Chapter 12 Nonrenewable Energy Resources

Transcription

1 Chapter 12 Nonrenewable Energy Resources

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

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

4 Process of Energy Use

5 Overall Fuel Efficiency of U.S. Automobiles

6 Per capita energy consumption of selected developed and developing countries

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8 III. Electricity Generation A. The burning fuel from coal transfers energy to water, which becomes steam. B. The kinetic energy contained within the steam is transferred to the blades of a turbine, a large device that resembles a fan. C. As the energy in the steam turns the turbine, the shaft in the center of the turbine turns the generator. D. This mechanical motion generates energy.

9 Electricity Generation

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

11 V. Cogeneration A. Cogeneration- using a fuel to generate electricity and to produce heat. B. Example- If steam is used for industrial purposes or to heat buildings it is diverted to turn a turbine first. C. This improves the efficiency to as high as 90%.

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

13 Coal

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15 Advantages and Disadvantages of Coal Advantages Energy-dense Plentiful 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 atmosphere. Ash is left behind Carbon is released into the atmosphere which contributes to climate change

16 E. Making Coal Cleaner 1. Scrubbers 2. Fluidized Bed Combustion (below) mixes crushed coal with particles of limestone in a strong air current during combustion Lower temp. and fewer nitrogen oxides are produced sulfur reacts with the calcium in the limestone so scrubbers are not needed

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

18 Petroleum

19 E. Petroleum Refining 1. Numerous hydrocarbons present in crude oil (petroleum) are separated Based on boiling point 2. Natural gas contains far fewer hydrocarbons than crude oil Methane, ethane, propane and butane

20 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

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

22 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

23 IX. Other Fossil Fuels A. Oil sands- slow-flowing, viscous deposits of bitumen mixed with sand, water, and clay. B. 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.

24 C. Synfuel Synthesized fuel from coal and other naturally occurring sources Used in place of oil or natural gas Include: Tar sands Oil shales Gas hydrates Liquefied coal Coal gas (right)

25 X. The Hubbert Curve A. 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.

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

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

28 1. Nuclear Fuel Cycle processes involved in producing the fuel used in nuclear reactors and in disposing of radioactive (nuclear) wastes

29 Nuclear Reactors

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31 B. Basic parts of the nuclear power plants water reactors 1. reactor core where fission occurs 2. steam generator heat produced by nuclear fission is used to produce steam from liquid water 3. turbine uses the steam to generate electricity 4. condenser cools the steam and converts it back to a liquid

32 C. Details of the nuclear fission process 1. the reactor core contains the fuel assemblies 2. above each fuel assembly is a control rod made of a special metal alloy that absorbs neutrons 3. the plant operator signals the control rod to move either up out of or down into the fuel assembly if the rod is out of the assembly, then free neutrons collide with uranium atoms in the fuel rods

33 4. Three water circuits a. primary water circuit heats water, using the energy produced by the fission reaction this is a closed system that circulates water under high pressure through the reactor core because of the intense pressure this water cannot expand to become steam so it remains in the liquid state b. secondary water circuit water is held here and heated from the water from the primary water circuit the water in the secondary water circuit is converted to steam which turns the turbine which spins a generator to produce electricity water then goes to a condenser where it becomes a liquid again c. tertiary water circuit provides cool water to the condenser which cools the steam from the secondary water circuit the water from the tertiary water unit must move to a lake or cooling tower where it is cooled before returning to the condenser

34 5. reactor vessel huge steal reactor vessel surrounds the reactor core where fission occurs a safety feature designed to prevent the accidental release of radiation into the environment 6. containment building holds the reactor vessel and the steam generator steel reinforced concrete walls about 1 to 1.5 m thick and are build to withstand severe earthquakes and the high winds of hurricanes and tornadoes additional line of defense against accidental radiation leaks

35 D. Fuel rods- the cylindrical tubes that house the nuclear fuel used in a nuclear power plant. E. 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. F. Control rods- cylindrical devices that can be inserted between the fuel rods to absorb excess neutrons, thus slowing or stopping the fission reaction.

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

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

38 K. Long term solution to waste 1. Deep geologic burial Yucca Mountain 2. As of 2004, site must meet EPA million year standard (compared to previous 10,000 year standard) 3. Possibilities: Above ground mausoleums Arctic ice sheets Beneath ocean floor

39 70,000 tons of highlevel radioactive waste Tectonic issues have been identified

40 L. Temporary storage solutions In nuclear plant facility (require high security) Under water storage Above ground concrete and steel casks M. Need approved permanent options soon.

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

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43 A. Here is how conventional and fast reactors differ. 1. Conventional nuclear reactors bombard atoms of uranium fuel with neutrons. Under this bombardment, the atoms split, creating more neutrons and energy. The neutrons head off to split more atoms, creating a chain reaction. Meanwhile, the energy heats a coolant passing through the reactor, such as water, which then generates electricity in conventional turbines. - The problem is that in this process only around 1 percent of the potential energy in the uranium fuel is turned into electricity. The rest remains locked up in the fuel, much of it in the form of plutonium, the chief by-product of the oncethrough cycle. The idea of fast reactors (breeder reactors) is to grab more of this energy from the spent fuel of the conventional reactor. And it can do this by repeatedly recycling the fuel through the reactor. 2. The second difference is that in a conventional reactor, the speed of the neutrons has to be slowed down to ensure the chain reactions occur. In a typical pressurized-water reactor, the water itself acts as this moderator. But in a fast reactor, as the name suggests, the best results for generating energy from the plutonium fuel are achieved by bombarding the neutrons much faster. This is done by substituting the water moderator with a liquid metal such as sodium.

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46 XIII. Fusion A. 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. B. Fusion is a promising, unlimited source of energy in the future, but so far scientists have had difficulty containing the heat that is produced.

47 A. Objective 1: Increase Energy Efficiency and Conservation Requires many unpopular decisions Examples Decrease speed limit to conserve fuel Eliminate government subsidies B. Objective 2: Secure Future Fossil Fuel Energy Supplies 2 oppositions: environmental and economic

48 C. Objective 3: Develop Alternative Energy Sources Who should pay for this? Gas taxes? D. Objective 4: Meet the First Three Objectives Without Further Damage to the Environment Example 5 cent tax on each barrel of domestically produced oil or ton of domestically produced coal to establish a reclamation fund for some of the environmental damage caused by drilling or mining, production, and refining

49 1989 Alaskan Oil Spill Exxon Valdez hit a reef and spilled 260,000 barrels of crude oil into sound Second largest oil spill in US history Led to Oil Pollution Act of 1990

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52 Gulf Oil Spill April 22, 2010 Worst spill in US History and worst accidental oil spill in the world s history 206 million gallons were released Deepwater Horizon rig had a gas explosion 11 people were killed Oil gushed for 85 days before a cap could be placed on the well - oil covered 572 miles of Gulf shoreline 1.82 million gallons of dispersant were used unknown effects on humans

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59 A Congress declared a section of northeastern Alaska protected because of its distinctive wildlife B Congress expanded this wilderness area to form the Arctic National Wildlife Refuge (ANWR) C. the Department of the Interior was given permission to determine the potential for oil discoveries in this area, but exploration and development could proceed only with congressional approval D s pressure to open the refuge to oil development 1994 the US imported more than 50% of their oil concluded that oil drilling would harm the ecosystem but the Senate and House of Representatives passed measures to allow it but President Clinton vetoed the bill

60 E President George W. Bush announced his support for opening the refuge to drilling but after many debates, the Senate voted against doing so F. still continues to be a debate that plays heavily in Presidential elections G. Pros and Cons Pros economic Cons habitat damage

61 A. Process - After a well is drilled, the casing is perforated, typically with explosive charges. A pad of fluids is then injected, at a sufficient pressure and rate, to fracture the formation surrounding the perforations. The fractured formations are typically located thousands are feet below the water table. Next, producers inject a slurry, which consists of fracking fluids and sand, to extend and develop the fracture.

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65 B. Economic Benefits to Fracking a. Development of a domestic energy resource (reducing foreign influences on price). b. Creation of jobs. c. Financial gains to individuals who lease their property to the natural gas companies.

66 C. Environmental Drawbacks of Fracking a. Habitat fragmentation/destruction can occur from setting up the drilling site or from building roads. b. Earthquakes can result from the drilling/fracking process. c. Methane can leak (into the atmosphere) during the process, resulting in an increase of greenhouse gases. d. Subsidence of the land can occur once fracking fluids are removed. e. Trucks and drilling equipment consume a nonrenewable fuel and release CO2 (greenhouse gases) and, potentially, SOx (which produce acid rain) and NOx (which produce acid rain and photochemical smog). f. Noise pollution is caused by the drilling rigs and by increased truck traffic. g. Soil salinization or heavy metal contamination can result from the spraying of wastewater. h. The drilling site increases the amount of particulate matter in the air.

67 D. Water Related Environmental Problems of Fracking 1. Ground water contamination (a) Fracking liquids or chemicals can contaminate drinking water or groundwater. (b) Liquid waste stored in waste lagoons can leach into groundwater (aquifer). (c) Drilling can allow methane (or natural gas) to seep into groundwater. (d) Leaks from the well casings can contaminate the water with either fracking liquids or flowback liquids. (e) Radioactive isotopes used as tracers in fracking fluids can contaminate groundwater.

68 2. Surface water contamination (a) Brine (or wastewater) sprayed on roadways can run off and contaminate rivers, streams, and lakes. (b) Spills of brine (or wastewater) can contaminate rivers, streams, and lakes. (c) Wastewater disposed of in streams and rivers may contain salts, heavy metals, benzene, and/or other components of fracking liquid.

69 3. Excessive water use or consumption (a) Considerable amounts of water are used in the fracking process. This can result in overdrafts of aquifers. (b) Water demands for the fracking process compete with water demands for drinking or irrigation (agriculture).

70 A most serious reactor accident in US B. 50% meltdown of reactor core Containment building kept radiation from escaping No substantial environmental damage No human casualties C. Elevated public apprehension of nuclear energy Led to cancellation of many new plants in US

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72 A worst accident in history B. 1 or 2 explosions destroyed the nuclear reactor Large amounts of radiation escaped into atmosphere C. Spread across large portions of Europe

73 D. Radiation spread was unpredictable and uneven E. Death toll was around 10,000 but might be higher

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75 1. Following a major earthquake, a 15-metre tsunami disabled the power supply and cooling of three Fukushima Daiichi reactors, causing a nuclear accident on March 11, All three cores largely melted in the first three days. 3. The accident was rated 7 on the INES scale, due to high radioactive releases in the first few days.

76 4. After two weeks the three reactors (units 1-3) were stable with water addition but no proper heat sink for removal of decay heat from fuel. By July they were being cooled with recycled water from the new treatment plant. Reactor temperatures had fallen to below 80ºC at the end of October, and official 'cold shutdown condition' was announced in mid December. 5. Apart from cooling, the basic ongoing task was to prevent release of radioactive materials, particularly in contaminated water leaked from the three units. 6. There have been no deaths or cases of radiation sickness from the nuclear accident, but over 100,000 people had to be evacuated from their homes to ensure this.

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