Influence of dust accumulation and light intensity on output power of photovoltaic modules

Abstract: Due to the exposed soil in the farmland and the absence of the building occlusion, the dust accumulation on the surface area is especially serious when the photovoltaic equipment is used for field operations. Dust blocks the photovoltaic panels and reduces the light transmittance, thus reducing the amount of electricity generated by the photovoltaic system. For photovoltaic agricultural equipment, dust on photovoltaic panels will severely reduce the reliability of power supply. To solve this problem, the indoor test method of artificial dust was used in this paper, and the maximum power tracking device of solar energy was used to test the influence of dust particle size, dust density and light intensity on the photovoltaic power generation. The dust particle size was divided into 4 groups, the dust density range was 0～50 g/m2, and the light intensity was set to 3 levels. The effect of dust particle size, dust density and light intensity on the photovoltaic power generation was tested. A predictive model of output power reduction rate under significant influencing factors was established, and the model was verified under outdoor natural lighting conditions. The results showed that: 1) The dust accumulation had significant inhibitory effect on the power output of the photovoltaic modules, when the dust particle size was constant, the output power reduction rate of the photovoltaic modules increased with the increase of the dust density, but the growth rate gradually became slower. The shielding area of the dust on the photovoltaic modules was inversely proportional to the particle size of the dust. The larger the particle size, the smaller the shielding area of the photovoltaic modules, and the smaller the output power reduction rate. When the dust density was 10 g/m2, the output power reduction rates of the 0-38, 38-75, 75-110 and 110-150 μm particle size groups were 15.96%, 12.51%, 8.16%, and 5.39%, respectively. In addition, when the amount of dust was same, the output power reduction rate of the photovoltaic modules increased with the increase of the illumination intensity, but the growth was not obvious. 2) The variance analysis of the dust particle size and dust density, light intensity and dust density showed that the dust particle size, dust density and the interaction between the 2 had significant impact on the output power reduction rate of photovoltaic modules. However, the light intensity had less influence on the output power reduction rate. 3) Through theoretical analysis, the concept and calculation formula of equivalent particle size based on the same occlusion effect were proposed. On this basis, the polynomial fitting in MATLAB was used to establish the output power reduction rate, dust density and equivalent particle size prediction model of photovoltaic modules (R2=0.986). The solar water and fertilizer integrated device was used for outdoor verification test, and the environmental conditions were similar and no wind was used for 4 days. The absolute value of the error between the calculated and measured values of the model was less than 1.5%, indicating that the model can be directly applied to outdoor nature and has good practical application value. When the photovoltaic agricultural equipment is operated in different regions, the local output power reduction rate and the dust density change model can be determined according to the model, which provides a design basis for the optimal configuration of the photovoltaic power supply system. The study is mainly carried out from the perspective of dust particle size and dust deposition density. The next step is to further develop the impact of dust particle size distribution, types and chemical composition on the output power of photovoltaic modules, and further improve the prediction model of the impact of dust deposition on photovoltaic power generation.