Towards More Efficient Modeling and Simulation of Large-scale Thermal Energy Storages in Future Local and District Energy Systems

Large-scale hot-water underground tank and pit thermal energy storages have a high potential to massively increase the proportion of renewable energy in future local and district energy systems. To fully exploit the potential of these large-scale thermal energy storage (LTES) technologies, comprehensive planning and tuning of the overall system by dynamic system simulations is necessary. Modelica-based simulation tools show many advantages over other established system simulation tools. However, suitable LTES models in Modelica are limited or lack essential features. Consequently, it is the intention of this study to develop a novel Modelica LTES model. Existing models served as the basis for the development. A validation case study involving a real Danish pit storage was performed to assess the accuracy of the new model under real conditions. The results show that the new model adequately represents the physical behavior and interaction with the surrounding soil. This study is a first step towards more efficient modeling and simulation of LTES in dynamic system simulations in the future.