Characterization of dust particles in South India and investigation on soiling image analysis for photovoltaic...

The present work aims at the characterization of the dust particles in South India through an image analysis of glass samples inclined at a tilt of 0° and 13° for four different exposure periods (approximately 30 to 40 days/exposure period). It aims as well at the study of the different factors influencing the accuracy of the image analysis of dust particles. The analysis of the shape factor reveals that the dust particles on tilted surface (13°) have regular shapes, and irregular shapes are more observed in horizontal surfaces. The size analysis of the dust particles with magnification of 20 × has revealed that the size distribution is in the range of 0-4 µm but more concentrated in the range of 0-1 µm. However, with 10 × magnification, larger particles are more detected. Furthermore, average results from three sample images seem to be more precise and representative than results from two images. The fractional coverage area of the dust particles on the sample has been calculated and compared with the transmittance losses. These two variables are found to be proportional with an R² of 53%. Nevertheless, the comparison showed again that three images give better results with an R² of 75% against 11% for two images. The results obtained in this study are very useful for the development of high precision soiling sensors that are based on image analysis and outdoor soiling microscopes, which are the main components for an efficient and economic cleaning of solar PV modules.