Geothermal energy is produced by the heat of the earth and is often associated with volcanic and seismically active regions. California has 25 known geothermal resource areas, 14 of which have underground water temperatures of 300 degrees Fahrenheit (149 degrees Celsius) or greater.
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 your home through a ground-source heat pump.
Forty-six of California's 58 counties have lower temperature resources for direct-use geothermal. In fact, the City of San Bernardino has developed the largest geothermal direct-use projects in North America, heating at least three dozen buildings - including a 15-story high-rise and government facilities - with fluids distributed through 15 miles of pipelines. Environmentally benign fluids are discharged to surface water channels after heat is used.
When added together, California's geothermal power plants have a dependable installed capacity of about 2,030 megawatts. They produced 4.8 percent of California's total electricity in 2004 (about 14,000 gigawatt/hours).
The most developed of the high-temperature resource areas of the state is the Geysers. North of San Francisco, the Geysers was first tapped as a geothermal resource to generate electricity in 1960. It is 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).
Other major geothermal locations in the state include the Imperial Valley area east of San Diego and the Coso Hot Springs area near Bakersfield. It is estimated that the state has a potential of more than 4,000 megawatts of additional power from geothermal energy, using current technologies.
Additionally, two forms of geothermal energy - Hot Dry Rock and Magma - have the potential to provide thousands of megawatts in California. Recent investigations in Hot Dry Rock were focused in the Clear Lake area of Lake County; Magma research occurred in the Long Valley Caldera of Mono County.
For more information on geothermal energy, contact:
California Energy Commission
1516 Ninth Street, MS-43
Sacramento, CA 95814
Department of Energy
Office of Efficiency and Renewable Energy
1000 Independence Ave., S.W.
Washington, DC 20585
Geothermal Education Office
Marilyn Nemzer, Executive Director
664 Hilary Drive
Tiburon, CA 94920
Geothermal Resources Council
P.O. Box 1350
Davis, CA 95617
Oregon Institute of Technology
3201 Campus Drive
Klamath Falls, OR 97601