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A novel failure mode known as spontaneous glass breakage has emerged as a critical reliability concern in the solar industry, with instances first noted approximately five years ago. According to an article by pv magazine, the phenomenon now ranks among the top issues for the sector, though manufacturing cost pressures and a lack of dedicated standards are impeding progress on solutions.
Scientists, operators, and testing laboratories have observed glass breakage on solar modules since around 2021, occurring without any apparent external cause such as impacts or severe weather. Kiwa PVEL, a testing lab, has described spontaneous glass breakage in glass-glass modules as the most significant reliability problem currently affecting modules. The lab reported that the issue has been observed across multiple countries, module model types, and mounting systems.
Tristan Erion-Lorico, vice president of sales and marketing at Kiwa PVEL, linked the phenomenon directly to cost-saving measures within the industry. He noted that glass, frames, and encapsulant have been thinned, and mounting has become more aggressive. While these designs may work theoretically, safety margins have been eroded, allowing microscopic defects, improper adhesive application, edge pinch, or pressure from busbars to cause breakage.
Kiwa PVEL’s mechanical stress sequence testing in the second quarter of 2025 recorded a historic high, with approximately one-third of module glass breaking. In the final quarter of that year, results improved slightly, with roughly one-quarter of samples failing. Erion-Lorico indicated that modules failing static or dynamic mechanical load tests are unlikely to endure for 30 years in the field.
Current PV modules in power plants are larger than ever, with glass on both sides accounting for more than half a module’s weight. While previous generations used 3.2 mm glass, current modules typically use glass around 2.0 mm thick. Pradeep Kheruka, chairman of Borosil and Borosil Renewables, stated that the shift to thinner glass is entirely customer-driven, requiring glass manufacturers to invest in new equipment. He added that responsibility for breakage is shared, with factors including high pressure from thick soldered joints, improper sealant filling, and poorly finished holes in the backsheet.
The US National Laboratory of the Rockies (NLR), formerly the National Renewable Energy Laboratory, surveyed potential causes of spontaneous glass breakage in late 2024. The survey identified contributing factors such as reduced thermal strengthening in thinner modules, microscopic flaws, lamination-induced stresses like edge pinch, increasing module size without corresponding mounting changes, and contact between glass and frame or trapped debris. For a 2026 paper, NLR focused on the first cause, developing a non-destructive method to measure glass surface stress on finished solar panels. Researcher Elizabeth Palmiotti confirmed that most 2.0 mm glass is fully tempered but remains weaker than traditional 3.2 mm glass, with a clear correlation between lower surface stress and increased susceptibility to breakage.
Palmiotti noted that while 2.0 mm glass can meet fully tempered thresholds under certain standards, its surface compressive stress is generally lower and the compressive layer thinner. Henry Hieslmair, principal engineer at DNV, said investors are concerned, observing that as safety margins shrink, smaller factors play a larger role. Farid Samara, senior engineer at DNV, added that projects with thinner glass and large module formats require deeper review, and that a blame game exists between module manufacturers and tracker suppliers regarding structural testing responsibilities.
This points to a deeper issue: the absence of a clear, PV-specific standard for glass. Palmiotti stated that no such standard currently exists, meaning glass and module manufacturers are not reporting glass properties in a meaningful way. She suggested that aligning on definitions for glass surface stress would represent a significant step forward.
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