Coober Pedy Australia is a rather hot and forbidding place to live. Temperatures in the summer hit 114 degrees and the first tree in the town history was welded together out of scrap steel. The town industry is primarily opal mining with a sideline of providing alien deserts for the movie industry; abandoned space ships litter the country side. But the opal miners figured out quite quickly that it was reasonably cool in the mines and expensive to air condition houses on the surface; so houses, churches, hotels and business often are mined right into the rock to take advantage of the stable temperature of the earth.
You see, once you get down a ways into the earth the surface temp doesn’t matter. Freezing or frying, the temp below remains a constant year round. It’s why well water tastes cold on a hot day, and miners in Coober Pedy stay cool beneath the surface, and it’s why pipes when laid below the frost line don’t freeze in North Dakota. It’s also the fundamental principle on which geothermal heat pumps work.
Heat pump technology is not new by any means; it’s how a refrigerator works. To oversimplify greatly the heat pump takes the heat from the inside of the refrigerator and transfers it to those coils on the back of the unit. Traditional home heat pumps do the same thing on a big scale. They take the heat from within your house and transfer into the air outside. When reversed it takes the heat from the outside air (I don’t care how cold it is, there is some heat) and concentrate it into the house to warm it. Heat pumps are not so efficient in very cold climates for obvious reasons.
What is relatively new is that the Geothermal Heat Pump (purists cringe at this name because geothermal properly refers to taking heat from the earth’s core) instead of trading heat with the widely varying outside air temperature exchanges heat with the more stable temperature of the earth. To accomplish this in a closed loop system pipes are placed underground, either vertically or horizontally (depending on the available space and environment) and the heat pump is attached to pump liquid through these pipes. The heat pump then distributes the (or pulls the heat out) by way of air or water circulation through the stricter. In a open loop system pipes are sunk deep into the aquifer and water is pulled from the ground, through the system then returned; using the water in the ground as the transfer partner. In some situations a closed loop system can be placed at the bottom of a pond.
So, while this system costs several times the amount of your average traditional heating and cooling system the typical payback period is under five years. Energy usage is reduced anywhere from 30 to 70 percent overall. The systems are smaller, quieter, and last considerably longer than traditional home heating and cooling options. If you want to learn more about geothermal heat pump options, visit the Geothermal Heat Pump Consortium.