Comparison of detailed large-scale Thermal Energy Storage simulation models

Numerical modelling of large-scale thermal energy storage (TES) systems plays a fundamental role in their planning, design and integration into energy systems, i.e., district heating networks. This work presents a comparison of the implementation of numerical models of buried TES in Matlab and Comsol. Both tools allow the modelling of the surrounding ground with the finite-element method, while the water domain is modelled one-dimensionally. The Comsol model allows a high level of detail and flexibility and is recommended for TES optimization in a system context. The Matlab model, on the other hand, is more simplified with a focus on fast system simulations. The models are compared in terms of energy flows, temperature stratification and simulation performance. Different TES geometries are investigated, i.e., tank and pit with various slopes, different envelope qualities (i.e., insulation) are considered. In terms of energy flows, the two models are in good agreement, however, deviations in the thermal stratification are found between the two modelling approaches