Absorption heat pumps use an ammonia-water absorption cycle, instead of a vapor-compression cycle, to transfer heat. Ammonia would be the refrigerant, and drinking water could be the absorber. The ammonia condenses at one of the method’s coils to release heat and evaporates at the opposite coil to soak up heat. https://purethermal.co.uk/media-news/can-gas-absorption-heat-pumps-provide-an-alternative-heat-pump-option-in-2025/