Geothermal heating harnesses natural thermal energy from within the Earth’s crust for water and space heating. This method of heating is hailed for its energy efficiency, lack of pollution, and financial benefits. Areas such as Iceland with abundant geothermal sources, called hot spots, can freely use the energy for heating. Regions lacking hot spots can also achieve geothermal heating, however, using a geothermal heat pump.
Originally, heat within the Earth was created during the formation of the planet by the energy of impact from meteorites and the heat of compression. Today, the heat of compression at the core of the Earth and the decay of radioactive materials in the mantle of the Earth continue to generate heat. Hot spots, where the surface of the Earth has denser pockets of heat, occur when magma is closer to the surface and are usually marked by volcanoes.
A prime example of a hot spot, Iceland has set up geothermal power plants to transform the heat into electricity and uses district heating to heat the water and space in most buildings. Geothermal district heating takes heat from the site of the hot spot and distributes hot water or steam through insulated pipes to buildings. A form of this method has been used since the Roman Empire, which used geothermal heat in its spas and some buildings.
For geothermal heating to be possible in areas without the benefits of a hot spot, a pump must be used. Most places on Earth maintain a temperature of fifty to fifty-five degrees Fahrenheit (50-54°F, 0-12°C) below the surface, regardless of the weather above. A geothermal heating pump uses this constant temperature to conduct space and water heating and cooling in a building, typically a residence.
A series of pipes are set up in a loop beneath the house and cooled water is pumped through. As the water passes through the ground, it conducts heat, which is then re-extracted in a heat exchanger below the house. The heat that the exchanger pulls from the water and the heat created as a byproduct of the exchanger’s work are used to heat the house. When the loop is reversed and warmed water is pumped through the ground to lose heat in the relatively cooler soil, the system can be used to cool the house. Geothermal heating uses far less energy than electric heating and cooling or an air source heat pump.
Geothermal heating is celebrated for several environmental and financial reasons. This method of heating draws energy from a renewable source and creates less of the pollution common to burning fossil fuels. From a financial perspective, geothermal heating systems require less maintenance, last for decades, raise the value of a building, and cut costs normally accrued in monthly oil or electric bills. The initial installation of the system, however, can be very expensive and requires adequate knowledge of the site’s geology so that groundwater is not contaminated and the soil’s integrity is not damaged. Geothermal heating pumps also require electricity to run the pumps, which often necessitates the burning of fossil fuels, and may employ a toxic coolant in the water that runs through the pipes.