Need input from a panel Guru

JR HillJR Hill Registered Users Posts: 12
Not sure I like what I saw this AM so I snapped the attached picture of a suspicious panel. Any input?


Attachment not found.


  • BB.BB. Super Moderators, Administrators Posts: 32,005 admin
    Re: Need input from a panel Guru

    Looks like frost and dappled shade--With possible water spotting/mineral build up.

    What are you looking for/at?

    I had dark staining on the lower part of the panels on the glass... A hose would not rinse it off--and looked very much like overheated browning. Took some soap/glass cleaner and the brown came off... Sort of like staining from a "tea" of tree leaves in our area.

    I also had what looked like light coffee+milk or hot chocolate staining under the glass above the J-Boxes underneath. Turned out that was overheating which caused panels to eventually failed (low output current in full sun). Vendor replaced all the panels after ~6 years of Grid Tied operation.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • JR HillJR Hill Registered Users Posts: 12
    Re: Need input from a panel Guru

    At least two of the segments on one panel would seem to be creating heat that is thawing the frost. All of the other panels thaw evenly - even those with some shading.
  • WNY DaveWNY Dave Registered Users Posts: 23 ✭✭
    Re: Need input from a panel Guru

    Looks like frost or fog build up, just the way they are heating up, maybe a slight difference in soldering of the cells, maybe a few are heating up when the sun hits them, maybe a slight resistance in them, cause a little be of heat to be generated in certain spots when trying to generate power.
    Looks like you have a little bit of shading from a tree? Maybe the sun got thru in a couple spots and melted the frost.
  • waynefromnscanadawaynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: Need input from a panel Guru

    Definitely a lot of shading going on there. That shading is not good, will result in very little output..
  • JR HillJR Hill Registered Users Posts: 12
    Re: Need input from a panel Guru

    We're on the north facing side of a canyon and the panels are picking up what's available this time of the year - sigh. But it's only for two months. Eight months of the year the generator never runs 'sept for high loads in the shop.

    I still don't like the fact that a few certain segments on a given panel thaw when the sun hits them. Out of 15 panels it only happens on the panel in this picture. The panel that is suspect was in full sun when I took the picture. Your point is well taken and it's not about shade. If I understand correctly, if one panel in a sting is having problems it will affect the whole string. Since I have two 3x2 strings and one 3x1 string feeding into separate breakers and some shade on some of them at any given moment (this time of the year), I can't take any meaningful readings. And I'm not going to get on a frosty metal roof to break the connectors for readings. I was just wondering if anyone has seen something similar that might be a heads up for concern.
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Need input from a panel Guru

    if it is resistive heating going on there it would make sense that the current output would be slightly diminished compared to the other pvs. verify its short circuit current compared to the others.

    it may be good to also measure the temp with a good ir temp thermometer during times of equal insolation to rule out solar heating on just one area of the pv.
  • RandomJoeRandomJoe Solar Expert Posts: 472 ✭✭✭
    Re: Need input from a panel Guru

    How early in the morning was this? My first impression, taking into account the frost still on the panels above, is that the sun is angling up into the sky. If you look at the tree's pattern on the lower-right panel there are gaps of sunnier areas toward the bottom and just above center. If you move the shadows up/left at a slight angle those sunnier patches would line up nicely with the more-thawed areas on the panel to the left. The top of the shadow would also land on the bottom of the top-left panel.

    If that's the case, those clearer patches just got more sun than the rest of the panel and warmed up a bit more.
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