Environmental Science: A Study of Interrelationships - Chapter 9: Energy Sources, Study notes of Environmental Science

Download Environmental Science: A Study of Interrelationships - Chapter 9: Energy Sources and more Study notes Environmental Science in PDF only on Docsity! Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Enger & Smith Environmental Science A Study of Interrelationships Twelfth Edition Chapter 9 Energy Sources Energy Sources e nm uw wo wu ° ° o Greenland mass balance (Gt/yr) s ii o 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 w a on o -150 250 c > a OQ a yu = & a a wa a a — Q Z 2 8g < < -350 -450 — 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 Energy Sources  Nonrenewable energy sources are those whose resources are being used faster than can be replenished. – Coal, oil, and natural gas  Renewable energy sources replenish themselves or are continuously present as a feature of the environment. – Solar, geothermal, tidal, etc. – Some forms are referred to as perpetual energy. ‘Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Nuclear / energy (6.3%) Biomass and waste (10%) Coal (25.3%) Renewable), (12.7%) Natural gas (20.7%) renewable (0.5%) Data from International Energy Agency, 2007. All energy sources Fossil Fuel Formation  Coal • 300 million years ago, plant material began collecting underwater, initiating decay, forming a spongy mass of organic material. • Due to geological changes, some of these deposits were covered by seas, and covered with sediment. • Pressure and heat over time transformed the organic matter into coal. Fossil Fuel Formation Recoverable coal reserves of the world 2004 Fossil Fuel Formation  Oil and natural gas probably originated from microscopic marine organisms that accumulated on the ocean floor and were covered by sediments. • Muddy rock gradually formed shale containing dispersed oil. • Natural gas often forms on top of oil. Issues Related to the Use of Fossil Fuels  Coal is most abundant fossil fuel. • Primarily used for generating electricity.  There are four categories of coal: Lignite, Sub- bituminous, Bituminous, and Anthracite. • Lignite – High moisture, low energy, crumbly, least desirable form. • Sub-bituminous – Lower moisture, higher carbon than lignite. – Used as fuel for power plants. • Bituminous – Low moisture, high carbon content – Used in power plants and other industry such as steel making. – Most widely used because it is easiest to mine and the most abundant, supplying 20% of the world’s energy requirements. • Anthracite – Has the highest carbon content, and is relatively rare. – It is used primarily in heating buildings and for specialty uses. Issues Related to the Use of Fossil Fuels Issues Related to the Use of Fossil Fuels  There are two extraction methods: • Surface mining (strip mining), which is the process of removing material on top of a vein, is efficient but destructive. • Underground mining minimizes surface disturbance, but is costly and dangerous. – Many miners suffer from black lung disease, a respiratory condition that results from the accumulation of fine coal- dust particles in the miners’ lungs. Issues Related to the Use of Fossil Fuels Surface-mine reclamation Issues Related to the Use of Fossil Fuels Acid mine drainage Issues Related to the Use of Fossil Fuels  Oil is more concentrated than coal, burns cleaner, and is easily transported through pipelines. • These qualities make it ideal for automobile use. • It is difficult to find. • It causes less environmental damage than coal mining. Issues Related to the Use of Fossil Fuels Offshore drilling Issues Related to the Use of Fossil Fuels  Processing • As it comes from the ground, oil is not in a form suitable for use, and must be refined. • Multiple products can be produced from a single barrel of crude oil.  Oil Spills • Accidental spills only account for about 1/3 of oil pollution resulting from shipping. • 60% comes from routine shipping operations. Issues Related to the Use of Fossil Fuels Processing crude oil Renewable Sources of Energy Renewable energy as a share of total energy consumption (World 2006) Renewable Sources of Energy  Biomass Conversion • All biomass is produced by green plants that convert sunlight into plant material through photosynthesis. • Biomass is still the predominant form of energy used by people in less-developed countries. • It accounts for 10% of world energy use. Renewable Sources of Energy  There are several sources of biomass energy: • Fuel wood • Municipal and industrial wastes • Agricultural crop residues and animal wastes • Energy plantations Renewable Sources of Energy  Crop residues and animal wastes: • Materials left over following the harvest of a crop (e.g., straw and stalks) can be used as biomass fuel. • Animal dung is dried and burned or processed in anaerobic digesters to provide a burnable gas. Renewable Sources of Energy  Energy plantations: • Many crops, including sugar beets, sugar cane, corn, grains, kelp, and palm oil can be grown for the express purpose of energy production. • Two factors determine whether a crop is suitable for energy use: – Good energy crops have a very high yield of dry material per unit of land. – The amount of energy that can be produced from a biomass crop must be more than the amount of energy required to grow a crop. Renewable Sources of Energy  There are several technologies capable of converting biomass into energy. • Direct combustion – Burning biomass in fires to cook food or heat homes. • Biofuels production – Fermentation converts plant sugars to ethanol, which is used as an energy source. • Anaerobic digestion – Green, wet biomass and animal waste is broken down by anaerobic bacteria, producing methane and CO2. • Pyrolysis – A thermo chemical process that converts biomass to a more useful fuel such as charcoal. Renewable Sources of Energy  Hydroelectric power is created when flowing water is captured and turned into electricity. • Damming a river and storing water in a reservoir is the most common method. • Pumped storage plants use two reservoirs separated by a significant elevation difference. • The potential for developing hydroelectric power is best in mountainous regions and large river valleys. • The World Energy Council estimates that it would be technically possible to triple the electricity produced by hydropower with current technology. Renewable Sources of Energy  Hydroelectric power currently supplies 16% of world’s electricity. • In South and Central America, 65% of electricity used comes from hydroelectric power. • Norway gets 99% of its electricity and 65% of all its energy from hydroelectric power. • Construction of “mini hydro” (less than 10 megawatts) and “micro hydro” (less than 1 megawatt) plants is increasing; these plants can be built in remote places and supply electricity to small areas. Renewable Sources of Energy  Reservoir construction causes significant environmental and social damage. • Loss of farmland or forest land due to flooding • Community relocation • Prevention of fish migrations • Trapping of silt fills in reservoir and stops flow of nutrients downstream • Mercury accumulation Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Passive solar heating Renewable Sources of Energy Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Insulated water pipes h Solar -collectors—_* <—— fines aga Cold Heat from hot water Hot water radiator E-=+— .+=, Water ™Storage tank Solar heating designs School room Renewable Sources of Energy  In a passive solar system, light energy is transformed to heat energy when it is absorbed by a surface.  Buildings designed for passive solar heating in the Northern Hemisphere usually have large, south-facing windows.  Floors and walls, made of materials that absorb and store the sun’s heat during the day, slowly release heat at night when it is needed most. This feature is called direct gain. Renewable Sources of Energy  Improving solar cell efficiency while holding down the cost per cell is an important goal of the growing PV industry. • Solar electricity is 20 cents per kilowatt-hour, more than electricity from the power plant.  Photovoltaics are probably the most benign method of power generation known.  They are silent, produce no emissions, and use no fuel other than sunlight, but thermal systems use large amounts of land to position the mirrors. Renewable Sources of Energy ‘Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Solar generation of electricity Renewable Sources of Energy Photovoltaic shingles Renewable Sources of Energy  Heat pumps can be used in areas that are not geologically active.  The pump extracts heat from the Earth, and deposits it in a building.  Environmental Issues • Steam contains hydrogen sulfide gas. – It smells like rotten eggs. – Minerals in the steam corrode pipes and equipment. – The minerals are toxic to fish. Renewable Sources of Energy Copyri Geothermal power plant Renewable Sources of Energy  Wind Power • As warm air becomes less dense and rises, cooler, denser, air flows in to take its place. This flow of air is wind. • Wind has ground grain and pumped water. Now is it used to generate electricity. • Some areas are better suited than others, and winds are variable. Wind energy must be coupled with other sources of energy. • Only 0.5% of total worldwide electrical production is from wind. • Only 1% of U.S. electricity is from wind. 20% could be generated by 2030. Energy Conservation  Many conservation techniques are relatively simple and highly cost-effective. • Highly efficient fluorescent light bulbs give the same amount of light as incandescent bulbs for 25% of the energy, and produce less heat. • Lighting and air conditioning (removing the heat from inefficient incandescent lighting) account for 25% of U.S. electricity consumption. • Automatic dimming or light-shutoff devices are being used in new construction. Are Fuel Cells in the Future?  Hydrogen is abundant and generates heat and pure water when it reacts with air.  Hydrogen fuel cells are beginning to rise in popularity due to their high efficiency and low emissions. • They do not need to be recharged, unlike batteries. • They run continuously if provided with adequate fuel input—anything from which hydrogen can be extracted. Are Fuel Cells in the Future?  The most common form is the proton exchange membrane (PEM) fuel cell. • Pressurized hydrogen gas enters the fuel cell and contacts a catalyst that causes the hydrogen molecules to split into hydrogen ions and electrons. • A proton exchange membrane allows the hydrogen ions, but not electrons, to flow through it. • The electrons flow through an electric circuit to do work, such as powering motors or generating lights. • The hydrogen ions flow through the membrane and recombine with electrons that have passed through the circuit and with oxygen to form water. Are Fuel Cells in the Future? Experimental fuel cell bus Summary  Resources are naturally occurring substances of use to humans.  Reserves are known deposits from which materials can be extracted profitably with existing technology under present economic conditions.  Coal is the world’s most abundant fossil fuel.  The supply of oil is limited.  Natural gas is another major source of fossil-fuel energy, but transport of natural gas to consumers is problematic.