[RE-wrenches] PV Cell Temperature Variation

[bob at midnitesolar.com]

I've checked several PV modules under load in past years and they all 
seem to do this.

Just cell mis-match I was guessing.

boB


On 5/17/2018 3:19 PM, Corey Shalanski wrote:
> On a recent utility-scale PV installation we noticed a strange 
> phenomenon on a single string on a single inverter. An IV curve 
> (attached) reveals that the measured performance characteristics for 
> this string (solid line) are significantly less than the expected 
> values (dotted line). For reference, the ambient temperature was 31°C 
> and the irradiance was 1010 W/m².
>
> The phenomenon that more so caught our attention is apparent on a 
> thermal image (also attached) of the modules in this string. For lack 
> of a better term I would describe the distribution of cell 
> temperatures as resembling a "checkerboard" or "scattershot" (random) 
> pattern, ranging between roughly 55°C and 70°C. Interestingly this 
> phenomenon was only apparent while the inverter was operating, i.e. 
> with the inverter turned off the modules revert to a much more uniform 
> temperature distribution nearer to 55°C, instead varying by only a 
> couple degrees across the entire module/string.
>
> There was no apparent physical damage to the modules.
>
> Can anyone offer any suggestions about what might be causing this 
> phenomenon?
>
> --
> Corey Shalanski
> Joule Energy
> New Orleans, LA
>
>
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