What is a Geothermal Heat Pump?
Today’s energy conscious homeowners have many efficient options from which to choose regarding the heating and cooling of their homes. A geothermal heat pump is one of those options that is growing in popularity across the country. Also referred to as a ground source heat pump, it uses the constant ground temperatures of the earth to heat and cool the air while using less energy than traditional systems. Using the ground as an exchange medium is in stark contrast to other heat pump systems, which rely on outside air temperatures to provide the conditioned air. This makes a geothermal heat pump a highly efficient option for homeowners, which can lead to significant energy savings.
A geothermal heat pump can both heat and cool as well as provide domestic hot water with some models. Other options available with a geothermal heat pump include variable speed fans and two-speed compressors, which increase their efficiency in both performance and energy savings. The rugged systems require less maintenance, are quieter and have a longer life expectancy than other heat pump systems.
Some manufacturers combine the best of both a geothermal and an air-source heat pump. These models are referred to as a dual-source heat pump. Although these units are more efficient than a standard air-source heat pump, they fall short when compared to a stand alone geothermal system. One advantage of a dual-source system is that they are often less expensive to install.
Installing a geothermal heat pump does not come easy as the system can cost several times that of a traditional air-source system. However, you can realize a ROI “Return on Investment” for the additional installation costs in approximately five to ten years. Combine that with a life expectancy of 25 years for a geothermal heat pump’s interior components and 50 plus years for its exterior components and your savings can really add up in a hurry.
Basic Types of Geothermal Heat Pumps
Geothermal heat pumps are characterized into four groups. Three of the four named systems are of the close looped variety with the fourth being referred to as an open loop system. Several considerations must be made before choosing the right system for your home. Soil conditions, land space, climate and installation costs all come into play when choosing a geothermal heat pump system. These basic types of systems are suitable for both commercial and residential applications.
Closed versus Open-loop Systems
The difference between a closed and open-looped system is in the terminology, one utilizes a sealed loop of pipe while the other uses a closed loop of pipe. A closed-loop geothermal system uses a length of plastic tubing or pipe that is buried in the ground or submerged in a nearby lake or pond. An anti-freeze solution circulates through the tubing. A heat exchanger then transfers heat between the solution in the tubing and the refrigerant in the systems heat pump. The most common installation practices of a closed-looped system are as follows:
- Horizontal installation is a cost-effective method used in both new construction and sites with plenty of available land. Trenches are dug to a depth of at least 4 feet to house the tubing but can vary due to terrain and soil conditions. When space is limited for trench installation, a coiled version of pipe, referred to as a slinky is used that allows a shorter trench to house more tubing.
- Vertical installations are practical where land space may be limited such as commercial building sites and schools. This method of installation involves boring 4-inch diameter holes into the ground at approximately one hundred to four hundred feet in depth to house the loop of tubing or pipe. Each hole houses two sections of pipe that are joined together at the bottom by a special fitting called a U-bend to complete the loop. A horizontal trench is dug to house the run of tubing between the vertical holes and the heat pump.
- Sites with access to a lake or pond offer a cost-effective installation method. The pipes are run underground to the water source where they are looped at least 8 feet under the water’s surface.
Open-looped systems require a body of open water or a groundwater source to provide the solution in the tubing needed for the heat exchange with the heat pump compressor. As you may have figured, the open-looped system is only a viable option when an abundant water source is available.
Hybrid Geothermal Heat Pump Systems
The beauty of geothermal heat pump systems is that they can be adapted to combine with the best of traditional technologies to provide efficient heating and cooling systems in varying climates. These hybrid systems offer greater flexibility in extreme climates where weather conditions can vary significantly or in areas where a stand-alone geothermal heat pump is not practical.