Co-Simulation of Dynamic Energy System Simulation and COMSOL Multiphysics®
The efforts to integrate and/or expand the renewables into the overall energy scheme are drastically increasing in Europe. This integration might somehow alter the energy scheme resulting into shortcomings (e.g. security of supply is not met). Therefore, a number of strategies and technologies are introduced allowing the renewables to expand. Among the technologies, energy storage is often seen a key solution, especially seasonal thermal energy storage (STES) systems to bridge the gap between winter heating demand and solar heat availability in summer.
Yet, seasonal TES cannot be easily integrated into block and district heating (DH) systems because of a wide list of parameters and constraints influencing the integration and operation of this technology, such as the varying heat demand, temperature level, TES size, TES geometry, ground conditions (e.g. presence of groundwater), etc. Further, given the large-scale volume for such systems in order to fulfill the seasonal tasks, the investment cost is also a critical player that holds this technology from being experimentally examined. Therefore, numerical simulation-driven assessments and optimizations are of importance for investigation these complex systems and to overcome the risks and to avoid the high costs that can arise when experimenting on a system level.
In this context, COMSOL Multiphysics® is used to develop a numerical model for a large-scale STES in DH systems. This model investigates the thermo-hydraulic behavior of the storage medium under different operation schemes. Therefore, it is important to integrate the different operation schemes, configurations and technologies in a DH system model in order to obtain reliable results. However, given the finite element discretization method in COMSOL Multiphysics®, it is challenging to model dynamically the DH systems (heat sources, heat demand, etc.). Therefore, a dynamic simulation tool is undoubtedly needed in order to capture the entire dynamics of the systems.
Therefore, co-simulation approaches arise as a promising technique to couple a number of different simulation tools and provide detailed results that can help in assessment of complex systems. A key advantage of co-simulation is that it permits the utilization of particular simulation tools; each is sufficiently tailored to fulfill the needs of specific parts in the investigated system. In a co-simulation platform, the subsystems models are interconnected with each other at their behavioral levels though the models are given in different tools.
In this research, the authors highlight the limitations as well as the opportunities of COMSOL Multiphysics® in being coupled to other dynamic simulation tools that are widely used in industry and research of energy systems (e.g. TRNSYS, Modelica/Dymola, Simulink etc.). Then, the authors discuss the coupling of COMSOL® to Modelica/Dymola tool to run a system simulation in which STES is developed in COMSOL® and the system is modeled in Dymola. Moreover, this work pinpoints the research needs, existing shortfalls and challenges needs and, then, the promising approaches.
