Validation of a Low-cost Camera for Scalable HeliOstat calibRation sysTem (SHORT)

Current commercial solar tower power plants have bet to increase the thermal storage capacity and the electrical power in order to reduce generation costs, leading to solar fields with thousands of heliostats which must be calibrated to ensure the tracking accuracy, reduce the spillage, enhance the reliability and, thus, increase the energy production. The state-of-the-art of heliostat calibration methods, the so-called camera target-method, cannot face that amount of heliostats in a reasonable time and fails when applied to distant heliostats. This work presents a calibration system based on low-cost cameras mounted on heliostats that observe artificial lights distributed around the solar field. The method can calibrate the whole heliostat field in a single night without interfeting with the operation of the plant and without incurring additional costs. The calibration relies on finding the actual kinematic model of the heliostats so that the heliostat orientation is accurately characterized for whatever given heliostat angles allowing precise control over the heliostat orientation, and hence, their aim point. The method has been successfully tested at the Plataforma Solar de Almeria showing heliostat orientation accuracy below 0.5 mrad that would lead to sun tracking accuracy better than I mrad.