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

Mon May 14 21:25:43 PDT 2001

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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