Geothermal water source heat pump systems have rapidly gained popularity for residential and commercial applications because of their high efficiency, low carbon emissions and low life cycle costs. While their popularity is somewhat new, geothermal systems have been around for more than 30 years and have been applied in a multitude of applications including offices, schools, healthcare, recreational facilities, apartments, condominiums and single family residences. Both the U.S. Department of Energy and Environmental Protection Agency have long recognized geothermal systems as being among the most environmentally friendly energy saving systems available for heating and cooling buildings.
With this relatively newfound popularity has come a multitude of benefits that have made the economics of installing a geothermal system more attractive:
Geothermal system is ideally suited for projects with minimum available space, vertical bore holes are drilled 150 to 400-feet deep depending on design considerations necessary to condition the building. A plastic polyethylene supply/return pipe is inserted into the holes and wells are connected in a parallel reverse return arrangement to allow water to circulate evenly throughout the bore field. Loop temperatures range from 37°F to 95°F. Experienced designers should be used to determine the number and depth of bore holes.
Similar to a vertical loop system except that a series of parallel loops are installed in trenches approximately 5-feet below the ground and then back filled. The piping may be installed using a “four-pipe” or “six-pipe” design. This design is well suited for applications where physical space is available—between 1,500 and 2,000 square feet/ton of cooling is required—or where bore drilling is prohibitive. Horizontal loops are usually not used in urban areas due to the limited availability and high cost of land.
Geothermal system where the loop is directly installed in a lake or pond near the building (natural or constructed for aesthetic or drainage reasons), making it an extremely efficient, cost-effective application. Bundled polyethylene coils are used in a reverse return design. Experienced designers should be used to ensure that the body of water will meet building loads. Debris problems from flooding or the need for public access may limit the use of this application.
Systems use ground water to remove or add heat to the water loop; typically used in regions where ground water is plentiful. Water is typically discharged back to the aquifer. A major benefit is the constant well water temperature, approximately 50°F, which provides very efficient operation at a relatively low installed cost. An intermediate heat exchanger is added in many cases to isolate the loop serving the units from the well water to reduce maintenance costs. This system usually has supply wells and return wells. Some states have requirements on the depths of return wells that must be approved by the U.S. Environmental Protection Agency. Water should be tested and strainers are typically required as poor water quality can increase heat exchanger scaling and suspended solids can lead to heat exchanger erosion.
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