Geothermal heat pumps can be installed in both new and old homes, and can use 25-50% less energy than conventional heating and cooling systems.
Geothermal Energy is the energy obtained from below the earth’s surface that originates in its core. The word geothermal comes from the Greek words, geo (Earth) and therme (heat), so it can easily be thought of as, “Earth Heat.”
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| Geothermal mineral waters in Yellowstone National Park |
Ranging from ten feet below the surface, all the way to the Earth’s core, there is a substantial amount of heat within the Earth’s crust. Geothermal Power uses the heat within the Earth to help with heating and cooling. There are three main Geothermal Energy technologies used throughout the world, Geothermal Electricity Productions, Geothermal Direct Use, and Geothermal Heat Pumps. Geothermal Heat Pumps, also known as Ground Source Heat Pumps, are currently the only application of geothermal energy in Connecticut.
Geothermal systems can also be used as Geothermal Power Plants. They use steam produced from hot water reservoirs found a couple of miles or more below the surface to generate electricity. The steam rotates a turbine that activates a generator, which produces electricity. Most power plants that use steam use fossil fuels to boil water in order to create the steam. Geothermal power plants eliminate the need of fossil fuels and are sources of clean energy. There are three different geothermal power plants currently in existence, Dry Steam Plants, Flash Steam Plants, and Binary Cycle Plants. All three types require underground wells with temperatures greater than 360⁰F or underground resources of steam. Therefore, plants within the United States are mostly found in the western states, Alaska, and Hawaii.
Geothermal Heat Pumps or Ground Source Heat Pumps (GSHPs) use pipes buried below Earth’s surface in a continuous loop to circulate water or other liquids. Just a few feet below the surface, the soil or water remains a constant 50 to 60 degrees Fahrenheit, no matter what season it may be above ground. This natural heat is enough to heat or cool an entire house, office, or school with the use of a GSHP, which takes advantage of the relatively constant temperature by exchanging heat with the earth.
How do GSHPs work?
A good way to help understand the natural side of a GSHP is to think about a cave. In the winter time, the ground temperature is warmer than the air above it, helping to keep the cave warm in the cold, but cool in the hot summer months. A GSHP uses the constant ground temperatures in the winter and summer for heating and cooling buildings. GSHPs work very similarly to air-source heat pumps, except GSHPs exchange heat with the earth and not with the outside air.
Any sort of geothermal heat pump system consists of three basic components, a ground heat exchanger, a heat pump unit, and a load-side heat exchanger. The ground heat exchanger is a continuous loop of polyethylene tubing that is buried (horizontally or vertically) in the ground outside of the house or building. The tubing is filled with water and environmentally-friendly antifreeze that circulates through the tubing, absorbing heat from within the ground, or releasing heat from above into the earth. These machines are very similar to air source heat pumps, except they take advantage of the earth's constant temperature. In the heating mode, they cause refrigerant to become cold enough for heat from the earth to warm it inside of a special heat exchanger. That heat is then boosted just enough to warm the building. In the summer months, when cooling a building is desired, the process is reversed. The heat from indoors is transferred into the ground at that constant cool temperature, instead of the hot outside air.
For more information on geothermal heat pumps, visit Choosing and Installing Geothermal Heat Pumps; for all things geothermal, visit EIA: Renewable Energy - Geothermal.
Interested in geothermal? Right now rebates of $500 to $1,500 are available for qualifying systems provided by the Connecticut Energy Efficiency Fund. Please visit the Geothermal Heat Pump Rebates page to learn more.
Geothermal energy is listed as a Class I renewable energy source as defined in the Connecticut General Statutes (CGS) Section 16-1(a)(26)(iv).