A closed-loop geothermal heat pump system, also known as an indirect system, is a geothermal heat pump system that circulates a solution of water and antifreeze through a series of sealed loops of piping. Once the heat has been transferred into or out of the solution, the solution is recirculated. The loops can be installed in the ground horizontally (see horizontal ground loop) or vertically (see vertical ground loop), or they can be placed in a body of water, such as a pond (see surface water loop).

 

Compare with open-loop geothermal heat pump system.