| Abstract |
In support of the energy transition, Aquifer Thermal Energy Storage (ATES) systems are increasingly considered as a (cost-)effective method to seasonally store large amounts of sensible heat in the subsurface, at temperature levels ranging up to 100 °C. Although in the design of these systems it is typically considered to recover as much of the stored energy as possible, considerable amounts of heat are still lost to the subsurface (e.g. 10-30% annually), which is a concern for the potential impact on surrounding groundwater resources. Hence, it is important to have insight in how varying storage and hydrogeological conditions affect these thermal impacts, both spatially and temporally, particularly for high temperature ATES. Therefore, in this study, the thermal impact on confining layers, as well as the temperature effect within the ATES storage aquifer are assessed. The variation in operational conditions and subsurface properties, such as layering and well placement, are based on a recent case-study in Delft, the Netherlands. The results show that the thermal impact is stronger on overlying layers compared to underlying layers due to buoyancy-driven effects and that the vertical temperature effect is correlated in a limited way with the thermal recovery efficiency of the ATES system. Furthermore, the thermal impact is strongly determined by the thickness and thermal properties of the confining layers of the storage aquifer, as well as the hydraulic properties of the overlying aquifers. The insights obtained in this work feed into ATES well design methods to minimize thermal impacts. |