There are debris on the photovoltaic module cells

To reduce the degradation, it is imperative to know the degradation and failure phenomena. This review article has been prepared to present an overview of the state-of-the-art knowledge on the reliability of PV modules.

Nonetheless, all twenty PV modules experienced nearly the same degradation rate, at 1.04% per year. A reduction in light transmittance is the primary failure that occurs in PV glass and is potentially caused by glass breaking or shattering or by harsh weather conditions like ultraviolet exposure and dust accumulation [56, 57].

The degradation of photovoltaic (PV) systems is one of the key factors to address in order to reduce the cost of the electricity produced by increasing the operational lifetime of PV systems. To reduce the degradation, it is imperative to know the degradation and failure phenomena.

For instance, critical degradation in some PV modules in an array system leads to mismatch, increasing the PV module's temperature and subsequently leading to fire [40, 41]. Critical degradation in PV modules was also highlighted as initiating fire in a research project based in Germany .

The hotspot failure mechanism is considered the most severe failure and leads to catastrophic consequences. It deteriorates all PV module components if undetected, and a PV module affected by an elevated level of hotspots cannot reverse the degradation and often requires replacement.

The main degradation and failure modes of PV encapsulants include discolouration and delamination, such as in Fig. 5. Additionally, encapsulants are often partly responsible for degradation of other module components by facilitating or mediating degradation modes such as corrosion or potential induced degradation (PID) [25, 61, 104, 114, 115].