The correlation of EL image and shunt resistance of power degradation module installation on the field in Thailand over 10 years

The 83 PV modules that have been installed in Thailand for more than ten years are divided into two groups based on the power degradation: Group-I, which includes 17 modules with more than 70% of their nameplate (a normalized power range of 76%–89%), and Group-II, which includes 66 modules with less than 70% of nameplate (range of 19%–69%), as shown in Figure 1(a). The class AAA solar simulator in the standard testing laboratory measures electrical characteristics such maximum power (Pmax), shot circuit current (Isc), open circuit voltage (Voc), series resistance (Rs), and shunt resistance (Rsh). In the range of 257 Ω to 732 Ω, Group-I is given a high value of Rsh, but Group-II is given a low value of Rsh in the range of 5 Ω to 86 Ω. Every module uses an indoor EL camera to capture EL images. Figure 2(a) displays an example of an EL image from the Group-I module. A few examples of local shunt faults are shown. All cells, with the exception of a small portion of the cell area, can glow recombination; however, in Group-II in Figure 2(b), the majority of the cell area appears darker, indicating non-luminescent recombination. The purpose of this study is to correlate of Rsh, Pmax, and EL image. Figure 2's EL image, which has a darker call region, demonstrates low power and low Rsh. All modules have various faults including fractures, finger defects, and Rs in addition to the local shunt defect. The local shunt fault is the primary flaw in every module. In particular, a thorough analysis of the EL picture should be conducted in accordance with IEC 60904-13 and IEC 6320-2 standards.