Geothermal Heat Pumps for Your Home
Photo by Stig Nygaard
Geothermal heat pumps (GHPs) are not a new concept; according to the U.S. Department of Energy, people have been using them since the 1940s. There is, however, a resurgence of interest in these earth-based heating and cooling systems. What are GHPs? Are they better for the environment? Do they save money?
The earth naturally absorbs and stores energy from the sun. GHPs tap into this energy. Basically, they use the relatively constant temperature of the earth (below the frost line) rather than heating and cooling the highly variable, above-ground air.
In the winter, heat energy is extracted from the earth, which is much warmer a few feet below the surface. The warmth is then circulated through the building and returned to the earth to be warmed again. In the summer, the reverse occurs.
The temperature below the earth’s surface is cooler during warm months, and the system extracts heat from the building and puts it back into the earth, where it is cooled by the earth and returned to the building. This is why GHPs are sometimes called “Geo Exchange” systems.
There are two main types of GHPs: open loop and closed loop. Both types of systems have a heat pump that is installed inside the building, usually in the basement.
- Open loop systems tap into ground water that is of a relatively constant temperature. The water is pumped to the heat pump where it is warmed and returned to the earth. Or, the heated water can be harvested for other purposes.
- Closed loop GHPs involve a network of pipes laid underground, beginning and ending at the heat pump in the building’s basement. Water and eco-friendly anti-freeze circulates continuously through the pipes, which are set well below the frost line.
Both open-loop and closed-loop GHPs rely on the heat pump to heat or cool the fluid in the pipes; but because the fluid is a constant temperature, having come from the earth, the amount of energy required to get the fluid to the correct temperature is minimal.
Some of the advantages of GHPs are:
- Aesthetically pleasing – GHPs require no external heat pumps, cooling towers, etc. Their underground/indoors structure also keeps GHPs safe from vandalism.
- Versatility – GHPs are compatible with small spaces or large areas. They can be set underground vertically in drilled, well-like spaces or they can be laid horizontally. The pipelines are made of flexible material that can be coiled to increase surface area. They can even be placed on the bed of a sufficiently-sized body of water. GHPs can be installed under asphalt or concrete as well.
- Low operating cost – GHPs require little energy to operate and can save on utility bills.
- Eco-friendly – Geothermal heat pumps produce no emissions, nor do they use a great deal of electricity that is produced by a utility company by burning fossil fuels.
- Because of their fluctuating energy needs and high occupancy, office buildings and schools are especially suited to GHPs. Single family homes can certainly use GHPs as well.
