Application of Electroluminescence Imaging to Distinguish Ohmic and Non Ohmic Shunting in Inaccessible Cells Within a PV Module

Photovoltaic (PV) technology is susceptible to various defects and degradations. One such defect is shunts, which result in internal leakage paths, reducing cell performance and efficiency. Shunts can be categorised as either ohmic or non-ohmic based on the nature of sinking current with voltage. Understanding the nature of shunting is crucial for comprehending the physical phenomena occurring at shunted sites. However, current methods such as dark lock-in thermography and current-voltage (I-V) characteristics have limitations in nondestructive characterisation of cells within an intact PV module, which require individual cell access. This article presents a novel application of electroluminescence (EL) imaging to distinguish between ohmic and non-ohmic shunting in cells within a module nondestructively. The method involves a two-step process using three EL images at different currents. Firstly, shunted and nonshunted cells are differentiated based on low current EL image. In the second step, ohmic and non-ohmic shunted cells are distinguished using Shunt-Index value based on current-EL intensity characteristics. Non-ohmic shunted cells show a linear behaviour on a log-log scaled current-EL intensity characteristics, while ohmic shunted cells exhibit a linear behaviour. Experimental validation demonstrates the successful identification of shunted cells and their nature, providing valuable insights for shunt-related PV cell analysis.