Closed Loop

Closed loop systems are the second most common type of geothermal source. Closed loops utilize polyethylene piping buried or drilled into the ground, filled with a water/anti-freeze solution. The loop fluid circulating in this closed piping system absorbs heat or rejects heat into the surrounding earth. Typically, in the Midwest, loop systems are installed in a “horizontal” configuration as pictured above. In other parts of the country, where digging is more difficult or expensive, “vertical” loops are used. Vertical loops are placed in vertical holes usually drilled in the ground with a machine similar to a drill rig used to install water wells. Vertical loops are also commonly used in commercial applications or applications where there is not enough room for a horizontal loop. Closed loops are virtually maintenance free, and since they re-circulate the same fluid, have no need for a well or a place to discharge the water. However, closed loops, due to the excavation costs, are generally more expensive than open loop systems.