A geothermal heat pump is a system of heating and cooling that uses the natural features of shallow ground. Also known as GeoExchange, geothermal heat pumps draw energy from the top 10 feet of the earth's surface. The temperature of this area is generally stable between 50° to 61°F (10° to 16°C). During the winter, a geothermal heat pump will utilize this ground temperature for heating, while in the summer, the system will use it as a heat sink for cooling.
The geothermal heat pump is comprised of a loop that travels under the frost line, the point in which the surface temperature no longer affects the ground. A refrigerant is pumped through the loop and exchanges heat with the cooler or warmer ground. The refrigerant then proceeds back to the appliance, either warmed or cooled depending on the season. Known as direct exchange, this process is used most effectively in keeping an appliance or device at a stable temperature. Oftentimes this system is made from either copper tubing or a high-density polyethylene.
Two distinct types of geothermal heat pumps are commonly implemented in homes and businesses. Water-to-air systems replace forced air furnaces and sometimes central air conditioning systems. The refrigerant is used to heat or cool air that is forced from the geothermal heat pump. Radiators and underfloor heating systems use a water-to-water heat pump. This operates like a boiler, heating water ducts that control the temperature in a building. Unfortunately, these systems cannot be used for cooling.
Geothermal heat pumps were first developed in the 1940s. According to the U.S. Department of Energy, there are approximately 50,000 new units installed in the country every year. These pumps are most common in households as replacement for traditional heating and cooling systems. A geothermal heat pump costs roughly $2,500 US Dollars (USD) per ton of capacity. Most homes need a three-ton appliance in order to control the temperature. This means that the average consumer pays for the installation and equipment over the course of five to ten years with energy savings. The components of the heat pump itself have a lifespan of 25 years, while the ground loop lasts for nearly 50 years.
A geothermal heat pump is different from traditional forms of heating or cooling in that it does not use a fuel or chemical to maintain temperature. Furnaces and boilers transfer heat through a method of combustion. This creates carbon emissions that can pollute the atmosphere. According to the U.S. Energy Information Administration, the average home produces 5,550 tons of carbon emissions each year in heating or cooling. By using a geothermal heat pump, that number is essentially nullified.