Physicochemical Characterization of Naturally Deposited Dust and Spectral Optical Effects on PV Glass in Arid region, Morocco

Abstract

Soiling is a critical limitation to PV deployment in arid environments because deposited particles change the optical properties of the module cover glass. The present work studies the physicochemical characteristics of natural dust deposited on one side and its spectral optical effects on PV glass under outdoor conditions in Errachidia (south-east of Morocco) in contrast. Forty-eight glass samples were exposed at four tilt angles (0°, 32°, 45° and 70°) and analyzed periodically during a long exposure campaign. The dust sample taken from the site was characterized by X-ray diffraction and SEM-EDS and the spectral transmittance was measured from 200 to 1100 nm. XRD showed quartz and calcite as the dominant crystalline phases with some dolomite and aluminosilicate material. SEM-EDS showed irregular and heterogeneous particles, agglomerates and local Fe-, Ca- and Si-Al-rich areas. The optical measurements showed clear wavelength dependent attenuation and progressive degradation of transmittance with exposure. In July 2017, the VIS transmittance was between 68.54% and 76.64%, and the NIR transmittance was between 66.60% and 74.10%. By April 2018, the mean transmittance decreased to 46.77%, 48.63%, 49.65%, and 29.74% for 70°, 45°, 32°, and 0°, respectively. Rainfall has resulted in only temporary and uneven recovery. The results show the combined effect of dust composition, morphology, surface inclination and natural redistribution on PV-glass optical attenuation.