Geothermal energy

From Wikipedia, the free encyclopedia
Jump to: navigation, search
Steam rising from the Nesjavellir Geothermal Power Station in Iceland

Geothermal energy (from the Greek roots geo, meaning earth, and thermos, meaning heat) is energy made by heat inside the Earth's crust.[1] It's clean and sustainable.

Although the Sun does heat the surface of the Earth, heat from inside the Earth is not caused by the Sun. The geothermal energy of the Earth's crust comes 20% from the original formation of the planet, and 80% from the radioactive decay of minerals.[2][3] The Earth is hottest at its core and, from the core to the surface, the temperature gets gradually cooler.

Resources of geothermal energy range from the shallow ground to hot water and hot rock found a few miles beneath the Earth's surface, and down even deeper to the extremely high temperatures of molten rock called magma. It has been used for bathing from Paleolithic times, but is now better known for making electricity.[1]

All over the world, geothermal energy has been used to make about 10 gigawatts of electricity in 2007, and give 0.3% of the electricity needed around the world. When used to generate electricity, geothermal power plants typically offer constant output.[4]

Geothermal energy is also used directly for district heating, or in other heating and cooling applications. Buildings in Iceland are heated in this way from the country's many geothermal sites.

Power plants and thermal applications of geothermal energy are mature technologies, whereas enhanced geothermal systems (EGS) projects are a new type of application.[4]


Geothermal energy escapes as hot water at many hot springs or as steam at geysers.


Hot dry rock resources occur at depths of 3 to 5 miles (5-8 km) everywhere beneath the Earth's surface and at lesser depths in certain areas. Access to these resources involves injecting cold water down one well, circulating it through hot fractured rock, and drawing off the heated water from another well. Currently, nobody uses this method commercially. Existing technology also does not yet allow recovery of heat directly from magma, the very deep and most powerful resource of geothermal energy.

References[change | change source]

  2. How Geothermal energy works. Retrieved on 2013-04-24.
  3. Turcotte D.L. & Schubert G. 2002. Geodynamics. 2nd ed, Cambridge University Press, 136–137. ISBN 978-0-521-66624-4
  4. 4.0 4.1 IPCC (2011). "Special report: renewable energy sources". p. 4.

Other websites[change | change source]