Closed-loop systems circulate a water-based solution through a "loop" of small-diameter, underground pipes. Closed-loop systems can be installed horizontally, vertically or in a pond. Open-loop systems use an existing water well. Regardless of whether the system is open or closed, heat is transferred to or from the home to provide year-round comfort, no matter what the outdoor temperature is.
Four Basic Geothermal Energy Sources
|Horizontal Loops |
These are often considered when adequate land surface is available. Pipes are placed in trenches that range in length from 100 to 400 feet.
|Vertical Loops |
These are the ideal choice when available land surface is limited. Drilling equipment is used to bore small-diameter holes from 75 to 300 feet deep.
|Pond (Lake) Loops |
These are very economical to install when a body of water is available, because excavation costs are virtually eliminated. Coils of pipe are simply placed on the bottom of the pond or lake.
|Open loops |
These use groundwater as a direct energy source. In ideal conditions, an open-loop application can be the most economical type of geothermal system.