Lower panel angle or risk shadowing?

[bagman]

I'm fitting 4 panels on a flat, S facing roof in a row from S to N.
I am at 55 degrees, so I gather the optimum fixed angle is 55 degrees...

Problem is that at that angle, in Winter at least they will overshadow each other. Even at a lower angle, say 30 degrees they will shadow each other unless there are big spaces between them, which I don't have roof space for. I don't quite know how to calculate distances required to spread out the panels so they don't overshadow each other... but I am wondering if I should even bother. In December I will have sun at 20 degrees from the horizon, so the only way to capture that without shadowing others is to place them all flat.

So... I gather that the solar gain from angling panels is pretty minimal anyway, so I am wondering if I am just best to lie them flat (or at some small angle to drain water). I think the loss of power from putting part of a panel in shadow is much more than the gain from tilting up towards the sun. Any thoughts on this?

 

[SeaGal]

I think the loss of power from putting part of a panel in shadow is much more than the gain from tilting up towards the sun. Any thoughts on this?

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Optimum angle will likely be less than 55 degrees IMHO. But, at the end of the day avoiding overshadowing will be more important than perfect angle - it makes less difference than most people.

On a bright cloudy overcast day like today, makes no difference. My panels are at 15 degrees (in an E-W config) - as you say a small angle (10 to 15) is good to aid water run off.

As a side thought... Would an east-west config be a possibility with your topology to fit more panels in? 4 is not that many so you will need to ensure you have enough voltage for the inverter to kick in.

 

[bagman]

Would an east-west config be a possibility with your topology to fit more panels in?

no... it's on a dormer roof, just wide enough to get the panels on, but long enough to fit 4 in a row.

On a bright cloudy overcast day like today, makes no difference. My panels are at 15 degrees

I guess you mean the lower angle makes no difference? (not the overshadowing)

 

[ArthurEld]

I am making an awning out of panels. I was only planning to tilt them 5 degrees toward the south.
My panels are 36" and they will drop 3". It seems like that is enough for water to run off.
Mine will be low enough so I can clean them when needed.
I imagine you would be able to lower the angle enough to avoid shadowing
People put hinges on panels. I am not.

 

[SeaGal]

I guess you mean the lower angle makes no difference? (not the overshadowing)

Yes

 

[littleharbor2]

Probably a dumb question but, Are you laying the panels in a landscape orientation, and not portrait?