Where a mechanical heat pump is driven by electric energy, an absorption heat pump is driven by thermal energy. This thermal heat is delivered by steam or by combustion of natural gas. Absorption heat pumps are very useful in situations where both heating and cooling is required.
The principle of operation of an absorption heat pump is based on absorption and evaporation of a refrigerant. An absorption medium as wel as a refrigerant have to be chosen. Well known pairs are:
Principle of operation
The figure on the right shows the principle of operation of an absorption heat pump. It is based on a heat pump that uses the pair Ammonia and water (NH3/H2O). The absorption heat pump consists of two loops. The loop on the right represents the absorption medium and the circulation loop at the left represents the refrigerant.
Cycle of the absorption medium
Absorption heat pumps with natural gas as a heat source are commercially available. For the production of useful heat at a maximum temperature of 70 °C and cooling of the condensor with water or air, the efficiency is approximately 150%. In other words: the addition of 1 kWh of natural gas results in the production of 1,5 kWh of heat.