Solar mirror control by image analysis

The control of the profile on the surface of heliostats is crucial because the mirror can be imperfectly manufactured, and the distribution of solar irradiation on the receiver is sensitive to the curvature of the surface of the heliostat. In practice, irregularities in the surface of the heliostat introduce aberrations that contribute to enlarge the spot on the receiver and the resulting energetic losses depend on the collection characteristics of the solar plant. Since the solar field can be formed by thousands of mirrors, it is essential to have a quick and economical control method to be used during manufacturing operations and successively also in the field during installation. The proposed method of optical control is based on techniques of image analysis. It assesses the heliostat surface quality by means of the examination of the acquired image in comparison with a reference image. This on-site optical control could be applied on various mirror types. The application of this profile control requires only a photographic camera and a screen with a calibrated pattern. The main advantages are ease of application, low-cost equipment, and simplicity of processing.