Microstructural analysis of the cementation process during soiling on glass surfaces in arid and semi-arid climates

To investigate the soiling behavior of solar energy systems like photovoltaics or concentrated solar power, glass samples were exposed to outdoor conditions in Doha, Qatar for one month. Soil formation on the glass was characterized at microstructural level using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Further, elemental analysis of the crust was done with energy-dispersive X-ray spectroscopy (EDX). Small fibrous structures were found on the glass surface and dust particles, providing evidence of a cementation process leading to a strong adhesion of airborne dust particles. In contrast to the common perception, that cementation occurs via the precipitation of salt (sodium chloride) these needle structures were found to be mainly composed of oxides of Si, Mg and Al. This indicates that cementation processes in desert regions are enhanced by the growth of fibrous clay minerals. [GRAPHICS] Cross section of cemented dust particle, connected via small needles to the glass surface. (C) 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim