(unusual) warm summer of 2018, the heat price for operating the absorption chiller generator varied between 0 and 20 EUR/ MWh, whilst the electricity price saw big variations with an average of 190 EUR/MWh. Such a price scheme would give an advantage for absorption over mechanical cooling, despite the higher COP of the compression chillers. In cooling seasons to come, the input energy prices and resulting operation priorities may be opposite. But all together, the combined system forms a robust solution for the future. CONCLUSION Absorption heat pumps and chillers can play a key role in sustainable and flexible energy system. Absorption technology is ideal for utilizing heat at low temperatures, thus recovering energy that would otherwise be wasted. Unlike a conventional heat pump, the absorption heat pump is fueled by thermal energy, which means minimal electricity consumption and very low operating costs. An absorption heat pump is characterized by a minimal electricity consumption and low operating costs. Thus, the prerequisites for the investment are very robust, and payback times of less than 3 years can typically be achieved.
Figure 6: The new University Hospital DNU in Aarhus, Denmark has 3 MW absorption cooling installed, from which 7 MW of waste heat is reused for heating.
FLEXIBILITY OF FUEL The absorption chiller at DNU is installed in conjunction with mechanical cooling from compressor chillers. This is a big advantage for continuous cost optimization of the cooling plant. Heat prices as well as electricity prices may vary substantially during summer, depending on market spot prices. With both absorption and mechanical cooling capacity installed, production can be planned according to energy prices. In the
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