EVALUATION OF AN AQUIFER THERMAL ENERGY STORAGE (ATES) SYSTEM FOR THE CITY HOSPITAL IN KARLSRUHE (GERMANY)

Abstract: The objective of the present study is to evaluate the economic, technical and environmental feasibility of an Aquifer Thermal Energy Storage (ATES) system combined with groundwater heat pumps (GWHP) for providing space cooling and heating for the future surgery building at the city hospital in Karlsruhe. The base case system used as reference for comparison is a system similar to the one currently supplying space cooling from a GWHP system and space heating by the local district-heating network. In addition, two alternative systems were included in the analysis, an Absorption Chiller (AbC) and a Desiccative Evaporative Cooling (DEC) system, both fed from the district-heating network. The study shows that the ATES system combined with a GWHP system is the most environmentally and economically attractive system for the planned facility. The results for the AbC system and the DEC systems show a negative net present value, meaning that this alternative is economically unfeasible. Furthermore, the AbC system and the DEC system do not provide any environmental advantage, showing an annual increase in CO2 emissions compared to the base case. A similar system like the one already providing cooling to some of the facilities would have several advantages over these two alternatives. However, it cannot compete with the ATES system together with GWHP, which apart from providing cooling at slightly higher efficiencies than the base case also delivers heating at high efficiencies. Therefore, it offers great potential savings and also provides an annual reduction in green house gas emissions. Concerning the technical feasibility of the four studied systems, no obstacle or significant barrier could be identified yet.