1 Monday, May 16, 16

Transcription

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2 Chapter 12 Nonrenewable Energy Resources

3 Nonrenewable Energy Nonrenewable energy resources- fossil fuels (coal, oil, natural gas) and nuclear fuels.

4 U.S. Energy Use 13% 1% 19% 42% 25% Coal Natural Gas Nuclear Renewables Oil 4

5 Arkansas Energy Use 7% 3% 26% 44% 20% Coal Natural Gas Nuclear Hydro Biomass 5

6 Energy Use Commercial energy sources- those that are bought and sold, such as coal, oil and natural gas. Subsistence energy sources- those gathered by individuals for their own use such as wood, charcoal and animal waste.

7 First law of thermodynamics Energy is neither created or destroyed. You can t get something from nothing.

8 Second law of thermodynamics When energy is transformed, the quantity of energy remains the same, but its ability to do work diminishes.

9 Second law of thermodynamics Energy Efficiency- the ratio of the amount of work that is done to the total amount of energy that is introduced into the system.

10 Process of Energy Use

11 Overall Fuel Efficiency of U.S. Automobiles

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13 Electricity Generation

14 Electricity Generation The burning fuel transfers energy to water, which becomes steam. The kinetic energy contained within the steam is transferred to the blades of a turbine, a large device that resembles a fan. As the energy in the steam turns the turbine, the shaft in the center of the turbine turns the generator. This mechanical motion generates electricity.

15 Energy Efficiency Most coal burning power plants are about 35% efficient.

16 Cogeneration Cogeneration- using a fuel to generate electricity and to produce heat. Example- If steam is used for industrial purposes or to heat buildings it is diverted to turn a turbine first. This improves the efficiency to as high as 90%. Combined Cycle - combustion products turn a gas turbine as well as heat water for steam production.

17 Power Plants Capacity - the maximum electrical output per day. Typically reported as megawatts (MW). Capacity factor - the fraction of time a plant is operating. Most operate around 0.9 or 90% of capacity Example: A 500 MW plant with a capacity factor of 0.9 would generate 450 MW per hour on a typical day. 17

18 Coal Coal- a solid fuel formed primarily from the remains of trees, ferns, and other plant materials that were preserved million years ago. Four types of coal ranked from lesser to greater age, exposure to pressure, and energy content. These four types are: lignite, sub-bituminous, bituminous, and anthracite. The largest coal reserves are in the United States, Russia, China, and India.

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20 Advantages and Disadvantages of Coal Energy-dense Plentiful Advantages Easy to exploit by surface mining Technological demands are small Economic costs are low Easy to handle and transport Needs little refining Disadvantages Contains impurities Release impurities into air when burned Trace metals like mercury, lead, and arsenic are found in coal Combustion leads to increased levels of sulfur dioxide and other air pollutants into the Ash is left behind Carbon is released into the atmosphere which contributes to climate change

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22 Petroleum Petroleum- a mixture of hydrocarbons, water, and sulfur that occurs in underground deposits. Oil and gasoline make this ideal for mobile combustion, such as vehicles. Formed from the remains of ocean-dwelling phytoplankton that died million years ago. Countries with the most petroleum are Saudi Arabia, Russia, the United States, Iran, China, Canada, and Mexico.

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25 Advantages and Disadvantages of Petroleum Advantages Convenient to transport and use Relatively energy-dense Cleaner-burning than coal Releases sulfur, mercury, lead, and arsenic into the atmosphere when burned Disadvantages Releases carbon dioxide into atmosphere Possibility of leaks when extracted and transported

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27 O.P.E.C. Organization of the Petroleum Exporting Countries Members: Algeria, Angola, Ecuador, Indonesia, Iran, Iraq, Kuwait, Libya, Nigeria, Qatar, Saudi Arabia, United Arab Emirates and Venezuela 40% of worldwide production 73% of proven reserves 27

28 Natural Gas Natural gas- exists as a component of petroleum in the ground as well as in gaseous deposits separate from petroleum. Contains 80 to 95 percent methane and 5 to 20 percent ethane, propane, and butane.

29 Advantages and Disadvantages Natural Gas Advantages Contains fewer impurities and therefore emits almost no sulfur dioxide or particulates Emits only 60% as much carbon dioxide as coal Disadvantages When unburned, methane escapes into the atmosphere Exploration of natural gas has the potential of contaminating groundwater

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31 Other Fossil Fuels Oil sands- slow-flowing, viscous deposits of bitumen mixed with sand, water, and clay. Bitumen (tar or pitch)- a degraded type of petroleum that forms when a petroleum migrates close to the surface, where bacteria metabolize some of the light hydrocarbons and others evaporate.

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36 Oils Sands Trade-offs Disadvantages Low net energy yield Releases CO 2 Severe land disruption High water use Advantages Large potential supply Easily moved from country to country Distribution system in place (oil pipelines) 36

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38 The Hubbert Curve Hubbert curve- a graph that shows the point at which world oil production would reach a maximum and the point at which we would run out of oil.

39 The Future of Fossil Fuel Use If current global use continues, we will run out of conventional oil in less than 40 years. Coal supplies will last for at least 200 years, and probably much longer.

40 Nuclear Energy Fission- a nuclear reaction in which a neutron strikes a relatively large atomic nucleus, which then splits into two or more parts.

41 Nuclear Reactors

42 Nuclear Reactors Fuel rods- the cylindrical tubes that house the nuclear fuel used in a nuclear power plant. Nuclear power plants work by using heat from nuclear fission to heat water. This water produces the steam to turn the turbine, which turns a generator. Control rods- cylindrical devices that can be inserted between the fuel rods to absorb excess neutrons, thus slowing or stopping the fission reaction.

43 Advantages and Disadvantages of Nuclear Energy Advantages Disadvantages No air pollution is produced Possibility of accidents Countries can limit their need for imported oil Disposal of the radioactive waste

44 Radioactive Waste Radioactive waste- once the nuclear fuel can not produce enough heat to be used in a power plant but it continues to emit radioactivity. This waste must be stored in special, highly secure locations because of the danger to living organisms.

45 Radioactive Waste High-level radioactive waste- the form used in fuel rods. Low-level radioactive waste- the protective clothing, tools, rags, and other items used in routine plant maintenance.

46 Yucca Mountain Located in Nevada Was to be the worlds first large scale, high-level waste storage facility. Late 70 s and early 80 s - studies of the area and project approval funds run out, facility is never completed 46

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48 Accidents Three Mile Island, Pennsylvania Partial melt-down, due to human error No deaths Chernobyl, Ukraine During a test, no coolant and no control rods Against safety regulations 31 deaths, ~ 4,000 additional deaths (cancer) Fukushima, Japan Failure of back-up cooling systems No immediate deaths, potentially 1000 s in future due to cancer 48

49 Fusion Nuclear fusion- the reaction that powers the Sun and other stars. This occurs when lighter nuclei are forced together to produce heavier nuclei and heat is released. Fusion is a promising, unlimited source of energy in the future, but so far scientists have had difficulty containing the heat that is produced.