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Geothermal Energy


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 Geothermal Energy


Note that this topic is limited to geothermal energy as a source of electric power generation. Geothermal energy used to provide heating, air conditioning and/or hot water to end-users is discussed in the topic "Geothermal Heat Pumps."

Geothermal energy is produced by the heat of the earth and is often associated with volcanic and seismically active regions. Hot water and, in some instances, steam can be used to make electricity in large power plants. Hot water can also be put to direct use, such as heating greenhouses or other buildings. The constant temperature below ground can also be tapped to warm and cool homes through a ground-source heat pump.

Geothermal energy offers several competitive advantages in localities where the resource is available. Geothermal electric power plants can be tailored to individual supply needs. Current geothermal power generation technologies enable economic use of many moderate temperature (<150 degrees C) geothermal resources, which will be the predominant source for near-term geothermal development in the U.S. In addition, geothermal energy is relatively benign to the environment as technologies to abate problematic emissions are well developed.

According to the Geothermal Energy Association, in 2007 geothermal was the fourth largest source of renewable energy in the United States, generating 14,885 gigawatt-hours (GWh) of electricity. Today the U.S. has about 3,000 MW of geothermal electricity connected to the grid. The U.S. continues to produce more geothermal electricity than any other country, comprising approximately 30 percent of the world total. In California, the state with the largest amount of geothermal power on-line, electricity from geothermal resources accounted for 5 percent of the state’s electricity generation in 2003, significantly exceeding the contribution of wind and solar combined.

As of August 2008, almost 4,000 MW of new geothermal power plant capacity was under development in the U.S. (this includes projects in the initial development phases). Those states with projects currently under consideration or development are: Alaska, Arizona, California, Colorado, Florida, Hawaii, Idaho, Nevada, New Mexico, Oregon, Utah, Washington, and Wyoming. Combined, these states have approximately 103 projects in development ranging from initial to advanced stages.

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 References, Sources, and Other Useful Data

California Energy Commission, “Geothermal Energy”

California has 25 known geothermal resource areas, 14 of which have underground water temperatures of 300 degrees Fahrenheit (149 degrees Celsius) or greater. The most developed of the high-temperature resource areas of the state is the Geysers. North of San Francisco, one of only two locations in the world where a high-temperature, dry steam is found that can be directly used to turn turbines and generate electricity (the other being Larderello, Italy).

Geothermal Energy Association

The Geothermal Energy Association is a trade association composed of U.S. companies who support the expanded use of geothermal energy and are developing geothermal Resources worldwide for electrical power generation and direct-heat uses. GEA advocates for public policies that will promote the development and utilization of geothermal resources, provides a forum for the industry to discuss issues and problems, encourages research and development to improve geothermal technologies, presents industry views to governmental organizations, provides assistance for the export of geothermal goods and services, compiles statistical data about the geothermal industry, and conducts education and outreach projects.

U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, “Geothermal Technologies Program”

EERE's Geothermal Technologies Program works in partnership with U.S. industry to establish geothermal energy as an economically competitive contributor to the U.S. energy supply.

U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, “Geothermal Basics”

Learn about geothermal energy and enhanced geothermal systems. Information includes FAQs, geothermal development history, and successes in geothermal technologies.

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Last revised: Dec. 11, 2009.