Geothermal energy in the United States
Geothermal energy in the United States generated a record of about 16.792 million megawatt-hours in 2012, narrowly beating the previous record of 16.789 set in 1993. In 2012, the United States led the world in geothermal electricity production with 3,386 megawatts (MW) of installed capacity; the largest group of geothermal power plants in the world is located at The Geysers, a geothermal field in California. The United States generates an average of 15 billion kilowatt hours of geothermal power per year, comparable to burning some 25 million barrels (4,000,000 m3) of oil or 6 million short tons of coal per year. In the twelve months through April 2013, geothermal energy generated 16.9 million megawatt-hours, 0.41% of total US electricity.
Geothermal power plants are largely concentrated in the western states. They are the fourth largest source of renewable electricity, after hydroelectricity, biomass, and wind power. A geothermal resource assessment shows that nine western states together have the potential to provide over 20 percent of national electricity needs.
According to archaeological evidence, geothermal resources have been in use on the current territory of the United States for more than 10,000 years. The Paleo-Indians first used geothermal hot springs for warmth, cleansing, and minerals.
The first commercial geothermal power plant producing power to the U.S. utility grid opened at The Geysers in California in 1960, producing eleven megawatts of net power. The Geysers system continues to operate successfully today, and the complex has grown into the largest geothermal development in the world, with an output of 750 MW.
The largest dry steam field in the world is the Geysers, 116 km (72 mi) north of San Francisco. It was here that Pacific Gas and Electric began operation of the first successful geothermal electric power plant in the United States in 1960. The original turbine lasted for more than 30 years and produced 11 MW net power. The Geysers has 1517 megawatt (MW) of active installed capacity with an average capacity factor of 63%.Calpine Corporation owns 15 of the 18 active plants in the Geysers and is currently the United States' largest producer of geothermal energy. Two other plants are owned jointly by the Northern California Power Agency and the City of Santa Clara's municipal Electric Utility (now called Silicon Valley Power). The remaining Bottle Rock Power plant owned by the US Renewables Group has only recently been reopened. A nineteenth plant is now under development by Ram Power, formerly Western Geopower. Since the activities of one geothermal plant affects those nearby, the consolidation plant ownership at The Geysers has been beneficial because the plants operate cooperatively instead of in their own short-term interest. The Geysers is now recharged by injecting treated sewage effluent from the City of Santa Rosa and the Lake County sewage treatment plant. This sewage effluent used to be dumped into rivers and streams and is now piped to the geothermal field where it replenishes the steam produced for power generation.
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