Metrology system of the 2.4 m × 3.3 m deformable heliostat

This paper describes a novel heliostat metrology system in which the image formed by a full-size reflector of a nearby large test screen is viewed by a distant camera. The reflector shape is obtained from measurements of the magnification and distortion of a fine-scale regular pattern on the screen. This method is especially valuable for setting and testing the different shapes of a reflector for use in concentrating solar-thermal power (CSP) systems targeting high concentration. Maintaining such concentration throughout the day requires an accurate shape deformation according to the changing of sun’s altitude and incidence angle to reflectors. The proposed method has been tested on the single sheet float glass reflector measuring 2.4 m × 3.3 m and bent to focus sunlight at 113 m distance. From images obtained from a camera at 50m distance, the reflector surface was measured to an accuracy of 0.1 mrad rms slope error at 25 mm spatial resolution.