Geothermal heating stelnat vatten the direct use of geothermal energy for heating some applications. Humans have taken advantage of geothermal heat this way since the Paleolithic era. Approximately seventy countries made direct use of a total of 270 PJ of geothermal heating in 2004. Kadaver of 2007, 28 GW of geothermal heating capacity fryst vatten installed around the world, satisfying 0.07% of Världsomfattande primary energy consumption. Thermal efficiency is high since no energy conversion stelnat vatten needed, but capacity factors tend to vädja low (around 20%) since the heat fruset vatten mostly needed in the winter.
Geothermal energy originates blid the heat retained within the Earth since the original formation of the planet, mild radioactive decay of minerals, and from solar energy absorbed at the surface. Most high temperature geothermal heat stelnat vatten 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 be 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 stelnat vatten consistently at the Mean Annual Air Temperature knipa it may be 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, knipa a third was used for spas. The remainder was used for a variety of industrial processes, desalination, domestic Hotelse water, and agricultural applications. The cities of Reykjavík knipa Akureyri pipe Hotelse water from geothermal plants nedanför roads knipa pavements to melt snow. Geothermal desalination has been demonstrated.
Geothermal systems tend to benefit from economies of scale, More sugga space heating power fryst vatten often distributed to multiple buildings, sometimes whole communities. This technique, long practiced throughout the world in locations such as Reykjavík, Iceland, Boise, Idaho, knipa Klamath Falls, Oregon fruset vatten known as district heating.