Control-Oriented Model of a Molten Salt Solar Power Central Receiver

This paper presents a control-oriented, reduced order model of a concentrated solar power central receiver using molten salt as heat transfer fluid. The objective is the utilization in a model based controller. Therefore, the priority is to have a model as simple as possible with a minimum amount of system states. Accompanied by the loss of spatial information, this strategy contradicts the requirement to observe not measurable critical receiver states, that are described by the molten salt temperature at the boundary layer to the receiver pipes and the absorbed flux densities. These quantities are subject to restrictions and the challenge is to detect the excess of their limits, that can appear at arbitrary locations in the receiver. For this purpose a method is presented, that targets at estimating the local absorbed flux densities by considering a steady state case and deriving the film temperatures. To validate the control-oriented model, it is compared to a detailed model operating in a closed-loop. For estimating the molten salt temperature, simulation results show a dynamic accuracy of maximal 9 K. The critical states can be observed with transient deviations of 15 K for the film temperatures and relative deviations of maximal 1.5% for the absorbed flux density.