Geothermal offers solar energy solution

Q I moved into an old house that needs a new heating and cooling system. I have heard installing geothermal heating is a good choice today and for the future. Is this true? How do these systems work?

A: Geothermal heating (heat pump) is extremely energy efficient and generally yields the lowest utility bills of any residential system. In effect, these systems use renewable solar energy from the sun's rays, which get stored in the ground.

Geothermal heat pumps also provide the most energy-efficient cooling during summer. Some models can also be combined with solar systems.

In the heating mode, a geothermal heat pump can produce up to $5 worth of heat for each dollar on your electric bills. Unlike standard heat pumps, which lose efficiency and maximum heat output as the outdoor temperature drops, the efficiency and heat output from a geothermal heat pump remains relatively constant.

During summer, a regular heat pump or central air conditioner loses efficiency and cooling output when it is hotter outdoors. Unfortunately, this is when your house requires the greatest cooling capacity. Cooling efficiencies are as high as 30 EER (energy efficiency ratio). A standard heat pump or central air conditioner is typically less than half as efficient.

Another summertime advantage is free hot water when the geothermal heat pump is cooling your house. Instead of exhausting the heat to the outdoor air through outdoor condenser coils, this waste heat is diverted to your water heater. This device is called a desuperheater and it is included as a standard or optional feature on geothermal heat pumps.

A geothermal heat pump operates similarly to a standard heat pump except that it exchanges heat with the ground instead of the outdoor air. The temperature of the outdoor air can vary 30 degrees 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 antifreeze/water solution running through the pipe acts as the heat transfer medium. If there is a pond or wells can be dug, this water can run through the heat pump heat exchangers. Many 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. This also reduces wear and tear from constant exposure to outdoor weather and playing children.

Write for Update Bulletin No. 723, or instantly download it at www.dulley.com. It's a buyer's guide of 2007 geothermal heat pump models listing stages, efficiencies, outputs, features, freon/R410A, cost comparison chart and ground loop details. If writing for the bulletin, please include $3 and a business-size stamped, self-addressed envelope.

Send inquiries to James Dulley, The Post and Courier, 6906 Royalgreen Drive, Cincinnati, OH 45244 or visit www.dulley.com.