inter-row shading [RE-wrenches]

[William Miller]

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Wrenches:

Here are two ideas for solving the inter-row shading issue:

1. Set up the south row (in the northern hemisphere) of modules and place 
your Pathfinder behind it.  Move up the roof (or north in the field) until 
your desired time and date becomes free of obstruction.  Extend a line from 
the top of the obstruction through your pathfinder to the roof surface to 
find where the second row should start.

2. I have written an Excel spread sheet this evening that should answer any 
inter-row shading questions for flat and sloped installation surfaces with 
some degree of precision.  I have published it to my web 
site:  http://mpandc.com/resources/resources.html. Click on "Inter-row 
shading solution spreadsheet."

This solution is much easier to follow than the previous solutions I had 
offered here (and one previous version had an error, my apologies) and is 
more precise than "rules of thumb".  You will have to answer for yourself 
the time and date that you want the back row of modules to become free from 
shade and obtain the sun altitude from the web, computer or Palm Pilot 
software or observation. Here is one web resource for 
this:  http://www.susdesign.com/sunangle/.  These tools require that you 
enter your latitude so this is where that factor is considered.

This spreadsheet will also allow you to determine how far back from a fixed 
object you need to be to avoid shading.  Just enter the vertical height of 
the fixed object as the panel dimension and the panel tilt as 90.  The 
fixed object acts as a vertical panel in this case.

If any of you use this solution, let me know how it works out for 
you.  I've tested it with a variety of values, but consider this a "Beta" 
version.  It can easily be tested by going on a roof with a stick, 
inclinometer and a tape measure.  Note the time and date, roof pitch and 
shadow length and compare to results from the spread sheet.

William Miller

PS: I routinely solve these types of problems in the field with my Palm 
Pilot using two tools:

         Total Trig from:  http://www.multiology.com/totaltrig.htm

         Sun Angle from:  http://sunangle.sourceforge.net/

If you have a Palm Pilot, these are "must have" tools.

WM



At 09:28 AM 1/26/2007, you wrote:

>Can anyone recommend a web page or other resource for calculating
>interrow shading?  Something that factors in the latitude at the site
>(not just CA).
>
>Much thanks in advance -- Kurt
>
>----------------------------------------------------------------
>
>Kurt Nelson
>PO Box 309
>Cornucopia, WI 54827
>715-742-3406
>sunwise at cheqnet.net


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