Alternative Energy Sources
Alternative energy sources (Encyclopedia of Environmental Issues, Revised Edition)
Both the extraction and the burning of fossil fuels have caused severe and growing damage to the environment, contributing to such problems as air pollution, the release of greenhouse gases (which retain heat and contribute to climate change), and sulfuric acid in rainfall. Nuclear energy sources are very limited in supply and expensive, require extreme amounts of processing, and produce long-lasting radioactive waste. In the long term, energy release from nuclear fusion has been proposed as a limitless supply of power, but industrial-scale production of fusion power continues to pose large and uncertain obstacles and hazards.
(The entire section is 96 words.)
Solar Power (Encyclopedia of Environmental Issues, Revised Edition)
The sun powers winds, ocean currents, rain, and all biomass growth on the earth’s surface. Because the availability and extraction means for each of these secondary sources of solar power are diverse, each forms a different field of alternative energy technology. Where solar power is extracted and converted to energy directly, the capture can be by means of flat-plate receivers that collect at the incident intensity but can operate in diffuse light, or by means of concentrators that can achieve intensities of several hundred suns but work poorly in diffuse light.
In solar photovoltaic power (PV) technology, solar radiation is directly converted to useful power through PV cell arrays, which require semiconductor mass-production plants. PV cell technologies have evolved from using single-crystal silicon to using thinner polycrystalline silicon, gallium arsenide, thin-film amorphous silicon, cadmium telluride, and copper indium selenide. The needed materials are believed to be abundant enough to meet projected global growth. The process of purifying silicon requires large inputs of energy, however, and it generates toxic chemical waste. Regeneration of the energy required to manufacture a solar cell requires about three years of productive cell operation.
Solar cell technology continues to evolve. Broadband solar cell technologies have the potential to make cells sensitive to as much as 80 percent of the energy in the solar...
(The entire section is 388 words.)
Wind Power (Encyclopedia of Environmental Issues, Revised Edition)
Winds are driven by temperature and pressure gradients, ultimately caused by solar heating. Wind energy is typically extracted through the operation of turbines. Power extraction is proportional to the cube of wind speed, but wind-generated forces are proportional to the square of wind speed. Wind turbines thus can operate safely only within a limited range of wind speed, and most of the power generation occurs during periods of moderately strong winds. Turbine efficiency is strongly dependent on turbine size and is limited by material strength. The largest wind turbines exceed 5 megawatts in capacity. Denmark, the Netherlands, and India have established large wind turbine farms on flat coastal land, and Germany and the United Kingdom have opted for large offshore wind farms. In the United States, wind farms are found in the Dakotas, Minnesota, and California, as well as on Colorado and New Mexico mountain slopes and off the coasts of Texas and Massachusetts.
Because of wind fluctuations and the cubic power relation, wind power is highly unsteady, and means must be established for storing and diverting the power generated before it is connected to a power grid. In addition, offshore and coastal wind farms must plan for severe storms. Smaller wind turbines are sometimes used for power generation on farms and even for some private homes in open areas, but these tend to be inefficient and have high installation costs per unit power....
(The entire section is 320 words.)
Hydroelectric Power and Tidal Power (Encyclopedia of Environmental Issues, Revised Edition)
Large dams provide height differences that enable the extraction of power from flowing water using turbines. Hydroelectric power generated by dams forms a substantial percentage of the power resources in several nations with rivers and mountains. However, the building of large dams raises numerous technical, social, and public policy issues, as damming rivers may displace human inhabitants from fertile lands and may result in the flooding of pristine ecosystems, sometimes the habitats of endangered species. Increased incidence of earthquakes has also been associated with the existence of very large dams.
In some of the world’s remote communities, micro hydroelectric (or micro hydel) plants provide power, generating electricity in the 1-30 megawatt range. Very small-scale systems, known as pico hydel, extract a few kilowatts from small streams; these can provide viable energy sources for individual homes and small villages, but the extraction technology has to be refined to bring down the cost per unit of power.
Although tidal power is abundant along coastlines, the harnessing of that power has been slow to gain acceptance, in part because of the difficulties of building plants that can survive ocean storms. Tidal power is extracted in two principal ways. In one method, semipermeable barrages are built across estuaries with high tidal ranges, and the water collected in the barrages is emptied...
(The entire section is 340 words.)
Biomass Power (Encyclopedia of Environmental Issues, Revised Edition)
Biomass, which consists of any material that is derived from plant life, is composed primarily of hydrocarbons and water, so it offers several ways of usage in power generation. Combustion of biomass is considered to be carbon-neutral in regard to greenhouse gas emissions, but it may generate smoke particles and other pollution.
One large use of biomass is in the conversion of corn, sugarcane, and other grasses to ethyl alcohol (ethanol) to supplement fossil petroleum fuels. This use is controversial because the energy costs associated with producing and refining ethanol are said to be greater than the savings gained by using such fuel. It is argued that subsidies and other public policies and rising energy prices entice farmers to devote land to the production of ethanol crops, thus triggering shortages and increases in food prices, which hurt the poorest people the most. Brazil has advanced profitable and sustainable use of ethanol extracted from sugarcane to replace a substantial portion of the nation’s transportation fossil-fuel use.
Jatropha plants, as well as certain algae that grow on water surfaces, offer sources of biodiesel fuel. Biodiesel from jatropha is used to power operations on several segments of India’s railways, and vegetable oil from peanuts and groundnuts, and even from coconuts, has been used in test flights of aircraft ranging from strategic bombers to jetliners.
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Biogas and Geothermal Energy (Encyclopedia of Environmental Issues, Revised Edition)
Hydrocarbon gases from decaying vegetation form large underground deposits that have been exploited as sources of energy for many years. Technology similar to that used in extracting energy from these natural deposits, which are not considered a renewable energy source, can be used to tap the smaller but widely distributed emissions of methane-rich waste gases from compost pits and landfills. Creating the necessary infrastructure to capture these gases over large areas poses a difficult engineering challenge, however. In addition, care must be taken to avoid the release of methane from these deposits into the atmosphere, as methane is considered to be twenty times as harmful as carbon dioxide as a greenhouse gas.
Geothermal energy comes from heat released by radioactive decay inside the earth’s core, perhaps augmented by gravitational pressure. Where such heat is released gradually through vents in the earth’s surface, rather than in volcanic eruptions, it forms an abundant and steady, reliable, long-term source of thermal power. Hot springs and geothermal steam generation are used on a large scale in Iceland, and geothermal power is used in some American communities and military bases.
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Further Reading (Encyclopedia of Environmental Issues, Revised Edition)
Charlier, R. H., and C. W. Finkl. Ocean Energy: Tide and Tidal Power. London: Springer, 2009.
Edwards, Brian K. The Economics of Hydroelectric Power. Northampton, Mass.: Edward Elgar, 2003.
Klass, Donald L. Biomass for Renewable Energy, Fuels, and Chemicals. San Diego, Calif.: Academic Press, 1998.
Pollan, Michael. The Omnivore’s Dilemma: A Natural History of Four Meals. New York: Penguin Press, 2007.
Traynor, Ann J., and Reed J. Jensen. “Direct Solar Reduction of CO2 to Fuel: First Prototype Results.” Industrial and Engineering Chemistry Research 41, no. 8 (2002): 1935-1939.
Vaitheeswaran, Vijay. Power to the People: How the Coming Energy Revolution Will Transform an Industry, Change Our Lives, and Maybe Even Save the Planet. New York: Farrar, Straus and Giroux, 2003.
Walker, John F., and Nicholas Jenkins. Wind Energy Technology. New York: John Wiley & Sons, 1997.
Wenisch, A., R. Kromp, and D. Reinberger. Science or Fiction: Is There a Future for Nuclear? Vienna: Austrian Ecology Institute, 2007.
(The entire section is 147 words.)
Alternative Energy Sources (Encyclopedia of Science)
Alternative energy is energy provided from sources other than the three fossil fuels: coal, oil, and natural gas. Alternative sources of energy include nuclear power, solar power, wind power, water power, and geothermal energy, among others.
Current sources of energy
As of the beginning of the twenty-first century, fossil fuels (fuels formed over millions of years from the remains of plants and animals) provide more than 85 percent of the total energy used around the world. In the United States, two-thirds of the electricity is currently generated by burning fossil fuels like coal, gas, and oil. According to the U.S. Department of Energy and the Environmental Protection Agency, such combustion pumped almost 2.5 billion tons (2.3 billion metric tons) of carbon dioxide into the atmosphere in 1999. Over the last 150 years. some 270 billion tons (245 billion metric tons) of carbon in the form of carbon dioxide have been released into the air as a result of the burning of fossil fuels.
(The entire section is 2087 words.)