Absorption heat pump

An absorption heat pump (AHP) is a heat pump driven by thermal energy such as combustion of natural gas, steam solar-heated water, air or geothermal-heated water differently from compression heat pumps that are driven by mechanical energy. AHPs are more complex and require larger units compared to compression heat pumps. In particular, the lower electricity demand of such heat pumps is related to the liquid pumping only. Their applications are restricted to those cases when electricity is extremely expensive or a large amount of unutilized heat at suitable temperatures is available and when the cooling or heating output has a greater value than heat input consumed. Absorption refrigerators also work on the same principle, but are not reversible and cannot serve as a heat source. The heat pump system is made up of some main units such as the generator, condenser, evaporator, absorber and heat exchanger, as well as the suction device, shielding pump (solution pump and refrigerant pump). In the simplest case, five heat exchangers are also required (at each component and an internal heat exchanger). Other components include solution heat exchangers, valves, as well as the suction device, shielding pump (solution pump and refrigerant pump) and other auxiliary parts. For the absorption heat pump circulation, the absorber, generator and pump can be regarded as a "thermal compressor". The absorber is equivalent to the inlet side of the compressor, and the generator is equivalent to the outlet side of the compressor. The absorbent can be regarded as a carrier liquid that transports the generated refrigerant gas from the low-pressure side of the cycle to the high-pressure side. Since the main components of devices that achieve three purposes are the same, there is a heat pump that enables it to realize all working modes: heat pump mode, cooler mode and heat transformer mode. The absorption heat pump can be used as a cooler during summer while, during winter, it can be used on heat pump or heat transformer mode according to the available heat source.