Geothermal heating and cooling systems are the highest efficiency option available to homeowners and are 45% higher efficiency than air source heat pumps, according to the Department of Energy. A geothermal heat pump uses the relatively stable temperature of the ground as a source and sink for thermal energy for the building. A geothermal heating and cooling system will require a geothermal heat exchanger: there are a wide variety of geo exchange designs but the most common are vertically drilled or horizontally trenched closed-loop heat exchangers that use high-density polyethylene pipe to absorb and disperse thermal energy. Think of this as the “geo well” or geo heat exchanger,” the underground part of the system; the pipe used as the heat exchanger is drilled down to residential depths of approximately 500 ft using the same drill rig that might drill a water well.
Geothermal heat pumps can move and concentrate heat from one place to another. Though this may sound very high tech, most geo heat pumps use similar technology to the refrigerator that you have in your home. A refrigerator moves heat from inside its walls to outside; people of a certain age will probably remember the pleasant hot air blown from the bottom of older refrigerator models on a cold winter day. The energy that is being rejected from a refrigerator was originally inside it, making it cooler inside the box and the heat rejected is a higher temperature than the kitchen air. Geothermal heat pumps use the same principle in the summer, they can move the heat from inside the building into the ground, which makes the building cooler and the ground absorbs and diffuses that heat energy to its surroundings. In the winter, the cycle is reversed, and low temperature energy is drawn from the ground, concentrated, and rejected to the home as hot air or water at temperatures reaching up to 120°F. The size of a geothermal heat exchanger will depend on a number of factors such as the heating and cooling demands of the building and local ground conditions.
