Identifying aquifer thermal energy storage (ATES) key locations for hospitals in Lower Saxony, Germany

• 57 % of porous aquifer areas in Lower Saxony are well or very well suited for ATES. • No ATES systems exist in Lower Saxony, despite favorable hydrogeological conditions. • Hospitals show significant cooling capacities of up to 5.9 MW, with a mean of 0.9 MW. • 60 out of 113 hospitals are located in areas suitable for ATES implementation. In a decade of advancing energy transition, European countries, including Germany, face the challenge of managing seasonal imbalances in heating and cooling demands. Aquifer thermal energy storage (ATES), which uses groundwater as a storage medium in an open-loop geothermal system, offers a promising solution. Infrastructure requiring both heating and cooling, such as universities, data centers, shopping malls, office buildings, and hospitals, are particularly suited for ATES. Especially hospitals have high heating and cooling demands, making them promising candidates. This study evaluates the ATES suitability in the state of Lower Saxony, Germany, where geological conditions in many areas resemble those in the bordering Netherlands, the worldwide leader in the application of ATES. Hence, the study focuses on identifying ATES key locations in Lower Saxony by estimating the cooling capacities of 113 hospitals using visible compression chiller fans. Cooling capacities of up to 5.9 MW are detected, with a mean of 0.9 ± 1.2 MW. The results show that 57 % of the area with shallow porous aquifers in Lower Saxony is well or very well suited for ATES, with 60 hospitals located in these areas. ATES offers payback times of 2–10 years and CO 2 savings of up to 74 % compared to conventional systems, highlighting its economic and environmental advantages. However, no system is currently operating in Lower Saxony and the lack of specific regulation for ATES hinders their development. Establishing supportive and novel policy frameworks could unlock the potential of this sustainable thermal energy storage technology.