Absorption heat pumps use an ammonia-h2o absorption cycle, rather than a vapor-compression cycle, to transfer heat. Ammonia will be the refrigerant, and drinking water is definitely the absorber. The ammonia condenses at one of several system’s coils to launch heat and evaporates at the 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/