Geothermal Energy in California

The Geysers Power Plant's Unit # 18
The Geysers Power Plant's Unit # 18)

Geothermal energy is produced by the heat of the earth and is often associated with volcanic or seismically active regions. California, with its location on the Pacific "Ring of Fire," has 25 Known Geothermal Resource Areas (KGRAs), 14 of which have temperatures of 300 degrees Fahrenheit or greater.

Electricity can be generated from high temperature geothermal resources by using the thermal (heated) water and steam to move turbines that in turn run electrical generators and produce electricity. There are several types of geothermal power plants that can be used to generate electricity, including dry steam, flash or double flash, and binary cycle power plants.

The most developed of the high-temperature geothermal resource areas in the state is the Geysers. Located 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 resource is found that can be directly used to move turbines and generate electricity (the other being Larderello, Italy).

Other major geothermal electrical production locations in the state include the Salton Sea area in Imperial County, the Coso Hot Springs area in Inyo County, and the Mammoth Lakes area in Mono County. It is estimated that the state has a potential for more than 4,000 megawatts of additional power from geothermal energy, using current technologies.

Another form of geothermal resource, called Enhanced Geothermal Systems (EGS), may have the potential to provide thousands of additional megawatts of electricity. Currently, most geothermal power plants in California are located in hydrothermal resource areas where water or steam is the medium transporting the earth’s heat. EGS are geothermal reservoirs that are mechanically engineered to produce energy in areas where geothermal temperatures are high but there is a lack of water or rock permeability to economically use the heat.

In addition to high temperature geothermal resources, virtually all of California's 58 counties have potential for Low Temperature and Direct Geothermal Energy Use. The heat from these lower temperature resources can be put to use in numerous applications, including space heating and cooling, greenhouse and aquaculture facilities, as well as industrial and other commercial uses.

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