Criticality of cracks in PV modules

Abstract

The evaluation of cracks in PV modules is a difficult task: cracks do not necessarily lead to a strong degradation in the power output of the module directly after the crack initiation. However, PV modules with cracks suffer from a lower stability of the power output under artificial ageing. This is partly because cracked cell areas can become electrically disconnected from the active cell area. Here we present the analysis of the criticality of cracks formed in a uniform load test. For this we evaluate cracks which may isolate cell areas. We observe 667 cracked cells in 27 PV modules with 60 cells each. Cracks parallel to the busbars constitute 50 % of the crack orientations in our experiments. This crack orientation has a high probability of having a potentially separated cell area Acrack of 16 to 24 % and can thus be considered to be of high criticality. We proceed by subjecting 12 of these PV modules to 200 cycles of a humidity-freeze test. A significant part of 29 % of the cracked cells shows an increased resistance across the cracks and 7% show isolated cell areas.