This chapter discusses various energy sources and their pros and cons. It begins by outlining learning outcomes related to dominant energy sources, issues around peak oil production, the importance and environmental effects of coal, how nuclear reactors work, renewable energy sources, and debates around biofuels. Key sources discussed include fossil fuels (oil, gas, coal), nuclear power, wind and solar energy, water power, and biofuels. Challenges and potentials around each source are summarized.

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2. Learning Outcomes After studying this chapter, you should be able to answer the following questions: • What are our dominant sources of energy? • What is peak oil production? Why is it hard to evaluate future oil production? • How important is coal in domestic energy production? • What are the environmental effects of coal burning? Is clean coal possible? • How do nuclear reactors work? What are some of their advantages and disadvantages? • What are our main renewable forms of energy? • Could solar, wind, hydropower, and other renewables eliminate the need for fossil fuels? • What are photovoltaic cells, and how do they work? • What are biofuels? What are arguments for and against their use? 12-

3. We are not only responsible for what we do, but also for what we do not do. –Moliere 12-

4. 12.1 Energy Resources and Uses Throughout Denmark, the state has subsidized wind power research, so that now Danes are world leaders in this fast-growing industry. 12-

5. How do we measure energy? 12-

6. Fossil fuels supply most of our energy Fossil fuels (petroleum, natural gas, and coal) now provide about 87 percent of all commercial energy in the world. Renewable sources — solar, wind, geothermal, and hydroelectricity—make up about 7 percent of our commercial power (but hydro accounts for almost all of that). 12-

7. 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. Oil supplies over 40 percent of U.S. energy demands and over 99 percent of fuel for cars and trucks, according to the U.S. Department of Energy (fig. 12.4). Coal-fired power plants supply most of our electrical energy. 12-

8. Coal resources are vast World coal deposits are vast, ten times greater than conventional oil and gas resources combined, and one-quarter of global coal deposits are in the United States (fig. 12.5). But coal mining is a dirty, dangerous activity . 12-

9. New plants can be clean 12-

10. Have we passed peak oil? We have already used more than 0.5 trillion bbl—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. 12-

11. 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. Nuclear power now amounts to about 8 percent of U.S. energy supply (1 percent more than the world average). Half of the U.S. plants (52) are more than 30 years old and are thus approaching the end of their expected operational life. 12-

12. 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. 12-

13. 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. 12-

14. 12.4 Energy Conservation Much of the energy we consume is wasted. U.S. automobile gas mileage averages more than doubled from 13 mpg in 1975 to 28.8 mpg in 1988. Unfortunately, the oil glut and falling fuel prices of the 1990s discouraged further conservation. By 2004 the average slipped to only 20.4 mpg. 12-

15. 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. 12-

16. Green building can cut energy costs by half 12-

17. 12.5 Energy from Biomass Firewood is our original source of fuel. Biofuels, ethanol and biodiesel, are by far the biggest recent news in biomass energy. In the United States, both farm policies and energy policies have promoted biofuel crops. Small amounts of ethanol have been added to gasoline for years, because oxygen-rich ethanol molecules help gasoline burn (oxidize) more completely. 12-

18. 12.6 Wind and Solar Energy 12-

19. Wind energy is our fastest growing renewable It is estimated that wind could produce about 50 times the total capacity of all nuclear power plants now in operation. Wind farms are large concentrations of wind generators producing commercial electricity. 12-

20. Solar energy is diffuse but abundant Passive solar absorption has been updated in modern homes with massive, heat-absorbing floors and walls, or with glass-walled “sun spaces” on the south side of a building. Active solar systems generally pump a heat-absorbing fluid medium through a relatively small collector, rather than passively collecting heat in a stationary medium, such as masonry. Photovoltaic cells capture solar energy and convert it directly to electrical current. 12-

21. 12.7 Water Power The invention of water turbines in the nineteenth century greatly increased the efficiency of hydropower dams (fig. 12.31). By 1925 falling water generated 40 percent of the world’s electric power. Fossil fuel use has risen so rapidly that water power is now only one-quarter of total electrical generation. Ocean tides and waves contain enormous amounts of energy that can be harnessed to do useful work. 12-

22. Geothermal heat, tides, and waves could supply substantial amounts of energy in some places 12-

23. 12.8 Fuel Cells Fuel cells are devices that use ongoing electrochemical reactions to produce an electrical current. 12-

24. 12.9 What Is Our Energy Future? 12-

25. Practice Quiz 1. Where are Samsø and Ærø islands, and how do they supply their 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. Who is the leading supplier of oil to the United States? 6. What are proven-in-place reserves? 7. How much coal do we have, and how long will it last? 8. Why don’t we want to use all the coal in the ground? 9. Where is most liquid oil located? How long are supplies likely to last? 10. What are tar sands and oil shales? What are the environmental costs of their extraction? 11. Why is natural gas considered to be a superior fuel to either coal or oil? 12. How are nuclear wastes now being stored? 13. Explain active and passive solar energy. 14. How do photovoltaic cells work? 15. What’s a fuel cell, and how does it work ? 16. What are biofuels, and how could they contribute to sustainability? 12-