Geothermal Heating and Cooling 101

What’s the most ecologically conscious way to heat and cool your home? While a number of green alternatives exist, geothermal technology is one that’s been gaining ground in recent years. According to the U.S. Department of Energy (DOE), geothermal heat pump installations have seen strong growth over the past 6 years, and, as of 2008, totaled over 1 million nationwide. Approximately 100,000 to 120,000 systems are installed annually in the U.S. in about 1 out of every 38 new U.S. homes.

While the popularity of geothermal heating and cooling may be new, the technology itself has been around since the late 1940’s. Geothermal heat pumps work by exploiting a natural fact: no matter how large the atmospheric temperature fluctuations in different regions of the world, the temperature just a few feet below the earth’s surface remains a steady 45°F (7°C) to 75°F (21°C).

CPUC Geothermal

image via Ram Power

How It Works

The parts of a geothermal heat and cooling system include a heat pump, an air delivery system (i.e., ductwork), and a heat exchanger. The heat exchanger is, essentially, a system of pipes buried in shallow ground. In the winter, when above-ground temperatures drop, the heat pump removes heat from the below-ground air inside the heat exchanger and pumps it into the building via the indoor air delivery system. In the summer, the process is reversed, and the heat pump pulls air from inside the building into the heat exchanger, where heat is removed, thanks to cooler temperatures below-ground. As an added bonus, heat removed from the indoor air during the summer can also be used to provide a free source of hot water.

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