Monday, November 16, 2009

Metro will tap Earth's crust to help keep homes comfy

Nashville has its share of temperature swings, with wintertime lows below freezing and summertime highs in the triple digits. But just beneath the Earth's surface, the temperature never changes, remaining an even 55 degrees.
The Metro Development and Housing Agency plans to tap into that steadiness. The public housing agency has received a $1.8 million federal stimulus grant to install geothermal units in two developments for the elderly and disabled, a project that could improve living conditions and cut heating costs by as much as 70 percent.

The grant is part of a nationwide study of geothermal technology by the Department of Energy.

"Residents are going to get a quality HVAC (heating, ventilation and cooling) system, which they hadn't had," said Phil Ryan, the agency's executive director. "And obviously this is going to reduce the carbon footprint, which has not just been MDHA management's goal but also one of Nashville's goals for some time."

The grant is part of a $338 million package of DOE awards made late last month to study geothermal energy. A total of 123 projects were funded, including a group of 37 projects that will look specifically at the best ways to heat and cool buildings using the natural temperature of the Earth's crust.

The project calls for MDHA to install geothermal heat pumps in 183 cottages for the elderly in the Gernert Studios and Edgefield Manor developments.

These cottages' current heating systems basically work by using electricity to heat electrical coils that raise the temperature. In January, this would require expending enough energy to bring the temperature up about 44 degrees from the average low air temperature of 28 degrees.

The geothermal heat pumps work by circulating water through pipe loops to a depth of more than 200 feet underground, where the temperature always hovers around 55 degrees, and back up to the surface. The water naturally heats the air around it, which means the system only has to expend enough energy to raise the temperature an additional 17 degrees to heat the room.

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