Including thermal network operation in the optimization of a Multi Energy System

The combined production of different energy vectors with Multi Energy Systems is a very attractive opportunity to increase the generation efficiency, compensate the oscillations of renewable sources, and improve the flexi-bility in power generation. Optimizing their operation is a complex task, since the problem can easily reach high dimensions, representing a challenge for commercial solvers. The inclusion in the optimization of a thermal network whose simulation is based on temperatures and flowrates allows to significantly improve the applica-bility of the obtained results. In addition, the effect of the operating temperatures on the performances of thermal components should be included as well. With these purposes, the present study proposes a strategy for the operation optimization of a MES and its internal thermal network. The model relies on a decomposition approach, where the original problem is divided in two subproblems. In the first one, the MES operating costs are minimized without considering the effects of the thermal network, while in the second one, the thermal network operation is optimized in order to find the operating conditions that are more favourable to the ones found for the MES. These subproblems are iteratively solved until the process converges to a stable solution. Some efforts are taken to keep the mathematical formulation as simple as possible (the MES is a Mixed Integer Linear Pro-gramming, while the heating network is a Quadratically Constrained Programming). The developed model al-lows to find near-optimal solutions which satisfy the numerous physical and technical constraints addressed. The results provide an optimized schedule for the thermal storage in terms of mass flowrates and temperature. One of the strengths of the model is the relatively low computational time required to reach the convergence and, despite not being the global optimum, the high quality of the solution obtained.