PV degradation [RE-wrenches]

[Bill Brooks]

Allan,

The browning is due to the clear EVA in the module turning brown. This
problem was fixed about 10-12 years ago when manufacturers realized that the
slow-cure EVA was the source of the problem. As far as I know, no
manufacturer uses that type of EVA anymore. There have been some isolated
reports of EVA browning, but nothing compared with what used to happen with
the M-55.

The EVA browning effects both current (light hitting cell) and cell voltage.
Typical reports were about 20-30 loss due to browning. It is likely the 50%
you discovered was due to the fact that the array max power voltage was
below the operating voltage of the battery.

Bill.

> -----Original Message-----
> From: Allan Sindelar [mailto:allan at positiveenergysolar.com]
> Sent: Saturday, December 16, 2006 11:37 AM
> To: RE-wrenches at topica.com
> Subject: Re: PV degradation [RE-wrenches]
> 
> 
> I have not found a lot of consistency regarding degradation. I have seen
> numerous first-generation Photowatts (imported from France by Windy in the
> early 80s) still at 100% of rated power. Most of the ASI 16-2000s I see
> are
> close to original output, depending on degree of discoloration. At the
> same
> time, I have one long-time off-grid customer with 16 tracked Arco M55s
> (which at one time were Arco's premium 36-cell module at 53/55 watts) that
> are seriously browned and putting out about 50% of rated power (loosely
> measured).
> 
> The 0.6%/year I heard as a ROT from some NREL study is a statistical
> average
> based on many varied module specimens, not a predictable structural
> degradation common to all crystalline silicon modules. I suspect that
> early
> Tedlar browning is the cause of much of that figure.
> 
> Allan at PosE


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