Ultrasonic guided waves interaction with cracks in the front glass of thin-film solar photovoltaic module

As the solar photovoltaics power system sees rapid growth in installed capacity and plays a significant role in the future global energy mix, its reliability becomes a crucial factor in maintaining the stability of the electricity supply. Manufacturing imperfections and harsh operating environments may compromise the module's structural integrity, leading to performance deterioration and power loss. Therefore, nondestructive inspection becomes an indispensable part of the quality assurance or maintenance program to detect defects at any stage of the module's lifecycle. Ultrasound is an essential method for material inspection, and ultrasonic-guided waves have been long explored as a flaw detection technique on plate-like structures, taking advantage of its long-range detection that yields an efficient inspection process superior to the conventional pulse-echo technique. Inspired by the same idea, this work assesses the prospect of harnessing ultrasonic guided waves, particularly Lamb waves, to detect cracks, as they exist in an actual module. However, unlike the commonly investigated plates, solar photovoltaic modules contain stacks of a-few-microns-thick layers of different materials that add complexities to the structure. The investigated specimen is a thin film photovoltaic module with cracks caused during transportation and handling. It, therefore, represents a real-life research case that may occur in situ. Numerical and experimental methods are performed to reveal various Lamb modes that propagate in the structure, where the results of both methods are mutually confirmed. Unlike other works, this investigation is not confined to the utilization of the non-dispersive mode but attempts to find the defect-sensitive mode that can be used to detect cracks. An analysis of the experimental results reveals the mode most sensitive to cracks, while numerical simulations explain the corresponding phenomena.