Effect of calcium sulphate dihydrate on dust adhesion on photovoltaic panel surfaces under condensation

The components of dust accumulation on PV panel surfaces under three different scenarios were analyzed, the adhesion strength between dust and PV panels under condensation conditions was measured, the microstructure of the adhesion interfaces, using metallographic microscopy and environmental scanning electron microscopy, was observed, the main factors of dust-PV panel adhesion were investigated, and the adhesion mechanism was explored. The results showed that calcium sulfate dihydrate (CSD) was the main soluble component in most PV panel dusts. It significantly increased the adhesion strength of the dust to the PV panels under the effect of condensation. The kinetic friction coefficients of the dust adhered samples after 150 condensation cycles increased by approximately 100% and 170% when the CSD content increased from 0 to 2.8% and 5.53%, respectively. This was attributed to the recrystallization of the CSD into blocky and rod-shaped particles. The blocky CSD particles wrapped and cemented other particles while promoting adhesion through a larger contact area with the PV panel surface and formation of hydrogen bonds. A rod-shaped CSD was interlaced to enhance agglomeration and increase friction at the adhesion interface to improve the adhesion. Moreover, CSD caused the decrease of power generation of PV panels. For 150 condensation cycles and the same cleaning conditions, dust sample with 2.88% CSD resulted in a power generation reduction of about 2.37% compared to that of dust sample without CSD. It was recommended that a hydrophobic or super hydrophobic surface was used on PV panels to reduce the residence time and contact area of water on the surface to inhibit the recrystallizing of CSD on PV panels.