Geothermal Exchange - geoexchange - heat pumps use the earth as both a heat source and a heat sink depending on the heat pump's mode of operation - heating or cooling.
Geothermal heat pumps are either open or closed systems and typically consist of a loop of pipe, a compressor and a pump.
Closed systems circulate a fluid which never leaves the heat pump system. Open systems pump a fluid from one place to another - aquaified, lake, pound, etc - remove some of the heat and and then return that fluid.
The pipe is installed under the surface of the earth below the frost line in either a horizontal layout or a vertical layout for space restricted areas. The length of the pipe varies with the heating/cooling requirements, the soil type, pipe installation layout and the location of the installation. The pipe can be installed in several different configurations including both a spiral pattern and a straight pattern.
A typical 2000 square foot residence will require four tons of heating capacity. Each ton of heating capacity requires approximately 91 metres (300 feet) of vertical loop or 122 metres (400 feet) of horizontal loop. Thus the residence will require 366 metres (1200 feet) of vertical loop or 488 metres (1600 feet) of horizontal loop.
A fluid is circulated through the pipe and absorbs heat from the earth in heating mode or sinks heat into the earth in cooling mode. The fluid is often water but in the case of closed systems is sometimes denatured ethanol or methanol.
The earth remains at a relatively constant temperature year round, usually between 7-21° celcius (45-70° Farenheit) depending on geographical location.
In heating mode, the fluid returns from the earth at 8° celcius, the compressor compresses the fluid to increase the heat per unit of volume. This heat is hotter than the temperature inside your house and is tranfered to your heating system. The fluid is then depressurized back into the loop running outside of your house where its heat per unit of volume is lower than the heat of the earth and it once again absorbes the heat from the earth and the cycle repeats.
In cooling mode, the fluid circulates around your house absorbing heat from the air. The fluid is then pumped into the loop external to your house where the fluid deposits the heat in excess of the ambient ground temperature.
Heating Mode
Cooling Mode
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