Model based optimization of a combined biomass-solar thermal system

This paper presents the model based optimization of the control parameters of a combined biomass-solar thermal system for heating and domestic hot water supply, designed for small residential applications. The system consists of a thermal storage with an integrated pellet burner and a heat exchanger to feed solar energy from a small collector field into the storage. By using a physical model of the existing system, the time for optimizing the control system can be reduced significantly. To optimize the given system, it was desired not to vary the system specific parameters such as the collector or the storage size. However, the control parameters (i.e.: set-points of local control loops of the combined system) of the system are supposed to be optimized. The system was simulated with the dynamic thermal simulation environment TRNSYS using validated models. Monitored data was used to estimate several model parameters. The control strategy of the off-the-shelf product was implemented using MATLAB. In this study it was clearly shown that the performance of the described system can be improved by optimizing the control parameters upon a model based approach. A complete system model was set up and the control strategy was reproduced within the simulation environment.