Residential heating and cooling with Aquifer Thermal Energy Storage (ATES) on city scale

Aquifer thermal energy storage (ATES) is a promising technology for sustainable and climate-friendly space heating and cooling which can contribute to the energy transition, as it causes significantly less greenhouse gas (GHG) emissions than conventional space heating and cooling technologies. Using 3D thermo-hydraulic numerical models, this study quantifies the technical potential of shallow low-temperature ATES in the city of Freiburg, Germany. The numerical models consider various ATES configurations and different hydrogeological subsurface characteristics relevant for the study area. Based on the modeling results, spatially resolved ATES power densities for heating and cooling are determined and compared to the space heating and cooling energy demand. High ambient groundwater flow velocities of up to 13 m d^-1 cause relatively high storage energy losses resulting in maximum ATES power densities of 3.2 W m^-2. Yet, these still reveal substantial heating and cooling energy supply rates achievable by ATES systems. While heating energy supply rates of larger than 60 % are determined for about 50 % of all residential buildings in the study area, the cooling energy demand could be supplied entirely by ATES systems for 92 % of the buildings. Also, ATES heating alone could allow for greenhouse gas emission savings of up to about 70,000 tCO_2eq a^‑1, equivalent to 40 % of the current greenhouse gas (GHG) emissions from space and water heating in the study areas’ residential building stock. The proposed modeling approach in this study can also be applied in other regions with similar hydrogeological conditions to obtain estimations of local ATES supply rates and support city-scale energy planning.