PV degradation [RE-wrenches]

[Allan Sindelar]

Bill,
Thank you for correcting my mistake about EVA, as opposed to Tedlar, being
the component causing the browning. I am surprised that it was only 10-12
years ago, but I guess I am regularly reminded by things like this just how
young this industry really is.

The 50% was not lack of voltage, though. It's an old 12V system, and one
upgrade several years ago was a Solar Boost 50 running 24V in/12V out, in
order to minimize line losses and the very problem you describe. The
combined output to the batteries is reduced by roughly that amount.

Allan

----- Original Message ----- 
From: "Bill Brooks" <bill at brooksolar.com>
>
> 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]
> >
> > 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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