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May 9, 2008 -
Design & Construction
I’m Ed Sullivan, editor of Building Operating Management magazine. Today’s topic is geothermal heat pump systems.
Geothermal systems have garnered new attention because of the growing interest in green design. Geothermal systems work by transferring heat to and from the ground or ground water. In cold weather, the liquid in the pipes draws heat from the subsurface; in warm weather, heat from the building is transferred into the ground.
In the most common design, closed loops of pipes are placed into the ground. In vertical systems, wells are dug 300 or more feet deep for the pipes. In horizontal systems, the pipes are laid in trenches 6 to 10 feet underground and are usually used for smaller buildings.
The environmental benefit is simple: Geothermal systems provide heating and cooling without the use of fossil fuels. What’s more, they use technology that is simple, reliable and efficient, with operating costs up to 60 percent less than conventional systems. But they are significantly more expensive to install. Paybacks range from 5 to 12 years. The systems may qualify for tax deductions under the federal Energy Policy Act of 2005. Geothermal systems are good candidates for those tax benefits.