Geothermal heat pumps (GHPs), also known as ground source heat pumps, are gaining more attention as a clean and efficient source of heating and cooling for businesses. Because geothermal systems take advantage of the relatively constant temperature of the ground, they operate efficiently during extreme outdoor climate conditions. The average efficiency of a new system is about 400%. This proven technology offers benefits in increased comfort, as well as lower energy and maintenance costs.

Geothermal advantages

The most significant benefit of GHPs is their lower energy consumption; they use 25% to 50% less than conventional heating and cooling systems. Additional benefits include:

• Humidity control. GHPs provide excellent humidity control, maintaining about 50% 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.

How GHPs work

To provide cooling, geothermal systems use a four-step process:

1. A fluid absorbs heat from indoor air through a heat exchanger.
2. The heat pump moves the heated fluid through a series of underground pipes.
3. The heat is discharged to the relatively colder ground around it.
4. The fluid returns to the building at a lower temperature, where it absorbs more heat.

In winter, this process is reversed, as heat from the ground is transferred into the building. 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 commonly used. Plastic tubing is buried in the ground or submerged in water and connected to the heat pump in the building. Horizontal and vertical configurations are available. In horizontal systems, piping is laid out in shallow trenches. Vertical designs are commonly used in commercial buildings because they require less land area. 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. A hybrid system with supplemental heat rejection from a cooling tower is an alternative for commercial applications that might not have the land area for a full-sized ground coil.

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 good return on investment. Financial incentives can help to cover initial costs. Your local electric cooperative even offers Power Moves rebates for qualifying geothermal heat pump upgrades for businesses. Contact your local electric co-op’s energy advisor for details.