Analysis of the impact of ambient groundwater flow on the aquifer thermal energy storage systems

Abstract

Heating and cooling significantly contribute to the world’s total energy consumption, and this demand is steadily rising due to population growth and the impact of climate change. Among various renewable energy technologies, aquifer thermal energy storage (ATES) stands out for its efficient energy utilization, ability to reduce CO₂ emissions, and significant energy storage capacity. The question of whether the effect of ambient groundwater flow (AGF) on the recovery efficiency of ATES can be ignored has been a long-standing debate, as recovery efficiency serves as an indicator of how much of the injected thermal energy can be retrieved from the aquifer. This paper aims to construct numerical models using COMSOL Multiphysics to determine under what conditions AGF can be disregarded for the ATES systems. The results show the following: 1) The injection rate of ATES is positively correlated with the recovery efficiency, while aquifer thickness is negatively correlated with the recovery efficiency. 2) A higher AGF velocity results in a lower recovery efficiency. 3) There is a linear correlation between the AGF velocity and the radial flow velocity (generated by the thermal operational well) at the thermal operational wellbore surface, suggesting a specific threshold beyond which the influence of AGF on recovery efficiency cannot be ignored. This research has important implications for providing recommendations for the application of ATES and exploring the potential for expanding renewable energy.