Geo-Thermal Heat Pumps
What is a geothermal heat pump?
A geothermal heat pump is an extremely efficient heating and cooling system that uses the earth's energy storage capability to heat and cool your home or business. Like all heat pumps, a geothermal heat pump simply moves heat from one place to another. In the summer, the compressor moves freon through a coil (the evaporator) in the duct system where it absorbs heat from the indoor air. The compressor then moves the freon to the center tube of a coaxial coil. The outer tube of the coaxial coil contains transfer fluid (a water and methanol mixture) which absorbs the heat from the freon. This liquid is then circulated through a loop in the ground, where it is cooled. In the winter, the process is reversed. The freon in the coaxial coil absorbs heat from the transfer liquid and then releases it to the coil in the air distribution system, warming the air passing over it.
Why is a Geothermal Heat Pump so Efficient?
Most heating systems convert energy from one form to another to create heat - for example, gas to flame, liquid to flame, and electric energy to heat energy. They can only supply as much heat energy as the original form contained. Most cannot convert at even 100% efficiency because heat escapes up the flue with hot exhaust gases. A heat pump does not change energy forms to create heat. It simply moves free heat from one place to another. A geothermal heat pump is even more efficient than a "standard" air-to-air heat pump because it gets its heat from the ground, where the temperatures are more constant and warmer than outside air.
How does the geothermal heat pump get its heat from the ground?
A geothermal heat pump can use one of several methods to get heat from the ground. These methods can be categorized as "open loop" or "closed loop" systems. An open loop system uses well or lake water cycled through the system to deliver heat to the unit. Although open loops are the least expensive to install, they are usually not the best option. Minerals and impurities can form deposits in the coaxial coil; clogging the system or lowering the efficiency of the unit. With flow rates of 3-6 gallons per minute, water requirements are quite high, creating supply and disposal problems for open loop systems. A closed loop system uses a continuous loop of buried pipe to circulate the exchange fluid through the ground. This loop can be installed horizontally, vertically in 150-foot deep wells, or in coils at the bottom of a pond or lake. These loops should be installed using high-density polyethylene or polybutylene pipe. The only acceptable method of connecting these pipes is by thermal fusion, which makes the joint stronger than the pipe. Mechanical connections or glued joints are certain to result in loop failure. For this reason, loop installation should only be done by professional, trained installers.
How does the geothermal heat pump get its cold from the ground?Actually, the heat pump does not get its cold from the ground. The geothermal heat pump cools your home by collecting the heat inside and then rejecting it to the ground by circulating the heat transfer fluid through the loop. Because the ground temperature is lower than the outside air, the geothermal system can reject this heat much more efficiently than a standard air conditioner or heat pump, which rejects the heat to the outside air.
Are there any other advantages to a geothermal heat pump?
Yes, there are several advantages of a geothermal heat pump over other heating and cooling systems. One of these is hot water. In the summer, when the system is trying to get rid of the heat from indoors, the unit will transfer this heat to your hot water system. This is "free" heat. During the winter, the system will take a portion of the heat it gets from the ground and transfer it to the hot water system. Although this is not "free" heat since the system must work to obtain it, it is manufactured at a much higher efficiency than typical hot water systems. Actually, a geothermal system can provide 40% to 50% of your hot water requirements. A geothermal heat pump also has no equipment outdoors. If you enjoy sitting outside, you will never have to listen to an outdoor unit and its noisy fan again. And, because the unit is indoors in conditioned space, it is subject to less maintenance and will have a longer life expectancy than other heating and cooling systems.