Heating buildings with direct use geothermal energy systems requires that site are located in areas that have ready access to underground supplies of heated water. In Colorado, geothermal waters tend to be in the mountains and on the Western Slope. There are no identified areas on the Eastern Plains.
The underground heated water is used like a regular hot water heater, but this source comes preheated from within the earth and does not require additional heating. Geothermally-heated waters can also be used for hot springs, pools, spas, and greenhouses.
Water temperatures ranging from 65oF to 175oF are best for successfully heating buildings with geothermal energy. The water is typically brought to the surface by the use of a well. The water itself is used to heat the building; a heat exchanger is not usually a part of this system. The water is used like a hot water heating system with radiators or a radiant floor system. Ideally, the cooled water is returned to the ground through an injection well but may also be stored in a pond. Colorado’s Division of Water Resources determines whether the water must be re-injected or can be disposed of at the surface.
In municipalities that have significant geothermal resources, heating districts may be formed. In those cases, water is typically pumped from the ground, sent through a processing facility, and then used to heat another liquid to provide direct heat to buildings. Heating districts can benefit from economies of scale that individual businesses or homes could not. District geothermal heating systems can save between 30 and 50% on heating costs compared to natural gas systems.