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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