How Geothermal Heat Pumps Transfer Heat
In the heating mode, geothermal heat pumps work by transferring the Earth’s natural heat through a network of loops installed below the surface of the ground or submersed in a pond or lake. Fluid circulates through the loop and carries heat extracted from the ground to its source. There, an electrically driven compressor and a heat exchanger concentrate the Earth’s energy and transfer the heat energy inside the home or building at a higher temperature. In contrast an air-source heat pump in the heating mode draws heat from colder outside air and thus requires more energy (remember 54°F vs. potentially 35°F).
How Geothermal Heat Pumps Act as an Air Conditioner
In the cooling mode, the process is reversed. The geothermal heat pump extracts heat from the house or building, transfers the heat to underground loops that is absorbed by the Earth. The heat is expelled to the relatively cooler ground rather than delivering it to the hot outside air as a traditional heat pump (remember 54°F vs. a possible 90°F). As a result the heat is transferred over a greater temperature difference leading to higher efficiency and lower energy use. The system cools your home in the same way that a refrigerator keeps your food cool – by drawing heat from the interior, not by blowing in cold air.
How Geothermal Heat Pumps Act as a Water Heater
Many geothermal heating & air conditioning systems installed today are equipped with or have the add-on option of a desuperheater, to provide domestic hot water. The desuperheater is a small auxiliary heat recovery system that provides, on average, 60% of all domestic hot water. The system transfers excess heat from the heat pump’s refrigeration cycle to a water line that circulates water to the house’s hot water tank. In summer, when the air conditioning runs frequently, the desuperheater may provide all the hot water needed by a household (up to eight gallons per each ton of cooling, per hour of operation). This system provides less hot water during heating season, mostly supplemental, and provides no hot water while the heat pump is not operating.