Geothermal power plant is power extracted from heat stored in the
earth. This geothermal energy originates from the original formation of the
planet, from radioactive decay of minerals, and from solar energy absorbed at
the surface. It has been used for bathing since Paleolithic times
and for space heating since ancient Roman times, but is now better known for
generating electricity. Worldwide, geothermal power plants have
the capacity to generate about 10 gigawatts of electricity, and in practice
supply 0.3% of global electricity demand. An additional 28 gigawatts of direct
geothermal heating capacity is installed for district heating, space heating,
spas, industrial processes, desalination and agricultural applications.
Geothermal power plant is cost effective, reliable, sustainable, and
environmentally friendly, but has historically been limited to areas near
tectonic plate boundaries. Recent technological advances have dramatically
expanded the range and size of viable resources, especially for applications
such as home heating, opening a potential for widespread exploitation.
Geothermal wells release greenhouse gases trapped deep within the earth, but
these emissions are much lower per energy unit than those of fossil fuels. As a
result, geothermal power has the potential to help mitigate global warming if
widely deployed in place of fossil fuels.
The Earth's geothermal resources are
theoretically more than adequate to supply humanity's energy needs, but only a
very small fraction of it may be profitably exploited. Drilling and exploration
for deep resources costs tens of millions of dollars, and success is not
guaranteed. Forecasts for the future penetration of geothermal power
plants depend on assumptions about technology growth, the price of
energy, subsidies, and interest rates.
Twenty-four countries generated a total of
56,786 gigawatt-hours (GW·h) (204 PJ) of electricity
from geothermal power plant, accounting for 0.3% of worldwide
electricity consumption. Output is growing by 3% annually, keeping pace with
global electricity generation from all sources. Growth is being achieved
through a growing number of plants as well as improvements in their capacity
factors. Because geothermal power does not rely on variable sources of energy,
unlike, for example, wind or solar, its capacity factor can be quite large—up
to 96% has been demonstrated. The global average was 73% in 2005. The global
installed capacity was 10 gigawatts (GW).
The largest group of geothermal
power plants in the world is located at The Geysers, a geothermal field in
California, United States. As of 2004, five countries (El Salvador, Kenya, the
Philippines, Iceland, and Costa Rica) generate more than 15% of their
electricity from geothermal sources.
Geothermal electric plants have until recently been built exclusively on
the edges of tectonic plates where high temperature geothermal resources are
available near the surface. The development of binary cycle power plants and
improvements in drilling and extraction technology may enable enhanced
geothermal systems over a much greater geographical range. Demonstration
projects are operational in Landau-Pfalz, Germany, and Soultz-sous-Foręts, France, while an earlier effort in Basel,
Switzerland was shut down after it triggered earthquakes. Other demonstration
projects are under construction in Australia, the United Kingdom, and the
United States of America.