Melbourne Polytechnic Green Skills Centre

Ground Based Air Conditioning


A geothermal heat pump or ground source heat pump (GSHP) is a central heating and/or cooling system that pumps heat to or from the ground. It uses the earth as a heat source (in the winter) or a heat sink (in the summer). This design takes advantage of the moderate temperatures in the ground (typically 15 – 20 degrees C) to boost efficiency and reduce the operational costs of heating and cooling systems. Geothermal heat pumps are also known by a variety of other names, including geoexchange, earth-coupled, earth energy or water-source heat pumps.

Like a refrigerator or air conditioner, these systems use a heat pump to force the transfer of heat. Heat pumps can transfer heat from a cool space to a warm space, or they can enhance the natural flow of heat from a warm area to a cool one. The core of the heat pump is a loop of refrigerant pumped through a pipe that transfers heat. Heat pumps are always more efficient at heating than electric heaters, even when extracting heat from cold winter air.

Unlike an air-source heat pump, which transfers heat to or from the outside air, a ground source heat pump exchanges heat with the ground. This is much more energy-efficient because underground temperatures are more stable than air temperatures through the year. Although the setup costs are higher than for conventional systems, the difference is usually returned in energy savings in 3 to 10 years. 

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Last Modified: 27th November 2014