The earth's interior is almost entirely molten iron and rock. The thin layer of cool earth, upon which humankind builds their homes and follows their dreams, varies in its depth, bringing heat in a few locations close enough to the surface to form volcanoes, geysers and hot springs. Heat from the earth's interior, if it is close enough to the surface, can be directly tapped and used as a source of renewable, sustainable energy. Throughout history people have used heat from these surface level sources for everything from heating their homes to objects of worship.
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One of the most productive global areas for gaining access to geothermal energy sources is the "Ring of Fire", a result of shifting of tectonic plates that form a boundary between the Pacific Ocean and the land masses surrounding it. Along that boundary, magma from the earth's interior rises to where it is close enough to the surface to allow access to the heat it carries. Both volcanoes and earthquakes can result, but the same heat can also be accessed by drilling and tapping into the earth.
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There are three types of plants used for capturing geothermal energy:
- Dry Steam Plants - direct use of steam from a geothermal reservoir to drive a generator turbine
- Flash Steam Plants - convert high pressure water from the earth's interior to steam for driving generator turbines
- Binary Cycle Power Plants - geothermal hot water is used to heat another liquid to steam, which is used to drive a generator turbine
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Geothermal power is generated with very low impact on the environment. There is no fuel used, so there are virtually no greenhouse gasses emitted. There are some sulfur compounds that come from the geothermal reservoirs, so scrubbers are needed to remove those compounds.
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The principal impediments to the development of geothermal energy are a set of engineering problems that must be solved in order to make exploration, drilling, extraction and conversion of geothermal energy substantially less risky and more potentially profitable than is currently the case. The basic task is to make the cost of geothermal power competitive with power generated from currently available sources of energy - mostly coal, natural gas, and nuclear energy.
The areas in which research is being conducted are:
- reducing the uncertainties in locating and analyzing geothermal resources
- developing drilling techniques necessary for reaching depths of 7 - 10 miles below the surface
- creating fractured rock conditions at those depths where the heat of the rock can be effectively and renewably tapped
- developing a practical Enhanced Geothermal System (EGS) to make geothermal energy more widely available