On the effect of thermal models on the operation of Multi-Energy Systems providing flexibility services

Multi-Energy Systems (MES) are acknowledged for their potential to enhance energy system flexibility. However, they pose several challenges to the conventional optimization models in addressing local flexibility market interactions and fulfilling internal thermal demands. Given these considerations, the paper introduces a novel Energy Management System (EMS), with a hierarchical architecture that comprehensively addresses the thermal sub-section within a MES framework. The proposed methodology integrates an intra-hour Model Predictive Control (MPC) strategy, leveraging a linearized thermal model to balance heat equations and accurately describe thermal energy storage dynamics, incorporating considerations for delivery temperature to thermal loads during the provision of flexibility services. The results show that the conventional optimization model underestimates the operational cost of a MES by an amount ranging from 2% to 12%, depending on the delivery temperature to the thermal loads. Moreover, the proposed MPC can operate the MES in real-time with a reduced impact when compared to a rule-based thermal control (with savings of up to 7%), while ensuring commitment to local flexibility markets.