Editor’s note: While we’ve discussed home geothermal systems a number of times around the Green Options Media network (see the list at the bottom), we’re glad to bring you today’s post from GreenBuildingTalk on the subject. They not only provide an overview of the technology, but point you to some cutting-edge models of geothermal heat pumps. This post was originally published on Thursday, May 15, 2008.
With energy costs on the rise, homeowners are looking for ways to offset higher bills. Geothermal heat pumps are one of the best options, as they currently offer the highest efficiencies of any heating and cooling system available today. A study by MIT emphasizes the potential for geothermal, and manufacturers are offering more options for consumers. While at the Midwest Builders show, I stopped by ClimateMaster and WaterFurnace booths to learn more about their newest offerings. Before diving into the respective systems, let’s review the three main components of a geothermal system; the heat-pump unit, the liquid heat-exchange medium (open or closed loop), and the air-delivery system (ductwork).
The heat pump simply moves heat energy from one place to another, just like your refrigerator or air conditioner. But a major difference is that air conditioners and refrigerators transfer heat in only one direction, while a heat pump can transfer heat in two directions, thereby heating or cooling the space. In the cooling mode, the geothermal heat pump takes heat from indoors and transfers it to the colder earth through either groundwater or an underground earth loop system. In the heating mode, the process is reversed.
The buried pipe, or earth loop, is the most important technical advancement in heat pump technology to date. The idea to bury pipe in the ground to gather heat energy began in the 1940s. But it’s only been in the last twenty-five years that new heat pump designs and more durable pipe materials have been combined to make geothermal heat pumps the ultimate in efficiency. The two main types of loops available are open and closed. An open loop system is less expensive to install, but over time could require more maintenance. A closed loop system is more expensive up front, but requires almost no maintenance. As manufacturers phase out R-22 (HCFC) refrigerant, there have been more environmentally friendly liquid mediums brought into the marketplace to use in your system. The most common antifreeze solutions in the U.S. and Canada are propylene glycol, methyl alcohol, and ethyl alcohol.
Finally, ductwork must be installed in homes that don’t have an existing air distribution system. If you have existing ductwork, geothermal systems will likely work, but you may have to do some minor modifications. Another method of delivery worth looking into is in-floor radiant heating, in which hot water circulating through pipes under the floor heats the room. For more detailed information on geothermal systems, visit the Basic Geothermal Info thread on GBT.
ClimateMaster showcased their Tranquility 27 series at the builder’s show. Both the Tranquility 27 two-stage system and the Tranquility 27 two-stage split geothermal system are the highest efficiency water-source heat pumps on the market, offering 27EER to 31EER. The energy-efficiency criteria for geothermal heat pumps to qualify for the Energy Star program requires an EER rating of 14.1 (closed) or 16.2 (open). The Tranquility 27 has an EER rating of 27. This system also use Earthpure, a new refrigerant that is non-chlorine based with zero ozone depletion potential.
Read the rest of this post at GreenBuildingTalk