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