Nondestructive techniques to determine degradation modes: Experimentation with 18 years old photovoltaic modules

Photovoltaic (PV) module degradation in the field is a known issue; however, understanding the modes and mechanisms in which modules degrade is still a major undertaking for researchers. To understand the degradation modes and mechanisms, both nondestructive and destructive characterization techniques need to be employed. This paper presents the results and conclusions obtained based on a few major nondestructive techniques. In this paper nine, 18 years old modules exposed in a hot-dry climate were acquired and investigated in the laboratory to identify the degradation modes and to determine the degradation rate. The nondestructive techniques utilized in this work are: current-voltage measurements (I-V), visual inspection (VI), diode failure (DF), infrared (IR) imaging, electroluminescence (EL) imaging, dark current-voltage (D-I-V) nondestructive cell-module quantum efficiency (C-M-QE), and module level reflectance spectroscopy (M-RS).