Journal of Refrigeration Magazines Agency Co., Ltd.
Abstract
The application of large-scale water pit thermal energy storage(PTES)systems can increase the share of renewable energy in district heating systems. Currently, most available models for PTES systems are based on numerical models, lacking fast calculation and accurate analytical or semi-analytical models. Based on this, this study proposes a semi-analytical model suitable for PTES. The model solves separately for the water domain and the soil domain and then couples them through the pit sidewall and bottom temperatures and boundary heat fluxes. In the heat transfer analysis for water domain, a "three-zone" model is proposed, dividing the cross-section into a central zone, a transition zone, and an edge zone. Compared to simple one-dimensional models, this "three-zone" model takes into account horizontal water flow, providing more accurate dynamic simulation of water temperature. In the heat transfer analysis for soil domain, the finite cylindrical source model used in the field of ground source heat pumps was improved to make it suitable for the modeling of PTES. Furthermore, the semi-analytical model was validated using 10 years of measured data from a 60,000 m³ PTES in Denmark. The average temperature errors at the top, upper-middle, middle, lower-middle, and bottom positions were 0.233%, 0.44%, 0.445%, 0.316%, and 1.27%, respectively, all less than 1.5%, indicating that the model has high accuracy and reliability
