10 Module Deployment and Energy Rating
269
10.4.4 Unrecoverable Failure Modes
10.4.4.1 Microcracks
Among the most problematic unrecoverable failure modes are microcracks, and the
reason is that they cannot be detected by visual inspection: instead, only advanced
imaging techniques (e.g. electroluminescence imaging, Fig. 10.11) can indicate their
presence.
Modules with microcracks will typically show no initial degradation, but
likely deteriorate in the medium and long term. Now, if microcrack degradation
occurs typically in midlife, the generation of microcracks takes place most often
during module production, transportation and installation.
During the lifetime of a PV plant, natural hazards may also generate microcracks.
Detection: by electroluminescence imaging.
Prevention: quality control from production to installation; glass-glass modules are
naturally less prone to microcracks; the effect of microcracks is also minimized with
multi-wire modules.
Fig. 10.11 Microcracks are an example of unrecoverable failure modes: they cannot be detected
by the naked eye (left), but only by advanced imaging techniques, such as electroluminescence
imaging (right, showing an electroluminescence image of the module pictured on the left)