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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chapter 12 Energy
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Chapter 12
Energy
We are not only responsible for what we do, but also for what we do not do.
–Moliere
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CASE STUDY: Renewable Energy in China
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12.1 Energy Resources and Uses
• Currently, fossil fuels (petroleum, natural gas, and coal) supply about 88% of the world’s commercial energy needs.
• The U.S. spends about $400 billion every year on imported oil.
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How Do We Measure Energy?
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Fossil Fuels Supply Most of Our Energy
• Like most other industrialized nations, the U.S. gets a vast majority of its energy from fossil fuels.
• 20 richest countries consume 80% of natural gas, 65% of the oil, and 50% of the coal.
• Renewables make up only 7% of U.S. power.
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How Do We Use Energy?
• The largest share of the energy used in the U.S. is consumed by industry.
• Residential and commercial customers use roughly 41%.
• Transportation consumes the remaining 28%
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12.2 Fossil Fuels
• Fossil fuels are organic (carbon-based) compounds derived from decomposed plants, algae, and other organisms buried in rock layers for hundreds of millions of years.
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Coal Resources Are Vast• World coal deposits are vast, ten times greater than
conventional oil and gas resources combined.
• The total resource is estimated to be 10 trillion metric tons. If all this coal could be extracted, this would amount to several thousand years’ supply.
• But coal mining is a dirty, dangerous activity. Underground mines are notorious for cave-ins, explosions, and lung diseases, such as black-lung suffered by miners. Surface mines leave huge holes where coal has been removed and vast piles of discarded rock and soil.
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Mountain Top Removal in Appalachia
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Coal Burning Releases Huge Amounts of Air Pollution
• Every year the roughly one billion tons of coal burned in the U.S. releases close to a trillion metric tons of carbon dioxide (CO2). This is about half of the industrial CO2 released by the United States each year.
• Coal also contains toxic impurities, such as mercury, arsenic, chromium, and lead, which are released into the air during combustion.
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New Plants Could Be Cleaner
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Have We Passed Peak Oil?
• We have already used more than half of all the oil estimated on the planet. almost half of proven oil reserves.
• Competition has already raised oil prices, from around $15 per barrel in 1993 to more than $150 per barrel in 2008.
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Domestic Oil Supplies are Limited• The U.S. has used more than half of its
technically recoverable petroleum resources.
• At 2010 rates of consumption, that’s enough for about 4.2 years, if we were to stop all imports. Opening the Arctic National Wildlife Refuge to drilling would only add enough for another 4–10 months, according to the U.S.G.S.
• Other U.S. regions with potential for new oil discoveries include the continental shelf on the coast of California, the Arctic Ocean, and the Grand Banks.
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Oil Shales and Tar Sands ContainHuge Amounts of Petroleum
• The World Energy Council estimates that oil shales, tar sands, and other unconventional deposits contain ten times as much oil as liquid petroleum reserves.
• However, this costly, energy-intensive extraction only becomes economically justified when oil prices rise above about $50 per barrel.
• There are severe environmental costs, though. A typical plant creates about 15 million m3 of toxic sludge, releases 5,000 tons of greenhouse gases, and consumes billions of liters of water each year.
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Natural Gas is the World’s Third Largest Commercial Fuel
• The total ultimately recoverable natural gas resources in the world are estimated to be 10,000 trillion ft3. Current gas reserves represent roughly a 60-year supply at present usage rates.
• Because natural gas produces only half as much CO2
as an equivalent amount of coal, substitution could help reduce global warming.
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Special Refrigerated Ships TransportLiquefied Natural Gas (LNG)
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12.3 Nuclear Power
• In 1953 President Dwight Eisenhower presented his “Atoms for Peace” speech to the United Nations.
• He announced that the United States would build nuclear-powered electrical generators to provide clean, abundant energy.
• Today there are about 440 reactors in use worldwide, 104 of these in the United States.
• Half of the U.S. plants (52) are more than 30 years old and are thus approaching the end of their expected operational life.
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Nuclear Reactors in Southern California
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How Do Nuclear Reactors Work?
• Radioactive uranium atoms are unstable—that is, when struck by a high-energy subatomic particle called a neutron, they undergo nuclear fission (splitting), releasing energy and more neutrons.
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Pressurized Water Nuclear Reactor
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We Lack Safe Storage for Radioactive Waste
• One of the most difficult problems associated with nuclear power is the disposal of wastes produced during mining, fuel production, and reactor operation.
• How these wastes are managed may ultimately be the overriding obstacle to nuclear power.
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We Lack Safe Storage for Radioactive Waste
• In 1987 the U.S. Department of Energy announced plans to build the first high-level waste repository on a barren desert ridge under Yucca Mountain, Nevada.
• President Obama cut off funding for the project in 2009 after 20 years of research and $100 billion in exploratory drilling and development.
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12.4 Energy Conservation
• Our ways of using energy are so inefficient that most potential energy in fuel is lost as waste heat.
• Conservation involves technology innovation as well as changes in behavior, but we have met these challenges in the past.
• In 2010, however, the Obama administration mandated an average fleet fuel efficiency of 35.5 mpg (14.6 km/l) for cars and light trucks by 2016.
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Per Capita Energy Consumption in the U.S. Since the 1950s
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What Can You Do?Steps to Save Energy and Money
1. Live close to work and school, or near transit routes, so you can minimize driving.
2. Ride a bicycle, walk, and use stairs instead of elevators.
3. Keep your thermostat low in winter and high in summer. Fans are cheaper to run than air conditioners.
4. Buy fewer disposable items; producing and shipping them costs energy.
5. Turn off lights, televisions, computers, and other appliances when not needed.
6. Line-dry your laundry.
7. Recycle.
8. Cut back on meat consumption; if every American ate 20 percent less meat, we would save as much energy as if everyone used a hybrid car.
9. Buy some of your food locally, to reduce energy in shipping.
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Green Building Can Cut Energy Costs by Half
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12.5 Energy From Biomass
• Firewood is our original source of fuel. For more than a billion people in developing countries, burning biomass remains the principal energy source for heating and cooking.
• In developed countries, where we depend on fossil fuels for most energy, wood burning is a minor heat source.
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A Charcoal Market in Ghana
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Power Generation from Wood Chips
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Ethanol and Biodiesel canContribute to Fuel Supplies
• Biofuels, ethanol and biodiesel, are by far the biggest recent news in biomass energy.
• Globally, production of these two fuels is booming, from Brazil to Southeast Asia to the U.S. and Europe.
• Small amounts of ethanol have been added to gasoline for years, but it takes about 3 to 5 liters of water for every liter of fuel produced.
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Effects on Food and Environment are Uncertain
• Will biofuel production affect food costs? Yes, but the seriousness of the problem depends on where you look.
• In developing countries, more than 50% of household income may be spent on food. Higher costs of cooking oil and grain can be devastating for family budgets.
• In Indonesia, conversion to oil palm plantations has become an important threat to primary rainforest habitat.
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12.6 Wind and Solar Energy
• In China’s efforts to reduce dependence on fossil fuel imports, wind power has been the principal focus.
• Relative to other alternative sources, wind is cheap and available almost everywhere.
• Wind turbines have a small footprint, so they don’t displace farming and other land uses.
• How people feel about a wind farm depends on their views about energy alternatives, whether it earns money for their community, and which particular view is obstructed by the turbines.
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U.S. Wind Resources by Region
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Wind Energy is Our Fastest Growing Renewable
• U.S. is the world leader of installed wind generating capacity.
• Wind farms are large concentrations of wind generators producing commercial electricity.
• The key to making wind energy successful is reliable energy storage technology, so we can grab it when it is available and release it when it is needed. 12-35
Solar Energy is Abundant• The Sun is a giant nuclear furnace in space,
constantly bathing our planet with a free energy supply.
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Passive Solar Absorbs Heat;Active Solar Pumps Heated Fluids
• Passive Solar uses thick adobe or stone walls to absorb daytime heat and release it gradually at night.
• Active solar pumps a heat-absorbing fluid medium through a relatively small collector and then transfers the heat to create hot water or heat the air in the home.
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Concentrating Solar Energy Generates Electricity
• Solar thermal energy can also be used to generate electricity.
• Concentrating trough systems use long rows of parabolic mirrors to heat a transfer fluid to temperatures as high as 400°C.
• The hot liquid is pumped to a central plant, where it heats water to produce steam that spins a turbine to produce electricity.
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Solar Thermal Electric Plant in California Desert
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Solar Thermal Electric Plant Using Heliostats
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Photovoltaic Cells Generate Electricity Directly
• Photovoltaic cells capture solar energy and convert it directly to electrical current
• Over the past 25 years, the efficiency of energy captured by photovoltaic cells has increased from less than 1% of incident light to more than 10%.
• New Amorphous silicon collectors can be made into lightweight, paper-thin sheets that require much less material than traditional crystalline silicon pv cells.
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How a Photovoltaic Cell Operates
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12.7 Water Power
• Much of the hydropower development since the 1930s has focused on enormous dams because of their efficiency of size.
• Water power is only one-quarter of total electrical generation.
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Environmental Issues
• Flooding of large tracts of land
• Dams block the migration of fish, such as salmon
• Sediment trapping
• Conversion of river ecosystems to lakes
• Increased loss of water to evaporation
Unconventional HydropowerComes from Tides and Waves
• Ocean tides and waves also contain enormous amounts of energy that can be harnessed to do useful work.
• A tidal station works like a hydropower dam, with its turbines spinning as the tide flows through them. A high-tide/low-tide differential of several meters is required to spin the turbines.
• Unfortunately, variable tidal periods often cause problems in integrating this energy source into the electric utility grid. 12-45
The Pelamis Wave-Power Generator Now inOperation Off the Coast of Portugal
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Geothermal Heat Could Supply Substantial Amounts of Energy
• The Earth’s internal temperature can provide a useful source of energy in some places.
• This geothermal energy is expressed in the form of hot springs, geysers, and fumaroles.
• Iceland, which sits on a midoceanridge, has abundant geothermal energy.
• Iceland has ambitious plans to be the first carbon-neutral country, largely because the Earth’s heat provides steam for heat and electric energy.
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Geothermal Heat Pumps Can Heat and Cool Efficiently
• While few places have geothermal steam, the Earth’s stable subsurface temperatures can help reduce energy costs nearly everywhere.
• Pumping fluids through deeply buried pipes can exchange temperatures with the soil to efficiently heat or cool a home.
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12.8 Fuel Cells
• Fuel cells are devices that use ongoing electrochemical reactions to produce an electrical current.
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Fuel Cells in Long Island, NY
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Utilities are Promoting Renewable Energy
• Utility restructuring currently being planned in the U.S. could include policies to encourage conservation and alternative energy sources. Among the proposed policies are:
– (1) “distributional surcharges” in which a small tax is levied on all utility customers to help finance renewable energy.
– (2) “renewables portfolio” standards to require power suppliers to obtain a minimum percentage of their energy from sustainable sources.
– (3) green pricing that allows utilities to charge premium prices for energy from renewable sources.
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Potential Renewable Energy Mix for a Typical Day in California
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Practice Quiz
1. Where is Rizhao, and how does it supply its energy needs?
2. Define energy, power, and kilowatt-hour (kWh).
3. What are the major sources of global commercial energy?
4. How does energy consumption in the United States compare to that in other countries?
5. Why don’t we want to use all the coal in the ground?
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Practice Quiz
6. Where is most liquid oil located? How long are supplies likely to last?
7. What are tar sands and oil shales? What are the environmental costs of their extraction?
8. How are nuclear wastes now being stored?
9. Explain active and passive solar energy.
10.How do photovoltaic cells work?
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