Absorption heat pumps use an ammonia-drinking water absorption cycle, as opposed to a vapor-compression cycle, to transfer heat. Ammonia would be the refrigerant, and drinking water will be the absorber. The ammonia condenses at among the system’s coils to launch heat and evaporates at one other coil to absorb heat. https://purethermal.co.uk/media-news/can-gas-absorption-heat-pumps-provide-an-alternative-heat-pump-option-in-2025/