Technological watch

The photovoltaic (PV) power plants’ power generation is affected obviously by the cleanliness of the photovoltaic modules. The dust is the primary source causing the pollution. Natural dust deposition is affected by human activities and meteorological factors such as temperature, humidity, wind speed and PM10 concentration in the region where PV modules are installed. The research efforts so far have been focused on predicting PV power outputs, however, in the real operations the PV outputs can significantly deviate from the prediction due to the dust pollution which, unfortunately, has not been fully investigated. This paper, to the authors’ best knowledge, is the first research to analyze the dust composition and evaluate its impacts on the PV power outputs with the real field test data in East China Collected through a series of experiments completed in the lab of the Institute of Distributed Generation and Microgrid, Zhejiang University of Technology, in East China. A PV output forecasting model was set up first based on the irradiance and the component’s temperature. Then a complete meteorological and electrical data online monitoring system was developed for data acquisition. The morphology of the dust particles on the investigated photovoltaic modules was observed by a scanning electron microscope, and the composition of the dust particles was measured by X-ray fluorescence. The research found that the dust accumulated on the surface of photovoltaic modules tend to form clusters under the influence of rainfall which is one major cause on fast dropping PV outputs. The analysis shows the dust deposit mainly comprises of SiO2 and CaCO3. Further analysis indicates in East China, the average dust density on PV modules is 0.644 g/m2 in a week and consequently the dust reduces the PV output power by 7.4% one week. The research is of significance not only in terms of giving the real-data based analysis on dust properties deposited on PV panels, but also on revealing the relationship between power output attenuation and dust deposition, which helps improve the PV power output prediction accuracy and develop efficient cleaning strategies for photovoltaic modules.