[RE-wrenches] mix-n-match Unisolar

[Darryl Thayer]

Hi Geoff
The Unisolar have the same cells just in different number of cells which determines the lengths.  If the cells have similar exposure, all that is needede is the same number of cells in each string.  Each cell has the same current thus each string wheather composed of 9 foot or 18 foot modules can be parralled without loss of performance as long as the strings have the same number of cells in them (or very close). 

So I would say the engineer is correct.  Further, If one cell is shaded the bypass diodes will allow operation of the string.
Darryl
 
--- On Thu, 10/30/08, Geoff Greenfield <geoff at third-sun.com> wrote:

> From: Geoff Greenfield <geoff at third-sun.com>
> Subject: [RE-wrenches] mix-n-match Unisolar
> To: "RE-wrenches" <re-wrenches at lists.re-wrenches.org>
> Cc: "Randy" <Randy at third-sun.com>
> Date: Thursday, October 30, 2008, 3:29 PM
> I thought I knew the answer to this one, but wanted to run
> it by the list. 
> 
> 
> 
> We are responding to a bid where the electrical engineer
> has designed a system with different sized Uni-solar
> laminates in some series strings paralelled with consistant
> full size strings.  (this was done to work around skylights
> etc). 
> 
> 
> 
> We suggested that this was a poor design and will lead to
> "least common denomenator" performance,
> exacerbated by MPPT confusion.  The EE responded that
> "the bypass diodes allow for this". 
> 
> 
> 
> Any experience with this in practice? 
> 
> 
> For a brighter energy future, 
> 
> Geoff Greenfield 
> Founder and CEO 
> Third Sun Solar & Wind Power Ltd. 
> 340 West State Street, Unit 25 
> Athens, OH 45701 
> 
> 740.597.3111     Fax 740.597.1548 
> www.Third-Sun.com 
> 
> Clean Energy - Expertly Installed 
> 
> 
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