 The air/water-brine/water heat pump is a hybrid heat pump, developed in Rostock, Germany, that uses only renewable energy sources.Unlike other hybrid systems, which usually combine both conventional and renewable energy sources, it combines air and geothermal heat in one compact device.The air/water-brine/water heat pump has two evaporators — an outside air evaporator and a brine evaporator — both connected to the heat pump cycle.