[RE-wrenches] cell thickness and handling modules (was Sunpower modules)

[Bill Brooks]

Joel,

My understanding is that some of the manufacturers are able to cut so thin
with current wire saws that the cells become flexible--almost like paper. It
presents other concerns, but these newer technologies might actually be
solving some of the cracking problems of the past. It is a brave new
world--with good and bad consequences at every turn.

Bill.

-----Original Message-----
From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Joel
Davidson
Sent: Friday, March 20, 2009 2:54 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] cell thickness and handling modules (was Sunpower
modules)

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" <bteitelbaum at aeesolar.com>
To: "RE-wrenches" <re-wrenches at 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-bounces at lists.re-wrenches.org 
> [mailto:re-wrenches-bounces at 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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