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Powerful Living


Geothermal Heat Pumps Effi ciency from the Ground Up


By James Dulley G


eothermal heat pumps are extremely energy effi cient and gener- ally yield the lowest utility bills of any residential heating and cooling systems available. With the high cost of energy today and the available energy tax credit, installing a geothermal heat pump could make economic sense for many families.


A geothermal heat pump operates similarly to a standard heat pump except it exchanges heat with the ground instead of the outdoor air, essentially using renewable energy from the sun’s rays that are stored as heat in the ground. The temperature of the outdoor air can vary 40 degrees or more from day to night and more than 100 degrees from the coldest winter night to the hottest summer day. In contrast, the temperature several feet below the ground surface varies relatively little.


In order to capture the heat energy from the ground (in the winter) or exhaust the heat during summer, a long pipe is usually buried in the ground. An anti- freeze/water solution running through the pipe acts as the heat transfer medium. If there is a pond or well, which can be dug on your land, this water can run through the heat pump heat exchangers. All of the new models use earth- friendly R410A refrigerant instead of freon. Since no outdoor condenser coils and fans are needed, the entire heat pump and all mechanical components are located in an indoor unit. It operates quietly and, with no outdoor fan or compressor, there is no noise to bother neighbors or your family at night. This also reduces wear and tear from constant exposure to outdoor weather (and playing children).


During winter in the heating mode, a geothermal heat pump can produce up to $5 worth of heat for each dollar on your electric bill. Unlike standard heat pumps, which lose effi ciency and maximum heat output as the outdoor tem- perature drops, the effi ciency and heat output from a geothermal heat pump remains relatively constant.


Moist ground has a huge thermal energy storage capacity so the amount of heat your system pulls out to warm your house all winter has little effect on the ground temperature. Some models can also be combined with solar systems to gain more free heat. The most effi cient models use a two-stage compressor and variable-speed indoor blower for the best comfort.


During summer months, a regular heat pump or central air conditioner loses


effi ciency and cooling output when it is hotter outdoors. Unfortunately, this is when your house requires the greatest cooling capacity. Cooling effi ciencies for geothermal units are as high as 30 EER (energy effi ciency ratio). A standard heat pump or central air conditioner is typically less than half as effi cient. Another summertime advantage is free hot water when the geothermal heat pump is cooling your house. Instead of exhausting the waste heat to the outdoor air as a standard heat pump does, this waste heat is diverted to your water heater. This device is called a desuperheater and it is offered as a standard or optional feature on most geothermal heat pumps. The initial cost of installing a geothermal heat pump is signifi cantly more expensive than a standard air-to-air heat pump, and the fi nal cost of the instal- lation depends upon the type of ground loop needed and the topography of your land. But the federal energy tax credit, which provides a 30 percent tax credit covering the entire cost of installing a geothermal heat pump, does make the initial expense more affordable.


For units installed from 2009 through 2016, you can take advantage of the full 30 percent tax credit. File for the credit by completing the Renewable Energy


6 WWW.OK-LIVING.COOP


Typical layout for a vertical ground loop for a geothermal heat pump. The holes are drilled 100 or more feet into the ground. The heat pump can be located in a utility room, basement or attic. Photo courtesy of Climate Master


This schematic shows how a geothermal heat pump works during winter and summer. Photo courtesy of WaterFurnace


Credits subsection on your tax return form. No proof of purchase is re- quired; however, in case of an audit, keep a detailed invoice of your pur- chase. The contractor who sold and installed the product should list the purchase as a “Geothermal Heat Pump” on the invoice and that it “Exceeds requirements of Energy Star program currently in effect.” The following companies offer effi cient geothermal heat pump systems: Climate Master, 800-299-9747, www.climatemaster.com; WaterFurnace, 800-436-7283, www.waterfurnace.com, and Bosch, 800-283-378, www.bosch- climate.us.


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