- Geothermal heat pumps use the constant temperature of the ground to provide heating and cooling.
- Advantages include up to 50 percent less energy than conventional systems and less maintenance.
- Although they're expensive to install, heat pumps can pay for themselves in lower operating costs.
Geothermal heat pumps (GHPs), also known as ground source heat pumps, have gained attention recently as a clean and efficient source of heating and cooling for commercial and institutional facilities. About 1.5 million units are currently installed in the U.S., according to the Geothermal Exchange Organization, with new installations averaging about 85,000 a year.
Because geothermal systems take advantage of the relatively constant temperature of the ground, they provide more heating and cooling output than the energy they use. The average efficiency of a new system is about 400 percent. This well-established technology offers benefits in increased occupant comfort, as well as reduced energy and maintenance costs.
Advantages of geothermal heat pump systems
The most significant benefit of GHPs is their lower energy consumption; they use 25 to 50 percent less than conventional heating and cooling systems. Additional benefits include:
- Humidity control. GHPs provide excellent humidity control, maintaining about 50 percent relative humidity indoors, making them effective in humid climates.
- Design flexibility. Geothermal systems are a good fit for both new construction and retrofits. They require less space than conventional HVAC systems, freeing up space in equipment rooms.
- Zoning. GHP systems provide zone space conditioning, allowing separate areas to be heated and cooled at different temperatures.
- Low maintenance. GHPs have few moving parts; this reduces maintenance needs and increases system durability. Geothermal systems typically last 20 years or more.
Geothermal heat pumps transfer heat that's stored in the ground into a building during the winter. In summer, this process is reversed as heat is moved out of the building and back into the ground. Closed- or open-loop designs are available. Deciding which is best for your facility will depend on the climate, soil conditions and available land at the site.
Closed-loop systems are the most common. Plastic tubing is buried in the ground or submerged in water and connected to the heat pump in the building. A heat exchange fluid circulates through this tubing. Horizontal and vertical configurations are available. In horizontal systems, piping is laid out in trenches at least four feet deep. Vertical designs are commonly used in commercial buildings because the land area required for a horizontal loop may not be available. Piping is looped through holes drilled up to 400 feet deep.
Open-loop systems use pond or well water as the heat exchange fluid, which circulates directly through the heat pump. These systems are only practical if there's an adequate supply of relatively clean water, and if local groundwater regulations allow them.
Cost and payback
Geothermal heat pumps do cost more to install than conventional heating and cooling systems. However, their lower maintenance and operational costs, as well as system durability, can provide a reasonable return on investment. Financial incentives can help to cover initial costs. Search the Database of State Incentives for Renewables & Efficiency® for incentives available in your area.