best angle for solar panels.
 

Hi Everyone, I have been given 6x 80 watt solar panels, but only have 2 places left they could go. I can either bolt them flat to a wall, or lay them on a flat roof. I am at 51 degrees north. The main array is set at 37 degrees slope, but takes up the whole roof. So which is best? 90 degrees or 0 degrees?

Thanks,
Nex

I assume that neither the wall nor the roof get shade and the wall faces south.

My guess is the wall - you'll get a better angle during the colder months. Is there any way to mount them slightly sloped, like put a spacer at the bottom of the wall mount?

Thanks for the quick reply. I can put spacers on then bring the angle to 66 degrees, which will be better for winter. It is shade free and exact south.

couldn't you put an adjustable mounting rack on either the flat roof or the wall?
at 51 degrees typical angles would be 36 summer, 51 fall/spring, 66 winter.
of course that means getting up there and adjusting them. smile.
do you get much snow/ice rain? I suppose the wall mount offers some protection.

I like using the PVWatts estimator from the National Renewable Energy Lab. PVWATTS version one works for international locations too.

It lets you adjust tilt and azimuth, panel attributes, and then gives projected annual output for average weather for that location.

It won't let me link (I'm too new), but if you google "nrel pvwatts viewer" the first link will be the one.

I input numbers roughly corresponding to your location and set-up and the location of wall + spacer vs flat roof didn't seem to make much different. Seems like wall would be better if snow or dust were issues.

warning: I've only used this to cross check the information my contractor gave me, and can't guarantee results. But it seemed to work well for what I was doing.

Best bet is at close to 0deg but not 0 deg. Slope it 10 deg so the rain does not sit on the panel. Any rack you use can be ballasted by some cement pads without weighing down the roof too much and 10deg doesn't present much wind load.

Point is, you will get much more light and power in the summer than you ever will in the winter so there is no point in trying to optimize for winter use.