Exposure Conditions Effect on Soiling of Solar Glass Mirrors

Soiling phenomenon is very critical phenomenon that directly affects the optical performances of mirrors reflectors used in solar field of Concentrated Solar Power plant, CSP. It is caused by a deposition of various particles, with diameter less than 63 mu m in suspension in the air, upon mirrors surfaces.Soiling deposition rate depends on several parameters that are related to the surface nature, climatic parameters and the mirrors exposure conditions. The present work is a part of project of collaboration between MAScIR foundation in Morocco and CEA-LITEN in France which aims to evaluate the durability of various solar mirrors under Morrocan climate. For the study related to the soiling phenomenon, it was evaluated the effect of exposure conditions on the variation of soiing deposition rate. Tests were made on second surface silvered glass mirrors exposed in Moroccan desert site near to Noor station in Ouarzazate. During this study, it was evaluated the effect of inclination angle, exposure height and orientation according to predominant wind direction. Obtained results show that an inclination of 0 degrees according to the horizontal plane is the worst configuration which presents the higher loss in specular reflectivity of studied mirrors. In addition, it was found that in case of high wind, samples exposed in height may present less soiling deposition rate in comparision with others due to the natural cleaning effect of wind speed. Finally, concerning the effect of orientation, it was relieved that in case of low wind speeds in the region, the orientation of samples present very low effect on variation of the soiling deposition rate.