Early degradation of silicon PV modules and guaranty conditions

► The fast growth of the number of PV modules installed needs a study of common defects that appear. ► Some defects of PV modules can appear in the first months of operation. ► A PV module that has passed the test of IEC61215 norm could present hidden-defects. ► To find defects the techniques used are infrared images, electroluminescence or power measurement. ► Common defects found: yellowing, delamination, bubbles, cracks, ARC defects and burnt cells. The fast growth of PV installed capacity in Spain has led to an increase in the demand for analysis of installed PV modules. One of the topics that manufacturers, promoters, and owners of the plants are more interested in is the possible degradation of PV modules. This paper presents some findings of PV plant evaluations carried out during last years. This evaluation usually consists of visual inspections, I– V curve field measurements (the whole plant or selected areas), thermal evaluations by IR imaging and, in some cases, measurements of the I– V characteristics and thermal behaviours of selected modules in the plant, chosen by the laboratory. Electroluminescence technique is also used as a method for detecting defects in PV modules. It must be noted that new defects that arise when the module is in operation may appear in modules initially defect-free (called hidden manufacturing defects). Some of these hidden defects that only appear in normal operation are rarely detected in reliability tests (IEC61215 or IEC61646) due to the different operational conditions of the module in the standard tests and in the field (serial-parallel connection of many PV modules, power inverter influence, overvoltage on wires, etc.).