1. Net energy yield is an important factor in evaluating energy resources, as it accounts for the energy needed to extract and produce the resource.
2. While fossil fuels like oil, natural gas, and coal are plentiful, they have high environmental impacts, especially coal which is a major contributor to air pollution and carbon emissions.
3. Nuclear power has low carbon emissions but produces long-lived radioactive waste and has high costs, low net energy yield, and safety concerns that have limited its expansion.
3. 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
4. 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
• Net energy ratio: ratio of energy produced to energy
used to produce it
• Conventional oil: high net energy ratio
7. 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
8. 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
9. 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
10. 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
12. 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%
13. 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
15. Crude Oil in the Arctic National Wildlife
Refuge
Fig. 15-5, p. 376
16. 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
20. Bird Covered with Oil from an Oil Spill
in Brazilian Waters
Fig. 15-7, p. 377
21. 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?
23. 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
24. Oil Shale Rock and the Shale Oil Extracted
from It
Fig. 15-9, p. 379
25. Natural Gas Is a Useful and Clean-Burning
Fossil Fuel
• Natural gas: mixture of gases
• 50-90% is methane -- CH4
• Conventional natural gas
• Sits above oil
27. 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
30. 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
31. 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
32. Air Pollution from a Coal-Burning Industrial
Plant in India
Fig. 15-16, p. 383
33. CO2 Emissions Per Unit of Electrical Energy
Produced for Energy Sources
Fig. 15-17, p. 383
34. World Coal and Natural Gas Consumption,
1950-2009
Figure 7, Supplement 9
35. Coal Consumption in China and the United
States, 1980-2008
Figure 8, Supplement 9
38. 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
39. How Does a Nuclear Fission
Reactor Work? (1)
• Controlled nuclear fission reaction in a reactor
• Very inefficient
• Fueled by uranium ore and packed as pellets in fuel
rods and fuel assemblies
• Control rods absorb neutrons
40. 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
42. 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
45. 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
47. 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
49. 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
50. What Do We Do with Worn-Out Nuclear
Power Plants?
• Decommission or retire the power plant
• Some options
1. Dismantle the plant and safely store the radioactive materials
2. Enclose the plant behind a physical barrier with full-time
security until a storage facility has been built
3. Enclose the plant in a tomb
• Monitor this for thousands of years
51. Can Nuclear Power Lessen Dependence on
Imported Oil & Reduce Global Warming?
• Nuclear power plants: no CO2 emission
• Nuclear fuel cycle: emits CO2
• Need high rate of building new plants, plus a storage
facility for radioactive wastes
52. Will Nuclear Fusion Save Us?
• “Nuclear fusion
• 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
54. 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
• Opponents of nuclear power
• Fund rapid development of energy efficient and renewable
energy resources
55. 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.
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.
Editor's Notes
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 )
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.
Figure 15.3: S cience. 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, 198 1)
Figure 15.4: S cience. 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 .
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 Counc il)
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?
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.
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.
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.
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 CO 2 , soot, and other air pollutants to the atmosphere. Question: Can you think of an alternative to burning off this 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?
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.
Figure 15.16: This coal-burning industrial plant in India produces large amounts of air pollution because i t has inadequate air pollution controls.
Figure 15.17: CO 2 emissions, expressed as percentages of emissions released by burning coal directly, vary with different energy resources. Question: Which produces more CO 2 emissions per kilogram, burning coal to heat a house or heating with electricity generated by coal? (Data from U.S. Department of Energy )
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?
Figure 2.9: There are three types of nuclear changes: natural radioactive decay (top), nuclear fission (middle), and nuclear fusion (bottom).
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.
Figure 15.24: S cience. 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?
Figure 2.9: There are three types of nuclear changes: natural radioactive decay (top), nuclear fission (middle), and nuclear fusion (bottom).