Closed-loop ground-coupled heat pump systems offer several advantages over conventional HVAC systems. For instance, they collect renewable ground heat or recuperate building heat rejection that accumulated in the ground during the cooling season. Furthermore, because of their relatively high coefficient of performance (COP) in both heating and cooling they are, as noted by the U.S. Department of Energy and the U.S. Environmental Protection Agency, among the most energy-efficient and environment-friendly heating and cooling systems.