PV roof mounting - fixing options

[The Lame Goat]

Hi fellow fasteners,

 

I'm planning a self-install solar system and the most challenging bit for me is the mechanical fixing. I'm using framed panels and need them to sit above the mushroom vents, fixed in a horizontal position, above my 4mm curved steel roof.

 

I've seen panels mounted using quite strudy aluminum extrusion for brackets, which seem like the best option if I can find something suitable, any ideas?

 

But my main question is how to fix the brackets to the roof, given I don't want to take the ceiling down and will only have access from the outside. My first thought is to drill and tap some holes and use aluminium bolts. Any thoughts on this? Have you seen this done or tried it, and did you use stainless steel bolts? What size? Any tips for tapping - I last did this at school which is some decades ago :-) ?

 

I also wondered about using adhesive - any experience or thoughts on that? What kind?

 

Also, one boat I saw had a neoprene layer between its roof and brackets which I think would be a good idea to reduce vibration. Any thoughts on that, what to use and where to get the material?

 

Any other thoughts or experiences (or links to relevant threads) welcome.

 

The panels themselves may be anything from 60cm x 110cm to 100cm x 160 cm - undecided as yet.

 

For info I have found the thread "bolts into my cabin roof" from which I take the best options to be:

1. use clamping magnets as feet bolted to a rigid frame (panel being top horizontal edge). I really like this so have ordered a magnet to do some testing.

2. Sikaflex 512 to stick the brackets down - avoids holes, messy, probably using rigid frame as in 1)

3. M4 stainless set screws into tapped holes - seems good, but does involve holes in roof

 

Assuming 1 or 2, any ideas for what to buy (and where) to make the frame (I guess extreded aluminium). Is it easy / cost effective to have something like that made up?

 

Thanks for any helpful input you can provide.

 

Mark

[Ex- Member]

I developed my own method a swivel ball array which is working extremely well on 2 x joined 250watt panels array I made up myself. No fixings on roof required.

 

I'm just now purchasing a single panel I recall 1.6m X 0.95m this will be fitted in the same way, but much simpler this time as it's just one single panel. Very simple to do. Basically making a box with a large hole in it, and fitting a piece of plywood accross the back centre of the solar panel, again with a large hole in the centre. The panel will sit on the box with an 11 inch ball inbetween set in the 2 holes.

 

You then end up with a full 360 degree swiveling panel. The weight of the unit allows it to freestand on the roof. you can add an S/S eye plate and chain the frame of the panel to it for security, that entails 4 x 6mm tapped holes for the eye plate.

 

 

I'll be building this week after next. I'll happily post step by step instructions on how I do this.

Edited September 14, 2013 by Julynian

[Nickhlx]

Doesn't it obscure the view to the pointy end a bit ?

 

Nick

 

[The Lame Goat]

Thanks Julynian - I saw this (or something almost identical) on another thread some while ago. It looks ingenious and very effective for moving the panel, though unless you auto track I don't think tilting is worth it (only 10% more than flat mounting apparently). Auto tracking would be more effective and could probably be added to your setup using linear activators and some purpose built controllers I saw from the states at about $28. However, for me, using bigger panels should do the trick and be a lot simpler/more reliable!

 

How does your system cope in the wind? I would think that relying on weight alone is not good enough. You could probably fit some magnets under the box, but would need a way to hold the panel down as I assume the ball is just resting in place.

 

It does look great! Good luck with it.

 

BTW your location says Dorset DT6 but there are no canals there! You marooned? :-)

 

Mark

Edited September 14, 2013 by The Lame Goat

[Ex- Member]

Doesn't it obscure the view to the pointy end a bit ?

 

Nick

 

 

Believe it or not, No LOL

 

It probably looks that way though

 

When we cruise the panel will be set flat so I can see clearly over the top of it to the pointy bit. The brackets for doing that will be here next week, 4 S/S eye plates fixed to the roof and 4 to the array corners will be connected with heavy rubber Tarp straps tensioned to keep the panel flat when cruising or in high winds. Currently though, in the photo you'll notice the array is set to the Left. When the panel is tilted and flush to the side of the boat I can see clearly forward that way too.

 

The second single panel will sit the other side of the Green chimney but will be set lower so I can see over that one too.

Edited September 14, 2013 by Julynian

[Nickhlx]

OK - I assumed you laid it flat on the roof when underway, but if you can cruise with it in place, even better... not that you need the power, I guess, when the engine running..

 

Great and simple idea which I may use myself as well... Still thinking about a tracker though

 

Nick

[Biggles]

I didn't bother with the movable stuff. I won't go into too much detail as its pretty boring, but I made or rather had made some C shaped brackets but a square type C like a capital E without the center bit. I then tapped the roof and used 6mm SS security screws.

 

The reason I decided not to make them movable is because I just cant be assed for the extra 10% I might get.

 

Not that mine can't be removed but the way I have then set up it would take a fair while to unscrew them assuming you had the right security coded bits.

[Ex- Member]

Thanks Julynian - I saw this (or something almost identical) on another thread some while ago. It looks ingenious and very effective for moving the panel, though unless you auto track I don't think tilting is worth it (only 10% more than flat mounting apparently). Auto tracking would be more effective and could probably be added to your setup using linear activators and some purpose built controllers I saw from the states at about $28. However, for me, using bigger panels should do the trick and be a lot simpler/more reliable!

 

How does your system cope in the wind? I would think that relying on weight alone is not good enough. You could probably fit some magnets under the box, but would need a way to hold the panel down as I assume the ball is just resting in place.

 

It does look great! Good luck with it.

 

BTW your location says Dorset DT6 but there are no canals there! You marooned? :-)

 

Mark

 

Hi Mark

 

Youll be surprised how much more energy you can glean by tilting AND swiveling the panel. I've done several tests between flat and S/tilt and I glean between 5 and 9 additional amps when pointed in the sun's general direction on a btright day. We only need to adjust every couple of hours, because it only needs to be in the general direction to make this gain. A panel on a boat roof that just tilts side to side though will not make such a gain, and that's where the 10% figure I would say is coming from.

 

We also line up the panel to catch sunrise, on several mornings over the past 3 weeks we've woken to almost full batteries and at float charge by 10.30

 

The array weighs 49 kilos in total. I have set up a system of heavy duty rubber straps to set the panel flat for high winds and cruising.

 

We're from Dorset but moored near Devizes.

 

Good luck with what ever option you go for though. You can't beat this solar energy though. Now 23 days solely on 500 watts of solar. Happy Days LOl

Edited September 14, 2013 by Julynian

[AndrewIC]

I drilled and tapped some holes in the roof earlier this year for mushrooms, and used stainless steel countersunk hex pin head security screws. Being of a paranoid disposition I put a lock nut on the inside as well, although I realise you won't have that option. I would suggest using proper size tapping drill bits and good quality taps, not ones from a cheapo set as they seem to be made of finest cheese. Rocol makes the cutting operation much easier as well.

 

ETA: as noted in the other threads, this is only really good for small holes or thick roofs. My roof is almost as thick as a M5 nut, but anything bigger wild be struggling.

Edited September 15, 2013 by AndrewIC

[Jambo]

Looking at the PVGIS calculator, and just considering inclination, the annual difference in generation you get between flat panels and panels inclined at 38 degrees (the optimum inclination for London latitudes) the difference is about a 4% increase in generation across the year. But from November to January you get a 30% increase and from October to February you get a 25% increase.

 

Just for fun, if you had fully automated two axis tracking you'd get 41% greater generation across the year with a 68% increase November to January and a 60% increase October to February but I don't think Julynian is going to spend his whole year up on his roof shuffling his panels round to follow the sun...

 

Thankfully technology is catching up and soon he'll be able to buy robots to do this for him (video)...

[Bee]

There are such things as rivet nuts or blind nuts, screwfix used to do them but the best source is some sort of industrial factor or just have a google search.

Richard Cooper

[trackman]

Those increases in power in winter sound impressive.

However, the power to be had in winter isn't great surely? That being so, even a 60% improvement may not be much. 1.6 times almost nothing is still pretty close to nothing.

How much is tilting these panels really worth?

[Ex- Member]

Those increases in power in winter sound impressive.

However, the power to be had in winter isn't great surely? That being so, even a 60% improvement may not be much. 1.6 times almost nothing is still pretty close to nothing.

How much is tilting these panels really worth?

 

On a nice clear winter day with decent light then quite a lot. We've found so far the worst weather for solar is overcast Grey cloud. In overcast white cloud and with panels directed to the brighter part of the sky, ie sun behind cloud, we get between 5 and 8 amps more than the panel laying flat. We've tested this numerous times now. In clear sky tilted we can get well over 10 amps extra.

 

Bear in mind our array swivels and tilts, so can be aimed in the suns general direction.

 

In winter the sun is much lower in the sky. Our panel tilts enough to stay pretty much on target, then taking into account we can track the sun every couple of hours or even shorter, then significant gain can be made.

 

Most panels on 95% of the boats I've seen don't tilt enough for the low winter sun, let alone swivel to follow it through the day.

[Jambo]

Those increases in power in winter sound impressive.

However, the power to be had in winter isn't great surely? That being so, even a 60% improvement may not be much. 1.6 times almost nothing is still pretty close to nothing.

How much is tilting these panels really worth?

 

This is true, but I'll take it. Especially when the alternative is burning diesel in a generator or engine at... 30% efficiency?

 

The key of course is to drive your electricity demand down as far as possible, but being able to satisfy that demand as far into winter as possible without running the generator is quite important to me.

[Ex- Member]

 

This is true, but I'll take it. Especially when the alternative is burning diesel in a generator or engine at... 30% efficiency?

 

The key of course is to drive your electricity demand down as far as possible, but being able to satisfy that demand as far into winter as possible without running the generator is quite important to me.

 

And very satisfying.

 

There's something pleasingly surreal about gleaning energy in such a way after a lifetime of taking it so for granted, and the money saving aspect really is a no brainer. It really surprises me how few boats have solar. Probably not members of CWF LOL

[Grace and Favour]

I've fixed my panels on an horizontal fixed plane above the level of the mushrooms, using stainless steel brackets (I had fabricated because I found nothing suitable ready made).

I fixed these to the panels using a unique 6mm security bolt, and fixed the brackets to the roof (with neoprene gaskets) using security bolts into stainless steel Rivnuts. (All the work was done externally)

 

 

I've still got the line drawings for the brackets and can send a copy if required.

 

Must admit - am very happy with the end-result.

Edited September 16, 2013 by Grace & Favour

[Ex- Member]

I've fixed my panels on an horizontal fixed plane above the level of the mushrooms, using stainless steel brackets (I had fabricated because I found nothing suitable ready made).

I fixed these to the panels using a unique 6mm security bolt, and fixed the brackets to the roof (with neoprene gaskets) using security bolts into stainless steel Rivnuts. (All the work was done externally)

 

 

I've still got the line drawings for the brackets and can send a copy if required.

 

Must admit - am very happy with the end-result.

 

Very neat job, you can't beat good over engineering.

 

Out of interest how much was each bracket in stainless steel and labour cost. If someone could knock those up at a reasonable cost they would sell to boaters for sure.

[The Lame Goat]

I've fixed my panels on an horizontal fixed plane above the level of the mushrooms, using stainless steel brackets (I had fabricated because I found nothing suitable ready made).

I fixed these to the panels using a unique 6mm security bolt, and fixed the brackets to the roof (with neoprene gaskets) using security bolts into stainless steel Rivnuts. (All the work was done externally)

 

[photo snipped]

 

I've still got the line drawings for the brackets and can send a copy if required.

 

Must admit - am very happy with the end-result.

 

Wow. Very nice and thanks for the photo. I may well go with this approach (still considering various options).

 

What size are your panels?

 

Did you slide the panel into the backets after fixing? - wondering how feasible with a large panel (say 2m x 1m)

 

Thanks for offer of drawings - will be in touch if I decide to take this approach. I'm glad to hear of your success with Rivnuts. The other thread contains a scarey cautionary post about this, so as I'm not experienced wonder if you already had expertise, had any problems etc?

 

What roof thickness - any problem sourcing rivnuts with large enough grip range?

 

For over mushroom solution I'm also considering building a top box with panel as lid so not sure yet if I'll use brackets & rivnuts.

 

Mark

[FidoDido]

I went for 4 clamping magnets. Each is equiv to 9 kilos IIRC, but is quite small - fag packet sized. Very difficult to budge it - if you tried to pull it off, you would assume its bolted down. You can move the panel by pulling them off the roof 1 by 1. It would certainly withstand any sort of wind etc. I didnt like the idea of holes in my roof.

[George94]

Another approach would be to lay the panels flat, and have a large reflective sheet mounted behind them, but in away that would allow it to be moved easily to follow the sun.

 

This would actually increase your solar capture, and for little outlay. The panels could be attached very securely using patented Scrote-Pruf fixings.

[Mat B]

Another vote for magnets:

 

 

 

[The Lame Goat]

Another vote for magnets:

 

 

 

Looks good - can you detail what you have here?

 

Thanks, M

[Ex- Member]

I have a couple of those magnets, they're on ebay used for TAXI roof signs and learner car signs. Really strong magnets rubber base, I must fine a use for them LOL

[peterboat]

You can buy from screwfix a self cutting bolt roofers use them the end bit is a drill then its threaded if you bolt it down on a bed of sicoflex their will be no leaks and theft is hard work to its what I did on my old boat

 

Peter

[Jambo]

If anyone is interested in the magnet approach then http://www.first4magnets.com has a dazzling array.