Cavity receivers in solar dish collectors: A geometric overview

Many studies, as numerical and experimental, regarding the applications of solar dish concentrators have been performed. Most researchers focused on the maximum thermal efficiency, the minimum heat loss, and their relations to the solar receiver geometries. This paper presents and discusses the previous studies investigating different cavity receiver geometries and their optimization methods with parabolic dish collectors. More specifically, cylindrical, hemispherical, conical, and flat sides cavity receivers are investigated in this manuscript. For an inlet operating temperature of 200 degrees C, the conical cavity shape has shown a thermal efficiency of around 70%, exergy efficiency of 30%, and optical efficiency of around 87%. The working fluid temperature is often around 650 degrees C-750 degrees C in the solar dish collectors. Due to high working temperature and cavity shape, heat losses such as radiation, conduction, and convection losses are highlighted that could provide adverse effects upon the system thermal efficiency. Besides, the diameter aspect ratio, the cavity inclination angle, type of tube, and the tube shape can be impressive on the cavity heat losses value. Therefore, the optimized geometry of the cavity receiver is a vital subject. Based on the analyzed issues, some suggestions and concluding remarks are presented. (C) 2021 Elsevier Ltd. All rights reserved.