Chapter 15 Nonrenewable Energy

Case Study: A Brief History of Human Energy Use Everything runs on energy Industrial revolution began 275 years ago, relied on wood, which led to deforestation Coal Petroleum products Natural gas All of these are nonrenewable energy resources

Energy Use: World and United States Figure 15.1: We get most of our energy by burning carbon-containing fossil fuels (see Figure 2-14, p. 46). This figure shows energy use by source throughout the world (left) and in the United States (right) in 2008. Note that oil is the most widely use form of commercial energy and that about 79% of the energy used in the world (85% of the energy used the United States) comes from burning nonrenewable fossil fuels. (These figures also include rough estimates of energy from biomass that is collected and used by individuals without being sold in the marketplace.) Question: Why do you think the world as a whole relies more on renewable energy than the United States does? (Data from U.S. Department of Energy, British Petroleum, Worldwatch Institute, and International Energy Agency) Fig. 15-1, p. 370

Nuclear power 6% Geothermal, solar, wind 1% Hydropower 3% Natural gas 21% RENEWABLE 15% Biomass 11% Coal 24% Figure 15.1: We get most of our energy by burning carbon-containing fossil fuels (see Figure 2-14, p. 46). This figure shows energy use by source throughout the world (left) and in the United States (right) in 2008. Note that oil is the most widely use form of commercial energy and that about 79% of the energy used in the world (85% of the energy used the United States) comes from burning nonrenewable fossil fuels. (These figures also include rough estimates of energy from biomass that is collected and used by individuals without being sold in the marketplace.) Question: Why do you think the world as a whole relies more on renewable energy than the United States does? (Data from U.S. Department of Energy, British Petroleum, Worldwatch Institute, and International Energy Agency) Oil 34% NONRENEWABLE 85% World Fig. 15-1, p. 370

Nuclear power 8% Geothermal, solar, wind 1% Hydropower, 3% Natural gas 23% RENEWABLE 7% Coal 22% Biomass 3% Figure 15.1: We get most of our energy by burning carbon-containing fossil fuels (see Figure 2-14, p. 46). This figure shows energy use by source throughout the world (left) and in the United States (right) in 2008. Note that oil is the most widely use form of commercial energy and that about 79% of the energy used in the world (85% of the energy used the United States) comes from burning nonrenewable fossil fuels. (These figures also include rough estimates of energy from biomass that is collected and used by individuals without being sold in the marketplace.) Question: Why do you think the world as a whole relies more on renewable energy than the United States does? (Data from U.S. Department of Energy, British Petroleum, Worldwatch Institute, and International Energy Agency) Oil 40% NONRENEWABLE 93% United States Fig. 15-1, p. 370

15-1 What is Net Energy and Why Is It Important? Concept 15-1 Net energy is the amount of high-quality energy available from an energy resource minus the amount of energy needed to make it available.

Basic Science: Net Energy Is the Only Energy That Really Counts (1) First law of thermodynamics: It takes high-quality energy to get high-quality energy Pumping oil from ground, refining it, transporting it Second law of thermodynamics Some high-quality energy is wasted at every step

Basic Science: Net Energy Is the Only Energy That Really Counts (2) Total amount of useful energy available from a resource minus the energy needed to make the energy available to consumers Business net profit: total money taken in minus all expenses Net energy ratio: ratio of energy produced to energy used to produce it Conventional oil: high net energy ratio

It Takes Energy to Pump Petroleum Figure 15.2: We can pump oil up from underground reservoirs on land (left) and under the sea bottom (right). Today, high-tech equipment can tap into an oil deposit on land and at sea to a depth of almost 11 kilometers (7 miles). But this requires a huge amount of high-quality energy and can cost billions of dollars per well. For example, the well that tapped into BP’s Thunder Horse oil field in the Gulf of Mexico at water depths of up to 1.8 kilometers (1.1 miles) took almost 20 years to complete and cost more than $5 billion. And as we saw in 2010 with the explosion of a BP deep-sea oil-drilling rig such as that shown here, there is a lot of room for improvement in deep-sea drilling technology. Fig. 15-2, p. 372

Net Energy Ratios Figure 15.3: Science. Net energy ratios for various energy systems over their estimated lifetimes differ widely: the higher the net energy ratio, the greater the net energy available (Concept 15-1). Question: Based on these data, which two resources in each category should we be using? (Data from U.S. Department of Energy; U.S. Department of Agriculture; Colorado Energy Research Institute, Net Energy Analysis, 1976; and Howard T. Odum and Elisabeth C. Odum, Energy Basis for Man and Nature, 3rd ed., New York: McGraw-Hill, 1981) Fig. 15-3, p. 373

Electric heating (coal-fired plant) 0.4 Space Heating Passive solar 5.8 Natural gas 4.9 Oil 4.5 Active solar 1.9 Coal gasification 1.5 Electric heating (coal-fired plant) Figure 15.3: Science. Net energy ratios for various energy systems over their estimated lifetimes differ widely: the higher the net energy ratio, the greater the net energy available (Concept 15-1). Question: Based on these data, which two resources in each category should we be using? (Data from U.S. Department of Energy; U.S. Department of Agriculture; Colorado Energy Research Institute, Net Energy Analysis, 1976; and Howard T. Odum and Elisabeth C. Odum, Energy Basis for Man and Nature, 3rd ed., New York: McGraw-Hill, 1981) 0.4 Electric heating (natural-gas-fired plant) 0.4 Electric heating (nuclear plant) 0.3 Fig. 15-3a, p. 373

High-Temperature Industrial Heat 28.2 Surface-mined coal Underground- mined coal 25.8 Natural gas 4.9 Oil 4.7 Figure 15.3: Science. Net energy ratios for various energy systems over their estimated lifetimes differ widely: the higher the net energy ratio, the greater the net energy available (Concept 15-1). Question: Based on these data, which two resources in each category should we be using? (Data from U.S. Department of Energy; U.S. Department of Agriculture; Colorado Energy Research Institute, Net Energy Analysis, 1976; and Howard T. Odum and Elisabeth C. Odum, Energy Basis for Man and Nature, 3rd ed., New York: McGraw-Hill, 1981) Coal gasification 1.5 Direct solar (concentrated) 0.9 Fig. 15-3b, p. 373

Transportation Natural gas 4.9 Gasoline (refined crude oil) 4.1 Biofuel (ethanol) 1.9 Coal liquefaction Figure 15.3: Science. Net energy ratios for various energy systems over their estimated lifetimes differ widely: the higher the net energy ratio, the greater the net energy available (Concept 15-1). Question: Based on these data, which two resources in each category should we be using? (Data from U.S. Department of Energy; U.S. Department of Agriculture; Colorado Energy Research Institute, Net Energy Analysis, 1976; and Howard T. Odum and Elisabeth C. Odum, Energy Basis for Man and Nature, 3rd ed., New York: McGraw-Hill, 1981) 1.4 Oil shale 1.2 Fig. 15-3c, p. 373

Energy Resources With Low/Negative Net Energy Yields Need Marketplace Help Cannot compete in open markets with alternatives that have higher net energy yields Need subsidies from taxpayers Nuclear power as an example

Reducing Energy Waste Improves Net Energy Yields and Can Save Money 84% of all commercial energy used in the U.S. is wasted 43% after accounting for second law of thermodynamics Drive efficient cars, not gas guzzlers Make buildings energy efficient

15-2 What Are the Advantages and Disadvantages of Oil? Concept 15-2A Conventional oil is currently abundant, has a high net energy yield, and is relatively inexpensive, but using it causes air and water pollution and releases greenhouse gases to the atmosphere. Concept 15-2B Heavy oils from tar sand and oil shale exist in potentially large supplies but have low net energy yields and higher environmental impacts than conventional oil has.

We Depend Heavily on Oil (1) Petroleum, or crude oil: conventional, or light oil Fossil fuels: crude oil and natural gas Peak production: time after which production from a well declines Global peak production for all world oil

We Depend Heavily on Oil (2) Oil extraction and refining By boiling point temperature Petrochemicals: Products of oil distillation Raw materials for industrial organic chemicals Pesticides Paints Plastics

Science: Refining Crude Oil Figure 15.4: Science. When crude oil is refined, many of its components are removed at various levels, depending on their boiling points, of a giant distillation column (left) that can be as tall as a nine-story building. The most volatile components with the lowest boiling points are removed at the top of the column. The photo above shows an oil refinery in the U.S. state of Texas. Fig. 15-4, p. 375

Lowest Boiling Point Gases Gasoline Aviation fuel Heating oil Diesel oil Naphtha Figure 15.4: Science. When crude oil is refined, many of its components are removed at various levels, depending on their boiling points, of a giant distillation column (left) that can be as tall as a nine-story building. The most volatile components with the lowest boiling points are removed at the top of the column. The photo above shows an oil refinery in the U.S. state of Texas. Grease and wax Heated crude oil Asphalt Furnace Highest Boiling Point Fig. 15-4a, p. 375

How Long Might Supplies of Conventional Crude Oil Last? (1) Rapid increase since 1950 Largest consumers in 2009 United States, 23% China, 8% Japan, 6%

How Long Might Supplies of Conventional Crude Oil Last? (2) Proven oil reserves Identified deposits that can be extracted profitably with current technology Unproven reserves Probable reserves: 50% chance of recovery Possible reserves: 10-40% chance of recovery Proven and unproven reserves will be 80% depleted sometime between 2050 and 2100

World Oil Consumption, 1950-2009 Figure 1, Supplement 2

History of the Age of Conventional Oil Figure 9, Supplement 9

OPEC Controls Most of the World’s Oil Supplies (1) 13 countries have at least 60% of the world’s crude oil reserves Saudi Arabia: 20% United States: 1.5% Global oil production leveled off in 2005 Oil production peaks and flow rates to consumers

OPEC Controls Most of the World’s Oil Supplies (2) Three caveats when evaluating future oil supplies Potential reserves are not proven reserves Must use net energy yield to evaluate potential of any oil deposit Must take into account high global use of oil

Crude Oil in the Arctic National Wildlife Refuge Figure 15.5: The amount of crude oil that might be found in the Arctic National Wildlife Refuge (right), if developed and extracted over 50 years, is only a tiny fraction of projected U.S. oil consumption. In 2008, the DOE projected that developing this oil supply would take 10–20 years and would lower gasoline prices at the pump by 6 cents per gallon at most. (Data from U.S. Department of Energy, U.S. Geological Survey, and Natural Resources Defense Council) Fig. 15-5, p. 376

Barrels of oil per year (billions) 14 13 12 11 10 Projected U. S. oil consumption 9 8 7 Barrels of oil per year (billions) 6 5 4 Figure 15.5: The amount of crude oil that might be found in the Arctic National Wildlife Refuge (right), if developed and extracted over 50 years, is only a tiny fraction of projected U.S. oil consumption. In 2008, the DOE projected that developing this oil supply would take 10–20 years and would lower gasoline prices at the pump by 6 cents per gallon at most. (Data from U.S. Department of Energy, U.S. Geological Survey, and Natural Resources Defense Council) 3 Arctic refuge oil output over 50 years 2 1 2000 2010 2020 2030 2040 2050 Year Fig. 15-5a, p. 376

The United States Uses Much More Oil Than It Produces Produces 9% of the world’s oil and uses 23% of world’s oil 1.5% of world’s proven oil reserves Imports 52% of its oil Should we look for more oil reserves? Extremely difficult Expensive and financially risky

U.S. Energy Consumption by Fuel Figure 6, Supplement 9

Proven and Unproven Reserves of Fossil Fuels in North America Figure 18, Supplement 8

Conventional Oil Has Advantages and Disadvantages Extraction, processing, and burning of nonrenewable oil and other fossil fuels Advantages Disadvantages

Trade-Offs: Conventional Oil Figure 15.6: Using crude oil as an energy resource has advantages and disadvantages (Concept 15-2a). Questions: Which single advantage and which single disadvantage do you think are the most important? Why? Fig. 15-6, p. 377

Trade-Offs Conventional Oil Advantages Disadvantages Ample supply for several decades Water pollution from oil spills and leaks Environmental costs not included in market price High net energy yield but decreasing Releases CO 2 and other air pollutants when burned Figure 15.6: Using crude oil as an energy resource has advantages and disadvantages (Concept 15-2a). Questions: Which single advantage and which single disadvantage do you think are the most important? Why? Low land disruption Efficient distribution system Vulnerable to international supply interruptions Fig. 15-6, p. 377

Bird Covered with Oil from an Oil Spill in Brazilian Waters Figure 15.7: This bird was covered with oil from an oil spill in Brazilian waters. If volunteers had not removed the oil, it would have destroyed this bird’s natural buoyancy and heat insulation, causing it to drown or die from exposure because of a loss of body heat. Fig. 15-7, p. 377

Case Study: Heavy Oil from Tar Sand Oil sand, tar sand contains bitumen Canada and Venezuela: oil sands have more oil than in Saudi Arabia Extraction Serious environmental impact before strip-mining Low net energy yield: Is it cost effective?

Strip Mining for Tar Sands in Alberta Figure 15.8: Producing heavy oil from Canada’s Alberta tar sands project involves strip-mining areas large enough to be seen from outer space, draining wetlands, and diverting rivers. It also produces huge amounts of air and water pollution and has been called the world’s most environmentally destructive project. For oil from the sands to be profitable, oil must sell for $70–90 a barrel. Fig. 15-8, p. 378

Will Heavy Oil from Oil Shales Be a Useful Resource? Oil shales contain kerogen After distillation: shale oil 72% of the world’s reserve is in arid areas of western United States Locked up in rock Lack of water needed for extraction and processing Low net energy yield

Oil Shale Rock and the Shale Oil Extracted from It Figure 15.9: Shale oil (right) can be extracted from oil shale rock (left). However, producing shale oil requires large amounts of water and has a low net energy yield and a very high environmental impact. Fig. 15-9, p. 379

Trade-Offs: Heavy Oils from Oil Shale and Oil Sand Figure 15.10: Using heavy oil from tar sands and oil shales as an energy resource has advantages and disadvantages (Concept 15-2b). Questions: Which single advantage and which single disadvantage do you think are the most important? Why? Fig. 15-10, p. 379

Heavy Oils from Oil Shale and Tar Sand Trade-Offs Heavy Oils from Oil Shale and Tar Sand Advantages Disadvantages Large potential supplies Low net energy yield Easily transported within and between countries Releases CO 2 and other air pollutants when produced and burned Figure 15.10: Using heavy oil from tar sands and oil shales as an energy resource has advantages and disadvantages (Concept 15-2b). Questions: Which single advantage and which single disadvantage do you think are the most important? Why? Efficient distribution system in place Severe land disruption and high water use Fig. 15-10, p. 379

15-3 What Are the Advantages and Disadvantages of Using Natural Gas? Concept 15-3 Conventional natural gas is more plentiful than oil, has a high net energy yield and a fairly low cost, and has the lowest environmental impact of all fossil fuels.

Natural Gas Is a Useful and Clean-Burning Fossil Fuel Natural gas: mixture of gases 50-90% is methane -- CH4 Conventional natural gas Pipelines Liquefied petroleum gas (LPG) Liquefied natural gas (LNG) Low net energy yield Makes U.S. dependent upon unstable countries like Russia and Iran

Natural Gas Burned Off at Deep Sea Oil Well Figure 15.11: Natural gas found above a deep sea oil well deposit or in a remote land area is usually burned off (flared) because no pipeline is available to collect and transmit the gas to users. This practice wastes this energy resource and adds climate-changing CO2, soot, and other air pollutants to the atmosphere. Question: Can you think of an alternative to burning off this gas? Fig. 15-11, p. 380

Is Unconventional Natural Gas the Answer? Coal bed methane gas In coal beds near the earth’s surface In shale beds High environmental impacts or extraction Methane hydrate Trapped in icy water In permafrost environments On ocean floor Costs of extraction currently too high

Trade-Offs: Conventional Natural Gas Figure 15.12: Using conventional natural gas as an energy resource has advantages and disadvantages (Concept 15-3). Questions: Which single advantage and which single disadvantage do you think are the most important? Why? Do you think that the advantages of using conventional natural gas outweigh its disadvantages? Fig. 15-12, p. 381

Conventional Natural Gas Trade-Offs Conventional Natural Gas Advantages Disadvantages Low net energy yield for LNG Ample supplies Releases CO2 and other air pollutants when burned High net energy yield Emits less CO2 and other pollutants than other fossil fuels Difficult and costly to transport from one country to another Figure 15.12: Using conventional natural gas as an energy resource has advantages and disadvantages (Concept 15-3). Questions: Which single advantage and which single disadvantage do you think are the most important? Why? Do you think that the advantages of using conventional natural gas outweigh its disadvantages? Fig. 15-12, p. 381

Methane Hydrate Figure 15.13: Gas hydrates are crystalline solids that can be burned as shown here. They form naturally from the reaction of various gases (commonly methane) with water at low temperatures and under high pressures. Natural gas hydrates form extensively in permafrost and in sediments just under the sea floors around all of the world’s continents. Methane hydrates, shown here, are a potentially good fuel. Fig. 15-13, p. 381

15-4 What Are the Advantages and Disadvantages of Coal? Concept 15-4A Conventional coal is plentiful and has a high net energy yield and low cost, but it has a very high environmental impact. Concept 15-4B Gaseous and liquid fuels produced from coal could be plentiful, but they have lower net energy yields and higher environmental impacts than conventional coal has.

Coal Is a Plentiful but Dirty Fuel (1) Coal: solid fossil fuel Burned in power plants; generates 42% of the world’s electricity Inefficient Three largest coal-burning countries China United States Canada

Coal Is a Plentiful but Dirty Fuel (2) World’s most abundant fossil fuel U.S. has 28% of proven reserves Environmental costs of burning coal Severe air pollution Sulfur released as SO2 Large amount of soot CO2 Trace amounts of Hg and radioactive materials

Stages in Coal Formation over Millions of Years Figure 15.14: Over millions of years, several different types of coal have formed. Peat is a soil material made of moist, partially decomposed organic matter and is not classified as a coal, although it too is used as a fuel. The different major types of coal vary in the amounts of heat, carbon dioxide, and sulfur dioxide released per unit of mass when they are burned. Fig. 15-14, p. 382

Bituminous (soft coal) Anthracite (hard coal) Increasing heat and carbon content Increasing moisture content Peat (not a coal) Lignite (brown coal) Bituminous (soft coal) Anthracite (hard coal) Heat Heat Heat Pressure Pressure Pressure Partially decayed plant matter in swamps and bogs; low heat content Low heat content; low sulfur content; limited supplies in most areas Extensively used as a fuel because of its high heat content and large supplies; normally has a high sulfur content Highly desirable fuel because of its high heat content and low sulfur content; supplies are limited in most areas Figure 15.14: Over millions of years, several different types of coal have formed. Peat is a soil material made of moist, partially decomposed organic matter and is not classified as a coal, although it too is used as a fuel. The different major types of coal vary in the amounts of heat, carbon dioxide, and sulfur dioxide released per unit of mass when they are burned. Fig. 15-14, p. 382

Increasing moisture content Increasing heat and carbon content Peat (not a coal) Lignite (brown coal) Bituminous (soft coal) Anthracite (hard coal) Heat Pressure Partially decayed plant matter in swamps and bogs; low heat content Low heat content; low sulfur content; limited supplies in most areas Extensively used as a fuel because of its high heat content and large supplies; normally has a high sulfur content Highly desirable fuel because of its high heat content and low sulfur content; supplies are limited in most areas Stepped Art Fig. 15-14, p. 382

Science: Coal-Burning Power Plant Figure 15.15: Science. This power plant burns pulverized coal to boil water and produce steam that spins a turbine to produce electricity. The steam is cooled, condensed, and returned to the boiler for reuse. Waste heat can be transferred to the atmosphere or to a nearby source of water. The largest coal-burning power plant in the United States, located in Indiana, burns three 100-car trainloads of coal per day. There are about 600 coal-burning power plants in the United States. The photo shows a coal-burning power plant in Soto de Ribera, Spain. Question: Does the electricity that you use come from a coal-burning power plant? Fig. 15-15, p. 382

Cooling tower transfers waste heat to atmosphere Coal bunker Turbine Generator Cooling loop Stack Pulverizing mill Condenser Filter Figure 15.15: Science. This power plant burns pulverized coal to boil water and produce steam that spins a turbine to produce electricity. The steam is cooled, condensed, and returned to the boiler for reuse. Waste heat can be transferred to the atmosphere or to a nearby source of water. The largest coal-burning power plant in the United States, located in Indiana, burns three 100-car trainloads of coal per day. There are about 600 coal-burning power plants in the United States. The photo shows a coal-burning power plant in Soto de Ribera, Spain. Question: Does the electricity that you use come from a coal-burning power plant? Boiler Toxic ash disposal Fig. 15-15b, p. 382

Air Pollution from a Coal-Burning Industrial Plant in India Figure 15.16: This coal-burning industrial plant in India produces large amounts of air pollution because it has inadequate air pollution controls. Fig. 15-16, p. 383

CO2 Emissions Per Unit of Electrical Energy Produced for Energy Sources Figure 15.17: CO2 emissions, expressed as percentages of emissions released by burning coal directly, vary with different energy resources. Question: Which produces more CO2 emissions per kilogram, burning coal to heat a house or heating with electricity generated by coal? (Data from U.S. Department of Energy) Fig. 15-17, p. 383

Coal-fired electricity 286% Synthetic oil and gas produced from coal 150% 100% Coal Tar sand 92% Oil 86% Figure 15.17: CO2 emissions, expressed as percentages of emissions released by burning coal directly, vary with different energy resources. Question: Which produces more CO2 emissions per kilogram, burning coal to heat a house or heating with electricity generated by coal? (Data from U.S. Department of Energy) Natural gas 58% Nuclear power fuel cycle 17% Geothermal 10% Fig. 15-17, p. 383

Coal-fired electricity 286% Synthetic oil and gas produced from coal 150% Coal 100% Tar sand 92% Oil 86% Natural gas 58% Nuclear power fuel cycle 17% Geothermal 10% Stepped Art Fig. 15-17, p. 383

World Coal and Natural Gas Consumption, 1950-2009 Figure 7, Supplement 9

Coal Consumption in China and the United States, 1980-2008 Figure 8, Supplement 9

Coal Deposits in the United States Figure 19, Supplement 8

Trade-Offs: Coal Figure 15.18: Using coal as an energy resource has advantages and disadvantages (Concept 15-4a). Questions: Which single advantage and which single disadvantage do you think are the most important? Why? Do you think that the advantages of using coal as an energy resource outweigh its disadvantages? Fig. 15-18, p. 384

Trade-Offs Coal Advantages Disadvantages Ample supplies in many countries Severe land disturbance and water pollution Fine particle and toxic mercury emissions threaten human health High net energy yield Figure 15.18: Using coal as an energy resource has advantages and disadvantages (Concept 15-4a). Questions: Which single advantage and which single disadvantage do you think are the most important? Why? Do you think that the advantages of using coal as an energy resource outweigh its disadvantages? Low cost when environmental costs are not included Emits large amounts of CO2 and other air pollutants when produced and burned Fig. 15-18, p. 384

Case Study: The Problem of Coal Ash Highly toxic Arsenic, cadmium, chromium, lead, mercury Ash left from burning and from emissions Some used as fertilizer by farmers Most is buried or put in ponds Contaminates groundwater Should be classified as hazardous waste

The Clean Coal and Anti-Coal Campaigns Coal companies and energy companies fought Classifying carbon dioxide as a pollutant Classifying coal ash as hazardous waste Air pollution standards for emissions 2008 clean coal campaign But no such thing as clean coal “Coal is the single greatest threat to civilization and all life on the planet.” – James Hansen

We Can Convert Coal into Gaseous and Liquid Fuels Conversion of solid coal to Synthetic natural gas (SNG) by coal gasification Methanol or synthetic gasoline by coal liquefaction Synfuels Are there benefits to using these synthetic fuels?

Trade-Offs: Synthetic Fuels Figure 15.19: The use of synthetic natural gas (SNG) and liquid synfuels produced from coal has advantages and disadvantages (Concept 15-4b). Questions: Which single advantage and which single disadvantage do you think are the most important? Why? Do you think that the advantages of using synfuels produced from coal as an energy source outweigh the disadvantages? Fig. 15-19, p. 385

Trade-Offs Synthetic Fuels Advantages Disadvantages Large potential supply in many countries Low to moderate net energy yield Requires mining 50% more coal with increased land disturbance, water pollution and water use Vehicle fuel Figure 15.19: The use of synthetic natural gas (SNG) and liquid synfuels produced from coal has advantages and disadvantages (Concept 15-4b). Questions: Which single advantage and which single disadvantage do you think are the most important? Why? Do you think that the advantages of using synfuels produced from coal as an energy source outweigh the disadvantages? Lower air pollution than coal Higher CO2 emissions than coal Fig. 15-19, p. 385

15-5 What Are the Advantages and Disadvantages of Nuclear Energy? Concept 15-5 Nuclear power has a low environmental impact and a very low accident risk, but its use has been limited by a low net energy yield, high costs, fear of accidents, long-lived radioactive wastes, and the potential for spreading nuclear weapons technology.

How Does a Nuclear Fission Reactor Work? (1) Controlled nuclear fission reaction in a reactor Light-water reactors Very inefficient Fueled by uranium ore and packed as pellets in fuel rods and fuel assemblies Control rods absorb neutrons

How Does a Nuclear Fission Reactor Work? (2) Water is the usual coolant Containment shell around the core for protection Water-filled pools or dry casks for storage of radioactive spent fuel rod assemblies 73

Water-Cooled Nuclear Power Plant Figure 15.20: Science. This water-cooled nuclear power plant, with a pressurized water reactor, pumps water under high pressure into its core where nuclear fission takes place. It produces huge quantities of heat that is used to convert the water to steam, which spins a turbine that generates electricity. Some nuclear plants withdraw the water they use from a nearby source such as a river and return the heated water to that source, as shown here. Other nuclear plants transfer the waste heat from the intensely hot water to the atmosphere by using one or more gigantic cooling towers, as shown in the inset photo of the Three Mile Island nuclear power plant near Harrisburg, Pennsylvania (USA). There, a serious accident in 1979 almost caused a meltdown of the plant’s reactor. Question: How do you think the heated water returned to a body of water affects that aquatic ecosystem? Fig. 15-20, p. 387

Useful electrical energy Small amounts of radioactive gases Uranium fuel input (reactor core) Control rods Containment shell Waste heat Heat exchanger Steam Turbine Generator Hot coolant Useful electrical energy about 25% Hot water output Pump Pump Coolant Pump Pump Waste heat Figure 15.20: Science. This water-cooled nuclear power plant, with a pressurized water reactor, pumps water under high pressure into its core where nuclear fission takes place. It produces huge quantities of heat that is used to convert the water to steam, which spins a turbine that generates electricity. Some nuclear plants withdraw the water they use from a nearby source such as a river and return the heated water to that source, as shown here. Other nuclear plants transfer the waste heat from the intensely hot water to the atmosphere by using one or more gigantic cooling towers, as shown in the inset photo of the Three Mile Island nuclear power plant near Harrisburg, Pennsylvania (USA). There, a serious accident in 1979 almost caused a meltdown of the plant’s reactor. Question: How do you think the heated water returned to a body of water affects that aquatic ecosystem? Cool water input Moderator Shielding Pressure vessel Coolant passage Water Condenser Periodic removal and storage of radioactive wastes and spent fuel assemblies Periodic removal and storage of radioactive liquid wastes Water source (river, lake, ocean) Fig. 15-20a, p. 387

Fission of Uranium-235 Figure 2.9: There are three types of nuclear changes: natural radioactive decay (top), nuclear fission (middle), and nuclear fusion (bottom). Fig. 2-9b, p. 43

Nuclear fission Uranium-235 Energy Fission fragment n n Neutron n n Figure 2.9: There are three types of nuclear changes: natural radioactive decay (top), nuclear fission (middle), and nuclear fusion (bottom). Radioactive isotope Radioactive decay occurs when nuclei of unstable isotopes spontaneously emit fast-moving chunks of matter (alpha particles or beta particles), high-energy radiation (gamma rays), or both at a fixed rate. A particular radioactive isotope may emit any one or a combination of the three items shown in the diagram. Fig. 2-9b, p. 43

What Is the Nuclear Fuel Cycle? Mine the uranium Process the uranium to make the fuel Use it in the reactor Safely store the radioactive waste Decommission the reactor

Science: The Nuclear Fuel Cycle Figure 15.21: Science. Using nuclear power to produce electricity involves a sequence of steps and technologies that together are called the nuclear fuel cycle. As long as a reactor is operating safely, the power plant itself has a fairly low environmental impact and a very low risk of an accident. But considering the entire nuclear fuel cycle, the financial costs are high and the environmental impact and other risks increase. Radioactive wastes must be stored safely for thousands of years, several points in the cycle are vulnerable to terrorist attack, and the technology used in the cycle can also be used to produce uranium in a form that can be used in nuclear weapons (Concept 15-5). All in all, an amount of energy equal to about 92% of the energy content of the nuclear fuel is wasted in the nuclear fuel cycle. As a result, electricity produced by this fuel cycle has such a low net energy yield that it cannot compete in the open marketplace with energy alternatives that have higher net energy yields, unless it is supported by huge government subsidies. Question: Do you think the market price of nuclear-generated electricity should include all the costs of the nuclear fuel cycle or should governments (taxpayers) continue to subsidize nuclear power? Explain. Fig. 15-21, p. 388

Spent fuel reprocessing Decommissioning of reactor Fuel assemblies Reactor Enrichment of UF6 Fuel fabrication (conversion of enriched UF 6 to UO2 and fabrication of fuel assemblies) Temporary storage of spent fuel assemblies underwater or in dry casks Conversion of U3O8 to UF6 Uranium-235 as UF6 Plutonium-239 as PuO2 Spent fuel reprocessing Low-level radiation with long half-life Figure 15.21: Science. Using nuclear power to produce electricity involves a sequence of steps and technologies that together are called the nuclear fuel cycle. As long as a reactor is operating safely, the power plant itself has a fairly low environmental impact and a very low risk of an accident. But considering the entire nuclear fuel cycle, the financial costs are high and the environmental impact and other risks increase. Radioactive wastes must be stored safely for thousands of years, several points in the cycle are vulnerable to terrorist attack, and the technology used in the cycle can also be used to produce uranium in a form that can be used in nuclear weapons (Concept 15-5). All in all, an amount of energy equal to about 92% of the energy content of the nuclear fuel is wasted in the nuclear fuel cycle. As a result, electricity produced by this fuel cycle has such a low net energy yield that it cannot compete in the open marketplace with energy alternatives that have higher net energy yields, unless it is supported by huge government subsidies. Question: Do you think the market price of nuclear-generated electricity should include all the costs of the nuclear fuel cycle or should governments (taxpayers) continue to subsidize nuclear power? Explain. Geologic disposal of moderate- and high-level radioactive wastes Mining uranium ore (U3O8) Open fuel cycle today Recycling of nuclear fuel Fig. 15-21, p. 388

What Happened to Nuclear Power? Slowest-growing energy source and expected to decline more Why? Economics Poor management Low net yield of energy of the nuclear fuel cycle Safety concerns Need for greater government subsidies Concerns of transporting uranium

Global Energy Capacity of Nuclear Power Plants Figure 10, Supplement 9

Nuclear Power Plants in the United States Figure 21, Supplement 8

Case Study: Chernobyl: The World’s Worst Nuclear Power Plant Accident April 26, 1986 In Chernobyl, Ukraine Series of explosions caused the roof of a reactor building to blow off Partial meltdown and fire for 10 days Huge radioactive cloud spread over many countries and eventually the world 350,000 people left their homes Effects on human health, water supply, and agriculture

Nuclear Power Has Advantages and Disadvantages

Trade-Offs: Conventional Nuclear Fuel Cycle Figure 15.22: Using the nuclear power fuel cycle (Figure 15-21) to produce electricity has advantages and disadvantages (Concept 15-5). Questions: Which single advantage and which single disadvantage do you think are the most important? Why? Do you think that the advantages of using the conventional nuclear power fuel cycle to produce electricity outweigh its disadvantages? Explain. Fig. 15-22, p. 389

Conventional Nuclear Fuel Cycle Trade-Offs Conventional Nuclear Fuel Cycle Advantages Disadvantages Low environmental impact (without accidents) Very low net energy yield and high overall cost Produces long-lived, harmful radioactive wastes Emits 1/6 as much CO2 as coal Figure 15.22: Using the nuclear power fuel cycle (Figure 15-21) to produce electricity has advantages and disadvantages (Concept 15-5). Questions: Which single advantage and which single disadvantage do you think are the most important? Why? Do you think that the advantages of using the conventional nuclear power fuel cycle to produce electricity outweigh its disadvantages? Explain. Low risk of accidents in modern plants Promotes spread of nuclear weapons Fig. 15-22, p. 389

Trade-Offs: Coal versus Nuclear to Produce Electricity Figure 15.23: The risks of using nuclear power, compared with the risks of using coal-burning plants to produce electricity. A 1,000-megawatt nuclear plant is refueled once a year, whereas a coal plant of the same size requires 80 rail cars of coal a day. Question: If you had to choose, would you rather live near a coal-fired power plant or a nuclear power plant? Explain. Fig. 15-23, p. 389

Trade-Offs Coal vs. Nuclear High net energy yield Very low net energy yield Very high emissions of CO2 and other air pollutants Low emissions of CO2 and other air pollutants High land disruption from surface mining Much lower land disruption from surface mining Figure 15.23: The risks of using nuclear power, compared with the risks of using coal-burning plants to produce electricity. A 1,000-megawatt nuclear plant is refueled once a year, whereas a coal plant of the same size requires 80 rail cars of coal a day. Question: If you had to choose, would you rather live near a coal-fired power plant or a nuclear power plant? Explain. Low cost when environmental costs are not included High cost (even with huge subsidies) Fig. 15-23, p. 389

Storing Spent Radioactive Fuel Rods Presents Risks Rods must be replaced every 3-4 years Cooled in water-filled pools Placed in dry casks Must be stored for thousands of years Vulnerable to terrorist attack

Dealing with Spent Fuel Rods Figure 15.24: Science. After 3 or 4 years in a reactor, spent fuel rods are removed and stored in a deep pool of water contained in a steel-lined concrete basin (left) for cooling. After about 5 years of cooling, the fuel rods can be stored upright on concrete pads (right) in sealed dry-storage casks made of heat-resistant metal alloys and concrete. Questions: Would you be willing to live within a block or two of these casks or have them transported through the area where you live in the event that they were transferred to a long-term storage site? Explain. What are the alternatives? Fig. 15-24, p. 390

Dealing with Radioactive Wastes Produced by Nuclear Power Is a Difficult Problem High-level radioactive wastes Must be stored safely for 10,000–240,000 years Where to store it Deep burial: safest and cheapest option Would any method of burial last long enough? There is still no facility Shooting it into space is too dangerous

Case Study: High-Level Radioactive Wastes in the United States 1985: plans in the U.S. to build a repository for high-level radioactive wastes in the Yucca Mountain desert region (Nevada) Problems Cost: $96 billion Large number of shipments to the site: protection from attack? Rock fractures Earthquake zone Decrease national security

What Do We Do with Worn-Out Nuclear Power Plants? Decommission or retire the power plant Some options Dismantle the plant and safely store the radioactive materials Enclose the plant behind a physical barrier with full-time security until a storage facility has been built Enclose the plant in a tomb Monitor this for thousands of years

Can Nuclear Power Lessen Dependence on Imported Oil & Reduce Global Warming? Nuclear power plants: no CO2 emission Nuclear fuel cycle: emits CO2 Opposing views on nuclear power Nuclear power advocates 2007: Oxford Research Group Need high rate of building new plants, plus a storage facility for radioactive wastes

Are New Generation Nuclear Reactors the Answer? Advanced light-water reactors (ALWR) Built-in passive safety features Thorium-based reactors Cheaper and safer But much research and development needed

Solutions: New Generation Nuclear Reactors Figure 15.25: Some critics of nuclear power say that any new generation of nuclear power plants should meet all of these five criteria. So far, no existing or proposed reactors even come close to doing so. Fig. 15-25, p. 393

Will Nuclear Fusion Save Us? Fuse lighter elements into heavier elements No risk of meltdown or large radioactivity release Still in the laboratory phase after 50 years of research and $34 billion dollars 2006: U.S., China, Russia, Japan, South Korea, and European Union Will build a large-scale experimental nuclear fusion reactor by 2018

Nuclear Fusion Figure 2.9: There are three types of nuclear changes: natural radioactive decay (top), nuclear fission (middle), and nuclear fusion (bottom). Fig. 2-9c, p. 43

Nuclear fusion occurs when two isotopes of light elements, such Reaction conditions Fuel Products Proton Neutron Helium-4 nucleus Hydrogen-2 (deuterium nucleus) 100 million °C Energy Figure 2.9: There are three types of nuclear changes: natural radioactive decay (top), nuclear fission (middle), and nuclear fusion (bottom). Hydrogen-3 (tritium nucleus) Neutron Nuclear fusion occurs when two isotopes of light elements, such as hydrogen, are forced together at extremely high temperatures until they fuse to form a heavier nucleus and release a tremendous amount of energy. Fig. 2-9c, p. 43

Experts Disagree about the Future of Nuclear Power Proponents of nuclear power Fund more research and development Pilot-plant testing of potentially cheaper and safer reactors Test breeder fission and nuclear fusion Opponents of nuclear power Fund rapid development of energy efficient and renewable energy resources

Three Big Ideas A key factor to consider in evaluating the usefulness of any energy resource is its net energy yield. Conventional oil, natural gas, and coal are plentiful and have moderate to high net energy yields, but using any fossil fuel, especially coal, has a high environmental impact.

Three Big Ideas Nuclear power has a low environmental impact and a very low accident risk, but high costs, a low net energy yield, long-lived radioactive wastes, and the potential for spreading nuclear weapons technology have limited its use.