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Islanders tap geothermal energy -

Heat pumps earned a bad reputation in years past for being ineffective in colder northern climates. However, Mr. Nelson said that because those old-style heat pumps extracted heat from the air rather than the earth, they were only efficient in temperatures down to about 60 to 65 degrees.

Two types of geothermal systems are water-based and direct-exchange, Mr. Nelson said. The decision on which one to use depends on soil conditions, space constraints, and other properties at the site, Mr. Nelson said.

Water-based systems use a black plastic pipe below the frost line containing a water/antifreeze mixture pumped by a circulator to and from the ground to the building. This heated liquid is then sent to a heat pump inside where a refrigerant loop moves the heat from the liquid into the building. In summer, this process is reversed.

A direct-exchange system uses copper tubing containing refrigerant in the ground outside the building. A heat pump inside the building sends the refrigerant into the loops outside in the ground to collect or discharge the heat, then sends it back inside to heat or cool the building.

Higher initial investment costs made geothermal systems less competitive until recently, when energy prices soared. "The geothermal folks who have been doing this forever are excited it is finally catching on in America," Mr. Nelson said.

A master plumber like Mr. Sprague, Mr. Nelson also holds a master's degree in mechanical engineering. Last summer, he and Mr. Sprague attended an international geothermal convention in Albany, N.Y., held by the International Ground Source Heat Pump Association (IGSHPA), a source of training and certification for the geothermal industry worldwide.

Mr. Nelson completed extensive training to qualify as a certified geo-designer and Mr. Sprague as an accredited installer. "It cost us at least $10,000 for training and to attend," Mr. Nelson said. "Basically, we took a gamble. We know the market is there, and it's important to get trained."

The IGSHPA and Association of Energy Engineers administer the licenses, which have been awarded to only a few in Massachusetts, Mr. Nelson said.

Putting geothermal to the test

His expansion into geothermal systems came at the right time for Sarah and Bruce Nevin when they decided to put an addition on their Edgartown home last year that utilized renewable energy. When they asked Mr. Nelson about incorporating solar energy into the plans, he suggested adding geothermal energy to the package.

The result, a computer-controlled mechanical system that manages a combination of solar, geothermal, and conventional energy sources, is the first of its kind on the Island.

The home's primary energy sources are solar and geothermal, with a conventional boiler for baseboard heat in the original part of the house and as a backup system. Solar collectors on the south-facing roof generate hot water year-round and provide the first stage of heat in the radiant floor heating system.

The geothermal system kicks in during the winter and on non-sunny days to produce hot water, also used in the radiant floors. In the summer, the heat pump switches over to cooling and produces chilled water for the radiant floors. Mr. Nevin estimated that over the next 10 years, he could save $50,000 by using the combination of solar hot water and geothermal radiant heat.

A direct digital control (DDC) system, which looks like a large-sized fuse box, provides the brains of the whole operation. It constantly monitors the different energy sources, staging solar power, geothermal energy, and the propane-fired boiler as needed.

If the DDC detects changes or anything abnormal in the system's settings, it can send routine or emergency calls to an e-mail address, cell phone, or land line, an enticing care-taking feature that might appeal to the Island's seasonal homeowners.

To install the geothermal system's copper tubing, excavating contractor John Keene dug out an area in the Nevins' yard about 2,500 square feet to a depth of six feet. About one square foot of ground heats one square foot in the house, Mr. Nelson said. The specially coated tubing, designed to last at least 50 years, was laid in a carefully configured looped grid pattern horizontally along the bottom of the pit and then buried.

A geothermal system can be adapted for use in any size building, Mr. Nelson said. He estimated a five-ton system would be good for a 3,000-square-foot house, at a cost of about $25,000. "It would pay for itself in about five years, and then you'll be getting your energy for about a quarter of the cost," Mr. Nelson said.
http://www.mvtimes.com/news/2007/02/22/geothermal_energy.php