Semi-analytical modeling of large-scale water tank for seasonal thermal storage applications

Buildings consume large amount of energy for cooling in summer and heating in winter. A renewable energy-based district heating using seasonal thermal storage can better serve for a lower carbon space heating for buildings. The research objective is to propose a first semi-analytical model of large-scale water tank storage as an efficient and flexible tool for further development of TES. A new idea of “three-zone method” is proposed for detailed heat and mass flow inside water storage with least increase in computational burden and better capture of internal non-uniform thermal distribution. All three modes of charging, discharging and standby are modeled separately with high flexibility. A modified finite cylindrical source model for TES was proposed, for the first time, for transient heat transfer in the ground, which is inspired by analytical model of ground source heat pump. A complete comparison was made between the new semi-analytical model and validated reference data, which shows a good match in temperature profile in different locations. This study will pave a way for a further systematical study on seasonal thermal storage.