Mahnoor Khawaja, Svenja Carrigan, Oliver Kornadt

• A novel heat generation system coupled with a hybrid latent–sensible thermal energy storage (TES) system has been developed as a part of a research project. This study presents the validation of a simulation model of this TES unit with the objective to reasonably model the internal heat transfer under realistic multi-seasonal operational conditions. The detailed geometry-based modelling approach retains the key physical mechanisms governing the thermal transport within the storage matrix while keeping the computational effort manageable. The software used is the thermal transport program “Voltra”. To the authors’ knowledge the presented approach is the first documented application of this software in such context. Unlike most existing studies that validate the models with geometrical simplifications and under ideal lab conditions, in the present contribution the complete internal geometry of the system has been modelled, and the system behavior has been validated against measured field data for the Autumn season. Despite the hysteresis of the PCM, not being explicitly modelled, which is the limitation of the Voltra software, results show strong agreement of the simulated vs. field measured temperature data with values of RMSE (Root Mean Squared Error) and MAE (Mean Absolute Error) both ranging between 0.17°C and 0.71°C. The applicability of the modelling framework is limited to TES systems with conduction as a key heat transfer mechanism and in which fluid dynamics contribute to only second-order effects. Accounting for internal structural heterogeneity and realistic boundary conditions, using this approach, improves the accuracy of the simulated TES thermal behavior and establishes confidence for the further design and optimization process. The study provides a validated foundation for subsequent design and systematic optimization of the TES systems.