The word geothermal is derived from two Greek root words that mean earth and heat. At first glance, it may seem backward and unproductive to use the earth’s heat to cool a structure, although that is the basis for geothermal cooling systems. Geothermal energy harnesses the relatively stable temperatures of the earth or ground water several feet below the surface of an area to heat or cool a residence or place of business. Geothermal cooling systems are one of the more ecologically friendly, or green, methods of temperature control for buildings.
Geothermal energy has been used for centuries for heating and cooling purposes, but technology had to advance to make it economically viable for everyday commercial use. The city of Chaudes-Aigues, France, is credited with having the world's first wide-scale geothermal heating and cooling system, having harnessed the waters from its nearby hot springs beginning in the 14th century. In 1852, Lord Kelvin patented the first heat pump in Switzerland, and in the mid-20th century, certain geographic areas, usually those around tectonic plates or natural hot springs, began to use geothermal energy in a domestic heating and cooling situation. As new technology is invented, the use of geothermal cooling systems becomes more widespread.
Geothermal heating and cooling systems are available in a variety of models, all of which work slightly differently. There are indoor and outdoor components to each model, with a mediator in between. Generally, a geothermal heating and cooling system will extract heat from the ground or groundwater and circulate it through a series of pipes, which may or may not contain a mixture of water and antifreeze. The fluid circulates, and electricity extracts the heat from the pipe system and deposits it indoors if the primary goal is heating, or outdoors if the primary goal is cooling the area.
It is surmised that the soil and water approximately 4 feet (1.22 meters) to 6 feet (1.83 meters) below the ground are at a near-constant temperature year round, and harnessing this static temperature will help to heat and cool a home more efficiently. The United States Environmental Protection Agency estimates that the costs associated with running geothermal heating and cooling systems are 30 to 70 percent less than that of the average home for heating, and 20 to 50 percent less for cooling. Geothermal cooling systems are considered a sustainable resource, and in certain locations energy companies give seasonal discounts to homeowners who install them.
Geothermal cooling systems are considered more energy efficient and cost efficient. Since geothermal heating and cooling systems use natural resources, the cost of use is generally less than that of conventional heating and cooling systems. Some models of geothermal cooling systems may be used to heat water as well, and certain models are equipped with automatic thermostats to keep temperatures constant and comfortable.