# CFD-DEM Simulation of Dust Deposition on Solar Panels for Desert Railways
###### Abstract  
With the greening of the railway energy supply chain, large-scale photovoltaic power stations will be the best choice to integrate with the railways. Understanding the deposition mechanisms and rules of dust grains on photovoltaic panels is of great guiding significance for the operation of photovoltaic (PV) power stations. In this paper, based on computational fluid dynamics (CFD) combined with the discrete element method (DEM), the dynamic dust deposition process on solar panels was simulated, and the flow field around solar panels and the movement of dust particles in the wind were calculated. The simulation results of clay particles (d = 10 mm) and fine sand particles (d = 100 mm) under different wind speeds showed that the clay particles could follow the air flow properly, and their deposition rate was only 4.6%, while the deposition rate of the fine sand particles was up to 32%, which was determined by the inflow wind speed and cohesion parameters. An image of the non-uniform distribution of particles on the panels was given in this paper for the first time. This will provide a basis for a more accurate assessment of the impact of dust accumulation on PV output in real-world environments. These results provide a critical reference for railway photovoltaic power supply development in desertification areas. photovoltaic power; dust deposition; CFD-DEM method; flow field; cohesion parameters +
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conditions, more and more researchers in related fields have carried out studies on the dust accumulation process and power generation efficiency degradation of photovoltaic modules as well as a lot of innovative works in dust removal [4; 5; 6]. In recent years, the research on the impact of dust deposition on the power generation efficiency of photovoltaic modules has mainly focused on in-field and indoor experiments. [PERSON] [7; 8; 9] gave the attenuation curve of solar intensity reduction versus the amount of dust deposition when a solar panel is covered by dust particles with a radius of 80 mm, and the results showed that the radiation intensity decreased to 30% of the original value when the dust amount was 250 g/m\({}^{2}\). [PERSON] et al. [10] pointed out that a solar panel near Saudi Arabia, Riyadh, had a 32% reduction in power generation due to 8 months of dust deposition. [PERSON] et al. [11] carried out indoor experiments with two kinds of artificial dust coverage, and the results showed that the power generation efficiency of dusty solar panels was reduced by 18% compared with clean panels. [PERSON] et al. [12] studied the relationship between dust cover and power generation by artificial sand cover, and they pointed out that power generation efficiency is closely related to the type and size of dust and that the dust deposition is directly proportional to the slope of a solar panel. [PERSON] et al. [13] studied the impact of pollutant types on the efficiency decline of solar panels and pointed out that it is urgent to establish a model that can reflect the impact of dust types on the efficiency of solar panels. [PERSON] et al. [14] studied dust deposition on solar panels in an in-field environment and pointed out that the power generation efficiency of solar panels decreased by 6.24% after one day, 11.8% after one week and 18.74% after one month. Generally speaking, the reduction in power generation efficiency is not proportional to the amount of sand dust coverage, which is consistent with the research results of [PERSON] et al. [15] who found that the area of the dust-free part of the surface of photovoltaic solar panels approximately presents an exponential change through laboratory experiments. The wind-flow field around a PV module has an important impact on the dust accumulation on the PV module [16]. Some scholars have studied the deposition process of particles based on fluid dynamics models. For example, [PERSON] et al.