The Time Has Come For Geothermal Heat Pumps
When the Tennessee Valley Authority backed a new kind of heat pump, it tried to jump-start sales by providing some parts free. It looked like a good deal for consumers. But a funny thing happened: The technology turned out to be far more expensive to install than anyone imagined.
What went wrong? Manufacturers, distributors, and contractors were charging much higher premiums for the new technology than for better-known alternatives, according to a study for the TVA by Steve Kavanaugh of the University of Alabama. The result: Installing the new heat pumps typically cost twice as much as putting in conventional central air conditioning or even another type of heat pump.
That's the problem with many technologies. The gizmo works, but the people who sell it and install it lack the experience and don't have the competition incentive to do it right. That's why several electric utilities and a new organization called the Geothermal Heat Pump Consortium are working to train and educate dealers and contractors.
"It's a large infrastructure problem," says Terry Statt, manager of residential systems for the Electric Power Research Institute in Palo Alto, Calif. "You need the distributors and contractors in place."
A geothermal heat pump sounds more exotic than it is. Most heat pumps work their magic using the outside air. The geothermal variety uses tubing buried underground.
Heat pumps work on the same principle as an air conditioner or refrigerator. Using a special fluid enclosed in a tube, an air conditioner compresses it, which momentarily raises the fluid's temperature, then blows away that heat. Then the fluid is decompressed, which temporarily lowers its temperature and cools the surrounding air. By constantly compressing and decompressing this fluid, air conditioners extract heat.
Heat pumps work that process both ways. In the summer, they extract heat from inside the house and blow it out; in the winter, they take heat from outside and blow it in. When the outside air is extremely hot or cold, air-based heat pumps have a hard time keeping up. Ground-based, or geothermal, heat pumps do a better job because the temperature underground varies a lot less.
Recent technological advances give heat pumps even more of an edge over conventional heating and air-conditioning systems. For example, they now operate at variable speeds, so that a unit can adequately heat a northern house during the winter without blasting it with too much cold air during the summer. Another big step forward: Heat pumps use the waste heat from the air conditioning and other systems to provide homes and commercial sites with hot water. Often, the hot-water savings alone can make heat pumps less expensive to operate than competing technologies.
Of course, all this depends on many factors: the climate, and the relative cost of other heat sources compared with electric-powered heat pumps. Other factors may play an even bigger role. Ground-based heat pumps have no outside units, so they run more quietly and aren't exposed to the elements. Schools, which need to meet certain ventilation requirements, are big buyers of ground-based heat pumps, because they can't be vandalized like outside or roof-top air conditioners. More than half the schools in Austin, Texas, use geothermal heat pumps, says Harvey Sachs, technical director of the Geothermal Heat Pump Consortium.
Proponents say ground-based heat pumps are poised to become big sellers. The consortium's goal is to capture 10 percent or more of the commercial and residential market by 2001, up from 1 percent or 2 percent today. But they'll need an infrastructure - a cadre of well-trained and competitive distributors - to make the technology a commercial success.
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