Development of a New High Dynamic Range Technique for Solar Flux Analysis Using Double-CCD Optical Camera

Abstract

In solar central receiver (SCR) systems, camera-based tracking and control strategies have been widely developed and tested. The camera, usually with a single CCD, captures images of the sun reflected by thousands of heliostats on the central receiver. The captured images are then analysed to allow the evaluation of solar flux. For accurate analysis process, the camera must have a high dynamic range (HDR) to give real and accurate information about the captured scene. In the present article, a new methodology has been developed using a double-CCD optical camera for improvement of dynamic range of the captured solar flux image. An experimental calibration set-up is adopted for accurate estimation of the camera response function. The double-CCD camera is used for acquiring two images at the same instant with two different levels of exposure. The two captured images are then merged into a single HDR image using a new proposed weighting function. The enhanced optical performance of the proposed weighting function has been demonstrated by comparison with the previous HDR image generation weighting functions at different levels of illumination. Investigation of the capability of the proposed methodology for the analysis of beam accuracy and optical quality of SCR systems show that the present proposed method leads to more accurate solar flux analysis because of the improvement in the resolution of details of the final merged image.