Solar Energy Materials and Solar Cells Detection of Corrosion on Silvered Glass Reflectors via Image Processing

Kurzfassung

In this article, a novel characterization technique based on image analysis is presented, intended to complement state-of-the-art reflectometer measurements. This technique is particularly valuable when the entire sample needs to be characterized rather than isolated microscopic areas, for example, to quantify advancing corrosion phenomena. The general concept of the technique is discussed among four groups of experts from different laboratories (OPAC, AGC, CEA and LNEG), which subsequently conduct two consecutive Round Robin experiments to validate the developed analysis technique. Regarding the comparability of various parameters, it is found that metrics such as the total corroded area and the maximum edge corrosion penetration on uncoated edges show good agreement, with coefficients of variation of 14.3% and 13.2%, respectively. Considering the four different custom-made setups and developed software, the participants are optimistic about incorporating this analysis into their future characterization toolbox, as it demonstrates promising comparability, simplicity and cost-effectiveness. The developed methodology is used for an analysis of outdoor exposed samples in the second part of this work. The relevant corrosion parameters are obtained from a 68- months field exposure campaign involving solar reflectors with two different coating types, subjected to environmental conditions at two representative outdoor sites. The results of the image analysis confirm the corrosivity classification of the respective sites and qualify the two coating types. Furthermore, the analysis highlights the importance of proper edge sealing for corrosion protection. It should be emphasized that these findings would not have been possible using state-of-the-art reflector qualification methods, such as reflectometry or microscopy