Flux-feedback as a fast alternative to control groups of aiming points in molten salt power towers

Abstract

The receiver is one of the critical elements in central tower concentrating solar power plants, which use molten salt as heat transfer fluid. Gradients in the incident flux, a consequence of the natural variability of the solar resource on the earth’s surface, and temperature limits must be considered in the operation of the system, due to corrosive phenomena caused by the interaction between the metal alloys used on the receiveŕs tubes and the molten salt. Furthermore, considering thermal stresses in the receiver as operational constraints leads to the prevention of fractures and has the potential to improve the lifespan of the subsystem. In this work, a novel control strategy is tested in a simulated power plant with a nominal thermal power of 450 MW and a solar field with 6482 heliostats. A flux-feedback closed-loop control law is proposed, which manipulates the swarm behavior of groups of aiming points for heliostats in the solar field and also reduces each iteration the information from the incident flux on the receiver’s surface into one variable per group. This work established that the proposed controller can reach a steady-state with a configuration of aiming points, which is close to the optimal solution obtained by a hybrid optimization approach, but much faster and with less computational resources. For the simulation and the optimization, a static coupled optical-thermal model is used.