PV Module Degradation (was PV Inverters module strings) [RE-wrenches]

[Lynne A Carter]

Jay I hear this question a lot from my customers.  It is a good question but
when I do the math on the prices why not go top of the line,  3.50 per w
now, or ??? in five years. maybe by then we will be powered by the septic
tank.
Lyn
Lyn at solarvillage.com
Solar Village Institute inc.
PO Box 14
Saxapahaw, NC  27340
Tel. 336-376-9530
Fax. 336-376-1809
www.solarvillage.com

----- Original Message -----
From: jay peltz <jay at asis.com>
To: <RE-wrenches at topica.com>
Sent: Monday, May 14, 2001 9:25 PM
Subject: Re: PV Module Degradation (was PV Inverters module strings)
[RE-wrenches]


> Hi Bill,
>
> The issue with warranty is a a big one.  I find that as with most things
it
> depends on whom you buy it from.  When I buy a car I don't call the
manufacuter
> directly, I go through the dealer as that is there job.
>
> When I have a problem with a panel, I go through the supplier and they put
the
> screws to the problem.  If they don't do that then time to look for a new
> supplier.
>
> In my experience I have seen manufactures replace out of warranty panels,
and
> some give real problems with in warranty situations.  And yes most folks
don't
> understand that out of spec panels get you the difference in watts not a
new
> panel, but hay watts is watts.
>
> I'd like to pose a question.  Since the industry is changing so fast, and
panel
> prices will most likely come down a lot in the next 5 years does it
warrant
> having a 25yr warranty? or going for less expensive panels with shorter
warranty
> with replacement by significantly cheaper panels in some 5-10 yrs?
>
> Thanks,
>
> jay
>
> peltz power
>
> Bill Brooks wrote:
>
> > Pat,
> >
> > It is not 1-2% module degradation. PVUSA proved that all system degrade
1-2%
> > per year as a system. This requires 6-8 years of constant monitoring to
> > actually detect. This is due to the fact that measurement uncertainties
are
> > higher than the degradation rates.
> >
> > How much of that is module, is hard to say. It is likely more than 0.5%
for
> > most modules. The system degradation is likely 75% of the system
degradation
> > if not more. This means that modules could be degrading slightly faster
than
> > their warranties allow (0.75%-1.5% per year). For a 20-year warranty
> > degradation to 80% of rating, this allows for a 1.1% degradation. A 1.5%
> > degradation will result in a final performance of 74%. Looks like you're
> > entitled to 6% from the warranty.
> >
> > However, have you ever tried to make a claim on a PV warranty from a
power
> > point of view (not failure)? Module warranties are great for module
failures
> > and very difficult for underperformance. It requires, removing the array
and
> > shipping it back to the manufacturer for flash testing. Then you have to
> > live with their results.
> >
> > Most people have the erroneous idea that if their array underperforms
that
> > they'll either get a new array or automatically get some new modules.
Not
> > so. These warranties are very carefully written and it will cost the
> > installer or system owner far more to collect on the warranty than the
> > warranty is worth. I went through the warranty process just to confirm
this
> > fact.
> >
> > Case in point as to why third party testing is so critical. We are at
the
> > mercy of manufacturers information and there is very little muscle any
one
> > customer (unless you buy Megawatts of PV) can bear to get satisfaction.
> >
> > This is not to say that manufacturers are routinely dishonest or trying
to
> > scam folks. They are trying to make money and until recently, this has
not
> > been a major issue. When you operate on-grid PV systems, you can more
> > accurately measure the performance of the PV system and show good or bad
> > performance with a simple meter. Off-grid systems are a little more
> > challenging in that regard, so we overdesign for a variety of reasons
> > (phantom loads--both real and imaginary) and it all comes out in the
wash.
> > Welcome to the real world of real-life performance.
> >
> > Our industry needs to grow up, but it is going to take all our help. The
> > federal DOE program unknowingly contributes to the problem because they
must
> > show continued improvement on costs and performance. To change the
> > performance metrics in mid-stream (kinda like Wag the Dog), this could
cause
> > some problems with explaining why the numbers all of a sudden got worse
> > instead of better.
> >
> > Bill.
> >
> > > -----Original Message-----
> > > From: Pat Kiernan, Eco Electric, Inc. [mailto:ecoelec at rof.net]
> > > Sent: Monday, May 14, 2001 6:00 PM
> > > To: RE-wrenches at topica.com
> > > Subject: PV Module Degradation (was PV Inverters module strings)
> > > [RE-wrenches]
> > >
> > >
> > > Bill Brooks,
> > >
> > > I would really like to see the PVUSA documentation you mention if it
is
> > > available. The reports I've seen indicate 0.5% power degradation per
year
> > > with voltage degradation largely due to increasing resistance in
> > > connections
> > > and current degradation due to optical degradation in the
> > > encapsulant/lamination.
> > >
> > > If 1-2% module power degradation per year is real than most PV
warranties
> > > are a hoax and RE is a little closer to snake oil than I would like.
> > >
> > >
> > > Pat Kiernan
> > >
> > > Eco Electric, Inc.
> > > PO Box 550
> > > Carbondale, CO 81623
> > > tel/fax (970) 963-3132
> > > e-mail: ecoelec at rof.net
> > > ----- Original Message -----
> > > From: Bill Brooks <billbrooks7 at earthlink.net>
> > > To: <RE-wrenches at topica.com>
> > > Sent: Thursday, May 10, 2001 1:40 PM
> > > Subject: RE: PV Inverters module strings (Last Call) [RE-wrenches]
> > >
> > >
> > > > Carl,
> > > >
> > > > No self-respecting PV manufacturer is going to share eventual
> > > > underperformance numbers. They are non-the-less very real and are
fairly
> > > > consistent with all PV technologies available. No special conspiracy
> > > theory
> > > > for a-Si. All systems degrade at 1-2% per year and most of the
> > > degradation
> > > > seems to occur in voltage. Documented at PVUSA with over 20
> > > systems of all
> > > > types over 10 years.
> > > >
> > > > Initial overperformance is probably only an issue if you start a
system
> > > > during the colder time of year. Most inverters, I believe this
includes
> > > > Trace Tech (Kent please chime in) will stay offline with a DC
> > > overvoltage
> > > > condition should the Voc get over 600 Volts initially. As the
> > > array warms
> > > in
> > > > the sun and degrades, that voltage will settle into the proper range
and
> > > the
> > > > inverter will start.
> > > >
> > > > Bill.
> > > >
> > >
> > >
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> > >
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