Closed-loop systems circulate a water-based solution through a “loop system” of small-diameter underground pipes made of high-density polyethylene. They can be installed horizontally, vertically, or in a pond.
- Horizontal Loop… often used when adequate land surface is available. Depending on geothermal system needs and space available, pipes are placed in trenches that range in length from 100 to 400 feet.
- Vertical Loop… an ideal choice for a geothermal heat pump when there is limited land surface. Well-drilling equipment is used to bore small-diameter holes from 100 to 400 feet deep.
- Pond (Lake) Loop… very economical to install when a large body of water is available for use by the geothermal heating and cooling system. Coils of pipe are simply placed on the bottom of the pond or lake to capture the geothermal energy.
Open Loops can be the most economical type of geothermal system, in ideal conditions. These use groundwater from a well as a direct energy source. Whether the system is open or closed, heat is transferred to or from the structure, regardless of outdoor temperature, to provide year-round comfort.