Microstructural analysis of the PV module cementation process at the Solar Platform of the Atacama Desert

Abstract

The understanding of soiling processes on photovoltaic modules is a necessary step for the development of cost-effective mitigation methods for the solar industry. This paper analyzes the soiling process for photovoltaic modules installed at the Atacama Desert. For this purpose, the dust deposited on photovoltaic modules and glasses (for one year) was characterized and the location's atmospheric parameters were monitored continuously. The dust samples were separated according to difference in solubility, obtaining three samples: soluble (recrystallized), insoluble (filtered), and original. Through x-ray diffraction measurements it was detected that the soluble part corresponds to gypsum and the other dust components are insoluble or low-solubility salts such as albite, anhydrite, calcite, quartz, and orthoclase. Scanning electron microscopy and energy dispersive x-ray spectroscopy of the dust on photovoltaic glasses show the presence of gypsum with a monoclinic prismatic structure covered with smaller dust particles. These prismatic crystals are also observed after recrystallization of the soluble sample suggesting that gypsum, as a soluble hygroscopic material, has a key role in the cementation process. Atmospheric parameters of each season were characterized through wind velocity, temperature, and relative humidity. All these parameters show large daily oscillation, which trigger a cementation process in which gypsum crystallization, after being completely or partially solubilized, causes the encapsulation of insoluble material.