Flat on a Flat roof

[andyyoyo]

Being a bit of a numpty when it comes to PV installs, I have a question: I have a flat roof 5m x 4.8m SE facing, Flat to the roof is not so good I know, but I can get away with 12 panels. If I were to use maybe 15 degree mounts I am guessing I could get away with maybe 8 panels.
If only for the sake of asthetics the flat arrangement will keep the neighbours quiet, its on my own property, & have easy access for the regular cleaning which I know would be required. I might be looking for some assistance with signing off if I go ahead, if any of you chaps might be interested (am NICEIC Approved, attended their PV course, but like many never got to the MCS stage for the usual reason).

 

[SpitfireW'sale]

Be careful to check the warranty conditions of the panel you plan to use as many will void the warranty if mounted on a pitch shallower than 5 degrees.

We have supplied ET Solar for a flat install before which they agreed to warranty, but only after details of the site and installer etc. were sent to them.

 

[andyyoyo]

Good point, thanks, I'm not too concerned as it only for myself. The tricky bit for me will be finding the best method to fix to the roof

 

[SpitfireW'sale]

Be happy to help with a design for the system, feel free to send over some details if you would like us to have a look at it.

edit: apologies just re-read your post, we only supply MCS companies, but will be happy to help out on the design in conjunction with whomever you find to do your install. Technically the MCS installer who is signing off the work should carry out the installation works as well

 

[danesol]

Being a bit of a numpty when it comes to PV installs, I have a question: I have a flat roof 5m x 4.8m SE facing, Flat to the roof is not so good I know, but I can get away with 12 panels. If I were to use maybe 15 degree mounts I am guessing I could get away with maybe 8 panels.
If only for the sake of asthetics the flat arrangement will keep the neighbours quiet, its on my own property, & have easy access for the regular cleaning which I know would be required. I might be looking for some assistance with signing off if I go ahead, if any of you chaps might be interested (am NICEIC Approved, attended their PV course, but like many never got to the MCS stage for the usual reason).

To be fair, this can be seen as an advantage as you could mount the PV panels on an adjustable frame, so you could change the angle for different times of the year, a client of mine does it with their installer and it works a treat for them !

 

[andyyoyo]

Thanks for the replies, will sort out some details in the next day or so any advice is much appreciated!

 

[Worcester]

Unistrut produce a mounting system for solar panels Plus if you look closely at most panel mounting fixings theyr are nothing more that pastic zebs on an aluminium version of unistrut.

If flat, you'll need to find a way to hold it down (wind) / or up off the roof, you could either use ballast or bolt the frame to the side of the building.

Before everyone and their dog cries foul, a) unsitrut produce a solr mounting systen and b) 25 years of north sea weather and storms, and the satelliete dishes installed that way are still as solid as ever ..

Just remember to use plenty of coats of galvafroid on the cut ends.

Solion mounts at 5 degrees back / back (east west) may work well also

 

[solarfred]

Cheapest option for flat roof if it is felted? ... is to screw down battens and felt over. Then get some rails and screw this down to the batten which gives you the ventilation gap. Fix panels to the rails as normal.
If you want an off the shelf ballast system then Clenergy do a good quick system that allows you to lift the panels to get underneath and all their stuff is anodised. Cost wise it is the same or better than others.
They also have jacking legs down to 10 degrees which I have used and simple to install.

 

[andyyoyo]

Thanks, its a new rubber roof, I dont mind screwing rails to it if anyone can recommend some self sealing fixing bolts

 

[Gnarly]

To be fair, this can be seen as an advantage as you could mount the PV panels on an adjustable frame, so you could change the angle for different times of the year, a client of mine does it with their installer and it works a treat for them !

Read more: http://www.electriciansforums.net/p...forum/66818-flat-flat-roof.html#ixzz2BCjFM97C

One thing you need to watch out for with rows of tilted panels is shadows. With very low winter sun in UK, this is a major problem as any shadow from the row in front will kill the output. I read somewhere that for no shading between 9am-3pm the inter-panel distance needs to be about 5x the height. E.g. lift the back of the panel up by 20cm, means you need 5x20cm = 1m horizontal distance to the start of the next row !!!

 

[Worcester]

@Gnarly, however just bear in mind that you also generate diddly squat in winter, so you may be better off closing up the rows to get more output from the saem space in summer.

We have some flat roof sites with the panels (992m wide) in landscape 25 degrees and the rows set @ 2m front of row to front of row precisely for that reason, the extra ooutput from the larger number of panels in summer more than makes up for the shadowing in winter - it's a balance, and you need professional design tools to optimise it for your specific site.

 

[SolarCity]

it's a balance, and you need professional design tools to optimise it for your specific site.

Agree 100%. On some sites it may be worth closing the gap to get an extra row in, for example. Or some sites will benefit from less rows yet a steeper mounting angle. It is worth spending some time trying different alternatives.

 

[andyyoyo]

Yes its definately all about compromise, realistically I will have to lay the panels virtually flat,partly because I dont want to upset the neighbours (or the wife!)

 

[Worcester]

in which case, go for 5 degrees, you'll be please (subject to shading) to see it generating at 5 am and 8pm in the summer as the sun goes all the way round! You could try the schletter Fixz-& which adds about 5 degrees just using a thicker rail, or the solion sunmount zero ballast (british made c**p website, good product). (blown plastic interlocking system)

 

[andyyoyo]

Ta, where can I find prices for the Solion mounts? It is a pretty dire website..

 

[Worcester]

Give them a call directly - Loey Salam - Residential Project Manager | [email protected] Tel: + 44 20 7815 7694 They are knowledgeable and helpful the website is attrocious though!

 

[solarfred]

How are they actually secured?

 

[Worcester]

They aren't they that's the advantage of them - they don't need any securing, there again, that depends how light fingered your neighbours are!

 

[solarfred]

Go on give us the science?? Gave up on the website.

 

[Worcester]

Aerodynamics, design it correctly and you can get the airflow to suck it onto the roof rather than blow it off.

 

[Earthstore]

I have seen this type of system, but not convinced about it myself, although I do understand how they should work.
How would it cope with gusty winds that change direction?
What would happen if we had a repeat of the wind in 1987?

 

[andyyoyo]

Thanks, will have to follow this up next week, am off to work in france- where I believe they might just still be getting their 43 cents per kw...