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Geothermal power is energy generated by heat stored beneath the Earth's surface. , a geothermal field in California. {Link without Title} Calpine Corporation page on The Geysers ELECTRICITY GENERATION Three different types of power plants - dry steam, flash, and binary - are used to generate power from geothermal energy, depending on Temperature , Depth , and Quality of the water and steam in the area. {Link without Title} , U.S. Department of Energy In all cases the condensed steam and remaining geothermal fluid is injected back into the ground to pick up more heat. In some locations, the natural supply of water producing steam from the hot underground magma deposits has been exhausted and processed waste water is injected to replenish the supply. Most geothermal fields have more fluid recharge than heat, so re-injection can cool the resource, unless it is carefully managed. Dry steam Geothermal Power Plant in Iceland]] A dry stream power plant uses hot steam, typically above 235°C (455°F), to directly power its turbines. This is the oldest type of power plant and is still in use today. Flash steam Flash steam power plants use hot water above 182°C (360°F) from geothermal reservoirs. As the water is pumped from the reservoir to the power plant, the drop in pressure causes the water to vaporize into steam to power the turbine. Any water not flashed into steam is injected back into the reservoir for reuse. Flash steam plants are the most common type of geothermal power generation plants in operation today. They use water at temperatures greater than 360°F (182°C) that is pumped under high pressure to the generation equipment at the surface. Upon reaching the generation equipment the pressure is suddenly reduced, allowing some of the hot water to convert or "flash" into steam. This steam is then used to power the turbine/generator units to produce electricity. The remaining hot water not flashed into steam, as well as the water condensed from the steam, is generally pumped back into the reservoir. An example of an area using the flash steam operation is the CalEnergy Navy I flash geothermal power plant at the Coso geothermal field. Binary-cycle The water used in binary-cycle power plants is cooler than that of flash steam plants. The hot fluid from geothermal reservoirs is passed through a Heat Exchanger which transfers heat to a separate pipe containing fluids with a much lower boiling point. These fluids, usually Iso-butane or Iso-pentane , are vaporized to power the turbine. Geothermal Energy for Electric Power . The advantage to binary-cycle power plants is their lower cost and increased efficiency. These plants also do not emit any excess gas and are able to utilize lower temperature reservoirs, which are much more common. Most geothermal power plants planned for construction are binary-cycle. Geothermal Energy for Electric Power Enhanced Geothermal Systems See Also: Hot dry rock geothermal energy Enhanced Geothermal Systems (EGS), also known as Hot-dry-rock systems, involve pumping water into hot rocks in the earth, rather than harvesting hot water already in the earth. This type of geothermal system has many advantages over the others, as it can be used anywhere, not just in tectonically active regions. However, it requires deeper drilling than the other forms of geothermal energy harvesting. ADVANTAGES Geothermal energy offers a number of advantages over traditional fossil fuel based sources. From an environmental standpoint, the energy harnessed is clean and safe for the surrounding environment. Geothermal Energy It is also sustainable because the hot water used in the geothermal process can be re injected into the ground to produce more steam. In addition, geothermal power plants are unaffected by changing weather conditions. Kenya Looks Underground for Power Geothermal power works continually, day and night providing baseload power. From an economic view, geothermal energy is extremely price competitive in some areas and reduces reliance on fossil fuels and their inherent price unpredictability. Overview , U.S. Department of Energy Given enough excess capacity, geothermal energy can also be sold to outside sources such as neighboring countries or private businesses that require energy. It also offers a degree of scalability: a large geothermal plant can power entire cities while smaller power plants can supply more remote sites such as rural villages. Geothermal Energy DISADVANTAGES |
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