Hybrid optical method for characterizing a heliostat field in a concentrated solar power plant

This paper describes the backward-gazing method with four cameras optimized by using different process of data treatments. The method could be useful for the heliostats characterization in a Solar Tower Power Plant (STPP), to detect heliostat pointing errors, mirrors canting and waviness without disturbing the daily electricity production process. The method is based on the use of four cameras near the receiver, all pointing to the heliostat to be characterized, and a fifth one taking images of the Sun. The theoretical principle is explained and different kind of data treatment process are tested and compared by using heliostat images from numerical simulations. Each process model is explained and the software used for simulations is described. The achieved accuracy of the best results is estimated to less than 0.05 mrad RMS in term of surface slopes.