[Greenbuilding] Electrical line shading of solar PV modules

[elitalking]

Gary

 

This would be very helpful.  I am sure this question comes up all the time.  Coincidentally, I was showing my client your web site and that particular installation in our discussion.  

 

Since sun's rays are parallel, I assume the shadow created on a clear day is the same as the thickness of the wire.  

 

Eli 

----- Original Message ----- 
  From: gdreysa 
  To: Green Building 
  Sent: Wednesday, April 06, 2011 9:49 AM
  Subject: Re: [Greenbuilding] Electrical line shading of solar PV modules


  Hi Eli,
  I'd agree with Keith that some caution is in order here.

  This is a picture of my Enphase PV array with some modest shading:
  http://www.builditsolar.com/Projects/PV/EnphasePV/Shading.htm

  You can see from the real time output plot that even the panel with just a line across it is very much effected.
  The shadow is wider than a power line would cast, and maybe the effect would diminish as the shadow gets narrower, but I'd be careful.

  If I think about it later today and the weather cooperates, I'll set up narrower shadow and let you know how that comes out.

  The micro inverters are good in that a shadow across one module only effects the output of that one module and not the whole string, but a wire shadow that goes across several modules could still have a serious effect.

  Gary


  On 12:59 PM, Keith Winston wrote: 
    I'm not quite sure what you mean by "smaller than the sun's disc"... larger power lines can cast distinct shadows. If those align with an axis of the modules, then they may shade an entire row of cells in a module, overcoming the ability of the bypass diodes to "bypass" the shaded cells (most modules are, I believe, still bypassed on a cell-by-cell basis, and are wired in series along one of their axis). So I'll stand by my earlier comment that a power line could very well create significant shading. But I agree with the microinverter suggestion.

    Keith



    On Mon, Apr 4, 2011 at 11:22 AM, Gordon Howell -- Howell Mayhew Engineering <ghowell at hme.ca> wrote:

      Thanks for your question Eli:

      It doesn't appear that the electrical lines would be a significant issue.  They are likely smaller than the sun's disc.

      If you use Enphase module-inverters (one inverter for each PV module) then any shaded module wouldn't affect the PV array's performance, because each PV string is a PV module.

      To clarify:  the industry term that is an internationally-recognised standard for PV modules is "module", not collector, not panel.  See attached file for pictoral description.







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