Comparing Modelling Approaches for the Thermal Behavior of a Vanadium Flow Battery used for Thermal and Electric Storage

This study presents the development and validation of two thermal models for a Vanadium Flow Battery (VFB) system installed in a student residence in Bruchsal, Germany. The VFB, rated at 21 kW/120 kWh, serves as both an electrical and thermal energy storage unit. To manage its thermal behavior, a newly developed Thermal Coupling Module (TCM) enables active heating and cooling of the electrolyte tanks via heat exchangers and a flow heater. Two distinct modeling approaches are explored: a physics-based model that applies thermodynamic principles and a zero-dimensional (0-D) heat distribution framework, and a simplified model relying solely on linear equations derived from measurement data. Both models are validated against real-world operational data across various scenarios, achieving a mean absolute error of less than 1 K. This level of accuracy is comparable to laboratory-scale models reported in literature. Importantly, the models require minimal knowledge of internal battery characteristics, making them highly suitable for real-time control and optimization in advanced energy systems, particularly in dual-use applications combining thermal and electrical storage.