Exploring Nonrenewable Energy Sources: Coal, Oil, and Natural Gas
E N D
Presentation Transcript
Chapter 10 Energy Sources: • As demand increased, reliable sources were required. • Oil, coal and natural gas represent 90% of world’s commercially traded energy. è nonrenewable energy source • Resource: useful to humans and can potentially be extracted. • Reserves: resources which can be profitably extracted under certain economic conditions with existing technology
Chapter 10 Nonrenewable energy: • Coal1 27% • Oil 40% • Natural Gas 23% nuclear = 7% 1 47% of electricity • Formation of Fossil Fuels: • 300 million years ago, many swamps occurred. • Plant and animal decomposition is inhibited under water. è peat
Chapter 10 • When buried under seas (weight of plants, sediments and water), higher pressures: • è lignite coal (40% water) • If enough pressure and heat (from the earth’s center): è bituminous (soft) coal (3% water) • Given enough time at high temperature and pressure: è anthracite (hard) coal
Chapter 10 • Oil: formed from vast pool of bodies of microorganisms which released droplets of oil on decomposition. • Sediments trapped oil • è shale (oil not very concentrated) • Sandstone layers above shale allows oil pools to develop (in pores of sandstone). • Natural Gas: similar to oil, but end products are more volatile
Chapter 10 Extracting Coal • Lignite: least desirable form. • Bituminous: easiest to mine, but not very “clean”. • 20% of energy requirements • Anthracite: most energy per ton, but found quite deep so it is expensive. • Cleanest burning
Chapter 10 • 2 methods of mining coal: • surface mining (strip mining) • < 100 meters deep • remove overburden • very efficient in terms of the percent of coal the mine recovers—down to 0.5 m thick seam • Method for 60% of US production • Underground mining • vertical shaft down to coal seam: flat land • horizontal shaft through seam: hilly land
Chapter 10 Problems: • land must be reclaimed after surface mining (costs passed to consumers). • subsidence can occur from underground mining. • black lung disease (costs not passed to consumers - externality). • transportation costs. • air pollution (dust and burning). • 150,000,000 metric tons of SO2 each year • acid mine drainage.
Chapter 10 Extracting Oil • Easy oil fields have already been tapped and drained. • Costs (in U.S.) continually increasing. • 1998: estimated 1,000 billion barrels of reserves (3/4’s are in OPEC). • About 66% of oil must be recovered by some means other than pumping. è secondary recovery - many methods
Chapter 10 Crude oil must be “refined”. • distillation tower allows various compounds to be separated. • “cracking” (heat and pressure and catalysts) produces more volatile chemicals. • products are raw materials for many other products (e.g. plastics)
Chapter 10 Problems: • many similar to coal. • oil spills in oceans • only about 40% of oil pollution in oceans is from spills....60% from routine handling. • oil in soils contaminates soil and underground water. • Ground level ozone from evaporation or incomplete combustion—air pollution ch 17
Chapter 10 Extracting Natural Gas • Supplies about 23% of the world’s energy. • Typically found by drilling wells, and often found with oil. • Long pipelines are expensive, so much natural gas is burned as a “waste” product at the well head. è can be liquefied at cold temperatures (liquefied natural gas). è can be converted to methanol (liquid alcohol).
Chapter 10 Natural Gas (cont’d) • Is used to make fertilizers and various petrochemicals. • Many countries increase use of natural gas when oil prices increase. • Major obstacle for using natural gas (especially in developing nations) is in distribution.
Chapter 10 Problems: • most environmentally friendly of the three major fossil fuels. • some odor • danger of explosion or fire • few known environmental problems if spilled • little air pollution when burned. • CO2 and some nitrogen compounds
Chapter 10 • Renewable Energy Sources • Together account for 3% of world energy use • 98% of that is through hydropower • - biomass • - solid wastes (e.g. paper, plastic) • - solar/wind • - geothermal • - tidal è technological problems in replacing fossil fuel supply
Chapter 10 Water Power • Long history of use (grain mills, saw mills, textile machines). • Hydroelectric power plants built on mountain streams, or included in dams. • Now produces about 2.5% of world’s energy. • Problems: - loss of farmland/reduction in silt - loss of stream/river habitat • species loss • undesirable species appear - relocation of people
Chapter 10 Tidal Power • Trapping the energy in moving water. • Only one large scale tidal generating station in the world (France). - 240 megawatt capacity - 62 megawatt production provide for 100k • England is considering a 7,200 megawatt plant (similar cost to a coal fired plant of same size). • Problems: - hydraulic disruption in estuary - pollutants concentrate
Chapter 10 Geothermal • Earth’s core reaches temperatures of 4400o C - volcanoes • - heats ground water (springs and geysers) • - can turn water into steam • è geothermal energy • Geothermal energy tapped by drilling well, and using steam to turn turbines. • U.S. has world’s largest geothermal plant (California)--- enough energy to supply San Francisco.
Chapter 10 Geothermal (cont’d) • Generates less air pollution. • Typically less expensive than fossil fuel power plants. • Many plants are operating or are in the planning stages. • Problems: • - good sites often require habitat destruction. • - hydrogen sulfide • - minerals are corrosive to pipes • - minerals are toxic to fish
Chapter 10 Wind Power • A form of solar energy. • Long history of use (grain mills, pump water, move ships). • Recently, used to generate electricity. (stationary and portable units) • Texas and Dakotas could supply nation but… • Problems: - need steady, dependable source of wind. - aesthetic impacts.
Chapter 10 Solar Energy • Sun’s energy is steady, and far exceeds world’s demand for energy (600 times greater than that produced by all other forms). • 1. Passive systems • Light energy converted to heat energy. • maintenance free • practical only in new building design • You can dry your clothes with it!
Chapter 10 Solar Power (cont’d) 2. Active systems • Passively heat liquid, and actively (pump) to transfer heat. • pumps require maintenance • must store heat for times when sun energy is low • can recoup construction costs in 3 to 10 years
Chapter 10 • Solar Energy (cont’d) • 3. Solar-generated electricity • Bell Labs invented photovoltaic cells in 1954. • Many small or remote location uses • Can use solar energy to heat oil and then water to drive steam generators. • Price is dropping for photovoltaic cells and for steam generators.
Chapter 10 Solar Power (cont’d) • Problems: • - Currently provides less than 1% of world’s energy. • - Intermittent supply of solar energy. • - Usually must supplement solar energy with some other form. • - Still relatively expensive technology. • H/w as fossil fuel costs increase…
Chapter 10 Fuelwood • Provides 10% of home heating energy in U.S. Provides 3% of total energy in Canada. • Primary source of energy for nearly half of the world’s population--cooking • Problems: • -transportation • -fuel is used at faster rate than it can be grown. • -desertification • -air pollution (fly ash, carbon monoxide) • -produces known carcinogens
Chapter 10 Biomass • Derives energy from chemical energy stored in biomass. • - Methane digesters. • - Alcohol production from fermentation. • - Wood burning electrical generators. • Problems: • - most often used in countries with food shortages • - nutrients removed from soils - more energy input than output
Chapter 10 Solid Waste • 1.8 kilograms solid waste discarded per person per day in New York. 80% of this waste is combustible. • Reduces volume of waste and can generate electricity. • U.S. does little “trash power”. • Cleburne, Texas • Problems: • - waste must be sorted • - waste stream must be steady • - air pollution: toxic compounds released • - Little energy produced: provide for plant
Chapter 10 Energy Conservation • Potential for 50% reduction in energy use. • stoves versus open fires • fluorescent lights (lights and air conditioning account for 25% of U.S. electricity use). • low emissive glass • automatic light shut off • Better mass transit • Economics - short term versus long term.
