Botkin Environmental Science Earth as Living Planet 8th txtbk

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292 CHAPTER 14 Energy: Some Basics Table 14.2 APPLIANCE POWER USE OF TYPICAL HOUSEHOLD APPLIANCES IN WATTS (W) POWER (W) Clock 2 Coffee maker 900–1200 Clothes washer 350–500 Clothes dryer 1800–5000 Dishwasher 1200–2400 (using the drying feature greatly increases energy consumption) Electric blanket - Single/Double 60/100 Fans Ceiling 65–175 Window 55–250 Furnace 750 Whole house 240–750 Hair dryer 1200–1875 Heater ( portable) 750–1500 Clothes iron 1000–1800 Microwave oven 750–1100 Personal computer CPU - awake/asleep 120/30 or less Monitor - awake/asleep 150/30 or less Laptop 50 Radio (stereo) 70–400 Refrigerator (frost-free, 16 cubic feet) 725 Televisions (color) 19” 65–110 36” = 133 W 53”–61” Projection 170 Flat screen 120 Toaster 800–1400 Toaster oven 1225 VCR/DVD 17–21/20–25 Vacuum cleaner 1000–1440 Water heater (40 gallon) 4500–5500 Water pump (deep well) 250–1100 Water bed (with heater, no cover) 120–380 *You can use this formula below to estimate an appliance’s energy use: Wattage Hours Used Per Day 1000 Daily Kilowatt-hour (kWh) consumption: remember 1kW = 1,000 watts, which is why we divide by 1,000 Multiply by the number of days you use a particular appliance during the year for the annual energy consumption. You can calculate the annual cost to run an appliance by multiplying the kWh per year by your local utility’s rate per kWh consumed. Example: Personal Computer and Monitor: (120 150 Watts 4 hours/day 365 days/year) 1000 394 kWh 11 cents/kWh (approx national average) $43.34/year *Note: To estimate the number of hours that a refrigerator actually operates at its maximum wattage, divide the total time the refrigerator is plugged in by three. Refrigerators, although turned “on” all the time, cycle on and off as needed to maintain interior temperatures. Source: Modified from U.S. Department of Energy. Your Home. accessed January 27, 2010 at http://www.energysavers.gov
14.4 Energy Sources and Consumption 293 We are now in a position to understand why the secondlaw efficiency is so low (5%) for the house-heating example discussed earlier. This low efficiency implies that the furnace is consuming too much high-quality energy in carrying out the task of heating the house. In other words, the task of heating the house requires heat at a relatively low temperature, near 18°C (65°F), not heat with temperatures in excess of 1,000°C (1,832°F), such as is generated inside the gas furnace. Lower-quality energy, such as solar energy, could do the task and yield a higher second-law efficiency because there is a better match between the required energy quality and the house-heating end use. Through better energy planning, such as matching the quality of energy supplies to the end use, higher second-law efficiencies can be achieved, resulting in substantial savings of high-quality energy. Examination of Table 14.1 indicates that electricitygenerating plants have nearly the same first-law and second-law efficiencies. These generating plants are examples of heat engines. A heat engine produces work from heat. Most of the electricity generated in the world today comes from heat engines that use nuclear fuel, coal, gas, or other fuels. Our own bodies are examples of heat engines, operating with a capacity (power) of about 100 watts and fueled indirectly by solar energy. (See A Closer Look 14.1 for an explanation of watts and other units of energy.) The internal combustion engine (used in automobiles) and the steam engine are additional examples of heat engines. A great deal of the world’s energy is used in heat engines, with profound environmental effects, such as thermal pollution, urban smog, acid rain, and global warming. The maximum possible efficiency of a heat engine, known as thermal efficiency, was discovered by the French engineer Sadi Carnot in 1824, before the first law of thermodynamics was formulated. 5 Modern heat engines have thermal efficiencies that range between 60 and 80% of their ideal Carnot efficiencies. Modern 1,000-megawatt (MW) electrical generating plants have thermal efficiencies ranging between 30 and 40%; that means at least 60–70% of the energy input to the plant is rejected as waste heat. For example, assume that the electric power output from a large generating plant is 1 unit of power (typically 1,000 MW). Producing that 1 unit of power requires 3 units of input (such as burning coal) at the power plant, and the entire process produces 2 units of waste heat, for a thermal efficiency of 33%. The significant number here is the waste heat, 2 units, which amounts to twice the actual electric power produced. Electricity may be produced by large power plants that burn coal or natural gas, by plants that use nuclear fuel, or by smaller producers, such as geothermal, solar, or wind sources (see Chapters 15, 16, and 17). Once produced, the electricity is fed into the grid, which is the network of power lines, or the distribution system. Eventually it reaches homes, shops, farms, and factories, where it provides light and heat and also drives motors and other machinery used by society. As electricity moves through the grid, losses take place. The wires that transport electricity (power lines) have a natural resistance to electrical flow. Known as electrical resistivity, this resistance converts some of the electric energy in the transmission lines to heat energy, which is radiated into the environment surrounding the lines. 14.4 Energy Sources and Consumption People living in industrialized countries make up a relatively small percentage of the world’s population but consume a disproportionate share of the total energy consumed in the world. For example, the United States, with only 5% of the world’s population, uses approximately 20% of the total energy consumed in the world. There is a direct relationship between a country’s standard of living (as measured by gross national product) and energy consumption per capita. After the peak in oil production, expected in 2020– 2050, oil and gasoline will be in shorter supply and more expensive. Before then, use of these fuels may be curtailed in an effort to lessen global climate change. As a result, within the next 30 years both developed and developing countries will need to find innovative ways to obtain energy. In the future, affluence may be related as closely to more efficient use of a wider variety of energy sources as it is now to total energy consumption. Fossil Fuels and Alternative Energy Sources Today, approximately 90% of the energy consumed in the United States is derived from petroleum, natural gas, and coal. Because they originated from plant and animal material that existed millions of years ago, they are called fossil fuels. They are forms of stored solar energy that are part of our geologic resource base, and they are essentially nonrenewable. Other sources of energy—geothermal, nuclear, hydropower, and solar, among others—are referred to as alternative energy sources because they may serve as alternatives to fossil fuels in the future. Some of them, such as solar and wind, are not depleted by consumption and are known as renewable energy sources. The shift to alternative energy sources may be gradual as fossil fuels continue to be used, or it could be accelerated by concern about potential environmental effects of burning fossil fuels. Regardless of which path we take, one thing is certain: Fossil fuels are finite. It took millions of years to form them, but they will be depleted in only a few hundred years of human history. Using even the most optimistic predictions, the fossil fuel epoch that started with the Industrial Revolution will represent only about 500 years of human history. Therefore, although fossil fuels have been extremely significant in the development of modern civilization, their use will be a brief event in the span of human history. 6, 7
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ENVIRONMENTAL SCIENCE Earth as a Li
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VICE PRESIDENT AND EXECUTIVE PUBLIS
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About the Authors Daniel B. Botkin
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Preface vii Themes Our book is base
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Preface ix Updated Critical Thinkin
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Acknowledgments Reviewers of This E
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Acknowledgments xiii Karen Swanson,
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Contents Chapter 1 Key Themes in En
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xviii Contents Summary 125 Reexamin
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xx Contents Chapter 13 Wildlife, Fi
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xxii Contents CRITICAL THINKING ISS
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xxiv Contents Availability and Use
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2 CHAPTER 1 Key Themes in Environme
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10 CHAPTER 1 Key Themes in Environm
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over 4 million in 1950. In 1999 Tok
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CHAPTER 2 Science as a Way of Knowi
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24 CHAPTER 2 Science as a Way of Kn
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42 CHAPTER 3 The Big Picture: Syste
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CHAPTER 5 Ecosystems: Concepts and
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82 CHAPTER 5 Ecosystems: Concepts a
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100 CHAPTER 5 Ecosystems: Concepts
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102 CHAPTER 5 Ecosystems: Concepts
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CHAPTER 6 The Biogeochemical Cycles
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106 CHAPTER 6 The Biogeochemical Cy
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128 CHAPTER 7 Dollars and Environme
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144 CHAPTER 8 Biological Diversity
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170 CHAPTER 9 Ecological Restoratio
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186 CHAPTER 10 Environmental Health
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212 CHAPTER 11 Agriculture, Aquacul
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236 CHAPTER 12 Landscapes: Forests,
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342 CHAPTER 16 Alternative Energy a
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344 CHAPTER 16 Alternative Energy a
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346 CHAPTER 17 Nuclear Energy and t
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CHAPTER 18 Water Supply, Use, and M
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370 CHAPTER 18 Water Supply, Use, a
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CHAPTER 19 Water Pollution and Trea
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400 CHAPTER 19 Water Pollution and
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CHAPTER 20 The Atmosphere, Climate,
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430 CHAPTER 20 The Atmosphere, Clim
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462 CHAPTER 21 Air Pollution CASE S
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464 CHAPTER 21 Air Pollution
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466 CHAPTER 21 Air Pollution Table
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470 CHAPTER 21 Air Pollution Air po
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472 CHAPTER 21 Air Pollution Mercur
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474 CHAPTER 21 Air Pollution (a) FI
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478 CHAPTER 21 Air Pollution The ga
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490 CHAPTER 21 Air Pollution chimn
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494 CHAPTER 21 Air Pollution SUMMAR
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496 CHAPTER 21 Air Pollution STUDY
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498 CHAPTER 22 Urban Environments C
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500 CHAPTER 22 Urban Environments I
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502 CHAPTER 22 Urban Environments o
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504 CHAPTER 22 Urban Environments K
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506 CHAPTER 22 Urban Environments 2
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508 CHAPTER 22 Urban Environments A
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510 CHAPTER 22 Urban Environments F
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512 CHAPTER 22 Urban Environments F
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518 CHAPTER 22 Urban Environments S
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520 CHAPTER 23 Materials Management
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552 CHAPTER 24 Our Environmental Fu
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Appendix A Special Feature: Electro
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Appendix A-3 VOLUME in 3 ft 3 yd 3
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Appendix A-5 Basic Chemistry
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Photo Credits CHAPTER 1 Ch Op 1: Im
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Glossary Abortion rate The estimate
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Glossary G-3 deposition of crustal
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Glossary G-5 high and the growth ra
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Glossary G-7 environmental impacts
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Glossary G-9 per unit time and some
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Glossary G-11 cooler than it is tod
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Glossary G-13 Nonpoint sources Poll
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Glossary G-15 Positive feedback A t
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Glossary G-17 Shelterwood cutting A
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Glossary G-19 Time series The set o
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Index Entries followed by an f may
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INDEX I-3 Sweetwater Marsh National
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INDEX I-5 dune succession, 96, 96f
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INDEX I-7 Colorado River, 114, 115f
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INDEX I-9 Lovelock, James, 10, 108
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INDEX I-11 Pelagic ecosystem, 85, 8
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INDEX I-13 Static systems, 44, 44f
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INDEX I-15 Watts, 291, 292t Weather
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N-2 NOTES 7. Schmidt, W.E. 1991 (Se
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N-4 NOTES 4. Christian, D. 2004. Ma
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N-6 NOTES 9. Collins, S.L., A.K. Kn
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N-8 NOTES 8. U.S. Department of Agr
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N-10 NOTES 19. O’Donnell, James J
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N-12 NOTES 19. Piore, 2002 (April 1
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N-14 NOTES application of secondary
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N-16 NOTES 22. Foukal, P., C. Frohl
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N-18 NOTES 54. Zummo, S.M., and M.H
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N-20 NOTES 38. Bullard, R.D. 1990.
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