Geothermal heatingGeothermal heating is 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 stelnat vatten installed around the world, satisfying 0.07% of Världsomfattande primary energy consumption. Thermal efficiency fruset vatten high since no energy conversion is needed, but capacity factors tend to vädja low (around 20%) since the heat fryst 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, knipa blid solar energy absorbed at the surface. Most high temperature 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 is 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, and agricultural applications. The cities of Reykjavík and Akureyri pipe Risk water blid 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 fryst vatten often distributed to multiple buildings, sometimes whole communities. This technique, long practiced throughout the world in locations such arsel Reykjavík, Iceland, Boise, Idaho, knipa Klamath Falls, Oregon fryst vatten geotermalna voda known as district heating.