How geothermal heat pumps work

Less than 10 feet beneath the surface, the earth’s temperature remains fairly constant year-round, ranging from 45º or so in northern latitudes to about 70ºF in the deep South. A geothermal heat pump takes advantage of this constant temperature to provide efficient heating and cooling.

In winter, a fluid circulating through pipes buried in the ground absorbs heat from the earth and carries it into the home. The geothermal system inside the building uses a heat pump to concentrate the earth’s thermal energy and then to transfer it to the interior space for warmth.

In the summer, the process is reversed: heat is extracted from the air in the building and transferred through the heat pump to the ground loop piping. The fluid in the ground loop then carries the heat back to the earth. The only external energy required is the electricity needed to operate the heat pump, ground loop pump and distribution fan or pump.

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A geothermal heat pump system includes three main components:

Earth connection: Using the earth as a heat source/sink, a series of pipes, commonly called a “loop,” is buried in the ground near the building to be conditioned. The loop can be installed either vertically or horizontally. It circulates a fluid (water, or a mixture of water and antifreeze) that absorbs heat from, or releases heat to, the surrounding soil depending on whether the ambient air is colder or warmer than the soil.

Heat pump subsystem: For heating, a geothermal heat pump removes the heat from the fluid in the earth connection, concentrates it, and then transfers it to the building. For cooling, the process is reversed.

Heat distribution subsystem: Conventional ductwork is generally used to distribute heated or cooled air from the geothermal heat pump throughout the building. Radiant floor heating is also a popular way to provide heat in residential applications. Domestic hot water and pool heating are other typical subsystems.