Absorption heat pumps use an ammonia-h2o absorption cycle, rather then a vapor-compression cycle, to transfer heat. Ammonia will be the refrigerant, and drinking water could be the absorber. The ammonia condenses at on the list of system’s coils to release heat and evaporates at the other coil to absorb heat. https://purethermal.co.uk/media-news/can-gas-absorption-heat-pumps-provide-an-alternative-heat-pump-option-in-2025/