar cells convert light energy directly to electrical power • With 15– 30% efficiency • Cells have no moving parts and last about 20 years • Silicon, one of the most abundant elements, is the main material used in solar cells • The cell’s cost lies mostly in its design and construction • Cells are used in calculators, watches, toys, rural homes, pumps, traffic signals, transmitters, lighthouses, satellites • Net metering: rooftop electricity is subtracted from power use from the power grid © 2011 Pearson Education, Inc.
Cost • The cost of PV power = 25 cents per kilowatt-hour • Other sources = 6– 12 cents per kilowatt-hour • More efficient cells and less expensive technologies • Dramatically reduce costs • Provide incentives for more applications, sales, and markets • This industry is the fastest growing energy technology • In 2008: existing PV panels turned sunlight into 16, 000 MW © 2011 Pearson Education, Inc.
The market for PV panels © 2011 Pearson Education, Inc.
Inverters: complicated yet necessary • Act as an interface between the solar PV modules and the electric grid or batteries • Convert incoming direct current (DC) to alternating current (AC) from the grid or for powering the devices • Also act as a control that detects and responds to fluctuations in voltage or current • Must be robust enough to withstand the heat of attics for rooftop PV systems • Costs have declined, but are still substantial • But they are eligible for subsidies © 2011 Pearson Education, Inc.
PV system inverter © 2011 Pearson Education, Inc.
Utilities • Utility companies are moving toward large-scale PV use • 53 plants worldwide (2008) generating 10 MW • The largest U. S. plant is in Nevada • The most promising future for PV power: rooftop panels • Unused space (e. g. , warehouse and factory roofs) • California, New York, New Jersey, Connecticut give incentives for home use • A 2 k. W system gives half the energy needed for 1 year • The 2008 Emergency Economic Stabilization Act gives tax credits for 30% of system costs © 2011 Pearson Education, Inc.
PV power plant © 2011 Pearson Education, Inc.
New PV technologies • Costs must decline to compete with other electricity sources • New technologies are in production or close to it • Thin-film PV cells: amorphous silicon or cadmium telluride • Instead of expensive silicon • The film is applied to roofing tiles or glass • Silicon crystals are sliced to make SLIVERs • Uses 10% of the silicon in normal cells • Light-absorbing dyes transmit energy to solar cells on the edge of the glass • Light passes through to conventional solar panels © 2011 Pearson Education, Inc.
Concentrated solar power (CSP) • Technologies convert solar energy into electricity • Reflectors (concentrators) focus sunlight on a receiver, which transfers the heat to a conventional turbogenerator • CSP works well in sunny, remote areas • Solar troughs: reflect sunlight onto a center pipe • Heat-absorbing liquid is heated to high temperatures, boiling water to produce steam for a turbogenerator • Energy can be stored for release at night • The Mojave Desert generates one-third the capacity of a nuclear power plant at a cost equal to coal-fired facilities © 2011 Pearson Education, Inc.
CSP technologies • Power towers: Sun-tracking mirrors focus sunlight onto a receiver mounted on a tower at the center of the area • Heated liquid flows to a heat exchanger to drive a turbogenerator or a tank to store the heat • A California facility generates electricity for 10, 000 homes • Dish-engine system: parabolic concentrators focus sunlight onto a receiver • Fluid is transferred to an engine that directly generates electricity at 30% efficiency © 2011 Pearson Education, Inc.
Power tower Solar Two © 2011 Pearson Education, Inc.
Solar dish-engine system © 2011 Pearson Education, Inc.
The future of solar energy • Solar energy: a $20 billion industry and is growing rapidly • It is hard to keep up with demand • But solar energy does have disadvantages • Technologies are more expensive than traditional energy sources (but subsidies help decrease costs) • A backup energy source, storage battery, or thermal storage for nighttime power is needed • Many areas are not sunny in winter • But other energies also have disadvantages • Mining, greenhouse gas emissions, nuclear waste, etc. © 2011 Pearson Education, Inc.
Matching demand • 70% of electrical demand is during the day – we can use solar • We can rely on conventional sources at night • Air-conditioning, the second largest power user (after refrigeration), is well-matched to energy from PV cells • Solar and wind can replace coal and nuclear electrical power • • • Can be planned and built in months, not years Can be installed in small increments Have less financial risk for utility companies Are less vulnerable to terrorist attacks Can provide energy for the 1. 6 billion in poor nations © 2011 Pearson Education, Inc.
Indirect solar energy • Energy from the Sun is the driving force behind dams, firewood, windmills, sails • The force of falling water can turn paddle wheels • To grind grain, saw logs, do other tasks • Hydropower: hydroelectric dams use water under high pressure to drive turbogenerators • In the U. S. , it generates 6% of electrical power • 300 large dams mainly in the Northwest and Southeast • Worldwide, dams generate 19% of electrical power • It is the most common form of renewable energy © 2011 Pearson Education, Inc.
Hoover dam © 2011 Pearson Education, Inc.
Trade-offs: benefits of dams • Dams, especially large ones, have benefits and serious consequences • Benefits • They eliminate the cost and environmental impacts of fossil fuels and nuclear power • Dams provide flood control and irrigation water • Reservoirs provide recreational and tourist opportunities • Pumped-storage power dams can pump water to a higher reservoir for later use during peak times © 2011 Pearson Education, Inc.
Trade-offs: disadvantages of dams • Reservoirs drown farmland, wildlife habitats, towns • Land of historical, archaeological, or cultural value • Reservoirs displace rural populations • In the last 50 years, 40– 80 million have been displaced • Dams impede or prevent migration of fish • Even if ladders are provided • Fish habitats are suffering • Dams wreak havoc downstream • Decreased sediment reaches the river’s mouth © 2011 Pearson Education, Inc.
More dams? • The U. S. and other developed nations have brought their hydropower to maximum capacity • The U. S. has 75, 000 dams 6 feet or higher • Two million smaller dams • The Wild and Scenic Rivers Act (1968) protects most of the last 2% free-flowing rivers • Many dams that impede river flow are being removed • Worldwide, dams are controversial • The projected benefits may not justify the ecological and sociological effects © 2011 Pearson Education, Inc.
The Nam Theun 2 Dam • A 50 -m-tall dam being completed on the Mekong River in Laos • Is projected to help Laos develop • The project has displaced 6, 200 people • It will damage or destroy 174 square miles of sensitive environments • It is being built to sell power to Thailand • Critics say the government cannot manage this project • Money will not be used to help the poor © 2011 Pearson Education, Inc.
Dam report • The Three Gorges Dam on the Yangtze River in China • • • Was completed in 2006 Is the world’s largest dam (1. 4 miles long) Displaced 1. 2 million people Will generate electricity and control floods Produces electricity equal to 12 coal-fired plants • The World Commission on Dams 2000 report found dams are a mixed blessing • They should be built only as a last option • Many more dams will be built in China, Brazil, India, etc. © 2011 Pearson Education, Inc.
Wind power • The Horse Hollow Wind Energy Center in Texas • The world’s largest wind farm • 304 turbines on 47, 000 acres produce electricity for 260, 000 homes • The U. S. is the world leader in wind energy • Germany is second • Wind capacity has increased 28%/yr • It is economically competitive • It could provide 12% of the world’s electricity by 2020 © 2011 Pearson Education, Inc.
Horse Hollow Wind Energy Center © 2011 Pearson Education, Inc.
Wind energy in the U. S. © 2011 Pearson Education, Inc.
Design • The most practical design is using wind-driven propellers • The propeller shaft is geared directly to a generator • Wind turbine: a wind-driven generator • Reliability and efficiency have reduced electric costs • Wind farms: arrays up to several thousand turbines • Produce pollution-free power competitive with traditional sources • The amount of wind that can be tapped is immense • Wind farms in the Midwest could meet U. S. needs • Farmers are paid well to put turbines on their land © 2011 Pearson Education, Inc.
Drawbacks • Wind is intermittent, so backup or batteries are needed • Wind farms can be visually unappealing • Turbines can be hazardous to birds • When placed on migratory routes or in critical habitat • But far fewer die than from cars, traffic, and windows • Offshore wind farms use dependable, strong winds • They have less of a visual impact • Land does not need to be bought • New turbines in 2008 displaced emissions from 40 coal plants © 2011 Pearson Education, Inc.
Biomass energy • Burning firewood for heat: the oldest form of energy • Renamed “utilizing biomass energy” • Biomass energy: energy derived from present-day photosynthesis • Leads hydropower in U. S. renewable energy • Most is used for heat • Produced by burning wood or municipal waste, generating methane, or producing alcohol © 2011 Pearson Education, Inc.
Burning firewood • With enough forests, burning firewood (fuelwood) can be a sustainable energy resource • The primary cooking and heating source for 2. 6 billion • Five million U. S. homes use only wood stoves for heat • Another 20 million use them for some heating • Pellet stoves use compressed pellets made from wood wastes • They need little attention and they burn efficiently © 2011 Pearson Education, Inc.
Pellet stove © 2011 Pearson Education, Inc.
Fuelwood crisis? • Consumptive fuelwood use: people get wood from forests for their daily needs • Productive use: people convert wood into charcoal to sell • Both can degrade local forests and woodlands • Global fuelwood use peaked in the 1990 s and is declining • With development, people switch to fossil fuels • The Millennium Ecosystem Assessment judged that fuelwood demand is not a significant cause of deforestation • But it could be if fossil fuel costs continue to increase • There also local areas of concern © 2011 Pearson Education, Inc.
Burning wastes • Facilities can generate electricity from burning • • Municipal wastes (waste-to-energy) Wood wastes: sawmills, woodworking companies Cane wastes: sugar refineries Olive oil wastes: provides electricity to 100, 000 homes in Spain • The power may meet only a small percent of electrical needs • But it is a productive, inexpensive way to dispose of biological wastes © 2011 Pearson Education, Inc.
Producing methane • Biogas: anaerobic digestion of sewage sludge to produce methane • Nutrient-rich sludge for fertilizer • Animal manure can also be digested • Millions of Chinese farmers have digesters: underground fermentation chambers with a dome on top to store gas • Fermented agriculture wastes (pig manure, cattle dung) • Biogas is used for cooking, heating, lighting • The residual slurry is used for fertilizer • India and China provide subsidies for home biogas plants © 2011 Pearson Education, Inc.
Biogas power © 2011 Pearson Education, Inc.
Renewable energy for transportation • The most critical need for a sustainable energy future: a new way to fuel vehicles • Biofuels: complex organic matter (plant and animal waste) • Ethanol and biodiesel • Biofuels produce only 1% of global transportation fuels • But they are expanding rapidly • High oil prices, new technologies, farmer support, subsidies, environmental concerns • Sources come from agricultural and food commodities © 2011 Pearson Education, Inc.
Ethanol • Produced by the fermentation of starches or sugar • Using corn, sugarcane, sugar beets, or other grains • Production costs make it more expensive than oil • Until oil sells for more than $55/barrel • Gasohol: 10% ethanol, 90% gasoline • Widely used in the U. S. Midwest • Provides another corn market to help local economies • The U. S. uses 10 billion gallons (240 million barrels)/yr • Equal to 160 million barrels of oil (ethanol contains two-thirds the energy of regular gasoline) © 2011 Pearson Education, Inc.
Farm production • 25% of U. S. corn is dedicated to ethanol • Ethanol facilities also produce corn oil and livestock feed • Future production will reach 12. 6 billion gallons/yr • The 45 cent/gallon tax credit helps it compete with oil • A renewable fuel standard (RFS) • • Requires renewable fuel in gasoline Mandated 9 billion gallons of renewable fuels in 2008 Increasing to 15 billion gallons by 2015 The 2002 36 billion gallon target will also use other sources © 2011 Pearson Education, Inc.
Can ethanol reduce oil imports and emissions? • Ethanol equals 5% of U. S. gasoline consumption • It could rise to 15% if all corn were used (impossible) • No more farmland is available for expansion • It may have contributed to recent increases in food costs • Producing (fertilizer, pesticides, machines), transporting, and operating ethanol plants use fossil fuels • Replacing oil with ethanol reduces greenhouse gases 13% • The primary strategy for ethanol? • Reducing reliance on imported oil © 2011 Pearson Education, Inc.
Second-generation biofuel • Made from cellulosic feedstocks • Crop residues, grasses (switchgrass), logging residues, fast-growing trees, fuelwood • Miscanthus: a giant perennial grass • Grows in poor soils • Outproduces corn and other grasses • Cellulosic technology uses enzymes to break cellulose • Cheaper and more energy efficient • 11 plants are being constructed in the U. S. • A $1. 01 tax credit helps increase this industry © 2011 Pearson Education, Inc.
Miscanthus x giganteus © 2011 Pearson Education, Inc.
Air quality • Ethanol substitutes for methyl tertiary butyl ether (MTBE) • A fuel additive that makes cleaner-burning gasoline • Reformulated gasoline: contains additives to improve air quality • MTBE is carcinogenic in animals • It is showing up in water supplies • The Energy Policy Act refused to grant the oil industry liability protection against MTBE • The industry is turning toward ethanol © 2011 Pearson Education, Inc.
Biodiesel • Biodiesel: made largely from soybean oil • But can come from any natural oil or fat • Even from recycled vegetable oil from frying • Competitive with petroleum diesel fuel • $1/gallon tax credit • Equals 1% of U. S. diesel fuel transportation use • Offbeat technologies can produce biodiesel • One Missouri plant uses turkey wastes • Converts 250 tons/day of wastes into 20, 000 gallons at a profit, plus fertilizer from wastes © 2011 Pearson Education, Inc.
Hydrogen: highway to the future? • Conventional cars can be adapted to run on hydrogen gas • Hydrogen is not a fuel but an energy carrier – like electricity • It must be generated using another form of energy • The only major by-product of burning H 2 is water • 2 H 2 + O 2 → 2 H 2 O + energy • There is almost no hydrogen gas on Earth • Atmospheric gas is ignited by lightning to form water • Soil bacteria produce hydrogen, which other bacteria use • Elemental hydrogen is combined with other elements © 2011 Pearson Education, Inc.
Hydrogen can be extracted from water • Electrolysis: extracting hydrogen from water • Requires an input of energy • Hydrogen can be derived from hydrocarbon fuels • Such as methane, petroleum oil, methyl alcohol • More energy is put into the process than is in hydrogen • It is better to use the hydrocarbons directly • Using hydrogen requires an cheap, abundant, nonpolluting energy source • Solar energy © 2011 Pearson Education, Inc.
Plants do it • Photosynthesis splits water into hydrogen and oxygen • Using light energy • One method can mimic this process: a catalyst of cobalt and phosphorus can be used to split water • The electricity could come from solar cells • It operates in neutral water and ambient temperature and pressure • Another process uses electrolysis to pass an electric current through water • Hydrogen gas is collected, compressed, and stored © 2011 Pearson Education, Inc.
Electrolysis has drawbacks • It is hard to store enough hydrogen to allow a vehicle to travel long distances • Compressing hydrogen requires energy • Reducing the energy efficiency involved • Hydrogen can be combined with metal hydrides to absorb the gas and release it when needed • Most hydrides are too heavy to use © 2011 Pearson Education, Inc.
Solar energy to hydrogen • Arrays of solar-trough or PV generating facilities would produce electricity • In deserts of the southwestern U. S. • The electrical power would produce hydrogen by electrolysis • Hydrogen would be moved through underground pipes • They already exist • Additional pipes would be expensive © 2011 Pearson Education, Inc.
The Model U • Ford’s concept car • Its internal combustion engine runs on hydrogen • It has a range of 300 miles • But there must be a hydrogen-fueling infrastructure • Cars like the Model U would be replaced by fuel cells • Fuel cells: devices that chemically combine hydrogen or some other fuel with oxygen • Produces an electrical potential, instead of burning • Emissions are water and heat © 2011 Pearson Education, Inc.
Fuel cells are being used • Fuel cells are 45– 60% efficient (combustion engines = 20%) • Vehicles have hundreds of fuel cells in a fuel-cell stack • Along with a hydrogen storage device, a cooling system, and a device to force oxygen into the fuel cell • Fuel cells power buses all over the world • GM’s Hy-wire and Sequel have no engine compartments • By-wire systems: electronically controlled units that replace steering, braking, and other mechanisms • All major car manufacturers are developing concept cars © 2011 Pearson Education, Inc.
Hydrogen-oxygen fuel cell © 2011 Pearson Education, Inc.
Freedom. CAR • Obstacles to fuel-cell-driven vehicles are their high cost and lack of infrastructure for refueling • President Bush’s Freedom. CAR and Fuel Partnership (2003) • A government-industry partnership to promote research • The National Research Council recommended shifting to developing plug-in hybrid electric vehicles (PHEVs) • Still support some fuel-cell vehicle research • The American Recovery and Reinvestment Act (2009) • Gives $2. 4 billion to help meet President Obama’s goal of 1 million PHEV vehicles by 2015 © 2011 Pearson Education, Inc.
The hydrogen economy • Will emerge when hydrogen infrastructure is in place • Vehicles powered by fuel cells are available • With a hydrogen economy, we will no longer be tied to nonrenewable, polluting energy sources • A hydrogen economy is still decades away • There are other renewable-energy options available © 2011 Pearson Education, Inc.
Geothermal energy • Around the world, springs yield hot, almost boiling, water • These areas also have natural steam vents and othermal features • These features occur where the hot molten rock of Earth’s interior is close enough to heat groundwater • Near volcanic regions • Geothermal energy: using naturally heated water or steam to heat buildings or produce electricity • In 2008, geothermal energy provided electricity equal to 10 large nuclear or coal-fired power plants © 2011 Pearson Education, Inc.
Geothermal energy © 2011 Pearson Education, Inc.
The U. S. : world leader in geothermal energy • The Geysers, 70 miles north of San Francisco • The largest electrical generating geothermal facility • Homes and buildings are also directly heated • Especially in Japan and China • Enhanced geothermal systems (EGS): produce electricity • Holes are drilled into granite that holds high temperatures • Water is injected into one hole and turns to steam • The steam flows up another hole to a power plant • The U. S. has widespread underground heat • $1 billion should be invested in EGS technology © 2011 Pearson Education, Inc.
Heat pumps • Earth can be used as part of a heat exchange system • Far more abundant than large geothermal power plants • The ground extracts heat in winter and absorbs it in the summer • Eliminates separate heating and air-conditioning systems • A geothermal heat pump (GHP) system: uses loops of buried pipes filled with antifreeze solution • Air is moved through the pump and the house • High costs are offset by being trouble-free and longterm savings © 2011 Pearson Education, Inc.
Geothermal heat pump system © 2011 Pearson Education, Inc.
Tidal and wave power • The twice-daily rise and fall of ocean tides have a phenomenal amount of energy • Tidal barrage: a dam is built across the mouth of a bay • Incoming and outgoing tides turn the turbines • 30 locations have tides high enough for this use • North America has one location: the Bay of Fundy • Adverse environmental impacts • Traps sediments, impedes fish migration, prevents navigation, and changes water circulation patterns © 2011 Pearson Education, Inc.
Ocean waves • It may be possible to harness energy in waves • But the technology is challenging • The ideal location must: • Receive the wave’s force before it hits the sea floor • Be close to shore to hook up with transmission cables • Be deep enough not to crash to the floor during storms • The U. S. ’s Pacific Northwest region qualifies • This technology is still in the early research and development stage © 2011 Pearson Education, Inc.
Ocean thermal-energy conversion (OTEC) • Most oceans have a thermal gradient between warm upper surface water and cool, deep water • OTEC uses this temperature difference to produce power • Warm surface water heats and vaporizes ammonia to drive a turbogenerator • Cool water recondenses the ammonia • There is little interest, due to its low economic promise • Unless it can be coupled with other operations (e. g. , cooling buildings) © 2011 Pearson Education, Inc.
Policies for a sustainable energy future • Global issues are clear: • Oil and gas will not last long • Fossil fuels produce pollution and greenhouse gases • Renewable energy means sustainable energy • Global targets need to stabilize levels of greenhouse gases • They must have a sustainable-energy developmentand-consumption pattern based on renewable energy • Energy conservation and efficiency: focus on consumption by increasing mileage standards and energy efficiency © 2011 Pearson Education, Inc.
National energy policy • The U. S. has a serious oil-transportation problem • $500, 000 leaves the U. S. each minute for imported oil • The U. S. has a serious energy security problem • We are vulnerable to terrorism and whims of others • Policy responses for U. S. energy include • The 2005 Energy Policy Act • The 2007 Energy Independence and Security Act • The 2009 American Recovery and Reinvestment Act • Gave $43 billion to renewable energy and conservation • Intends to double energy from renewables by 2012 © 2011 Pearson Education, Inc.
Supply-side policies for renewables • An RFS for ethanol and biodiesel to 15 billion gallons by 2015, 35 billion gallons by 2022 • Anything over 15 billion gallons must come from second-generation (non-corn) sources • Continue funding for research and development of renewable energy (solar and biomass) • Extend tax credits for electricity from wind, hydropower, geothermal, and biomass • Tax credits for heat pumps, solar heating, biofuels, PV • Enable geothermal energy to compete with fossil fuels © 2011 Pearson Education, Inc.
Demand-side policies • Focus on energy conservation and efficiency • Increase CAFE standards to 39 mpg for cars by 2016 • Extend the Energy Star Program to schools, homes, etc. • Tax credits for increasing energy efficiency in homes • Require 30% increase in lightbulb efficiency • Already met by fluorescent lightbulbs (CFLs) • The EPA will encourage waste-energy recovery • Efficiency standards and tax credits for most appliances • Funding and tax credits for the Freedom. CAR, hybrids, and PHEVs © 2011 Pearson Education, Inc.
Policies can do more • Recent policies did not establish a federal renewable portfolio standard (RPS) • Requiring utilities to provide increasing power from nonhydroelectric renewable energy sources • 16 states have set their own RPS • 10– 20% renewable energy by 2010– 2025 • Policies did not take direct action on global warming • But did expand DOE’s research on carbon capture and sequestration • Efficiency and renewable energy will reduce emissions © 2011 Pearson Education, Inc.
Final thoughts • The U. S. is making a serious effort to develop renewable energy sources and increase efficiency • We are also trying to move to a hydrogen economy • Current policy also promotes further use and development of fossil fuels • U. S. oil prices have been extremely low • Rising prices make consumers buy efficient or hybrid cars • A carbon tax levied on fuels based on their carbon emissions would encourage non-taxed renewable energies © 2011 Pearson Education, Inc.
CHAPTER 16 Renewable Energy Active Lecture Questions © 2011 Pearson Education, Inc.
Review Question-1 In 2001, the Environmental Protection Agency extended its ______ program to buildings and began awarding its label to energy-efficient buildings. a. solar power b. building collector c. Earth-sheltered d. Energy Star © 2011 Pearson Education, Inc.
Review Question-1 Answer In 2001, the Environmental Protection Agency extended its ______ program to buildings and began awarding its label to energy-efficient buildings. a. solar power b. building collector c. Earth-sheltered d. Energy Star © 2011 Pearson Education, Inc.
Review Question-2 The inverter on a photovoltaic cell must change the incoming ______ current from the photovoltaic cell to ______ current compatible with the electricity coming from the grid. a. direct; indirect b. direct; alternating c. alternating; direct d. indirect; direct © 2011 Pearson Education, Inc.
Review Question-2 Answer The inverter on a photovoltaic cell must change the incoming ______ current from the photovoltaic cell to ______ current compatible with the electricity coming from the grid. a. direct; indirect b. direct; alternating c. alternating; direct d. indirect; direct © 2011 Pearson Education, Inc.
Review Question-3 Which of the following are considered disadvantages of building and using dams? a. The reservoir created drowns the area behind the dam. b. Dams can displace large populations of humans. c. Dams can impede the migration of some fish. d. all of the above © 2011 Pearson Education, Inc.
Review Question-3 Answer Which of the following are considered disadvantages of building and using dams? a. The reservoir created drowns the area behind the dam. b. Dams can displace large populations of humans. c. Dams can impede the migration of some fish. d. all of the above © 2011 Pearson Education, Inc.
Review Question-4 All of the following are forms of biomass energy except a. burning firewood. b. burning animal wastes. c. producing methane. d. harnessing the wind. © 2011 Pearson Education, Inc.
Review Question-4 Answer All of the following are forms of biomass energy except a. burning firewood. b. burning animal wastes. c. producing methane. d. harnessing the wind. © 2011 Pearson Education, Inc.
Review Question-5 ______ are devices in which hydrogen or some other fuel is chemically recombined with oxygen in a matter that produces an electrical potential rather than initiating burning. a. Hybrid engines b. Fuel cells c. Electrolysis cells d. Photovoltaic cells © 2011 Pearson Education, Inc.
Review Question-5 Answer ______ are devices in which hydrogen or some other fuel is chemically recombined with oxygen in a matter that produces an electrical potential rather than initiating burning. a. Hybrid engines b. Fuel cells c. Electrolysis cells d. Photovoltaic cells © 2011 Pearson Education, Inc.
Interpreting Graphs and Data-1 According to Fig. 16 -3, which of the following is the greatest source of renewable energy in the United States? a. oil b. biomass energy c. hydropower d. natural gas © 2011 Pearson Education, Inc.
Interpreting Graphs and Data-1 Answer According to Fig. 16 -3, which of the following is the greatest source of renewable energy in the United States? a. oil b. biomass energy c. hydropower d. natural gas © 2011 Pearson Education, Inc.
Interpreting Graphs and Data-2 According to Fig. 16 -18, the cost of wind energy in the United States a. decreased dramatically from 1980 to 2000. b. increased dramatically from 1980 to 2000. c. remained the same between 1980 and 2000. © 2011 Pearson Education, Inc.
Interpreting Graphs and Data-2 Answer According to Fig. 16 -18, the cost of wind energy in the United States a. decreased dramatically from 1980 to 2000. b. increased dramatically from 1980 to 2000. c. remained the same between 1980 and 2000. © 2011 Pearson Education, Inc.
Thinking Environmentally-1 In about 30 locations around the world, tides of 20 feet or more are produced to generate a. geothermal energy. b. tidal and wave power. c. oceanic pumps. d. dams. © 2011 Pearson Education, Inc.
Thinking Environmentally-1 Answer In about 30 locations around the world, tides of 20 feet or more are produced to generate a. geothermal energy. b. tidal and wave power. c. oceanic pumps. d. dams. © 2011 Pearson Education, Inc.
Thinking Environmentally-2 How can hydrogen gas be produced using solar energy? a. with catalysts that allow us to mimic the process of photosynthesis b. by connecting photovoltaic cells to water c. by combining helium and oxygen d. by using solar power to drive hydrogen turbines © 2011 Pearson Education, Inc.
Thinking Environmentally-2 Answer How can hydrogen gas be produced using solar energy? a. with catalysts that allow us to mimic the process of photosynthesis b. by connecting photovoltaic cells to water c. by combining helium and oxygen d. by using solar power to drive hydrogen turbines © 2011 Pearson Education, Inc.
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