interrow shading [RE-wrenches]

Mark Frye markf at berkeleysolar.com
Fri Feb 2 07:27:49 PST 2007


Andrew,

Thanks for asking. I was referring to Sharp NT-185's etc.  These modules have 72 cells.  Looking at the module in portrait, there are 6 columns of 12 cells.  The cells are wired into 3 strings of 24, 2 columns of 6.  The three strings are paralleled together in the junction box. Other modules have there own cell/string layout.

To be clear, there is no difference in efficiency for each orientation when there is no shading on the module.

However, if the modules are mounted in portrait on a flat roof in rows, as the inter row offset is narrowed or as the sun drops lower in the sky, the shadow starts to creep up onto the module from the bottom edge.

Once about 5" of the bottom of the module is shaded, 6 out of 72 cells in the module are shaded.  In portrait, 2 out of 12 cells in each of 3 strings are now shaded.  This essentially turns off these string and therefore the entire module as the shaded cells are now dropping all the power of all the strings.

In landscape, however, as the bottom 5" of the module become shaded, 6 cells of only 1 string of 12 become shaded.  This turns of the string. But this is only 1 of three strings.  The other 2 strings are completely un-shading and running at near full power.

MPF

-----Original Message-----
From: Andrew Bortz [mailto:solarman2 at comcast.net]
Sent: Friday, February 02, 2007 7:11 AM
To: RE-wrenches at topica.com
Subject: Re: interrow shading [RE-wrenches]



Mark & all, This sounds to me like very useful (and new to me) info.

So, Questions:
    -Which module is this, that has WAY BETTER efficiency in landscape
orientation?
    -Can you tell us which other brands/models have this same property (or
advice as to how to find out)?

Andrew Bortz
Mr Sun Solar
solarman2 at comcast.net
Portland, OR


----- Original Message ----- 
From: "Mark Frye" <markf at berkeleysolar.com>
To: <RE-wrenches at topica.com>
Sent: Friday, January 26, 2007 1:19 PM
Subject: RE: interrow shading [RE-wrenches]


>
> To throw in another wrench...
>
> All of this is effected by the type, location, and orientation the modules
within the rows.
>
> For the module I use, a landscape orientation will cause only 1 of 3 of
the separate strings encapsulated within the module to become shaded,
dropping the power of the panel by only  33% to 50% depending.  Whereas if
the orientation is portrait, all 3 of 3 internal strings will become shaded
dropping power by 80% to 100%
>
>
> MPF

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