best arrangement for solar on a flat roof.

yp70479

I already have solar on my south and west facing roof, but also have a south facing flat roof, approx 2m x 5m. Can any one suggest a system and panels that would optimise solar on this area. I know you need to leave a bigger gap at the edges of the rood (up to 500m) which means that most solar panels are now to big to go up there. Any suggestions welcome. 

Screwdriva

I recommend Van Der Valk flat roof mounting systems, which rely on ballasts to weigh the mounted panels to the roof. If the roof area can accommodate landscape orientation panels, I recommend 2 X Sharp 590W bifacial panels (L 2.3m X W 1.1m each).

If you don't mind coating the roof in a white/  light grey colour, you will see an additional 10-15% in albedo gains in UK conditions. 

Ectophile

Make sure you check that your roof is strong enough to hold the weight.  You may need to find out where the roof beams are if the roof covering isn't very strong.

CuparLad

Also consider that your flat roof may not last as long as your solar installation so what are the costs of reinstallation if you need to recover the roof.

yp70479

Thanks everyone. I've just ha the roof replaced so it should be strong enough and good for another 15+ years. Screw driver - any chance of being able to go portrait to squeeze another panel on? I'd probably need smaller/shorter panels and they all seem so big these days

Martyn1981

There are quite a lot of panels that are approx 1.8m by 1.1m (around 440Wp). So potentially four of them if mounted flat, but that would be pushing the limits on the edges, and you'll need to clean them quite often as dirt and debris (leaves) won't wash/blow off easily.

Screwdriva

yp70479 said:

Screw driver - any chance of being able to go portrait to squeeze another panel on? I'd probably need smaller/shorter panels and they all seem so big these days

Only a PV surveyor can answer that for certain after measuring the dimensions accurately. The larger 2.3m Sharp bifacial panels I referenced generate > 35% more power than the more conventional 1.75m panels, so worth a discussion with the installer to maximize generation. 

Here's an image of the installed and optimized panel adjacent to a the conventional 1.8m alternative (taken in December when the sun was at its lowest)

ed110220

CuparLad said:

Also consider that your flat roof may not last as long as your solar installation so what are the costs of reinstallation if you need to recover the roof.

Panels on flat roofs typically aren't attached but just sit there, so taking them off and putting them back if the roof covering needs replacing shouldn't be much of an issue.