Simulation of Aquifer Thermal Energy Storage System under Continuous Flow Regime Using Two-well Model

Large-scale thermal energy storage can be accomplished in the aquifer through the installation of an array of vertical boreholes. Coupled hydrogeological-thermal simulation of the storage system is essential to provide an optimized configuration and operation schedule for wells on the site. This paper presents numerical investigations and thermohydraulic evaluation of two-well models of aquifer thermal energy storage system operating under continuous flow regime. A three-dimensional numerical model for groundwater flow and heat transport is used to analyze the thermal energy storage in the aquifer. The model includes the effects of convection and conduction heat transfer, heat loss to the adjacent confining strata, and hydraulic anisotropy. The operation scenario consists of continuous injection and recovery from two wells and four periods per year to simulate the seasonal temperature conditions. For different parameters of the system, performances were compared in terms of normalized energy storage. The calculated temperatures at the producing well were relatively constant within a certain range through the year and fluctuating quarterly a year. Operation schedules, injection temperature, injection/production rate, and geometrical configuration of the well and aquifer used in the model are shown to impact the predicted temperature profiles at each stage and the recovery water temperature. But aquifer thickness and hydraulic anisotropy have a minimal effect on the performance of aquifer thermal energy storage systems.