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The application of
geothermal
heating/cooling, also known as ground source heat pumps, has
been named "the most energy-efficient and environmentally sensitive
of all space conditioning systems", by the Environmental Protection
Agency. The system's basic concept takes advantage of the earth's
constant temperature, approximately 55 degrees, to heat and cool a
building. By tapping this steady flow of heat from the earth in the
winter, and displacing heat in the earth in the summer, a geothermal
heat pump can save homeowners 40 to 70 percent in heating costs and
30 to 50 percent in cooling costs compared to conventional systems.
Ground source heat pumps work in a similar manner as air source heat
pumps, minus the high cost. Atypical household can save $1500 a year
or more. This can give most systems a payback period of three to
five years. GSHP's are more than three times as efficient as the
most efficient fossil fuel furnace. By moving heat that already
exists in the earth, instead of burning a combustible fuel, GSHP's
deliver three units of energy for every one unit used to power the
heat-pump system.
Ground source heat pumps work by circulating water or a
water/antifreeze solution through a closed loop of polyethylene pipe
that is buried in the ground or set closed and open loop systems
beneath the water. GSHP systems can be lad out in different
orientations, depending on the situation. A closed loop system, the
most popular, can be laid out either vertically in 50 -250 foot deep
holes drilled like a well, or horizontally in 3-6 foot deep
trenches. The less common open loop system circulates a constant
source of ground water and dispels the water back to its origin,
such as a stream, well, or pond.
The principle action of a heat pump moves heat from lower
temperature location to a higher temperature location. This
principle can be witnessed in an air conditioning window unit, or
air source heat pump, where cold air is blown into the house and
warm air is released out of the back of the unit. A ground source
heat pump works in a similar manner, except that its heat source is
the warmth of the earth. The process of elevating low-temperature
heat to over 100 degrees F and transferring it indoors involves a
cycle of evaporation, compression, condensation and expansion. A
refrigerant, like freon, is used as a heat-transfer medium which
circulates within the heat pump.
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