Effect of soiling on photovoltaic modules

In the past, the phenomenon of dust deposition on the glass cover of photovoltaic modules has been studied mainly in the Middle East, but little is known about the phenomenon in Central Europe. This paper focuses on the magnitude of the problem in Belgium (Koppen climate classification: Cfb). A variety of measurements were performed to determine the effect of dust settlement on the power output of photovoltaic modules. The physical properties of the collected dust were examined using a scanning electron microscope (SEM). A potential solution for the phenomenon, namely the usage of special coatings on the cover glass, was investigated. The results show that the problem of dust settlement on photovoltaic modules in Belgium is not as severe as in the Middle East. Nonetheless the problem exists and results in a constant power loss between 3% and 4% for the optimal tilt angle in Belgium which is 35° and with periods of regular rainfall. Please note that these results do not reflect a one year energy loss, further experiments are needed. Rain seems to have little cleaning effect on smaller dust particles (2–10 μm), but on bigger particles (pollen, approx. 60 μm) the cleaning effect is clearly visible. The use of special coatings on the glass have a potential reduction in power loss caused by dust settlement. However, at this moment, the extra cost associated with these coatings is not justified for photovoltaic modules in Belgium. Cleaning panels should only be done when soft tap water or demineralized water is available.