Geothermal Heat Pumps
Geothermal heat pumps (GHPs) are among the most efficient and comfortable heating and cooling technologies available, according to the U.S. Department of Energy, because they use the earth’s natural ability to supply or absorb heat at extremely high efficiencies.
GHP systems are commonly used to provide heating and cooling to homes, schools, hospitals, as well as commercial and government buildings.
GHP systems take a fundamentally different approach to heating and cooling than conventional systems. Unlike conventional furnaces—which create heat by burning a fuel such as natural gas, propane, or fuel oil—GHP systems don’t create heat, so there’s no chemical combustion.
Instead, GHP systems move heat (thermal energy) stored in the earth or groundwater to the building during winter and remove heat from the building to the earth or groundwater during summer months.
According to the GeoExchange, there are more than 1 million GHP installations in the United States today. While this is a small percentage of the total HVAC market, the number of people choosing to install GHP systems is growing rapidly at a rate of about 50,000 installations a year.
What are the cost benefits of GHPs?
Even though the installation price of a geothermal system is more than that of conventional heating and cooling systems of the same capacity, the energy savings are significantly lower and therefore will offset the higher installation costs over time.
When the cost of a GHP system is included in a mortgage, your investment should produce a positive cash flow from the beginning. In other words, the extra cost of the GHP system to the total mortgage payment will likely be exceeded by energy cost savings over the course of each year.
Learn about various financing options by going to the U.S. Environmental Protection Agency’s Energy Star website.
Are there financial incentives to installing a GHP system?
Geothermal heat pump systems installed in new or existing homes by Dec. 31, 2016, are eligible for a 30 percent federal tax credit.
To learn more about residential and commercial federal, state, and local GHP tax incentives, click here.
What are the maintenance requirements of a GHP system?
System life is estimated at 25 years for the inside components and 50-plus years for the ground loop, according to the U.S. Department of Energy.
GHP systems have relatively few moving parts and those parts are sheltered inside a building, so the systems are durable and highly reliable. GHP systems usually have no outside compressors, so they are not susceptible to vandalism.
In addition, the components in the living space are easily accessible, which increases the convenience factor and helps ensure that the upkeep is done on a timely basis.
Depending on the size and complexity of a GHP project, multiple professionals may be involved. Large institutional, commercial, or industrial GHP projects could involve as many as 15 different types of professionals, such as those who:
- Design and engineer the systems
- Install system components
- Inspect and regulate the systems.
For residential GHP systems, one contractor with the necessary credentials may design and install the entire system. To learn more about choosing and installing a geothermal heat pump system, visit the U.S. Department of Energy website.
Can a GHP system be installed for any type of building?
There are four basic types of ground loop systems. Three of these—horizontal, vertical, and pond/lake—are closed-loop systems. The fourth type of system is the open-loop option. All of these approaches can be used for residential, commercial, and institutional buildings such as schools or government facilities. Which GHP option is best depends on the climate, soil conditions, available land, and local installation costs at the site.
Most closed-loop geothermal heat pumps circulate an environmentally friendly antifreeze solution through a closed loop—usually made of plastic tubing—that is buried in the ground or submerged in water. A heat exchanger transfers heat between the refrigerant in the heat pump and the antifreeze solution in the closed loop. The loop can be in a horizontal, vertical, or pond/lake configuration.
An open-loop system uses well or surface body water as the heat exchange fluid that circulates directly through the GHP system. Once it has circulated through the system, the water returns to the ground through the well, a recharge well, or surface discharge. This option is practical only where there is an adequate supply of relatively clean water.
A fifth type of hybrid heat exchanger is called a “standing column”—a system using a single water well for both extraction and return of groundwater for a ground source heat pump. Water may be discharged from the well to maintain operational groundwater temperatures.
GHP case studies:
Click here to view case studies of GHP projects and energy and cost savings.