How Ground Source Heat Pumps Work
Ground Source Heat Pumps (GSHPs) are known by several different names. In some regions they are referred to as Geothermal Heat Pumps (GHPs) in others GeoExchange Heat Pumps and sometimes, GHEX Systems. Regardless of the name, a Ground Source Heat Pump is an electrically powered system that uses the stored energy of the greatest solar collector in existence; the earth, to heat and/or cool a space.
In an average year, the earth absorbs roughly 47% of the energy delivered to its surface by the sun. This is 500 times more energy than we use in a given year and best of all, it is clean and renewable. Ground Source Heat Pumps tap into this endless source of renewable energy by exploiting the fact that the absorption of the sun’s rays by the earth creates a near constant deep earth temperature throughout the year.
In other words, when outside air temperatures reach 100˚F or even when they fall to -25˚F, the temperature of the earth just a few feet below the surface stays nearly constant (click on the map to see average deep earth temperatures across the United States). The actual deep-earth temperature varies depending on soil composition and yearly average air temperature but it is always cooler than the air temperature on your hottest summer days and warmer than the outside air temperature on your coldest winter days.
Driven by the basic vapor-compression refrigeration cycle, GSHPs extract heat from the earth during the winter months and reject heat to the earth during the summer months through a ground connection. A normal air source heating or cooling unit (air-source heat pump, ASHP) uses the outside air as its source when heating or cooling a space.
Because of this fact, an air-source heat pump has to use a lot more energy to bring that air to the desired temperature. Think about it this way, boiling an ice-cube will take more heat and more time than boiling tap water. This is where the advantage of the GSHP system resides, using the near constant moderate temperatures below the earth’s surface rather than using the extreme outdoor air temperatures as a heat source/sink.
Contact our engineering department to discuss possible options for your GSHP system and for geothermal design services.