Absorption heat pumps use an ammonia-h2o absorption cycle, rather than a vapor-compression cycle, to transfer heat. Ammonia may be the refrigerant, and drinking water would be the absorber. The ammonia condenses at one of several process’s coils to launch heat and evaporates at one other coil to soak up heat. https://purethermal.co.uk/media-news/can-gas-absorption-heat-pumps-provide-an-alternative-heat-pump-option-in-2025/