TYPES OF ENERGY RESOURCES Chapter 16 Nonrenewable Energy 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. TYPES OF ENERGY RESOURCES Floating oil drilling Oil and natural gas platform Oil storage Coal Oil drilling platform on legs Gas well Impervious rock Natural gas Oil Water Oil well Pipeline Valves Pump Mined coal Underground coal mine Geothermal Contour energy strip mining Hot water storage Geothermal power plant Area strip mining Pipeline Drilling tower Water Water is heated and brought up as dry steam or wet steam Nonrenewable energy resources and geothermal energy in the earth s s crust. Coal seam Hot rock Magma Water penetrates down through the rock TYPES OF ENERGY RESOURCES World Natural gas 21% Nuclear power 6% Hydropower, geothermal, solar, wind 7% RENEWABLE 18% Biomass 11% Coal 22% NONRENEWABLE 82% Oil 33% Commercial energy use by source for the world (left) and the U.S. (right).
United States Coal 23% Natural gas 23% Nuclear power 8% Biomass 4% RENEWABLE 8% Hydropower geothermal, solar, wind 3% Animation: Energy Use NONRENEWABLE 93% Oil 39% PLAY ANIMATION TYPES OF ENERGY RESOURCES Net Energy Ratios Net energy is the amount of high-quality usable energy available from a resource after subtracting the energy needed to make it available. The higher the net energy ratio, the greater the net energy available. Ratios < 1 indicate a net energy loss. Space Heating Passive solar 5.8 OIL Natural gas 4.9 Oil 4.5 Active solar 1.9 Coal gasification 1.5 Electric resistance heating (coal-fired plant) 0.4 Electric resistance heating (natural-gas-fired plant) 0.4 Electric resistance heating (nuclear plant) 0.3 High-Temperature Industrial Heat Surface-mined coal Underground-mined coal Natural gas 4.9 Oil 4.7 Coal gasification 1.5 Direct solar (highly concentrated by mirrors, 0.9 heliostats, or other devices) Transportation Natural gas 4.9 Gasoline (refined crude oil) 4.1 Biofuel (ethyl alcohol) 1.9 Coal liquefaction 1.4 Oil shale 1.2 25.8 28.2 OIL Crude oil (petroleum) is a thick liquid containing hydrocarbons that we extract from underground deposits and separate into products such as gasoline, heating oil and asphalt. Only 35-50% 50% can be economically recovered from a deposit. As prices rise, about 10-25% more can be recovered from expensive secondary extraction techniques. This lowers the net energy yield.
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. Heated crude oil Furnace Gases Gasoline Aviation fuel Heating oil Diesel oil Naptha Grease and wax Asphalt OIL OIL Eleven OPEC (Organization of Petroleum Exporting Countries) have 78% of the world s proven oil reserves and most of the world s unproven reserves. After global production peaks and begins a slow decline, oil prices will rise and could threaten the economies of countries that have not shifted to new energy alternatives. Inflation-adjusted adjusted price of oil, 1950-2006. Case Study: U.S. Oil Supplies Oil price per barrel ($) (2006 dollars) The U.S. the world s s largest oil user has only 2.9% of the world s s proven oil reserves. U.S oil production peaked in 1974 (halfway production point). About 60% of U.S oil imports goes through refineries in hurricane-prone regions of the Gulf Coast. Year
OIL Burning oil for transportation accounts for 43% of global CO 2 emissions. Ample supply for 42 93 years Low cost (with huge subsidies) Conventional Oil High net energy yield Easily transported within and between countries Low land use Need to find substitutes within 50 years Artificially low price encourages waste and discourages search for alternatives Air pollution when burned Technology is well developed Efficient distribution system Releases CO 2 when burned Moderate water pollution CO 2 Emissions Coal-fired electricity Synthetic oil and gas produced from coal 150% 286% Coal 100% Oil sand 92% Oil Natural gas 58% 86% CO 2 emissions per unit of energy produced for various energy resources. Nuclear power fuel cycle Geothermal 17% 10% Heavy Oils from Oil Sand and Oil Shale: Will Sticky Black Gold Save Us? Heavy and tarlike oils from oil sand and oil shale could supplement conventional oil, but there are environmental problems. High sulfur content. Extracting and processing produces: Toxic sludge Uses and contaminates larges volumes of water Requires large inputs of natural gas which reduces net energy yield. Oil Shales Oil shales contain a solid combustible mixture of hydrocarbons called kerogen.
Heavy Oils Heavy Oils from Oil Shale and Oil Sand It takes about 1.8 metric tons of oil sand to produce one barrel of oil. Moderate cost (oil sand) Large potential supplies, especially oil sands in Canada Easily transported within and between countries Efficient distribution system in place Technology is well developed High cost (oil shale) Low net energy yield Large amount of water needed for processing Severe land disruption Severe water pollution Air pollution when burned CO 2 emissions when burned 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 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 Conventional 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. Ample supplies (125 years) High net energy yield Low cost (with huge subsidies) Less air pollution than other fossil fuels Lower CO 2 emissions than other fossil fuels Moderate environmental impact Easily transported by pipeline Low land use Good fuel for fuel cells and gas turbines Nonrenewable resource Releases CO 2 when burned Methane (a greenhouse gas) can leak from pipelines Difficult to transfer from one country to another Shipped across ocean as highly explosive LNG Sometimes burned off and wasted at wells because of low price Requires pipelines
COAL Increasing moisture content Increasing heat and carbon content Peat (not a coal) Lignite (brown coal) Bituminous (soft coal) Anthracite (hard coal) Heat Heat Heat Pressure Pressure Pressure 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. Partially decayed plant matter in swamps and bogs; low heat content Low heat content; low sulfur content; limited supplies in most areas Extensively used as a fuel because of its high heat content and large supplies; normally has a high sulfur content Highly desirable fuel because of its high heat content and low sulfur content; supplies are limited in most areas Waste heat COAL Coal bunker Pulverizing mill Boiler Turbine Generator Condenser Filter Cooling loop Cooling tower transfers waste heat to atmosphere Stack 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 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. Toxic ash disposal 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 CO 2 into the troposphere. Coal Ample supplies (225 900 years) High net energy yield Low cost (with huge subsidies) Severe land disturbance, air pollution, and water pollution High land use (including mining) Severe threat to Well-developed human health mining and combustion technology High CO 2 emissions Air pollution can be reduced with improved technology (but adds to cost) when burned Releases radioactive particles and toxic mercury into air
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 CO 2 to the troposphere than burning coal. COAL Since CO 2 is not regulated as an air pollutant and costs are high, U.S. coal- burning plants are unlikely to invest in coal gasification. Synthetic Fuels Large potential supply Vehicle fuel Moderate cost (with large government subsidies) Lower air pollution when burned than coal Low to moderate net energy yield Higher cost than coal Requires mining 50% more coal High environmental impact Increased surface mining of coal High water use Higher CO 2 emissions than coal 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. Uranium fuel input (reactor core) Shielding Small amounts of radioactive gases Hot coolant Pump Coolant Moderator Coolant Pressure passage vessel Periodic removal and storage of radioactive wastes and spent fuel assemblies Control rods Containment shell Heat exchanger Steam Turbine Water Periodic removal and storage of radioactive liquid wastes Pump Waste heat Condenser Generator Pump Pump Hot water output Cool water input Electric power Useful energy 25% 30% Waste heat Water source (river, lake, ocean) 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 lined concrete container.
Enrichment of UF 6 Conversion of U 3 O 8 to UF 6 Fuel assemblies Reactor Fuel fabrication (conversion of enriched UF 6 to UO 2 and fabrication of fuel assemblies) Temporary storage of spent fuel assemblies Uranium-235 as UF 6 underwater or in dry Plutonium-239 as PuO 2 casks Spent fuel reprocessing Decommissioning of reactor Low-level radiation with long half-life life After spent fuel rods are cooled considerably, they are sometimes moved to dry-storage containers made of steel or concrete. Open fuel cycle today Closed end fuel cycle Geologic disposal of moderate & high-level radioactive wastes What Happened to Nuclear Power? After more than 50 years of development and enormous government subsidies, nuclear power has not lived up to its promise because: Multi billion-dollar construction costs. Higher operation costs and more malfunctions than expected. Poor management. Public concerns about safety and stricter government safety regulations. Case Study: The Chernobyl Nuclear Power Plant Accident The world s s worst nuclear power plant accident occurred in 1986 in Ukraine. The disaster was caused by poor reactor design and human error. By 2005, 56 people had died from radiation released. 4,000 more are expected from thyroid cancer and leukemia. Animation: Chernobyl Fallout PLAY ANIMATION NUCLEAR ENERGY In 1995, the World Bank said nuclear power is too costly and risky. In 2006, it was found that several U.S. reactors were leaking radioactive tritium into groundwater.
Large fuel supply Low environmental impact (without accidents) Emits 1/6 as much CO 2 as coal Moderate land disruption and water pollution (without accidents) Moderate land use Low risk of accidents because of multiple safety systems (except for 15 Chernobyl-type reactors) Conventional Nuclear Fuel Cycle Cannot compete economically without huge government subsidies Low net energy yield High environmental impact (with major accidents) Catastrophic accidents can happen (Chernobyl) No widely acceptable solution for long-term storage of radioactive wastes and decommissioning worn-out plants Subject to terrorist attacks Spreads knowledge and technology for building nuclear weapons NUCLEAR ENERGY A 1,000 megawatt nuclear plant is refueled once a year, whereas a coal plant requires 80 rail cars a day. Coal Ample supply High net energy yield Very high air pollution High CO 2 emissions High land disruption from surface mining High land use Coal vs. Nuclear Nuclear Ample supply of uranium Low net energy yield Low air pollution (mostly from fuel reprocessing) Low CO 2 emissions (mostly from fuel reprocessing) Much lower land disruption from surface mining Moderate land use 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. Low cost (with huge subsidies) High cost (even with huge subsidies) 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. Building more nuclear power plants will not lessen dependence on imported oil and will not reduce CO 2 emissions as much as other alternatives. The nuclear fuel cycle contributes to CO 2 emissions. Wind turbines, solar cells, geothermal energy, and hydrogen contributes much less to CO 2 emissions.
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. Each pebble contains about 10,000 uranium dioxide particles the size of a pencil point. Pebble Core Graphite shell Reactor vessel Helium Pebble detail Silicon carbide Pyrolytic carbon Porous buffer Uranium dioxide Recuperator Turbine Generator Water cooler Hot water output Cool water input 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 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.