Scalable heliostat calibration system (SHORT) - Calibrate a whole heliostat field in a single night

Efficient operation of a solar plant requires precise control of the solar field, in order to achieve the desired flux on the receiver. In order to do so, accurate knowledge about the relation between heliostat axis encoder values and the actual orientation of the reflective surface is essential. Such information is gained from heliostat calibration, making it an essential part of plant operation. Being able to perform such a calibration frequently allows maintaining high efficiency of the solar field, by compensating for drift or other deviations which can occur over time. Such a solution is imperative for using small sized heliostats, where the solar field potentially contains tens or even hundreds of thousands of them. Even for whatever heliostat such a calibration allows a more precise control on their aiming point leading to a better plant performance. The presented solution addresses this with an automatic procedure, which is able to calibrate a full solar field during one night by using cameras and artificial targets within the solar field. The method has been successfully tested at the Plataforma Solar de Almeria (PSA), showing that a beam accuracy of about 0.6 mrad can be achieved.