Brown Patches on the Panels over the Cells.

[GHTech]

Hi!

I have SolarWorld SW 175 panels installed 11 years ago in So. Cal.. Just noticed some brown patches on the top over the cells only on number of the panels. The patches do not show over the area between the cells. The panels have no shading and is connected to a PV Powered inverter. I had the original installers test the system and the system did performed close to spec. They did notice an issue with 2 panels from the top, and when they removed those panels, there were hot spots and bubbling underneath.

Not sure what the brown marks are and if there will be any issues long term. Thoughts please?

Thanks,

GHTech

[littleharbor]

Some of the older encapsulants used in panel manufacture were prone to "bronzing", likely from heat. Arco solar had experimented with concentrating sunlight onto some of their arrays in their experimental Carrizo Plain solar farm in California. They decommissioned this farm and sold off the used panels. The worst of the bronzed panels were rated as mud grade, while others were rated as gold, silver, and , I think bronze. When you see it only over the cells it seems that the heat source is internal. Are these particular panels getting any shading during the day? It doesn't take much of a shadow to affect the panels performance, activating the bypass diodes and possibly causing the cells to heat up. While they have since remedied the encapsulant problem I have seen this happen on panels from 2004 - 2005 vintage. These were BP Solar 175 watt panels so yours are quite similar, age and efficiency wise.
Hopefully other members chime in with definitive answers to the bronzing question.


Bronzing of solar panel.jpgBronz solar panel.jpg

[peakbagger]

Its highly likely that its UV damage to the encapsulant and I expect the variability is a consequence of some long ago production compromise. The panels will slowly lose performance as they age and encapsulant degradation seems to be one of the causes. I supposed you could try to rattle the manufacturer's cage but realistically the warranty is for performance not visual degradation. On occasion manufacturers have identified a run of panels produced at some point that were fundamentally defective and rarely they may proactively offer a replacement but I seriously doubt they would offer it on your panels.