Magic Heat Pumps
(Page 4 of 8)
April/May 2005
By Greg Pahl
Since operating costs for a heat pump are normally lower than those for conventional heating appliances, you should save on energy bills. The relative savings, however, will depend on whether you are currently using oil, propane, natural gas or electricity and the prices in your area. When you run a heat pump, you will use less fossil fuels but more electricity (except when compared to electric heating, in which case you’ll definitely use less electricity with a heat pump).
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Ground-Source Heat Pumps
You also can heat your home with earth or water — that’s the magic of ground-source heat pumps. Also known as geothermal or geoexchange, these heat pumps are not as common as their air-source cousins, but they have many advantages. They work well in almost any climate, especially colder areas where air-source heat pumps are not as well-suited. According to the Environmental Protection Agency (EPA), geothermal is the most energy-efficient, environmentally clean and cost-effective space- conditioning system available.
Compared to fossil-fueled systems, geothermal can save you 30 percent to 70 percent in heating costs and 20 percent to 50 percent in cooling costs. The Earth is a huge energy storage device that absorbs 47 percent of the solar energy that strikes its surface. A geothermal heat pump uses the earth, groundwater or surface water as sources of heat in the winter and as a sink for heat removed from your home during the summer. Heat is extracted from the earth by a liquid, such as water or antifreeze. The heat pump then amplifies this heat and transfers it into your house. Reverse the process, and the system provides cooling. Ground-source heat pumps also can filter air and control humidity.
Geothermal systems consist of three main components: a system of outdoor underground piping, a heat pump and a distribution system. Geothermal systems are best suited to new construction and are more expensive and complicated to install than their air-source counterparts. In a renovation, installing the necessary underground piping can be a challenge. The contractor will have to avoid disturbing existing water, sewer and underground utility lines. And as with air-source heat pumps, ground-source systems require 200-amp electrical service.
The two types of geothermal systems are open- and closed-loop. An open system uses the heat in a body of water (usually a well but sometimes a pond or stream) as its heat source. The water is pumped from the well or other source to the primary heat exchanger in the heat pump, where heat is extracted. After the heat has been extracted, the water is discharged back into the pond, stream or well. Regardless of the disposal method, no pollutants are added — the only result is a slight change in temperature. In a closed-loop system, however, heat from the ground is collected by a continuous loop of underground piping that contains an environmentally safe antifreeze solution that absorbs heat from the surrounding soil. The antifreeze solution is then drawn into the heat exchanger, and heat is extracted.
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