Assessment of soiling impacts and cleaning frequencies of a rooftop BAPV system in composite climates of India

As one of the pioneers in solar photovoltaic (SPV) installations, India has witnessed several challenges related to performance; dust accumulation is one among them which needs attention. On the other side, most installers and SPV system owners do not have informed knowledge of dust accumulation rates (DAR) and optimum cleaning frequencies (OCF). It is also a well-known fact that DAR varies based on the SPV system (e.g., ground-mount, roof-mount, building applied/attached, building integrated and many other types). Hence, this paper analyses the effect of soiling specific to rooftop building-applied photovoltaics (BAPV) systems, and the main objective is to estimate the OCF driven by DAR. A rooftop BAPV system installed in India's composite climate zone is chosen as a case study, and its daily performance is monitored. Also, the on-site DAR is measured with micro slides help each day. It is observed that the system has different DAR for different seasons, clearly showing the relationship between energy outputs and DAR. The annual average daily deposition rate of dust was measured as 0.122 gm/m²/day. The maximum soiling loss of 0.39%/day was recorded in spring, followed by 0.34%/day in winter. The minimum soiling loss of 0.24%/day was measured in monsoon owing to heavy rainfall. The rooftop BAPV optimum cleaning frequency has been determined based on the energy lost due to soiling and cleaning cost. Overall, this study reveals that the rooftop BAPV system needs cleaning twice a year, first in spring and second in winter.