Geothermal Heat Pumps (GHP), also known as Ground Source Heat Pumps (GSHP) are used in buildings for heating and cooling purposes. The heat pump pipes are inserted into the ground taking advantage of the ground’s constant temperature throughout the year. In this way, GHP systems can be used to control the temperature of a building. The ground temperature below 20ft (6 meters) is maintained constant between 50oF – 70oF (10oC – 21oC) depending on the latitude.
Unlike the geothermal energy for the production of electricity which uses geothermal reservoir and can be found on certain areas of earth (usually near tectonic plates), geothermal heat pumps can be used all over the world. Strictly speaking the heat used by geothermal heat pumps comes from the sun and not from the center of the earth.
A normal heat pump is used to transfer heat in the opposite direction that the heat normally flows. A geothermal heat pump, when used to heat a building or to provide hot water, it transfers the heat from the earth’s surface (higher temperature) to the building (lower temperature). To do, this a special fluid (usually environmentally friendly water with antifreeze) circulates inside the pipes. The fluid warms up while circulating through the underground pipes and transfers the heat inside the building. Then the colder liquid inside the building is transferred back into the ground in order to be circulated and warmed up again.
With the use of GHP we can significantly reduce the operational heating costs of a building as we will only need, if required, to supplement the heating from other sources to reach the required level (on many occasions the heating form a GHP system is enough to satisfy the building’s needs). Similarly, when the GHP system is reversed it can be used to cool down a building.
The benefits of using a GHP system for heating and cooling purposes are summarized below:
- Low operational and predictable yearly costs for the heating and cooling of a building. A GHP system can save up to 70% of the heating costs of a building.
- Low yearly maintenance costs for maintaining the GHP system.
- Long life expectancy. A typical GHP system’s life is estimated to be 25 years for the components inside the building and more than 50 years for the pipes inside the ground.
- No outside exposed equipment
- No environmental impact. According to the US Environmental Protection Agency, a GHP system is the most energy efficient and environmentally friendly system for a building’s heating and cooling requirements.
- GHP systems provide better aesthetic than conventional systems as they do not have large and visible components (like roof top equipment). They are also much more quite and improve humidity control.
Before the installation of a GHP system a number of design factors need to be taken into consideration, like the soil conditions, the building’s size, the climate conditions, the type of the loop of the GHP system that will be used (closed or open loop pipe system). The design and installation of a GHP system must be undertaken by a professional. A typical GHP system has high initial capital cost (CAPEX) but low operational costs (OPEX). The cost of a typical GHP system in US can vary from $8000 up to $15000 depending on all of the design factors specified above and with a payback period between 3 to 10 years.