#1 Aug. 8, 2013 12:46:00

Telegram Sam
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Sun "viewing angle" of panels - shading


In an ideal world an installation will be 100% shade free.  In practice it is often a matter of “managing” the shade that obstructs contact with Apollo during his daily trajectory. Eliminating shade that is (behind or) directly to either side of the panels will obviously have no effect.  I am trying to figure out what “viewing angle”, seen from an imaginary line at right angles to the panels, to focus on for shade clearance purposes. My suspicions are that in fact this angle is more restricted than I had anticipated - that the amount of energy generated when the sun is some way off to either side makes de-shading in these areas not really worth while.


Or it could be that similar to the performance of PC monitors and TV's some brands of panels are more receptive to side lights than others.  


Conceivably the answer is different in winter than in summer when the trajectory is lower, depends on roof pitch, and latitude.. Hopefully someone can come up with some conclusions which are general and not too complex.





Edited Telegram Sam (Aug. 8, 2013 12:46:00)

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#2 Aug. 8, 2013 17:06:00

Jamie
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Sun "viewing angle" of panels - shading


Here's a useful tool you can use in conjunction with a profile of the horizon in order to produce a sun-path diagram


Also:


Ke!son Online Calculator


SPP blog







Jamie Taylor (Sheffield Solar Team)

Edited Jamie (Aug. 8, 2013 17:06:00)

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#3 Aug. 8, 2013 19:43:00

Telegram Sam
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Sun "viewing angle" of panels - shading


Thanks I've had a quick look at these tools and it is apparent that quite some study will be required to make proper use of them.  However my train of thought was a bit different:  I had imagined that the “cut-off angle” (even if not exact) would be specific to the panel in question and its technical capabilities - regardless of where it is positioned.  One can imagine it (or them) sat in the middle of a northern desert for the sake of the argument, and the user just taking readings unobstructed by any shade whatsoever.  And then applying the cut-off angle obtained to the particular domestic location assuming that the same angle will apply.  Or is life not so simple?





Edited Telegram Sam (Aug. 8, 2013 19:43:00)

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#4 Aug. 20, 2013 18:41:00

Telegram Sam
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Sun "viewing angle" of panels - shading


I could perhaps make my original query less ambiguous:


Is it worth myself or anyone cutting back shade that is on either side of the panels at an angle of - say - 45° or more, measured from a centre line projecting perpendicular to / at right angles from the line of the panels?  If not 45° then where to draw the line?





Edited Telegram Sam (Aug. 20, 2013 18:41:00)

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#5 Aug. 27, 2013 11:58:00

OSHpvgen
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Sun "viewing angle" of panels - shading


Firstly it would depend on the orientation of your panels. If they are true south then 45 degrees either side might make sense.  If not then you might be looking to do, say 60 30.


Secondly, angles change (both in orientation and height) with the seasons.  But (generally) production is highest in Summer so it would seem better to focus on angles that are relevant to the Apr-Sep period.


Thirdly, consider the cost against the potential benefits.  If it is going to cost £300 to get a man in then you have to have an improvement (depending on FIT rate) of at least 600kWh before you see a benefit.  For most people that would be a significant increase.


Finally, consider the view and the environment.  Chopping down trees to improve the performance of your solar pv generation is not easily categorized as “green”.  I could improve the performance of my system by removing the holly tree we have in the way but we would lose out on the joy of all the birds that nest there, I would probably only generate a few extra £ income a year and my better half would probably take the chainsaw to my legs.


So, if it's easy, consistent with you view of life and the world and will reduce your anxiety about potential lost generation then go ahead.  Otherwise, sit in the garden and enjoy the benefits of the shade with a pleasant beverage.  Please sun-bathe and drink responsibly.





Edited OSHpvgen (Aug. 27, 2013 11:58:00)

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#6 Aug. 27, 2013 15:28:00

Telegram Sam
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Sun "viewing angle" of panels - shading


Tks for the “balanced view” reply.  


My orientation is roughly SSE and location a bit south of the Border.


The de-shading has been up to now a DIY job so no major outlay and relatively minor trimming rather than tree removal. Arguably the eco downside from defoliating could be balanced by greater eco-generation, but these are murky waters.


I have heard the argument previously about it being dependent on the season, so assume that this is valid but that I am just not with it. I can visualize a given panel in a shade-free test lab with a man in a white coat carrying an (artificial) sun in front from one side to the other and recording at what side angle the panel starts to generate, and to stop.  These angles (which may vary from one manufacturer to another, it would be interesting to know how they differ) would give the user guidance on sensible “viewing” angles, prior to de-shading and before getting bogged down with inverter trip loads or whatever.








Edited Telegram Sam (Aug. 27, 2013 15:28:00)

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#7 Sept. 11, 2013 11:04:00

Jamie
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Sun "viewing angle" of panels - shading


You may find this app of use when investigating sun viewing angles…


www.profactum.com/episuntools


It's currently only available for android devices but should be coming to iOS soon.


To install, you'll need to have checked the box that says “Unknown Sources” in your devices settings under security. Then navigate to the above website on your device and the app will download.


Jamie










Jamie Taylor (Sheffield Solar Team)

Edited Jamie (Sept. 11, 2013 11:04:00)

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#8 Sept. 11, 2013 13:34:00

Telegram Sam
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Sun "viewing angle" of panels - shading


Thanks. Unfortunately I have yet to catch up with Android technology (phones, not panels) so will have to remain ignorant till the download becomes available for PC's.  Is it possible to summarize briefly what it does?





Edited Telegram Sam (Sept. 11, 2013 13:34:00)

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#9 Sept. 11, 2013 14:34:00

Jamie
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Sun "viewing angle" of panels - shading


The main feature is to overlay the sun's path at various times throughout the year onto the phone's camera so you could hold the camera up and see which objects will cause shading and when. Also allows you to measure angles (not sure how accurately) using the phones camera. Probably won't come to PC i'm afraid as it's dependent on the devices camera.







Jamie Taylor (Sheffield Solar Team)

Edited Jamie (Sept. 11, 2013 14:34:00)

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