To enhance the understanding of the high adhesion of dust particles on photovoltaic modules and telescope mirrors, glass, and mirror samples were subjected to soiling tests in laboratory and field experiments. The specific objective of this study was to investigate glass contamination on a microstructural level using light and scanning electron microscopy (SEM). In addition, the dusts were analyzed for their main mineral components using X-ray diffraction. The study exposed samples to natural dust from Qatar, Chile, Morocco, and the standard Middle East Test Dust. The tests showed that the adhesive strength increases abruptly due to cementation when the surface temperature falls below a critical temperature difference to the dew point (ΔT _dp/critical / K). This work found values of ΔT _dp/critical from 1.9 K to >7 K. The analysis shows that cementation is initiated by precipitation of the main soluble component available and promoted by surface humidity. The contribution of the water solubility of the dust components to the cementation process is more significant than the hygroscopic properties of the dust. SEM images show different cementation structures on the sample surfaces. These structures range from needle-shaped deposits <1 μm to rod- and plate-shaped structures from 3 μm to 30 μm to cubes with edge lengths from 2 μm to 50 μm. All appearances of cementation lead to significantly increased particle adhesion so that wind speeds less than 10 m/s do not remove particles from the surface. This investigation compared, at a microstructural level, laboratory test samples with outdoor samples from Morocco, Qatar, and Chile. The findings showed that the laboratory tests are very well suited to reproduce the cementation effects from the outdoor tests. This article quantified cementation conditions for the first time in dependent on operating environments. These results will support the development of suitable prevention strategies against soiling on functional surfaces.

中文翻译：

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光伏组件和望远镜镜上污垢胶结的阈值条件分析

为了加深对灰尘颗粒在光伏模块和望远镜镜子上的高粘附性的了解，我们在实验室和现场实验中对玻璃和镜子样品进行了污染测试。本研究的具体目标是使用光学和扫描电子显微镜 (SEM) 在微观结构水平上研究玻璃污染。此外，还使用 ​​X 射线衍射分析了灰尘的主要矿物成分。该研究将样本暴露于来自卡塔尔、智利、摩洛哥的天然灰尘和标准中东测试灰尘中。测试表明，当表面温度低于与露点的临界温差（ΔT _dp/临界 /K）时，由于胶结，粘合强度突然增加。_{这项工作发现 ΔT dp/临界}值 从 1.9 K 到 >7 K。分析表明，胶结是由主要可溶成分的沉淀引发的，并由表面湿度促进。粉尘成分的水溶性对胶结过程的贡献比粉尘的吸湿性更重要。SEM 图像显示样品表面不同的胶结结构。这些结构的范围从 <1 μm 的针状沉积物到 3 μm 至 30 μm 的棒状和板状结构，再到边长从 2 μm 至 50 μm 的立方体。所有胶结的出现都会导致颗粒粘附力显着增加，因此小于 10 m/s 的风速不会从表面去除颗粒。这项调查在微观结构层面上将实验室测试样品与来自摩洛哥、卡塔尔和智利的室外样品进行了比较。研究结果表明，实验室测试非常适合重现室外测试的胶结效果。本文首次根据操作环境量化了固结条件。这些结果将支持制定适当的预防功能表面污染的策略。