Working towards the development of a standardized artificial soiling method

Solar glass coatings for photovoltaic (PV) modules include antireflection and antisoiling coatings. There are increasing number of claims related to dust resistant, abrasion resistant (during cleaning) and self-cleaning solar glass coatings. Currently, there is no standardized way of verifying the validity of such claims. As a first step towards validating such claims, the industry needs to develop a standardized artificial soiling method with actual laminated module construction of glass / EVA / cell / EVA / backsheet. This paper presents an approach for working towards the development of a standardized artificial soiling method for laminated photovoltaic (PV) cells or mini-modules. In this study, poly-Si mini-modules and single-cell mono-Si coupons were soiled and characterized using I-V, reflectance and quantum efficiency (QE) to calculate the effect of soiling on performance. From the results, the technique was found to be repeatable and soil pattern was uniform for both mini-modules and single cell coupons. The study compares poly-Si mini-modules with single-cell mono-Si to identify the ideal coupon for artificial soiling. Poly-Si mini-modules proved to be a good measure of soil uniformity, as any non-uniformity would effect the smoothness of curve at near Isc during I-V measurements. Single-cell mono-Si was identified to be more suitable for reflectance and QE measurements. This study indicates that the reflectance measurements between 600-700 nm wavelengths can be used as a direct measure to determined soil density on the modules.