Essentially, a geothermal heat pump is an air conditioner that provides heat in the winter and cooling in the summer. Besides having higher efficiencies than your conventional system, GHPs differ in that they rely on the relatively constant temperature of the earth instead of the fluctuating temperature of the air. With the rising costs of energy, geothermal technology is a great alternative and has many benefits including: energy savings, reduction in greenhouse gas emissions, lower electric bill, lower maintenance, and lower hot water costs.
The explanation of how GHPs draw heat from the ground sounds complicated, but the process is really quite simple. In the winter, a geothermal heat pump transfers energy from the ground into the pump; in the summer the process is reversed, transferring heat from the pump back into the ground. Because the ground temperature remains fairly constant year round, GHPs have high operating efficiencies year-round.
GHPs consist of three main parts: the fan & ductwork (a.k.a. air handling system), heat exchanger, and the refrigerant loop. In the air handling system, fans move heated or cooled air through ducts to the different rooms in your home, then back into the pump. From there, the heat exchanger, absorbs or discharges heat from or to the earth. The reversible refrigerant loop transfers heat between the air handling system and the heat exchanger.
The heat exchanger can be either an open-loop system or a closed-loop system. In an open-loop system, two wells are typically used. These wells are similar to a conventional water well where one acts as a water source and the other as a sink. A water-to-refrigerant heat exchanger pumps water from the source well and returns it to the second well (http://wellowner2.org). Except for the temperature, the water remains unaffected throughout the process.
A closed-loop system uses a sealed high density polyethylene piping buried in the ground either vertically or horizontally. Vertical systems are loops of piping inserted into a series of 4 to 6 inch boreholes, which are 150-300 feet deep. Horizontal systems are piping connected by headers and buried in 4 to 6 feet deep trenches.
As with any heat pump, geothermal and water-source heat pumps are able to heat, cool, and, if so equipped, supply the house with hot water. Some models of geothermal systems are available with two-speed compressors and variable fans for more comfort and energy savings. Relative to air-source heat pumps, they are quieter, last longer, need little maintenance, and do not depend on the temperature of the outside air (www.geothermalexperts.net).