Experimental study of PV strings affected by cracks

Tian Cheng,Dylan Dah‐Chuan Lu,Vassilios G Agelidis,Mohammad Al‐Soeidat

doi:10.1049/joe.2018.9320

Abstract

Crack is one critical factor that degrades the performance of photovoltaic (PV) panels. To gain a better understanding of the impacts of cracks appeared on PVs and also to mitigate it, its failure mechanism, detrimental effects, criticality, and potential risks on independent PV panels are firstly reviewed in this study. An experimental study which investigates the degree of series connected and parallel connected PV strings which are affected by cracked cells are presented. A comparison of impacts of the partially shaded PV panel string and cracked cells happened to the PV panel string is given to evaluate their criticality levels. The experimental results show that the series connected PV panel string is strongly affected once the cell is seriously cracked, as the current generation capability is clamped. Partial shading, however, shows better performance. In addition, though the overall power the parallel connected PV string is reduced, it is less affected by the cracked cells compared to the series connected one. Lastly, a bypass diode is added to a series connected PV panel string with cracked cells, and the experimental results show that it can be an effective way to minimise the negative impacts of cracks.

Highlights

With the increasing penetration of the photovoltaic (PV) in the energy market, its performance and reliability become critical issues
A series of experiment works are implemented to review the impacts of different crack types on independent PV strings
The outcomes verify that loss of electrical connection between PV cell and busbar would cause a great reduction of the entire PV string power generation capability

Summary

Introduction

With the increasing penetration of the photovoltaic (PV) in the energy market, its performance and reliability become critical issues. The panel with an efficiency of 80.73% indicates it is approaching its end-of-lifetime, which is much shorter than the expected 25-year and do not meet the manufacturer's warranty Based on this concern, micro-cracks failure mechanisms are reviewed. The cracks most likely are generated during the manufacturing, transportation and installation stages, and the mechanical stress such as snow loads could increase its possibility to develop to a larger size [4]. It is mentioned in [5] that, the direct impact of the micro-cracks on the solar panel is limited and no loss occurs when the separation area is under 8%. Comparisons among a panel with two cells are shaded, a panel with two cells are cracked and a normal panel is given

Review of impacts of different crack types on PV panel output performances

Conclusion

Findings

Performance evaluation of PV panel strings with different connection methods