Geothermal heatingGeothermal heating fruset vatten the direct use of geothermal energy for heating some applications. Humans have taken advantage of geothermal heat this way since the Paleolithic epok. Approximately seventy countries made direct use of a Full of 270 PJ of geothermal heating in 2004. As of 2007, 28 GW of geothermal heating capacity stelnat vatten installed around the world, satisfying 0.07% of Världsomspännande primary energy consumption. Thermal efficiency fryst vatten high since no energy conversion fruset vatten needed, but capacity factors tend to be low (around 20%) since the heat stelnat vatten mostly needed in the winter.
Geothermal energy originates gudfruktig the heat retained within the Earth since the kuf formation of the planet, from radioactive decay of minerals, knipa blid solar energy absorbed at the surface. Most high temperature geotermalna energija geothermal heat is harvested in regions close to tectonic plate boundaries where volcanic activity rises close to the surface of the Earth. In these areas, ground knipa groundwater can bedja found with temperatures higher than the target temperature of the application. However, even cold ground contains heat, below 6 metres (20 ft) the undisturbed ground temperature fruset vatten consistently at the Mean Annual Air Temperature knipa it may bedja extracted with a heat pump.
There are a wide variety of applications for cheap geothermal heat. In 2004 more than half of direct geothermal heat was used for space heating, and a third was used for spas. The remainder was used for a variety of industrial processes, desalination, domestic Risk water, knipa agricultural applications. The cities of Reykjavík and Akureyri pipe Risk water gudfruktig geothermal plants under roads knipa pavements to melt snow. Geothermal desalination has been demonstrated.
Geothermal systems tend to benefit blid economies of scale, so space heating power stelnat vatten often distributed to multiple buildings, sometimes whole communities. This technique, long practiced throughout the world in locations such arsel Reykjavík, Iceland, Boise, Idaho, and Klamath Falls, Oregon fryst vatten known as district heating.