Horizontal or vertical for a solar panel?

[Capt Slog]

I'm going to mount my new solar panel on my shed roof, it's an 80W and measures around 21" by 48".

I'm in the process of making the feet so that it stands off the roof by about an 1", and was thinking that I would lie it so that it's long edge was horizontal.

The thinking behind this was that it would be cooler this way, as the heat from the bottom of the panel has less distance to move before it escapes out of the top vent and hence doesn't warm up a lot more panel as it does so.

It also means that the panel is lower on the roof, easier to clean and less exposed to winds.

But I've seen a lot of panels mounted the other way, is this prefered or is it that they get more in a frame on a flat roof this way.?

[DamonHD]

You'll get better midwinter performance if it's vertical (actually, 70*-ish is best) and better midsummer performance from horizontal (actually, 35*-ish is best).

But maybe I'm misunderstanding you.

Rgds

Damon

[Flux]

Interesting reasoning. As long as there is reasonable space for air flow I really doubt that it makes any difference. You can only keep it to the circulating air temperature, As long as the air is not trapped to reduce the flow and let it heat above ambient I doubt that it will matter.

If it is convenient to mount it horizontally then fine, it may possibly be better.

Flux

[ghurd]

I mount them horizontal.

Less to catch the wind.

Less metal in the brackets.  If the angle is being changed, the legs on the high side will get Real Long if it's mounted verticle.

Less distance for the snow to slide down.

Really should get a lot more than 1" clearance.

Use Stainless Steel hardware, with a SS washer between the AL frame and steel feet.  Its best not to have the frame touch any regular steel.

I use lock nuts with the nylon insert.

Might need shims under the feet so the panel isn't sitting twisted.

Mount it so the box's wire entrances are down wind.

Make sure the wires have a drip loop.

G-

[Capt Slog]

Yes, I think you misunderstood, my fault for not saying it was a pitched roof.

This is what I meant....

[thirteen]

1 in clearence might not be the best if you are in a high winter snow area. You might think about adding roof support where you will walk inspecting the panels or cleaning them and a possible hand rail or tie off bracket for safty. A mesh wire around the spacing from the panel to the roof might help keep birds from building nests. Just some ideas.

[DamonHD]

Hi,

Ah, now I understand.

My panels are going vertically in that sense so as to leave more space at one end of my roof for other RE projects, but none of the installers that I dealt with mentioned anything about airflow and heating in that context, so I suspect that it cannot be terribly important.

Rgds

Damon

[DanG]

Horizontal (lower) on the roof makes for easier access and keeps panels out of the hottest air streams that rise up the roof surface like a chimney in calm air. If you don't have obstruction problems lowest is great except if they are accessible to people wanting to liberate them...

[Capt Slog]

The safety aspect of this won't be an issue, the edge of the roof is at head height so the panel is within reach for cleaning and instal.

The bird nest thing was one that I hadn't considered however, and I'll have to keep my eye on that.

[Capt Slog]

Thanks for all your replies.

They've made me realise that there were more issues than I had realised, for example...

Theft/vandalism, although it's in a closed garden, this is still possible.

Twist/flex, both in mounting the panels, and the roof itself when it's windy.

Birds nests.

The family cat walking over it!

Snow, unusual in the UK these days but still possible.