Geothermal heat systems are the most energy-efficient, environmentally
clean, and cost-effective space conditioning systems available today.
Conventional residential and light commercial heating and cooling systems
are generally fossil fuel and electricity based. Ground Source Heat Pumps
(GSHPs) are the most efficient types of geothermal systems and are becoming more common as the costs of energy and equipment maintenance rise.
When properly designed and installed, they not only reduce energy use but lower maintenance costs and extend equipment life, since they have no exposed outdoor equipment. Although somewhat higher in Most costs than other systems described in this booklet, this technology can, in the right application, quickly repay this differential. This is possible since a geothermal heat pump moves from a heat source to a heat sink and very little heat is actually produced from either fossil fuels or electricity. The GSHP uses electricity to run circulator pumps, fans, and compressors to move the heat.
This results in a minor increase in electricity costs with a major reduction
in fossil fuel costs. The same equipment can be used to heat in winter and
cool in summer by reversing the Now of heat transfer.
Geothermal technology utilizes a heat pump and a series of high
strength plastic pipes buried in the ground, either horizontally or vertically.
These systems can be open or closed-loop systems. Open-loop systems
use groundwater (well, pond, stream) as the heat/cooling source,
which is fed to the heat pump and is then discharged back to the ground.
Open-loop systems have higher pumping requirements and can cause
water usage and environmental problems, but they can be significantly
less expensive. Closed-loop systems circulate a water/glycol solution with
low energy pumps, but typically require longer pipe lengths and more
extensive drilling and trenching for an equivalent amount of heat transfer,
and are therefore typically more expensive to install. Using the earth
as a heat source and heat sink, polyethylene pipes circulate the
water/antifreeze solution from the earth to the heat pump, cooling the solution in summer and warming the solution in winter.
For summer cooling, the heat pump functions like an air conditioner,
transferring heat from the air in the building to the water/glycol solution
via a compressor and air-to-water heat exchanger. For winter heating, the
process is reversed and the heat pump transfers heat from the ground
sourced solution to the building air via a compressor and water-to-air heat
exchanger. The same systems can be used to provide heat for domestic hot
water, forced hot air, and hydronic radiant Noor space heating systems.
A geothermal heat pump is essentially an air-conditioner with one
extra valve that allows the condenser (hot coil) and evaporator (cold coil)
to reverse places in the winter. Thus the latent heat of the warm, ground
sourced water, when reversed by the condenser-evaporator function, produces hot water to warm the air circulated by the indoor fan. After passing through the expansion device, the refrigerant enters the outdoor coil at a low temperature. Because the temperature of the refrigerant is low,
heat can be transferred from the water to the refrigerant inside the evaporator.
If the ground sourced water loop is properly sized, the heating efficiency is exceptionally high compared to conventional systems. With the
addition of a water-to-water heat exchanger, the basic geothermal heat pump can be adapted to provide for domestic hot water and hydronic
radiant Noor heating systems.
Article by Don Wemple