Geothermal Heat Pumps (GHP)

Geothermal heat pumps (GHPs), also known as ground source heat pumps (GSHPs), exchange thermal energy between a building and the ground.

When the building needs heating, the system extracts energy from the ground and pumps it into the building where it is concentrated by the heat pump. When the building needs cooling, the heat from the building is concentrated by the heat pumps and pumped into the ground. This renewable energy source has had significant technological advances in recent years.

General Information

• There are several basic characteristics of GHP systems. The choice depends on the climate, soil conditions, available land, and local installation costs at the site:
  • Ground-coupled systems exchange heat with the ground itself. Ground-source systems tap into subsurface water supplies; water-source systems use ponds or other surface water.
  • The heat exchange is accomplished through the use of piping, which can be closed or open loop. Closed loop systems are most common for commercial/industrial applications. In these systems, pipes filled with an environmentally friendly antifreeze/water solution are buried in the ground in a horizontal, vertical, or in coiled configuration. The fluid in the pipes acts as the heat exchanger. In the winter, the system extracts heat from the earth and carries it into the building. In the summer, the system reverses and takes heat from the building and deposits it to the cooler ground.
  • All ground-coupled systems are closed-loop systems. Ground water and surface water systems may be open or closed loop.
• Geothermal heat pumps are not the same as geothermal heating. Geothermal heating is used in areas where exceptionally high underground temperatures, such as those at hot springs and steam vents, are used to heat indoor spaces without the use of a heat pump.
• The best time to consider a GHP system is when a new building is being planned or when replacement of an existing HVAC system is being considered.
• Geothermal heat pumps typically use 25%-50% less electricity than conventional heating or cooling systems.
• According to the EPA, "Every million square feet of space conditioned with geoexchange technology results in a combined savings of more than 7.6 million kWh and 38,207 MMBtus of fossil fuel". This is comparable to removing 1,200 cars from the highway, or planting 764 acres of trees.

GHP benefits are greatest in buildings with:

• Fairly balanced annual heating and cooling loads.
• A need for independent control of multiple rooms with the potential for heating and cooling different zones simultaneously.
• Where space is an issue. GHP systems provide both heating and cooling, are smaller than conventional furnaces, and don't require the large ductwork associated with HVAC systems.
• Where outdoor equipment, such as window units or rooftop air handlers, pose a problem.
• The amount of land available for the ground heat exchanger will be an important consideration in system design.

Typical Costs

• Payback periods generally range from 2-8 years.
• Long system life - 25 years for the inside components and 50+ years for the ground loop.
• Lower operating costs since there is no need to circulate large amounts of air around the building.
• Lower maintenance costs since there are relatively few moving parts, and because all equipment is housed inside the building.
• GHP systems are quiet.
• Heat pumps can be dedicated to meet hot water loads.

RPM can help. While the use of geothermal heat pumps is growing, use in commercial and industrial buildings remains limited. We can connect you with the best technical experts to inform sound economic and environmental choices.

Remember: Efficiency first. Renewables second.

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