Experimental investigation of soiling losses on photovoltaic in high-density urban environments

Soiling, the deposition of contaminants onto the front glass surface, is a significant challenge for photovoltaic (PV) performance. However, studies on this issue are minimal in urban scenarios despite the surging popularity of PVs. This research systematically measures the soiling losses in subtropical high-density urban environments. A hybrid method combining field exposure and in-lab characterization is proposed. Major soiling modes, temporal patterns of optical loss, and PV output loss are explored within continuous 108-day exposure. Due to the windy climate and low particle concentration, dust deposition and accumulation are insignificant. Meanwhile, abundant rainfall offers a good natural cleaning effect that can remove most dry deposits, including dull leaves, dust, etc. Rainwater residual after evaporation is a major soiling mode, but the optical loss is within 2%. Despite the favorable climate, bio-soiling, especially the bird dropping represents the most harmful soiling mode. The resulting contamination is stubborn, and even hefty rain cannot completely recover the soiling loss. A tiny residual can cause an optical and PV output loss of 2.5% and 15.5%, respectively. Finally, practical suggestions are provided to mitigate local soiling loss. These findings are essential for urban PV project planning and operation.