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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