discolored mono panels, should I worry?

Re: discolored mono panels, should I worry?

I'm with ;you vic,

There must be A VERY GOOD REASON that the junction boxes were removed. Must have been a fatal flaw that some MFG did not want to put their names on, or even have someone TRY to use them. They must have been on the way to the DUMP, for someone to go to the trouble of removing the boxes. Tho, whatta I know ??

Some of my MONO panels have a SLIGHT variation in the surface color twix cells in one panel, after exposure to the sun for six years. THis slight variation in color does not seem to corelated to any change in output.

GOOD LUCK!! Vic

Re: discolored mono panels, should I worry?

Well, my opinion FWIW, is that there must have been every expectation that all of the cells were good enough to meet (at least) the midpoint of power output for that family of panels, BUT, in the assembly process something must hve gone WRONG. May have been a power output issue, a hermicity issue etc. BUT, since all of the cells were certainly tested, perhaps more than once for output, that there must have been a surprising flaw with those assembled panels. Even the Chinese MFGs use the standard Quality Motto, "Good parts make good assemblies".

A few of these panels may fe fun to play around with, if one has the time.
Just more guiessing. Back to "work". Vic

Re: discolored mono panels, should I worry?

Humm... that is odd. None of my laminates have that (at least that I have seen... Im half way thru putting on the j-boxes).

Are you sure that is on the inside of the glass?

What are you using for framing? Looks nice.

Re: discolored mono panels, should I worry?

not exactly an answer to the OP's post, but suspect it might help some at some point, plus not sure where else to put something i remembered the other day.

back in the late 90's, we represented Raytheon Systems thermal imaging systems here in central VA, mainly to law enforcement.

A solar panel mfgr in Williamsburg, Va had contacted Raytheon and wanted a demo of one of their camera systems (raytheon had a thermal imaging camera that looked like those early 90s VHS camcorders, with interchangeable lenses - LE could mount one on a chimney quite a distance from a suspect's house and maintain surveilance thru out the nite).

Anyway, i was the one that went down to the mfgr's facility (for the life of me can't remember the name) - interesting operation, not terribly large but maybe 100,000 sq ft facility. They had about 20% of the building devoted to racks where they'd put the recently completed solar panels, flat to the floor (actually about 3' off the floor) and huge array of huge lamp housings hanging about 4-5' above them and they'd test the output from the panels and reject them based on output.

One of the issues was cells that had poor connections - but they knew those connections would arc, ie on a microscopic level - they wanted the camera system to see if they could use it to detect those cell connections arcing before even being placed under the lights (i'd hate to have their power bill). The camera worked (keep in mind, a good thermal imaging sensor, back then, could detect 1/2 degree F differential at 1000 yards - at 100 yards, depending on conditions, you could read the name tag sewn onto military uniforms - with more reliabiity you could make out a pen in someone's shirt pocket, as the pen would cause the shirt to press against the wearer's body and acquire more heat than the area around that wasn't pressed hard against his body.

They ended up building a large box area, over the assembly conveyor, that as the panel came down the line and went into the box (with lights), an operator would monitor the panel on his remote screen (kind of like the TSA scanner operator). They started on an automatic software program that would record each panel's image by S/N, and that system would detect any arcing between cells, for review later, in case there were issues.

not too long after that I dropped Raytheon as a supplier - don't even know if the solar mfgr is still in business

FWIW

Re: discolored mono panels, should I worry?

The discoloration is likely due to junction doping baking temp variation. Sometimes cells at the end of oven rack get more temp variation with quicker cooling. It can also be caused by contaminated doping gas mix at ends of oven. It doesn't necessary ruin the wafer but it is one of the reasons by some cells produce more illumination current then others.

As to thermal imagers, UL uses thermal imagers (IR camera) to detect hot spots caused by cell defects during qualification testing of panels. If manufacturer uses cells with severe shunt defects the cell can get very hot when shaded and other cells in series create high reverse voltage bias on the shaded cell. Bypass diodes every 12 to 24 cells keep the maximum reverse bias voltage down to less then 10 to 11 volts.