**2. Photovoltaic module defects and faults**

Prior to going deeper into this topic, the term *"*failure*"* in the PV context must be properly defined. The bibliography defines a failure in a photovoltaic module as *an effect that degrades the module power output which is not reversed by normal operation or which, on the other hand, creates a safety issue.* Evidently, both of these effects can occur at the same time.

As such, degradation of wiring or modules, PV cell defects and malfunctions, dust, and mismatches can be considered to be failures of PV modules [5] and purely esthetic problems are not.

The following subsections describe briefly all potential PV module failures.
