Geothermal energy
Geothermal energy is produced by tapping into the heat that exists below the earth's crust. Heat can be obtained by drilling into the ground and then carried by a heat-transfer fluid such as water, brine or steam. Geothermal energy can be harnessed for electricity generation and for heating. The use of geothermal energy is concentrated in regions where heat extraction is economical: a combination of heat, flow and high permeability is needed. Together with solar thermal, geothermal energy provided 2.2% of worldwide demand for heating in buildings in 2019.