[RE-wrenches] Inter row shading: Portrait V landscape

Jeff Clearwater jeffc at villagepower.com
Fri Apr 23 11:48:50 PDT 2010


All,

Thanks William for this!  I love it when someone 
comes up with a design parameter I've never 
thought of.  What would be great is if module 
manufacturer's would include in their manuals 
some quantitative data on how vertical and 
horizontal shading swaths affect output.

Any data you have would be invaluable as I 
imagine the rough ratio would apply to most 
modules wired in the same way.

I've always done my interrow shading calcs 
assuming any shading is bad and I think that 
folks should still hold to this standard.  It 
really irks me when some big company new to solar 
puts in a large ground mount array where they had 
plenty of room to work with but they still use 
the noon at Winter Solstice as their design input 
for shading threshold angle.  9 AM- 3PM for a 
couple of months surrounding that date and they 
are throwing their power away for no good reason.

So I just hope that William's revelation doesn't 
become an excuse for others to put rows closer in 
landscape than good design dictates.  I use 5º 
less than the Winter Solstice noon angle as my 
shading threshold angle for most jobs.  I 
encourage folks to consider sticking to this kind 
of standard whether landscape or not!

Best,

Jeff C.
Village Power Design




>Friends:
>
>We field tested the concepts this morning and 
>the answer is "yes" (inter-row shading in 
>portrait mode: bad -- in landscape mode: less 
>bad).
>
>William
>
>
>
>At 08:40 PM 4/22/2010, you wrote:
>
>>Friends:
>>
>>99% of the time, we install modules in portrait 
>>mode.  We find ourselves installing a set in 
>>landscape with some short inter-row spacing, 
>>due to roof vents.  We are using Solarworld 
>>SW230 modules.
>>
>>It is my understanding that shading the short 
>>edge of this type of module is much more 
>>detrimental to the output than shading a long 
>>edge.  This is because of the manner in which 
>>the cells within the module are arranged in 
>>series.  I understand that one string is on the 
>>bottom half of a module and the other on the 
>>top half of a module in the landscape 
>>orientation.  In order for the module to cease 
>>power production, you have to shade at least 
>>one cell from each of the two internal strings. 
>>Therefore, you need to shade more than half of 
>>a module in the landscape mode before the 
>>module before the output declines drastically.
>>
>>Is my understanding here correct?  I will be 
>>testing this tomorrow if weather permits.
>>
>>Thanks in advance.
>>
>>William Miller
>>
>>
>>Please note new e-mail address and domain:
>>
>>William Miller
>>Miller Solar
>>Voice :805-438-5600
>>email: william at millersolar.com
>>http://millersolar.com
>>License No. C-10-773985
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>Please note new e-mail address and domain:
>
>William Miller
>Miller Solar
>Voice :805-438-5600
>email: william at millersolar.com
>http://millersolar.com
>License No. C-10-773985
>
>_______________________________________________
>List sponsored by Home Power magazine
>
>List Address: RE-wrenches at lists.re-wrenches.org
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-- 
~~~~~~~~~~~~~~~~~~~
Jeff Clearwater
Senior Design Engineer
Village Power Design
Solar Design Consultation for the Commercial Sector
http://www.villagepower.com
gosolar at villagepower.com

Voice: 831-427-2799
Fax: 413-825-0703
245 Dufour St
Santa Cruz, CA 95060
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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