Nonlinear model predictive control for thermal balance in solar trough plants

Abstract

The size of existing commercial solar trough plants poses new challenges in applying advanced control strategies to optimize operation. One of these challenges is to obtain a better thermal balance of the loops’ temperature. Since plants are made up of many loops, the efficiency of the loops can vary substantially if a group has been cleaned or affected by dust. This leads to the need to defocus the collectors of the most efficient loops to avoid overheating problems, thus producing energy losses. In order to minimize these energy losses, the input valves have to be manipulated to reduce the temperature difference of the loops. However, when the pipes connecting the loops are very long, the pressure drop and energy losses in those pipes become notorious, affecting the flow distribution. The need to consider the hydraulic model becomes very important. In this paper, a non-linear model predictive algorithm is presented that uses a hydraulic model of the solar field to compute the aperture of the input valves. The results show that when the length of the pipes is increased, the algorithm proposed in this paper obtains better results than other algorithms proposed in the literature.