Absorption heat pumps use an ammonia-h2o absorption cycle, in lieu of a vapor-compression cycle, to transfer heat. Ammonia could be the refrigerant, and water could be the absorber. The ammonia condenses at on the list of program’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/