Arco Solar used inside diameter (ID) saws to cut wafer 3 mils (0.003 inches)
thick. I don't recall when Arco got wire saws. Solec also used ID saws until
1995. See http://dove.eng.sunysb.edu/~kao/Wiresaw/NSF-97.pdf Thinner cells
and wire sawing yields more kW/kg but require better handling equipment to
avoid breakage. Cells can crack even when they are laminated into glass
front and glass back modules so don't twist or flex modules when handling
them.
Joel Davidson
----- Original Message -----
From: "Brian Teitelbaum" <bteitelb...@aeesolar.com>
To: "RE-wrenches" <re-wrenches@lists.re-wrenches.org>
Sent: Friday, March 20, 2009 12:39 PM
Subject: Re: [RE-wrenches] Sunpower modules
Drake,
One thing about those old modules is that the cells are incredibly thick.
You can feel them on the back-sheet. They must be at least 1/16" thick.
Wire-saw technology was just not that good in the old days. Module
manufacturers say that the thickness of the cell has no effect on
performance, but I guess we will just have to see. If we're still around
in 2036, we can compare a set of 2009 modules with my old ones which will
be 54 by then!
Brian
-----Original Message-----
From: re-wrenches-boun...@lists.re-wrenches.org
[mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Drake
Chamberlin
Sent: Friday, March 20, 2009 1:07 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] Sunpower modules
Allan and Brian
Thanks for the answer to the problem. I think the Xantrex PWM
chargers are going to be the most appropriate for these modules.
The old Arco modules are incredibly long lasting. I hope the ones we
are putting in today will last as long.
Drake
At 01:40 PM 3/20/2009, you wrote:
Drake,
Just to add to Allan's excellent post, most of the Arco's made
before about 1985 had less than 36 cells. Some were 35-cell, most
were 33-cell, but there were also 32 and 30-cell units.
You might want to look into rewiring the modules in higher voltage
series strings to get more "oomph" out of the MPPT controller, and
reduce transmission losses. However, be aware that many of those old
Arco modules had a sticker on them that said something like "do not
operate above 50VDC"
I still have 12 Arco, 33-cell, model 16-2000 modules (16Vmp/2A) on
my off-grid house, wired in pairs for 24V and going through an
ancient Trace C-30A relay controller (not even PWM!). I've
contemplated wiring them for 36V and using MPPT, and I may someday,
but they have been working so well as is that I haven't bothered.
Even on hot days I often see 27.5V and 11-12A charging my 24V
battery bank, which I think is damn good performance from a set of
27-year-old modules.
Brian Teitelbaum
AEE Solar
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