Absorption heat pumps use an ammonia-h2o absorption cycle, as an alternative to a vapor-compression cycle, to transfer heat. Ammonia will be the refrigerant, and h2o may be the absorber. The ammonia condenses at one of the technique’s coils to launch 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/