According to data from the International Energy Agency, China added 34 GW of photovoltaic (PV) capacity in 2016, more than double that of the United States, accounting for half of the world's new installed capacity. If clean energy, represented by solar power, can replace the coal-fired power generation structure, it will greatly improve China's environmental situation. Huge investments in clean energy are one of the key initiatives of governments at all levels in China. Installing PV panels improves air quality—this is a cause-and-effect relationship we've always understood. But what about the reverse? Will the still-improving air quality negatively impact PV power generation? A recent study from Duke University confirms this question. Based on global climate model data from NASA's GISS, the study found that particulate matter in air pollution can significantly reduce PV power generation efficiency, by as much as 17%. Short-wave solar radiation is absorbed and scattered by dust and particulate matter; this phenomenon, known as solar dimming, reduces the intensity of radiation received by PV modules, resulting in power loss. According to the study, based on China's current PV power generation capacity, the power loss caused by smog is estimated at 11 GW, nearly one-third of China's new PV installed capacity. It is worth noting that the impact of human-caused particulate matter on photovoltaic power generation exceeds that of natural dust. Researchers sampled and analyzed the deposits on the surface of photovoltaic modules, finding that only 8% consisted of non-dust particles, i.e., particles generated by human activities. While this 8% may seem insignificant, it contains components such as organic carbon and carbon black. Carbon atoms have a stronger ability to absorb sunlight; moreover, due to their smaller size, sunlight is more easily scattered. Therefore, the loss in power generation efficiency due to human activities even exceeds that caused by the 92% dust. Yingli Group, one of the world's largest photovoltaic module manufacturers, has a deep understanding of this. Ni Jianxiong, Deputy General Manager of the Technology Center, explained that Yingli, through comparing and monitoring the outdoor power generation of photovoltaic modules equipped with automated cleaning robots with conventionally installed modules, found that in "famous" smog cities such as Xingtai and Baoding in Hebei Province, power generation can decrease by more than 80% during smoggy periods, and at the height of the smog, power generation is almost non-existent. Drew Shindell, a professor in the Department of Civil and Environmental Engineering at Duke University and a member of the research team, stated that these particulate matter generated by human activities cause China to face more severe losses in photovoltaic power generation than other countries. According to research, in central and eastern China, monthly cleaning of photovoltaic (PV) modules reduces their power generation efficiency by 17% to 25% due to particulate matter; a two-month cleaning interval further reduces efficiency by 25% to 35%. There is no unified standard for cleaning large-scale ground-mounted power plants in China; cleaning is generally determined by monitoring power generation. Geng Wenqiang, general manager of Sanas New Energy Technology Co., Ltd., headquartered in Qingdao, Shandong Province, specializing in the operation and maintenance of PV power plants, told China Dialogue that from a module maintenance perspective, large-scale ground-mounted power plants in northern China generally require four standard cleanings per year. In cases of severe pollution, the frequency of cleaning can be increased appropriately based on site conditions. The study indicates that cleaning increases the daily power generation of PV modules by 50%, a significant effect. Ni Jianxiong stated that keeping PV panels clean is undoubtedly crucial, improving power generation efficiency while effectively maintaining the modules, as long-term accumulation of particulate matter can cause excessive heat generation, leading to hot spots and threatening module lifespan. However, for companies, a more practical issue is the water required for cleaning. In Northwest China, where solar resources are abundant, water is often far more precious than electricity, making it clearly not worthwhile to increase power generation by increasing water consumption. Geng Wenqiang stated that because cleaning requires a significant investment of water resources, it represents a considerable cost. Therefore, companies need to comprehensively compare the cost of cleaning with the actual revenue generated to determine the frequency of cleaning. More professional photovoltaic operation and maintenance companies will also utilize the results of photovoltaic big data analysis and mining to determine the optimal cost-effectiveness of cleaning. Distributed power stations are actually the main victims of smog. Unlike large ground-mounted power stations that undergo regular cleaning and maintenance, small rooftop projects generally rely solely on natural weather conditions such as rain and snow for cleaning after construction, lacking subsequent operation and maintenance, which further exacerbates the impact of smog pollution. Zhang Weihong, Public Relations Director of Aikon Technology, told China Dialogue, "Few residential users would think of climbing onto their rooftops to clean their photovoltaic panels." Poor air quality reduces clean energy power generation; poor development of clean energy, in turn, hinders environmental improvement. Zhang Weihong frankly stated that for investors in the photovoltaic sector, frequent smog adds a systemic risk that is difficult to control. The main source of particulate matter affecting photovoltaic (PV) power generation efficiency in China is human activity, giving the government significant potential to reduce emissions and pollution. The government has various options, including fuel selection, emissions pricing, and renewable energy incentives. The benefits are obvious: in addition to increased PV power generation, considering the health risks of inhalable particulate matter, it will undoubtedly improve public health significantly. Furthermore, this also suggests that the compromise of developing PV power generation while continuing to build coal-fired power plants may not be a good idea, as the latter will significantly impact the operation of the former. Source: Chinadialogue (October 12, 2017) (Compiled by PIDC)
