Comparative Analysis of Layer Thickness Measurement Methods for Photovoltaic Modules: a Comprehensive Study

The growing volume of end-of-life photovoltaic modules presents a significant challenge, requiring the development of efficient and sustainable recycling processes. The PVReValue project focuses on creating a comprehensive methodology for the systematic separation and recycling of end-of-life PV modules. A key aspect of this approach is the accurate determination of layer thicknesses, which is essential for the effective characterization and separation of materials. This study compares various industrially applicable techniques for measuring layer thicknesses in PV modules, evaluating both destructive and non-destructive methods based on factors like time, cost, accuracy, and suitability. Techniques such as optical coherence tomography, coaxial multicolor confocal microscopy, and ultrasonic measurements are compared with traditional methods like calotte grinding and optical 3D microscopy. The results show that while optical coherence tomography and confocal microscopy offer high precision and non-destructive capabilities, they are more complex and expensive. In contrast, calotte grinding, though more affordable, provides localized data and poses challenges for polymer layers. Ultrasonic measurements proved to be unsuitable for this approach. The study concludes by comparing these methods into an industrial recycling workflow, emphasizing their potential to enhance the efficiency and sustainability of PV module recycling.