Dust Event Impact on Photovoltaic Systems: Role of humidity in soiling and self-cleaning

In the last decade, millions of dollars have been being invested in solar energy plants in regions prone to dust storms. Dust has a direct effect on the efficiency of solar energy plants by soiling and scattering of solar radiation. Hence it becomes necessary to analyse the potential of dust effect on Photovoltaic (PV) system performance as more solar energy is fed into national electricity grids. Dust impact on PV systems depends on how far the site is from dust sources in addition to wind speed and humidity. These factors in turn determine the soiling and scattering effect. Case studies are presented here to clarify the potential of dust impact from the main active dust sources in Western Asia. The results revealed a wide range of variability where the power output changed from-37% compared with the day before the impact of a 48 hour old dust cloud in one site, to +14.4% in another site. The case studies showed the importance of wind in cleaning the PV during dust events. It also shows the role of humidity in impeding self-cleaning. It turns out that a PV site influenced by dry desert air is more suitable for self-cleaning PV systems, compared with a site influenced by humid air. This outcome might help PV system investors to select a PV plant's location to be as far from the sea or extensive water sources as possible in regions prone to dust storms such as Western Asia.