Abstract
Aquifer thermal energy storage (ATES) mitigates the seasonal mismatch between summertime heat supply and wintertime heat demand, contributing to decarbonization of the heating and cooling sector. Conventional low-temperature ATES design targets high-transmissivity aquifers to achieve the pumping rates needed to meet energy demand. If geological constraints or competing subsurface uses require storage in lower-transmissivity formations, pumping rates may be restricted to limit hydraulic head changes or reduce the risk of well screen particle clogging. This restriction would increase the number of well doublets and potentially make well field layout a critical design challenge. To address this complexity at an early planning stage, an analytical approach is presented that determines the minimum number and distance of ATES well doublets assuming a checkerboard or a lane layout. The approach combines thermal and hydraulic constraints by determining a minimum well distance derived from the thermal radius and a maximum well distance necessary to limit pumping-induced head changes, explicitly accounting for hydraulic superposition effects in multi-doublet well fields. Applying this approach to a planned low-temperature ATES at Kiel University, Germany, shows that the checkerboard layout achieves the target pumping rate of 200 m 3 /h with nine well doublets, whereas the lane layout requires 11 well doublets. The analysis also indicates that reducing the distance between wells of the same type in low-transmissivity aquifers significantly increases the number of well doublets. The approach provides a practical tool for preliminary ATES design, supporting informed well field configuration under hydraulic constraints.