Open loop heat pumps from heat pump specialist Ecoliving
Open loop heat pump is the term used to describe when ground water is the heat source for ground (or water) source heat pumps. Ground water is pumped from one borehole through a heat exchanger and returned via a separate borehole to the same aquifer. In the heat exchanger, the ground water transfers its heat to the water & antifreeze mix which is, in turn, transported via a short plastic collector circuit to the evaporator in the heat pump. Some heat pumps are designed for open loop with a corrosion resistant heat exchanger inside the heat pump which means that the ground water can be pumped directly into it to heat the refrigerant.
Typical UK ground water temperatures average 8 - 12°C and remain fairly constant all year round. An open loop system is dependent on appropriate hydrological conditions on site.
Open loop as opposed to closed loop where the non-freezing solution is pumped around a closed collector loop in the case of vertical borehole collector, surface collector and lake collector.