Quality test to the parabolic trough solar collector surface using structured light

Abstract

Currently, there is considerable research on the study of solar collection systems to take full advantage of this resource. Several geometries, such as point-like, linear and non-focus, have been used for the concentration of solar radiation. Solar radiation concentrated by this system is sensitive to deformations on the reflecting surface. Therefore, several techniques of optical testing for quality control of the reflecting surface have been developed. In this work we developed an optical technique based on a laser triangulation method that used the projection of a laser beam onto the surface to be evaluated, a camera placed perpendicular to a reference plane, and the object under study. The technique associates lateral displacements of the laser beam, observed by the camera, with changes in height of the object relative to the reference plane, using a mathematical model. To obtain a digital reconstruction of the whole object, we scanned it using the projected beam. Through this method we evaluated the reflecting surface of a parabolic trough solar concentrator prototype with a 1 250 mm opening and 914 mm trough. As result, we obtained the real shape of the collector surface, which allowed calculating its real focus. Furthermore, the range of differences between the real and the best fit surface was approximately ± 10 mm. From this results, we concluded that the technique can be applied to improve the manufacturing processes of solar concentrating systems. The technique can be adapted to evaluate small objects with high sensitivity in the Z axis.