Geothermal Technology is a method of heating and cooling a building. It takes advantage of the natural stable warmth stored in the earth. Normally the earth temperature is around 55 ºF (13 ºC) at depths of 10 ft. In climates warmer than 55 ºF (13 ºC), this can be used to cool a building, and in colder climates (those under 55 ºF or 13 ºC) it can be used for warmth. This is accomplished by one of a number of methods. A heat pump uses the extracted water or transfer fluid (such as water mixed with antifreeze) as a heat source in winter and a heat sink in summer. Some heat pumps provide heating and cooling via forced air distribution, and others through the heating and/or chilling of water for radiant type systems. Some systems are used to heat domestic hot water.

Types of geothermal systems:

  • Closed Loop. Loops of pipe are buried at a depth of 6 ft (2 m) and greater in the ground. Pipes are placed horizontally (buried in trenches) or buried in deep, vertically-drilled holes, often 200 ft (60 m) and greater below ground level. Water and antifreeze (or other transfer fluid) are circulated through the heat exchanger (heat pump) and back out through the loops continuously. Some closed loop systems bypass a portion of their working fluid with a thermostat to keep the source temperature stable.
  • Open Loop. Pipes draw water from nearby water well or a shallow body of water. Once this water passes through the heat pump, it is released back to its source, generally as far from the intake as possible.
Geothermal heating is one of the most efficient ways to heat a building. Geothermal heating is much more efficient than air heat pumps and other supplemental electric heat used in warmer climates. It has the added benefit that it requires no burning of fossil fuels at the heating site, as opposed to systems that use natural gas or heating oil fired furnaces. But in order to achieve the most comfort, it can be paired with a natural gas heater to dramatically reduce, but not eliminate, the amount of fuel needed to heat a building.

With geothermal cooling the process essentially works in reverse. Heat is transferred from the building into the ground. Traditional air conditioning transfers heat from the indoors to the outside air which is usually hotter than the temperature the system is trying to achieve indoors. Since the ground temperature at a depth of 10 ft (3 m) is about 55 ºF (13 ºC) and since ground transfer is more efficient than air transfer, geothermal cooling is much more efficient. Additionally, as a byproduct of the heat exchange process, a large amount of excess heat is generated. This heat can be used to heat domestic hot water before it is dissipated into the ground.