Hi all

I guess there will be a lot of solar PV questions in the next few months. We've just started to think about it for obvious reasons. Not a huge system ~1.4-1.8kWp. Doesn't seem to be many installers locally (S.Oxfordshire) so I contacted one with my plan which is as follows: install panels on a lean-to pergola which will be built to stick out onto south facing patio. We were planning to build this anyway, so can easily build it robustly to hold the weight and account for wind lift etc. Advantages of this approach (to me) are that the panels are accessible, can be at optimum angle, no scaffolding, electrics relatively simple as it's close to where I've got a spare main cable running back to the consumer unit, and we get some shading for free. The feedback from the installer was that this was highly unusual and they didn't do any installations which weren't on a roof or freestanding. I thought that we effectively had a roof without the tiles, but no go apparently. They were helpful and suggested that other installers might use a Shuco system, I checked their website, very nice, can supply custom canopies with built in pv panels, but it just screams “expensive”. Any suggestions on mounting sytems or installers to contact, feeling a bit down about the whole thing!

Cheers and thanks in advance

Mike

I think the problem is you will need the panels angled to maximise yield and doing so will only allow for 2 or 3 panels as anything more than a single row will be shaded by the first row of panels. You could mount a large frame on top of the pergola to allow an array much like you would on on typical roof, but this with an array of 1.4kWp would weigh around 140kg which a pergola isn't designed to take and in strong winds it would be very dangerous. This type of install would fall way outside the working practises set out under MCS approval.

I have the new MCS approved 240w panels and very cost effective and attractive ground mounting systems coming in the new year. With this you can have a 3.6kWp (G83 compliant) array which will suffer no shading, an optimal angle and max FIT payments.

Its a marvelous idea, you can change the angle of them with the seasons so maximising your output. The weight is a consideration, you don't say what area the panels will be, i.e panels .5m high and 6m long would be excellent, 1m high and 2m long,is more difficult. As mentioned its best to only have the panels one high or its more frame work and more uglyness.
I can't see why you should have any need for mains, what you will need is BIG low voltage cables to your batteries and inverter (build a dog kennel out side to put the kit into). Persevere with getting a tradesman or do it yourself.
Frank

So where would you put them if you don't have a south facing roof? I would like to put some type of veranda/pergola/conservatory type thing on the end wall of my house, and am started to get tempted by the FIT.

Posted By: Carbon Free EnergyI think the problem is you will need the panels angled to maximise yield and doing so will only allow for 2 or 3 panels as anything more than a single row will be shaded by the first row of panels. You could mount a large frame on top of the pergola to allow an array much like you would on on typical roof, but this with an array of 1.4kWp would weigh around 140kg which a pergola isn't designed to take and in strong winds it would be very dangerous. This type of install would fall way outside the working practises set out under MCS approval.

I have the new MCS approved 240w panels and very cost effective and attractive ground mounting systems coming in the new year. With this you can have a 3.6kWp (G83 compliant) array which will suffer no shading, an optimal angle and max FIT payments.

Couple of things that I wasn't quite clear about:
Just wanted to clarify this is not the sort of pergola that one just buys in kit form from a builders merchant or DIY store. I was thinking of its "roof area" being around 3.5 x 2.5m, I'm aware that this wouldn't be a massive array but hopefully, combined with 1-2 panels mounted vertically on a wall could get me up to ~1.4 kWp with no shading. I'm sure it's possible to engineer a pergola with timbers to take a spread load of 140kg, even if for building control purposes I get a structural engineer to specify the timber sizes. Re wind lift, I know people have pergolas with that twinwall plastic roofing that also goes on conservatories, which ought to suffer the same issues, (as should the Shuco canopies)so again, surely it's handle-able. PS could you PM me any details of your ground-mounted panels.

You can mount the modules just off horizontal if you want; you won't actually notice a huge different in annual performance compared to mounting them at c.35o. The only reson wouldn't recommen lying them flat is that they will not be cleaned as well by the rain.

Wookey and acroiso - many thanks for your comments!

Heat-pipe ETs only need to be at more than 20° from horizontal. Would that be possible in your case?

I had the top end of a heat-pipe ET up to 195 °C while experimenting but the glass was quite comfortable to handle.

Often I'd say to consider PV for heating hot water but as you're considering it for space heating in the shoulder months that doesn't really apply here.

Thanks for the replies.

Unfortunately I can't put a slope onto the pergola roof as I don't have the available height. It's ashame as I'd much prefer heat pipes because the overheat protection would be built into the tubes and because they're more efficient and easier to maintain.

I'm planning on installing PV onto the East and West sides of the outhouse roof, so can't put the tubes there. As ST mentioned, I don't want to put PV on the pergola because I do want to have some sunlight coming through. I googled Solar Pergola water heating and saw some great images of what I'm trying to achieve. I'm looking to use green oak to make it as ascetically pleasing as possible.

Unfortunately not as the manifold end is just under the roofline of the outbuilding. If I slope it down from there, we'd be knocking our heads on the lower part.

I looked into this two years ago and concluded that the best support would be a custom frame by a local steel fabricator, of which we have a suitable one close by.

There is a thread around somewhere.

Also a Grand Designs passive house in the Cotswolds used PV panels as a Brieze Soleil very elegantly. It was the one where they built under an existing barn under the Gummer Clause , now para 55.

I am waiting for next door to pollard their trees and untikI have cash available.

Ferdinand