Non-Renewable Energy Sources • Conventional • Petroleum • Natural Gas • Coal • Nuclear • Unconventional (examples) • Oil Shale • Natural gas hydrates in marine sediment
Renewable Energy Sources • Solar photovoltaics • Solar thermal power • Passive solar air and water heating • Wind • Hydropower • Biomass • Ocean energy • Geothermal • Waste to Energy
TYPES OF ENERGY RESOURCES • About 99% of the energy we use for heat comes from the sun and the other 1% comes mostly from burning fossil fuels. • Solar energy indirectly supports wind power, hydropower, and biomass. • About 76% of the commercial energy we use comes from nonrenewable fossil fuels (oil, natural gas, and coal) with the remainder coming from renewable sources.
Oil and natural gas Floating oil drilling platform Coal Oil storage Geothermal energy Contour strip mining Oil drilling platform on legs Hot water storage Oil well Gas well Geothermal power plant Pipeline Mined coal Valves Area strip mining Pipeline Pump Drilling tower Underground coal mine Impervious rock Oil Natural gas Water Water is heated and brought up as dry steam or wet steam Water Water penetrates down through the rock Coal seam Hot rock Magma Fig. 16-2, p. 357
World Nuclear power 6% Hydropower, geothermal, solar, wind 7% Natural gas 21% RENEWABLE 18% Biomass 11% Coal 22% Oil 33% NONRENEWABLE 82% Fig. 16-3a, p. 357
World Total Primary Energy Supply in 1998 **Other includes geothermal, solar, wind, heat, etc.
United States Hydropower geothermal, solar, wind 3% Natural gas 23% Nuclear power 8% RENEWABLE 8% Coal 23% Biomass 4% Oil 39% NONRENEWABLE 93% Fig. 16-3b, p. 357
OIL • Refining crude oil: • Based on boiling points, components are removed at various layers in a giant distillation column. • The most volatile components with the lowest boiling points are removed at the top. Figure 16-5
OIL • Inflation-adjusted price of oil, 1950-2006. Figure 16-6
Coal-fired electricity 286% Synthetic oil and gas produced from coal 150% 100% Coal 92% Oil sand 86% Oil 58% Natural gas Nuclear power fuel cycle 17% 10% Geothermal Fig. 16-8, p. 363
Oil Shales • Oil shales contain a solid combustible mixture of hydrocarbons called kerogen. Figure 16-9
Heavy Oils • It takes about 1.8 metric tons of oil sand to produce one barrel of oil. Figure 16-10
NATURAL GAS • Natural gas, consisting mostly of methane, is often found above reservoirs of crude oil. • When a natural gas-field is tapped, gasses are liquefied and removed as liquefied petroleum gas (LPG). • Coal beds and bubbles of methane trapped in ice crystals deep under the arctic permafrost and beneath deep-ocean sediments are unconventional sources of natural gas.
NATURAL GAS • Russia and Iran have almost half of the world’s reserves of conventional gas, and global reserves should last 62-125 years. • Natural gas is versatile and clean-burning fuel, but it releases the greenhouse gases carbon dioxide (when burned) and methane (from leaks) into the troposphere.
NATURAL GAS • Some analysts see natural gas as the best fuel to help us make the transition to improved energy efficiency and greater use of renewable energy. Figure 16-11
COAL • Coal is a solid fossil fuel that is formed in several stages as the buried remains of land plants that lived 300-400 million years ago. Figure 16-12
Increasing heat and carbon content Increasing moisture content Peat (not a coal) Lignite (brown coal) Bituminous (soft coal) Anthracite (hard coal) Heat Heat Heat Pressure Pressure Pressure Highly desirable fuel because of its high heat content and low sulfur content; supplies are limited in most areas Extensively used as a fuel because of its high heat content and large supplies; normally has a high sulfur content Partially decayed plant matter in swamps and bogs; low heat content Low heat content; low sulfur content; limited supplies in most areas Stepped Art Fig. 16-12, p. 368
Waste heat Cooling tower transfers waste heat to atmosphere Coal bunker Turbine Generator Cooling loop Stack Pulverizing mill Condenser Filter Boiler Toxic ash disposal Fig. 16-13, p. 369
COAL • Coal reserves in the United States, Russia, and China could last hundreds to over a thousand years. • The U.S. has 27% of the world’s proven coal reserves, followed by Russia (17%), and China (13%). • In 2005, China and the U.S. accounted for 53% of the global coal consumption.
COAL • Coal is the most abundant fossil fuel, but compared to oil and natural gas it is not as versatile, has a high environmental impact, and releases much more CO2 into the troposphere. Figure 16-14
COAL • Coal can be converted into synthetic natural gas (SNG or syngas) and liquid fuels (such as methanol or synthetic gasoline) that burn cleaner than coal. • Costs are high. • Burning them adds more CO2 to the troposphere than burning coal.
COAL • Since CO2 is not regulated as an air pollutant and costs are high, U.S. coal-burning plants are unlikely to invest in coal gasification. Figure 16-15
NUCLEAR ENERGY • When isotopes of uranium and plutonium undergo controlled nuclear fission, the resulting heat produces steam that spins turbines to generate electricity. • The uranium oxide consists of about 97% nonfissionable uranium-238 and 3% fissionable uranium-235. • The concentration of uranium-235 is increased through an enrichment process.
Small amounts of radioactive gases Uranium fuel input (reactor core) Control rods Containment shell Heat exchanger Turbine Steam Generator Electric power Waste heat Hot coolant Useful energy 25%–30% Hot water output Pump Pump Coolant Pump Pump Waste heat Cool water input Moderator Coolant passage Pressure vessel Shielding 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) Fig. 16-16, p. 372
NUCLEAR ENERGY • After three or four years in a reactor, spent fuel rods are removed and stored in a deep pool of water contained in a steel-lined concrete container. Figure 16-17
NUCLEAR ENERGY • After spent fuel rods are cooled considerably, they are sometimes moved to dry-storage containers made of steel or concrete. Figure 16-17
Decommissioning of reactor Fuel assemblies Reactor Enrichment of UF6 Fuel fabrication (conversion of enriched UF6 to UO2 and fabrication of fuel assemblies) Temporary storage of spent fuel assemblies underwater or in dry casks Conversion of U3O8 to UF6 Uranium-235 as UF6Plutonium-239 as PuO2 Spent fuel reprocessing Low-level radiation with long half-life Geologic disposal of moderate & high-level radioactive wastes Open fuel cycle today “Closed” end fuel cycle Fig. 16-18, p. 373
NUCLEAR ENERGY • A 1,000 megawatt nuclear plant is refueled once a year, whereas a coal plant requires 80 rail cars a day. Figure 16-20
NUCLEAR ENERGY • Terrorists could attack nuclear power plants, especially poorly protected pools and casks that store spent nuclear fuel rods. • Terrorists could wrap explosives around small amounts of radioactive materials that are fairly easy to get, detonate such bombs, and contaminate large areas for decades.
NUCLEAR ENERGY • When a nuclear reactor reaches the end of its useful life, its highly radioactive materials must be kept from reaching the environment for thousands of years. • At least 228 large commercial reactors worldwide (20 in the U.S.) are scheduled for retirement by 2012. • Many reactors are applying to extent their 40-year license to 60 years. • Aging reactors are subject to embrittlement and corrosion.
NUCLEAR ENERGY • Building more nuclear power plants will not lessen dependence on imported oil and will not reduce CO2 emissions as much as other alternatives. • The nuclear fuel cycle contributes to CO2 emissions. • Wind turbines, solar cells, geothermal energy, and hydrogen contributes much less to CO2 emissions.
NUCLEAR ENERGY • Scientists disagree about the best methods for long-term storage of high-level radioactive waste: • Bury it deep underground. • Shoot it into space. • Bury it in the Antarctic ice sheet. • Bury it in the deep-ocean floor that is geologically stable. • Change it into harmless or less harmful isotopes.
New and Safer Reactors • Pebble bed modular reactor (PBMR) are smaller reactors that minimize the chances of runaway chain reactions. Figure 16-21
New and Safer Reactors • Some oppose the pebble reactor due to : • A crack in the reactor could release radioactivity. • The design has been rejected by UK and Germany for safety reasons. • Lack of containment shell would make it easier for terrorists to blow it up or steal radioactive material. • Creates higher amount of nuclear waste and increases waste storage expenses.
NUCLEAR ENERGY • Nuclear fusion is a nuclear change in which two isotopes are forced together. • No risk of meltdown or radioactive releases. • May also be used to breakdown toxic material. • Still in laboratory stages. • There is a disagreement over whether to phase out nuclear power or keep this option open in case other alternatives do not pan out.
Energy Inputs Outputs System 9% 7% 41% U.S. economy and lifestyles 85% 43% 8% 4% 3% Useful energy Nonrenewable fossil fuels Petrochemicals Nonrenewable nuclear Unavoidable energy waste Hydropower, geothermal, wind, solar Biomass Unnecessary energy waste Fig. 17-2, p. 385
REDUCING ENERGY WASTE AND IMPROVING ENERGY EFFICIENCY • Four widely used devices waste large amounts of energy: • Incandescent light bulb: 95% is lost as heat. • Internal combustion engine: 94% of the energy in its fuel is wasted. • Nuclear power plant: 92% of energy is wasted through nuclear fuel and energy needed for waste management. • Coal-burning power plant: 66% of the energy released by burning coal is lost.
WAYS TO IMPROVE ENERGY EFFICIENCY • Industry can save energy and money by producing both heat and electricity from one energy source and by using more energy-efficient electric motors and lighting. • Industry accounts for about 42% of U.S. energy consumption. • We can save energy in transportation by increasing fuel efficiency and making vehicles from lighter and stronger materials.
WAYS TO IMPROVE ENERGY EFFICIENCY • Average fuel economy of new vehicles sold in the U.S. between 1975-2006. • The governmentCorporate Average Fuel Economy (CAFE) has not increased after 1985. Figure 17-5
WAYS TO IMPROVE ENERGY EFFICIENCY • Inflation adjusted price of gasoline (in 2006 dollars) in the U.S. • Motor vehicles in the U.S. use 40% of the world’s gasoline. Figure 17-6
WAYS TO IMPROVE ENERGY EFFICIENCY • General features of a car powered by a hybrid-electric engine. • “Gas sipping” cars account for less than 1% of all new car sales in the U.S. Figure 17-7
Hybrid Vehicles, Sustainable Wind Power, and Oil imports • Hybrid gasoline-electric engines with an extra plug-in battery could be powered mostly by electricity produced by wind and get twice the mileage of current hybrid cars. • Currently plug-in batteries would by generated by coal and nuclear power plants. • According to U.S. Department of Energy, a network of wind farms in just four states could meet all U.S. electricity means.
Fuel-Cell Vehicles • Fuel-efficient vehicles powered by a fuel cell that runs on hydrogen gas are being developed. • Combines hydrogen gas (H2) and oxygen gas (O2) fuel to produce electricity and water vapor (2H2+O2 2H2O). • Emits no air pollution or CO2 if the hydrogen is produced from renewable-energy sources.