Effect of a Single Degraded PV Module on the Performance of a String: A Case Study of 100 kWp On-grid PV Plant in 13thYear of Its Operation

This research article presents the case study of a 100 kWp on-grid PV plant in 13
^th
year of its operation. The PV modules in the string have been affected by various types of visible degradations, like burn marks on their surface, heavy snail tracks and cracks, discoloration on metallization, and shattered front glass, causing underperformance from their nameplate capacity. We studied a string (E) having 20 PV modules (E1 to E20) in which one of the modules (E14) was severely damaged due to a lightning strike. The maximum output power and efficiency of E14 PV module was found to be 16.4 W and 1.1%, respectively. Output power and efficiency values were calculated by including and excluding the E14 module to study its effect on the string. The measurements showed that the E11-E20 series connected PV modules had 5% lower power compared to the E1-E10 series connected modules. This is attributed to the presence of a heavily degraded E14 module in the E11-E20 measurements. The performance of a PV string or plant can be severely affected if the heavily degraded modules are not replaced. The same plant was studied two years ago when it was in its 11
^th
year of operation. Here, we observe that the degradations increased significantly in two years, from the 11
^th
to the 13
^th
year of operation.