Geothermal energy is a HVAC (heating, ventilating, air conditioning) technique that harnesses the power from organic decay beneath the earth’s crust. It is a very clean process that captures and maintains a consistent temperature from just about two feet under the surface, keeping your house or building warm in the winter and cooler in the summer months. The earth has a fairly consistent temperature thus providing a great opportunity to harness that uniformity. Pipes run from beneath the earth’s surface and pumps in heat during the winter months, saving about 30-70% in heating costs. In the summer months it does the same process but in reverse, sending heat back into the earth’s surface, increasing efficiency as well as saving 20-50% in cooling costs. This not only reduced heating costs but with the application of a desuperheater you can save on heating the water pump. This device takes the hot air that would be expended back into the earth and directs it through a loop that heats household water. This device can heat your water for free during the hotter months and reduce your costs of heating your water by 50% in the cooler months.
There are many different variations when considering the appropriate geothermal application.
The horizontal ground source is the most cost effective if the circumstances are right. This application works best with large surface for excavating. This variation requires the laying of 400-600 feet of piping per ton of heating and cooling about three feet below the surface. This system is typically a closed system meaning that the fluid runs along the pipes continuously.
The vertical ground source is more appropriate if there is not much land available to excavate for the project or when the least disruption is desired. While this application is the most expensive to install it generally requires less piping because the system is set vertically into the ground where the earths temperature is more consistent. A hole, similar to that of a well, would be dug about 150-450 feet deep with pipes set vertically into the hole. These pipes would then be connected to a horizontal system connecting it to the interior unit. This system is also a closed system.
The pond closed loop circuit uses bodies of water surrounding the application site as a regulator. It is the most cost effective if the site is near a body of water. Since this application is a closed system there is no fear of aquatic organism disruption.
The open system is more commonly used when ground water is plentiful and if two operating wells are available for use. This application pumps water from an aquifer through a heat pump and then back to a discharge well. A heat pump recovers latent heat in the water. Although this system is not as frequently used it is still safe to apply after review of local discharge rules and consultation with local environmental official.
Although the initial cost of these devices is more expensive than a traditional heating and cooling system, this technology has a pay back period of about ten years and a long life span. The application of this technology will not only reduce building energy costs, but also reduces pollution by eliminating combustion of fossil fuels at the site.
Save Energy Maine, LLC www.saveenergymaine.com
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California Energy Commission. http://www.consumerenergycenter.org/home/heating_cooling/geothermal.html. 2006
Engineered Services Cooperation. http://www.engineeredservices.org/services.htm. June 22, 2007.
Geothermal Heat Pump Consortium Inc. http://www.geoexchange.org/.
Union of Concerned Scientists. http://www.ucsusa.org/clean_energy/renewable_energy_basics/offmen-how-geothermal-energy-works.html. June 19, 2008.