Nondestructive Quantification of Water Ingress in PV Modules via Spectroscopic and Chemical Analysis for Enhanced Quality Assurance and On-Site Inspection

This study presents a novel, nondestructive in situ method to quantify water ingress into solar modules and polymeric samples using near-infrared absorption (NIRA) spectroscopy, calibrated with absolute water content via Karl–Fischer titration (KFT). Calibration was performed on various polymer materials—encapsulants, backsheets, and their combinations—using three commercial NIRA spectrometers to assess reproducibility and suitability. The influence of glass type, cell type, sample thickness, and lamination on NIRA signals was also evaluated. The method was validated through two lab and two real-world case studies. The first lab study quantified moisture ingress in minimodules with PET- and PP-based backsheets, yielding diffusion coefficients consistent with literature. The second involved polymer coupons under accelerated weathering; cracks in the backsheet increased water uptake, while encapsulants reduced it. In the first case study, moisture distribution was mapped in rooftop modules with and without visible defects in the backsheet and cells. Modules with backsheet and cell cracking showed 50% higher water content, especially near cell cracks. The second case study compared field-retrieved modules with cracked and intact AAA backsheets immersed in water. The cracked module absorbed water more rapidly, with water content an order of magnitude higher than the intact one. The presented approach offers a powerful quality assurance and inspection tool for module manufacturers and solar developers, supporting improved moisture-resistant module designs, timely mitigation measures, and more precise durability forecasts.