Geothermal heat pumps draw heat from the ground during the winter since the upper 10 feet (3 meters) of the Earth, maintains a nearly constant temperature between 50° and 60°F (10°-16°C).
Since the 1980s at the University of Tennessee – Battelle, which operates ORNL (Oak Ridge National Laboratory) for the Department of Energy, research into the development of advanced home appliances has included a unit that combines water heating with heating and cooling, dehumidification and ventilation functions. ORLNL researchers have developed a heat pump water heater, which uses 50 percent less energy than standard heat pumps and water heaters.
Heat pumps work like a refrigerator in reverse, moving heat from one place to another. In the case of an air-source heat pump system that combines heating, cooling, and water heating, the system pulls heat indoors from the outdoor air in the winter and from the indoor air in the summer. Because the heat pump removes heat from the air, any type of air-source heat pump system works more efficiently in a warm climate.
These days in a cooler climate, new, green dream home builders take a new breath* and choose to install geothermal heat pumps—which draw heat from the ground during the winter and from the indoor air during the summer—for heating and cooling their homes. For water heating, you can add a “desuperheater” to a geothermal heat pump system, a.k.a., Ground Source Heat Pump.
- Desuperheater
- A small, auxiliary heat exchanger that uses superheated gases from the heat pump’s compressor to heat water. This hot water then circulates through a pipe to the home’s storage water heater tank.
Desuperheaters are also available for demand (tankless or instantaneous) water heaters. In the summer, the desuperheater uses the excess heat that would otherwise be expelled to the ground. Therefore, when the geothermal heat pump runs frequently during the summer, it can heat all of your water. During the fall, winter, and spring—when the desuperheater isn’t producing as much excess heat—you’ll need to rely more on your storage or demand water heater to heat the water. Some manufacturers also offer triple-function geothermal heat pump systems, which provide heating, cooling, and hot water. They use a separate heat exchanger to meet all of a household’s hot water needs, significantly contributing to a home achieving Zero Energy status.
* Note: Geothermal systems have pretty significant upfront costs, anywhere from $18,000 to $25,000.
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