German researchers say a gentle press on the back of a solar module can show how its plastic layers are aging, with no need to cut the panel apart. For anyone counting on a 25-year warranty, the finding carries a warning too: lab aging tests pushed too hard can paint a misleading picture.
The method is called compressive stress relaxation measurement, or CSRM. It's already used to check whether the encapsulant, the plastic that glues the cells inside the glass sandwich, has cured properly. A small steel tip is pushed into the rear surface and held in place while the team watches how quickly the force fades. That response reflects both the encapsulant and the backsheet, the plastic skin on the back.
The team, from Anhalt University of Applied Sciences and Fraunhofer CSP, built small test modules and baked them in two ways: long stretches of damp heat, and heat combined with UV light. They checked the plastics and the electrical output every 250 hours, and used solvent and thermal tests to tell encapsulant changes from backsheet changes.
In damp heat, the starting cure state mattered. Samples that began with different degrees of cross-linking, the chemical bonding that sets the encapsulant, kept those differences, and power loss followed them. By the end, both layers had degraded, and the backsheet's polymer chains had begun to break.
The heat-and-UV test told a different story. It added extra cross-linking early on, which leveled out the samples, and their power loss ended up similar. That's the trap: a harsher test can erase the very differences you wanted to see. The authors said over-acceleration should be avoided "by all means" if reliability predictions are to be realistic.
This is a lab study on small mini-modules. The source doesn't say how the method would do on full-size panels in the field or on other cell types. The work appears in Polymer Testing, and the team plans to calibrate CSRM against cross-linking density for better resolution and speed.
We could not find, in the coverage we checked, any independent expert comment on the work, exact figures for how much power loss differed between the samples, or word on whether CSRM is being adopted by manufacturers or taken up by standards bodies such as the IEC. That means nobody has yet said what share of power loss would matter for a warranty claim, or whether current test protocols would change.
If a faster aging test can hide the differences between good and bad panels, how much should buyers trust the numbers behind a long warranty?
Sources
- 1.Non-destructive testing tracks polymer degradation in PV modules - pv magazine Global · pv magazine Global
Reported by the WattsUpNext desk from the sources linked below. Spot an error? Tell us at corrections@wattsupnext.com.
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