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Geothermal Power - A Hot Way to Produce Electricity

Some Geothermal Facts

  • Geothermal energy provides more than 2700 megawatts (MW) of electric power to U.S. residents - comparable to 60 million barrels of oil per year, enough for 3.5 million homes. This is only a small fraction of the potential value of geothermal energy in the U.S.
  • Geothermal electricity is clean - no fossil fuels are burned. Geothermal electricity produced in the U.S. displaces the emission of 22 million tons of carbon dioxide a year!
  • Geothermal electricity is reliable - plants have average system availabilities of 95% or higher, compared to 60-70% for coal and nuclear plants.
  • Geothermal electricity is cost-effective - today's cost of geothermal electricity ranges from $0.05 to $0.08 per kilowatt-hour, and technology improvements are steadily lowering that range.
  • The average geothermal power plant requires only 400 square meters of land to produce a gigawatt of power over 30 years. Compare that with the enormous amount of land needed for coal and nuclear plants and all the open-pit and other mining required for fueling them.
  • Last but not least, geothermal electricity is homegrown - it reduces our need to import oil, reduces the trade deficit, and adds jobs to the U.S. economy.

Converting Steam and Hot Water to Electricity

Three power plant technologies are currently used to convert hydrothermal fluids to electricity:

  • Dry Steam
  • Binary Cycle
  • Flash Steam

The type of conversion used depends on the state of the fluid (whether steam or water) and its temperature.

Dry Steam Power Plants

Steam plants use hydrothermal fluids that are primarily steam. The steam goes directly to a turbine, which drives a generator that produces electricity. The steam eliminates the need to burn fossil fuels to run the turbine. It also eliminates the need to transport and store fuels! This is the oldest type of geothermal power plant. It was first used at Lardarello in Italy in 1904, and is still very effective.

Steam technology is used today at The Geysers in northern California, the world's largest single source of geothermal power. These plants emit only excess steam and very minor amounts of gases.

Dry Steam Power Plant diagram

For information on Binary Cycle and Flash Steam power plants, please follow this link: http://www.eren.doe.gov/geothermal/geopowerplants.html.

The Future of Geothermal Electricity

Steam and hot water reservoirs are just a small part of the geothermal resource. The Earth's magma and hot dry rock will provide cheap, clean, and almost unlimited energy as soon as we develop the technology to use them. In the meantime, because they're so abundant, moderate-temperature sites running binary-cycle power plants will be the most common electricity producers.

Before geothermal electricity can be considered a key element of the U.S. energy infrastructure, it must become cost-competitive with traditional forms of energy. The U.S. Department of Energy is working with the geothermal industry to achieve $0.03 per kilowatt-hour. We believe the result will be about 15,000 megawatts of new capacity within the next decade.

Source: DOE Office of Energy Efficiency and Renewable Energy, Geothermal Technologies Program

For more on Geothermal Energy:

U.S. Department of Energy (Geothermal Energy Technical Site):
http://geothermal.id.doe.gov

U.S. Department of Energy (Geothermal Energy):
http://www.eere.energy.gov/geothermal/

Sandia National Laboratories (Geothermal Research Department)
https://cfwebprod.sandia.gov/cfdocs/GPI/

Energy Quest - California Energy Commission
http://www.energyquest.ca.gov/

Energy Information Administration
http://www.eia.doe.gov/kids/energyfacts/sources/renewable/
geothermal.html

GeoHeat Center (Low Temperature Uses of Geothermal Water and Heat):
http://www.oit.edu/~geoheat

Geysers Geothermal Association (GGA)
http://www.thegga.org/

International Ground Source Heat Pump Association (Geothermal Heat Pumps):
http://www.igshpa.okstate.edu

International Geothermal Association
http://iga.igg.cnr.it/index.php

Geothermal Energy Association (Industry Trade Association):
http://www.geo-energy.org/

Geothermal Resources Council (Geothermal Industry Association):
http://www.geothermal.org

Geothermal Heat Pump Consortium
http://www.geoexchange.org

California Department of Conservation, Department of Oil, Gas and Geothermal Resources:
http://www.consrv.ca.gov/dog/

California Energy Commission (Geothermal Energy):
http://www.energy.ca.gov/geothermal

Geothermal Education Office:
http://www.geothermal.marin.org