Generalized quantitative electroluminescence method for the performance evaluation of defective and unevenly degraded crystalline silicon photovoltaic module

Abstract Photovoltaic (PV) module experiences multiple cell defects and degradation in a field operation, which significantly reduces module output. Hence, quantitative assessment of a PV module is essential to ensure module operation within a desirable limit. This article proposes the generalized quantitative electroluminescence ( g ‐QUEL) method to evaluate the performance of a defective and unevenly degraded PV module from the EL images. Four module classes are considered from the view of field applications, such as new, PID‐s affected, field aged shunted, and nonshunted modules. The effects of defects and degradation on fundamental cell electroluminescence (EL) characteristics and constants are analyzed for each class. Based on this analysis, the g ‐QUEL method is developed, which utilizes module multiple EL images, datasheet information, and terminal voltage measurements for quantification. First, a test module is qualitatively assessed to identify the present defects and classified into one of four classes. In the second part, the g ‐QUEL algorithm is applied to a test module in a customized manner to extract five or seven parameters of a PV cell. Subsequently, a single or two diode model simulation is carried out at a module, submodule, or cell level to estimate module output by generating I‐V curve. Experimental verification of the proposed method was conducted on five test modules of each class. Results demonstrate the accuracy and effectiveness of the g ‐QUEL method as it evaluates the output power of new to field‐aged modules with a relative error ≤±3%.