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