Multi-year field assessment of seasonal variability of photovoltaic soiling and environmental factors in a desert environment

In this study, we investigated multi-year seasonal trends of photovoltaic (PV) soiling in the desert environment conditions of Qatar. Field measurements of PV modules' power and environmental factors were recorded continuously from 2014 to 2019. The PV soiling loss varied significantly from month to month, showing repeated seasonal trends; the year-to-year variability was not significant. Soiling rates in cold, warm, and rainy seasons appeared to be quite different and influenced by environmental factors. Over the six years of study, 75% of days had a negative soiling rate (i.e., increase in soiling on the PV panels), while the remaining 25% of days had a positive value due to the resuspension of the dust from the panels occurring by the strong wind. Key influential factors in the seasonal soiling variability and their respective correlations were also presented. It was found that a minimum rainfall of 3 mm only was required to fully clean the PV modules. Dust storms mainly occurred in summer months, when soiling losses accumulated in these most soiled months, yet the impact of dust storms during the winter season was found to be more severe than during the summer. Overall, dust storms caused 8% attenuation of solar radiation reaching the PV panels and increased the annual average soiling rate by 23% comparatively to non-dust storm days. Our study shows seasonal soiling profiles in an Arabian desert environment, which may allow PV plant operators to optimize their cleaning schedules and thereby reducing plant operational and maintenance costs.