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Chapter 15: Nonrenewable Energy
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)
• Net energy • 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
Net Energy Ratios
Fig. 15-3, p. 373
• What are the pros and cons of using natural gas as a “bridge fuel”?• Explain at least three of each.
• How is much of the natural gas in the U.S. being extracted today?• What is that?
Summaries (Index Cards)
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.
Science: Refining “Sweet” Crude Oil
Fig. 15-4, p. 375
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
OPEC Controls Most of theWorld’s Oil Supplies (1)
• In accordance with its Statute, the mission of the Organization of the Petroleum Exporting Countries (OPEC) is to coordinate and unify the petroleum policies of its Member Countries and ensure the stabilization of oil markets in order to secure an efficient, economic and regular supply of petroleum to consumers, a steady income to producers and a fair return on capital for those investing in the petroleum industry.
• 12 countries have at least 60% of the world’s crudeoil reserves:• Saudi Arabia: 20%• United States: 1.5%
Crude Oil in theArctic National Wildlife Refuge (ANWR)
Fig. 15-5, p. 376
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
BP Oil Spill in Gulf of Mexico, 2010
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
Fig. 15-8, p. 378
Will Heavy Oil from Oil ShalesBe 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
Fig. 15-9, p. 379
Trade-Offs: Heavy Oils fromOil Shale and Oil Sand
Fig. 15-10, p. 379
• Define bitumen.• Why is the Keystone XL pipeline an issue? (And what is the issue?)• What are the pros/cons of constructing the Keystone XL pipeline?• How do oil sands compare to “sweet”/light crude oil in terms of
greenhouse gas emissions? Why the difference?• Carbon pollution in U.S., as %:
• Electric power plants• Vehicle emissions• Other
• If Keystone XL were approved, what would be net result for global carbon emissions?
• President Obama’s stance?
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.
• Using articles from last night on fracking, argue that we must continue to extract natural gas using this method (and why), and assure environmentalists that their three main concerns with fracking (what are they?) can be addressed.
Trade-Offs: Conventional Natural Gas
Fig. 15-12, 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, though percentage of plants using coal has reduced dramatically:• 2005: 50%• 2012: 34%
• 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
• Some released as acid rain• Large amount of soot• CO2
• Trace amounts of Hg and radioactive materials
Stages in Coal Formation over Millions of Years
Fig. 15-14, p. 382
Types of Coal
• Different types of coal resulted from differences in the pressure and temperature that prevailed during formation.
• The softest coal (about 50% carbon), which also has the lowest energy output, is called lignite. Lignite has the highest water content (about 50%) and relatively low amounts of smog-causing sulfur.
• With increasing temperature and pressure, lignite is transformed into bituminous coal (about 85% carbon and 3% water).
• Anthracite (almost 100% carbon) is the hardest coal and also produces the greatest energy when burned. Less than 1% of the coal found in the United States is anthracite.
• Most of the coal found in the United States is bituminous. Unfortunately, bituminous coal has the highest sulfur content of all the coal types. When the coal is burned, the pollutant sulfur dioxide is released into the atmosphere.
Science: Coal-Burning Power Plant
Fig. 15-15, p. 382
Coal Deposits in the United States
Figure 19, Supplement 8
Trade-Offs: Coal
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
Questions: What is coal ash, and why is it such a concern?
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
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.
Nuclear Energy Institute
Bottom Line: Energy Institute (U.K.)
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
Nuclear Accidents/Near-Accidents
• Chernobyl; Three Mile Island; Fukushima• Quick research, from reliable sources:• When and where?• What happened?• Short-term effects?• Long-term effects?• Did this accident/near accident result in
significant changes in the nuclear industry?
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
Fig. 15-20a, p. 387
Small amounts of radioactive gases
Uranium fuel input (reactor core)
Containment shellWaste heat
Control rods
Heat exchanger
Steam Turbine Generator
Hot coolant
Useful electrical energy
about 25%Hot
water output
Coolant
ModeratorCool water input
Waste heat
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)
Fission of Uranium-235
Fig. 2-9b, p. 43
What Is the Nuclear Fuel Cycle?
1. Mine the uranium
2. Process the uranium to make the fuel
3. Use it in the reactor
4. Safely store the radioactive waste
5. Decommission the reactor
Nuclear Power Plants in the United States
Figure 21, Supplement 8
Case Study: Chernobyl: The World’s Worst Nuclear Power Plant Accident
• Chernobyl• 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
Trade-Offs: ConventionalNuclear Fuel Cycle
Fig. 15-22, p. 389
• http://www.ne.anl.gov/jp/fukushima-facts-and-myths.shtml
Trade-Offs: Coal versus Nuclear to Produce Electricity
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
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 options1. Dismantle the plant and safely store the radioactive materials2. Enclose the plant behind a physical barrier with full-time
security until a storage facility has been built3. Enclose the plant in a tomb
• Monitor this for thousands of years
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
1. A key factor to consider in evaluating the usefulness of any energy resource is its net energy yield.
2. 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
3. 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.
