Absorption heat pumping systems for refrigerating and air-conditioning with large cooling capacities (of some 100 kW) are more or less state-of-the-art. With respect to the working pairs mainly ammonia/water is used for applications with evaporation temperatures below 0°C, and water/lithium bromide for air-conditioning applications.
In contrast to large-capacity applications up to now small-capacity absorption heat pumping systems have difficulties to get into the market due to relatively low efficiencies, control issues, and high first costs.
Recently small-capacity absorption chillers with the working pair water/lithium bromide have been developed and are partially available on the market, but up to now only a few installations of small-capacity ammonia/water applications can be found.
At the Institute of Thermal Engineering the new development of a small-capacity ammonia/water absorption heat pumping unit is going on. The heat pump can be used for both heating and cooling and shall be driven by a biomass boiler in order to reduce the energy demand as well as to increase the share of renewables.