Heat your house for one-fourth the cost
Geothermal means heat from the earth. The system uses traditional plumbing and HVAC ductwork, but a machine called a geothermal exchanger makes it work.
Science 101
At our altitude, the Earth's crust is consistently 55 degrees Fahrenheit at six or seven feet beneath the surface.
About 180 feet below the surface, water with some anti-freeze fluid circulates in a loop of 11/4-inch-in-diameter pipes connected to an exchanger in the Guptas' basement.
According to the second law of thermodynamics, heat only flows in one direction, from hot to cold. So the earth's warmth transfers to the water, which flows back into the house.
The water's heat is transferred to a liquid refrigerant -- don't confuse that with something cold; it's just a medium to transfer heat.
A compressor packs the heat in the refrigerant, which changes to a gas. That's the geothermal exchange. The change in phase increases the temperature to 150 degrees Fahrenheit, and that heats a series of coils, over which air is blown. That warms the air.
The hot air is delivered the same way as a regular furnace -- through ductwork that blows heat into the rooms.
"The difference is where the energy is coming from," said Brian Fowler, president of GeoSource Distributors, a company that sells the equipment. "With a furnace, you're taking a fuel and lighting it on fire to create heat. This is taking heat that is already there."
No fossil fuels are needed in this process, so you eliminate that expensive gas bill. In a sense, the system is indirectly solar-based because a percentage of heat from the sun is retained in the Earth, which keeps it warm.
Eliminating that costly gas bill is expensive by itself, however. Because geothermal technology is so advanced and still relatively uncommon, it's about twice the cost of a normal HVAC system.
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