Interesting info on Uni-Solar panel comparison [RE-wrenches]

[Doug Pratt]

Hey Marco,

  'Bout 4-5 years ago when the triple-junction modules were just
starting to show up I had the same concerns, based on the miserable
performance we'd been seeing from earlier amorphous products. I took 4
randomly-selected US64 modules out of Real Goods stock, and sent them to
Sandia Labs for some testing and light soaking. They all arrived with
original factory packaging intact, so there was no cherry picking. All 4
modules delivered 95 to 98 watts fresh out of the box. After 2 months
they'd all dropped about 15%, and after 4 months, and again at 6 months
they were still within +/- 2% of the 2-month performance figures.
(That's about 80-watts output.) With 4 modules, this is a much more
statistically accurate test that the Swiss test, which used only 1,
maybe 2 samples.
  At 6 months we ran a "solar shoot-out" at one of our summer Sol Fests
comparing the 4 US64s against 4 Siemens SP75s and 4 Astropower 75s. Each
module was monitored and data-logged individually, but all were charging
the same 12-volt battery pack.
  Since Uni-Solar performed substantially better than the single crystal
modules, which we were...and continue to...sell the most of, we never
published the results. Uni-Solar did use the info for a little while,
which the folks at Sandia were VERY unhappy about(what's wrong with
real-world, name-brand comparisons I'll never understand).
  The conclusions I saw were that Uni-Solar triple-junction comes out of
the box VERY hot; they degrade about 15% in the first 60 days or so, and
then degradation levels out. Will they make it to 20 years within 20% of
rated output? Nobody knows for sure. Uni-Solar is betting the company on
it. We do know there IS a substantial power bonus initially.

Best regards,
Doug Pratt

-----Original Message-----
From: Mangelsdorf, Marco [mailto:mmangelsdorf at hei.com]
Sent: Sunday, June 16, 2002 3:56 PM
To: RE-wrenches at topica.com
Subject: Interesting info on Uni-Solar panel comparison [RE-wrenches]


I recently came across some test data from a facility in southern
Switzerland that's been testing PV performance for decades.  The one
module that stood out in a table of 10 modules from different
manufacturers was the Uni-Solar 32W a-Si.  It was rated at 32W, tested
out of the box at 34W and put out 27 watts three, count 'em, three
months later, a reduction of 20 percent.  "Attentuation" you say, Bill?
I wonder if Uni-Solar dealers clue in their customers about such
dramatic drops in output taking place in such a short amount of time.
Not likely.  Instead, it's the "yeah, these modules are rated at 64
watts but they actually put out 80" pitch.  Or better yet, according to
a Uni-Solar fanatic in this here state, Uni-Solar modules actually put
out power in moonlight.  Yeah, definitely, if the moonlight you're
taling about is measured on the moon...Hey, but doesn't the very phrase
"triple-junction" sound so cool and high-tech?  I guess maybe there's
some reason why crystalline Si has been and still is so dominant across
the globe as far as the preferred semiconductor of choice for PV
manufacturers.  Oh wait, wait, what about Cad Tel and promises of
$2/watt?

Rant off.

marco
ProVision Technologies, Inc.
Hilo, Hawai'i
www.provisiontechnologies.com

>
> I just visited the North Coast Co-op where I helped install 2 arrays
1
> using
> unisolar 64's and the other with Siemens 130's.  Around 1.2 kw per
inverter
>
> Just wanted all to know that the Siemens are outperforming the
unisolar by
> around 5%.  And interestly this 5% seems to be consistent on sunny or
> cloudy/foggy days.
>
> System has been installed for a few months now.
>
> Both systems are south facing, same roof ( side of building actually),
no
> shading.
>
> Both use SMA 2500U's.
>
> Thanks,
>
> jay
>
> peltz power

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