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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

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Renewable Energy: PV panels - wind resistance.

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    I have been considering fitting PV panels on our roof, metal roofing at 45º pitch.

    One concern however is how they will stand up to the wind. We are almost on the sea shore but really not that exposed, the last two winters we have had storms where wind speeds have reached 38-42m/s (about 85-90mph in old money).

    I am just wondering how panels will stand up to this sort of treatment over the long term?

    I must admit that I haven't taken a close look at the panels and mounting systems so don't know how secure they are and whether anything is likely to break or work loose over time.

    Can anyone with first hand experience put my mind at rest?
    • CommentAuthorwindy lamb
    • CommentTimeFeb 25th 2014
     
    My neighbour has PV on his roof which are still there after 90mph winds. His wooden stable block blew off it's foundations and was turned upside down. So you must be able to secure the PV panels securely!
  3.  
    brackets and frame etc. should be designed for wind and snow loading relative to location. Uplift seems to be the stronger force.
    Info on how to do the calc. is out there on the web.
    Rule of thumb is mounting brackets about ever 1m for standard bars. Most seem to push it to nearest rafter so maybe 1.2m .
    You can get stronger bars and bracket ever 800mm if you're concerned.
    Other option is the in the roof sys. which would be less exposed
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      CommentAuthorSteamyTea
    • CommentTimeFeb 25th 2014
     
    Posted By: Chris P BaconCan anyone with first hand experience put my mind at rest?
    They use quite large screws into the rafters. So as long as your roof timbers are in good condition and secured to the walls you should not have a problem. Have not heard of any coming off down here in the last few weeks and we have had 100 MPH winds.

    The main thing to worry about is that the fitters really do screw into the rafters, I have seen them screw into the batten.
    If you have concrete tiles they can lift these, slate is a problem.
  5.  
    Super - thanks for the responses.

    I've had a quick look up in the attic and the rafters indeed are at 1.2m spacing. I'd be perfectly happy with the mounting bars being screwed them with long fixings.

    My concern was more so with the fixing of the panels onto the mounting bars and whether there is any scope for them to work loose over a long period from the annual battering they will get. I guess the judicious use of some nut lock would help in that department.

    Have to figure out now what the max. we can feed into the grid is. The house has a 3 phase supply currently with a 16A fuse on each phase, we can increase that to 20A or 25A but our standing charge goes up with each increase in fuse size.

    Based on the area of roof available we could fit a maximum of 10.2kWp but that would be in an inverted U shape around a large central dormer, I presume the best is to split it in 3 sections with an invertor on each so that when either of the two legs down the side of the dormer has some shadow on them we loose as little output as possible?
  6.  
    Most panel clips have thread seal already on bolts etc. with quarter turn and lock pins that drives into rail
    or fork like design that opens out into rail channel lugs with spreading pin driving into back of rail.
    Also anti-slip bolts or lug fixed to bottom panels above lower bars to stop potential of it sliding down in the event of lose clips
    16A per phase would be allowed, 3 inverters or one 3 phase inverter . (12kwp)
    anything over 16A (G83) would need checking with DNO prior to installation
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      CommentAuthorSteamyTea
    • CommentTimeFeb 25th 2014
     
    What are the rules in Sweden.

    We always used the Wurth fixing system, but they are pulling out of the PV market.
    • CommentAuthorjamesingram
    • CommentTimeFeb 25th 2014 edited
     
    I've used Schuco , Schletter and Sen sol50 all seem pretty robust and well design ( if not a little over designed)

    we have a strict rule of only using products beginning with S but I've yet to go to Sweden :bigsmile:
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      CommentAuthorSteamyTea
    • CommentTimeFeb 25th 2014
     
    Posted By: jamesingramwe have a strict rule of only using products beginning with S
    Sticky Tape
  10.  
    Posted By: SteamyTeaWhat are the rules in Sweden.

    I don't know of any restrictions demanded by the grid operator here. I think the grid is fairly robust and every electricity customer here is on a 3 phase supply.

    There are new tax credits being introduced here for domestic PV production with the max. allowable for that being 20kWp. There is no feed in tariff for PV here you just have to shop around the various electricity suppliers to get the best price for what you feed into the grid and then the tax credits are supposed to help bring you to a situation where it is financially comparable to nett metering (which is what they wanted to introduce here but is supposedly against EU rules).

    There is a new build a few miles away from me which has had a large system installed on it's roof in the last few weeks, I must stop the next time I am going past and count how many panels they have in total.

    Looks like I will be perfectly fine with a system of around 10kWp, I just have to see if I have enough pennies left in the wallet.
    • CommentAuthorJeff B
    • CommentTimeFeb 26th 2014
     
    We are near the west coast of Pembrokeshire which has taken a battering over the last few weeks. My 21 panels are still on the roof and I haven't heard of any coming off in our locality. I know someone in the village whose summerhouse was destroyed by the wind. It is the same model as ours and is a substantial beast with 35 x 150 T/G walls! Ours is ok thankfully, probably because I was a bit OTT with internal bracing bars etc!
  12.  
    Cheers Jeff, glad to hear you house is still standing!

    Posted By: Chris P BaconThere is a new build a few miles away from me which has had a large system installed on it's roof in the last few weeks, I must stop the next time I am going past and count how many panels they have in total.


    I took the scenic route home this afternoon to count up how many panels that new build has and as best I could figure they have 63 panels in total in 3 sections of roof on a T shaped building. Looks a dog's dinner to be honest, it's a huge log cabin with green felt shingle roofing and a huge expanse of PV arranged in uneven rows facing the main road. How they ever got planning permission I'll never know, the only saving grace is that it is in an area mainly made up of summer house which was a general blot on the landscape to begin with.

    In any case I recon 63 panels would be around 16kWp in total so I should be fine with a little under 10kWp on the rear of the house away from the road and laid out symmetrically! :cool:

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