Absorption heat pumps use an ammonia-water absorption cycle, as opposed to a vapor-compression cycle, to transfer heat. Ammonia may be the refrigerant, and drinking water will be the absorber. The ammonia condenses at one of many technique’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/