geothermal / ground-source heat pumps

The U.S. Environmental Protection Agency (EPA) called ground-source heat pumps the most energy-efficient, environmentally clean, and cost-effective space conditioning systems available. Heat pumps offer significant emission reductions potential, particularly where they are used for both heating and cooling and where the electricity is produced from renewable resources.

















image courtesy of greenbuilder.com

A geothermal heat pump system (also known as a GeoExchange system) is a central heating and/or air conditioning system that actively pumps heat to or from the shallow ground, using the earth as either a source of heat in the winter, or as a coolant in the summer. In typical systems, duct fans distribute the warm o/r cool air to various rooms within the building in the same manner as a conventional central heating or air-con system would).

The heart of the heat pump is a loop of refrigerant pumped through the “ground loop”, or more specifically, “vapour-compression refrigeration tubes” that moves heat either into or out of the ground. Working much like a refrigerator the system uses the heat pump to force the transfer of heat: capturing heat from a cool area and transferring it to a warm area, or they can enhance the natural flow of heat: from a warm area to a cool one. Heat energy always flows from areas of higher temperature to areas of lower temperature.

Geothermal heat pump systems are so efficient because underground temperatures are relatively stable through the year . The shallow ground temperature is warmer than the air above during the winter and cooler than the air in the summer. A ground-source heat pump extracts that ground heat in the winter (heating) and exhausts heat back into the ground in the summer (cooling).

In terms of residential use, home-owners who use GeoExchange systems rating them highly because of their ability to deliver comfortably warm air, even on the coldest winter days, and because of their very very low operating costs. In addition, once installed, they require little maintenance or attention. According to the U.S. Environmental Protection Agency, GeoExchange systems save home-owners 30-70 percent in heating costs, and 20-50 percent in cooling costs, compared to conventional systems.

In cooler climates, such as Europe & North America Geothermal systems are used predominantly for heating. Here in South Africa, heating can be useful when the correct conditions exist; however, the most use is the ability to reduce air- conditioning loads during the day when the air is warm and the ground is cool.

There are numerous options as to the types and size of systems, dependant on the size of the building, availability of land and cost. To compare these various options have a look at geoexchange.org