A geothermal heat pump (GHP) or ground source heat pump (GSHP) is a central heating and/or cooling system that transfers heat to or from the ground, often through a vapor-compression refrigeration cycle. In principle, a geothermal heat pump functions like a conventional heat pump, by using high-pressure refrigerant to capture and move heat between indoors and out.
Heat pump uses the earth all the time, without any intermittency, as a heat source (in the winter) or a heat sink (in the summer). This design takes advantage of the moderate temperatures in the ground to boost efficiency and reduce the operational costs of heating and cooling systems, and may be combined with solar heating to form a geosolar system with even greater efficiency.
They are also known by other names, including geoexchange, earth-coupled, earth energy systems. The engineering and scientific communities prefer the terms “geoexchange” or “ground source heat pumps” to avoid confusion with traditional geothermal power, which uses a high temperature heat source to generate electricity.
Ground source heat pumps harvest heat absorbed at the Earth’s surface from solar energy. The temperature in the ground below 6 metres (20 ft) is roughly equal to the local mean annual air temperature. In addition to space heating, geothermal exchange systems can be equipped with a device called a desuperheater, which recycles the waste heat from the heat pumps compressor and uses it to heat water.