[RE-wrenches] Wiley Asset

Wed Sep 8 23:21:07 PDT 2010

The problem with all shading analysis tools I've used, is that they can't take into account the effects partial shading has on string performance. You have to calculate that separately, based on how you'll be wiring the strings.
2nd, I know that usually power lines (if far enough away) won't have much of an effect, as the light refracts around them somewhat, so it doesn't cast a sharp shadow.
Same thing with tree branches. This is where it gets tricky, no hard and fast rules that someone can write some software for.
It's going to depend on the modules, too. (some have more bypass diodes, etc.) So the best you could do, is test with one module at the installed angle, and shade it with a thin branch or wire at varying distances to see what the effects are.
25 ft I'm not sure, at 50 ft, a power line or small branch is probably OK, and 10 ft. you'll have a problem for sure.
Just look at the shadows at the time of day you're worried about, to get some idea. I've often found a very fuzzy, almost indiscernible shadow at a distance that won't hurt performance too much.
The shadows seem to get fuzzier at early morning and late afternoon (smog effects?) which helps, too.
Basically if some cells are seeing 600 W/m2 while adjacent cells are getting 700 or 800 W/m2, its probably going to be fine. If several cells only get 100 W/m2 (full shading) while the rest get over 700 W/m2, that is going to cause real problems.
This would be another use for micro inverters, you won't lose whole strings, and even a partially shaded module will still have some usable output when wired to its own inverter.
Personally, though, I usually just relocate the array. 

R. Walters
ray at solarray.com
Solar Engineer

On Sep 8, 2010, at 11:30 PM, benn kilburn wrote:

> Thanks for the feed back guys, much appreciated!  
> 
> Now, how would you calculate for power/phone lines running thru the Pathfinder's reflection.  There are about 6 of them (the largest being at least 1") at least 25-30 ft away directly east of the proposed array location, and they are running straight north-south.  On the Pathfinder they run btwn 9 and 11am in June and btwn 10:30 and 11:30 in December.  
> 
> Would the pathfinder software, suneye or asset pick up on utility lines at that distance?  How much effect do they have on available sun output? And while i'm at it, how much do the 'software' tools pick up on the tips of leafless tree branches at say 25ft, 50ft?
> 
> i'll try out that spreadsheet idea, nice one!
> 
> cheers,
> benn
> 
> DayStar Renewable Energy Inc. 
> benn at daystarsolar.ca
> 780-906-7807 
> HAVE A SUNNY DAY
> 
> 
> 
> Date: Wed, 8 Sep 2010 20:05:08 -0700
> To: re-wrenches at lists.re-wrenches.org
> From: william at millersolar.com
> Subject: Re: [RE-wrenches] Wiley Asset
> 
> Benn:
> 
> A colleague has used the Wiley took and calls it 'marginal.'
> 
> I use the Pathfinder and I like the features Ray described.  I wrote a very simple spreadsheet using the teeny numbers on the month lines to create 100% of any month.  I highlight and delete any of the numbers that are shaded and the remainder is the percent of exposure for a given month.  You can multiply the output of PV watts or any other production result for a complete production prediction.  Easy and free.
> 
> William Miller
> 
> 
> At 05:38 PM 9/8/2010, you wrote:
> I've used the Pathfinder for decades, so I'm partial to them. Great for on-site discussions of shading issues with the customer, as multiple people can see the shading at the same time on the spot.
> I've also used their Assistant software, and it works pretty well. You take a photo of the actual pathfinder from above, and then download the photo into their software.
> You can then calculate total annual impact of any shading in Kwh, or percentage of annual production.
> I've been quite happy with the system, and the price for a Pathfinder, and the software is much less than the Suneye, I believe.
> 
> R. Walters
> ray at solarray.com
> Solar Engineer
> 
> 
> 
> 
> On Sep 8, 2010, at 3:46 PM, benn kilburn wrote:
> 
> Wrenches,
> 
> I'm looking at trying out another 'solar site evaluation tool', the ASSET (Acme Solar Site Evaluation Tool) from Wiley Electronics.  I'm looking for feedback on its performance and user-ability.
> I have been using the pathfinder which is great, but not the pathfinder software.
> 
> Any comments on the ASSET or Pathfinder software would be greatly appreciated.
> 
> Cheers,
> benn
> 
> DayStar Renewable Energy Inc. 
> benn at daystarsolar.ca
> 780-906-7807 
> HAVE A SUNNY DAY
> 
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