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Forum Index : Solar : Butting solar panels up against each other to make a roof.

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Gizmo

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Joined: 05/06/2004
Location: Australia
Posts: 4802
Posted: 10:42pm 08 Mar 2020
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Heya

I've got 6 solar panels that I will be mounting in a 3X2 grid over the garden shed. The existing garden shed is 2 by 2 meters, home made with 65mm galvanised pipe concreted into the ground and enclosed on 3 sides. The roof is angled towards the sun about 15 degrees.

The new solar panels will be a 3 by 3.4 meter area. Plan was to build a new roof frame, then screw on some corrugated iron ( I have heaps spare ), and mount the solar panels on that. But then I thought, why do I need the roofing iron? Why not just build a frame and mount the solar panels onto that. Sure would make access to the wires easy, and help with cooling.

Problem is, rain water over the panels will go down the gaps between panels, and my mower gets wet.

So thinking, I could butt the panels almost together with a little gap, like 2mm, then run some silicon between the panels to seal the gap. Or I could mount them say 10mm apart, buy some sponge rubber and poke that into the gap.

Any thoughts?

Glenn
Edited 2020-03-09 08:44 by Gizmo
People say 2020 is a terrible year, with the bush fires, COVID 19, and riots. But I see it as the year we woke up to ourselves.

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Warpspeed
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Joined: 09/08/2007
Location: Australia
Posts: 3263
Posted: 11:12pm 08 Mar 2020
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The way I would do it would be to put a good heavy coating of silicone sealer along the edge of each panel, then butt them up together, but with small temporary spacers in between  so all the silicon does not get squeezed right out. Maybe matchsticks or something similar.

Just do the row of securing bolts (fitted with large flat washers) between panels up only finger tight at first, and leave the whole thing for a week or two so the silicon is completely cured all the way through.

Then just nip up all the bolts half a turn each.

It would also be easiest to pre-assemble and drill the dozens of holes first dry, without the silicone to make sure everything fits and all the holes line up.
Cheers, Tony.
 
Revlac

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Joined: 31/12/2016
Location: Australia
Posts: 344
Posted: 11:17pm 08 Mar 2020
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I had thought of doing the same thing, I have built many solar panel frames and always left a 10mm or 50mm gap between panel for air/heat to pass through.
Have thought about cutting some suitable size PVC Pipe in halve length ways and mounting that under the panel gaps to take the water away, I thing it might work, would have some PVC pipe running cross-ways as well.
Cheers Aaron
Off The Grid
 
Warpspeed
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Posts: 3263
Posted: 11:33pm 08 Mar 2020
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The pvc pipe idea would certainly be well worth thinking about. Nothing worse than a dripping roof. Smaller diameter pipe cut in half could run across the roof.

Larger diameter pipe cut in half could run down the slope, so it passes beneath the smaller pipe where they cross over. A hole could be drilled in the smaller pipe at the cross over point to drain.

Its not just rain, a steel roof can sometimes drip from condensation at night (dew).
Cheers, Tony.
 
Gizmo

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Location: Australia
Posts: 4802
Posted: 12:16am 09 Mar 2020
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I did think of the PVC pipe cut length ways, but it would have got in the way of the mounting holes where they attach to the frame, and I would have to space the panels above the frame so the PVC can fit between.

The other thing I need to consider is any seal I apply needs to be done from under the panel, as I wont be able to reach over the top side to reach the gaps.

At the end of the day, the seal doesnt have to be perfect, its not a big issue if it leaks a little, as its a open sided shed anyway.

Glenn
People say 2020 is a terrible year, with the bush fires, COVID 19, and riots. But I see it as the year we woke up to ourselves.

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Davo99
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Joined: 03/06/2019
Location: Australia
Posts: 494
Posted: 08:18am 09 Mar 2020
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I'm thinking of doing a new machinery shed with the same Idea. I can get panels cheaper than roofing iron. Just need to change the framework a little to accommodate the panels. They can be screwed down from underneath along their framework.

I have done 4 panels and just siliconed the gaps thinly, let it cook off for a bit as I always do with anything like that then just tek screwed them together.

IMHO you don't really need any width of Silicone, just like a gasket you only need it to take up the irregularities and seal them. My little covering doesn't leak at all and I don't see why a larger one would either.

I think having the frames clamped tightly together adds more strength and  rigidity. Mine are only supported on the edges and haven't had a problem because there is no room for them to move outward if they flex.  Someone said heat expansion would be a problem but so far through a summer and winter it hasn't been at all. The would all expand and contract at the same rate no matter how many were together so I don't think it would matter.

You could use foam but that tends to gradually break down where a good roof and gutter sealant which is UV stabilised I think would last much longer.
 
sPuDd

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Joined: 10/07/2007
Location: Australia
Posts: 241
Posted: 11:36am 09 Mar 2020
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Gizmo,
  you could use gap foam & polyurethane sealant in sausage packs.

Polyurethane Sealant.
Gap fill foam.
Sausage Gun.

Polyurethane Sealant for concrete, windows, roofs & other gaps that have high thermal movement. Stuff is sticky as baby poo, wear old clothes, disposable gloves, clean up with turps. Can masking tape the areas for very neat results. Notice the rolls & tubes are bulk sized, the construction industry uses this stuff everywhere. Its also cheaper than silicone 300mL tubes.

Poke the foam in to a set depth (piece of wood cut right), then pump with sealant.
It should work ...in theory
 
gadgetjack
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Joined: 15/07/2016
Location: United States
Posts: 46
Posted: 02:48pm 09 Mar 2020
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I made a roof over my old golf cart with 3 100 watt panels , siliconed together. Worked great , no leaks , and they charged the batteries when left in the sun.
 
renewableMark

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Joined: 09/12/2017
Location: Australia
Posts: 1564
Posted: 11:23pm 09 Mar 2020
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  sPuDd said  Gizmo,
  you could use gap foam & polyurethane sealant in sausage packs.

Polyurethane Sealant.
Gap fill foam.
Sausage Gun.

Polyurethane Sealant for concrete, windows, roofs & other gaps that have high thermal movement. Stuff is sticky as baby poo, wear old clothes, disposable gloves, clean up with turps. Can masking tape the areas for very neat results. Notice the rolls & tubes are bulk sized, the construction industry uses this stuff everywhere. Its also cheaper than silicone 300mL tubes.

Poke the foam in to a set depth (piece of wood cut right), then pump with sealant.


Beat me to it. Polyurethane is awesome, million times better than silicone.
Cheers Caveman Mark
Off grid eastern Melb
 
brucedownunder2
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Joined: 14/09/2005
Location: Australia
Posts: 1425
Posted: 12:36am 10 Mar 2020
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Mark, Hi mate .

I see a lot of this polyurethane stuff in those tubes . But I've not really understood WHY it's better ?

Could you and others please tell us the difference-I've used it on my concrete expansion joints 15 years ago and even though the concrete slabs have subsided, the grey stuff(was fairly expensive compared to silicon) is stiff stuck .even though the subsidence is 10-15 mm in some places.. Ok thats what I know of the difference, but why?

Bruce
Bushboy
 
sPuDd

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Joined: 10/07/2007
Location: Australia
Posts: 241
Posted: 04:35am 10 Mar 2020
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Bruce,
   a quick search shows silicone is inorganic, while polyurethane is organic. The first few references I found seemed to be financially biased towards selling silicone. Where I live in the tropics, our buildings are primarily tilt wall poured concrete or cement block. Polyurethane is used to seal the expansion joints as it grips the masonry pores very well. Its used in driveway & concrete paths as well. Leaves a very neat joint.

I use silicone when filling road joints though as silicone has a tougher skin to endure the heavy traffic & higher temperatures. Also use silicone for metal roofing seals & joints.

I'm no chemist though... just know what works here.

I like Gizmo's idea though with a pure solar roof, I'll keep that one in mind for future small structures.
It should work ...in theory
 
brucedownunder2
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Joined: 14/09/2005
Location: Australia
Posts: 1425
Posted: 04:58am 10 Mar 2020
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Just remembered  ,  the stuff I used was called "Sikaflex".   You'll know it ,expensive.  But , builders, plumbers that I used to know ,would not use anything else.  I think it's in a yellowish plastic tube ,Bunnings have it.

as I said , mine has been on my driveway concrete joins for ,gee, must be 12-14 years. Some has stripped out ,where the joint is dropped severely. but apart from that ,it's still fairly continuous, just a few petty weeds coming through ,but I hit them with one of those week wands(there magic).

Bruce
Bushboy
 
renewableMark

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Joined: 09/12/2017
Location: Australia
Posts: 1564
Posted: 09:25am 10 Mar 2020
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  brucedownunder2 said  Mark, Hi mate .

I see a lot of this polyurethane stuff in those tubes . But I've not really understood WHY it's better ?

Could you and others please tell us the difference-I've used it on my concrete expansion joints 15 years ago and even though the concrete slabs have subsided, the grey stuff(was fairly expensive compared to silicon) is stiff stuck .even though the subsidence is 10-15 mm in some places.. Ok thats what I know of the difference, but why?

Bruce


Dunno why, and I don't want to study it either, just surviving a day confuses the crap out of me these days.
I just know from experience it's better. Even submerged for years it holds solid as the first week it went in.

If I were to do a roof, lay the panels face down, run a bead around the edges, tech screw the whole lot together, screw a frame to the outer exterior of all the panels, and probably one or two diagonal braces, then get a few mates to help flipping it over and erecting it.
This would only work with a fairly small roof.

Once you did it, you'de probably come up with a better idea.... always the way... that's progress.
Cheers Caveman Mark
Off grid eastern Melb
 
bob.steel
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Joined: 27/02/2020
Location: United Kingdom
Posts: 29
Posted: 03:13am 20 Mar 2020
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My roof of the same size is 2 panels with silicon between and bolted first. I made 3 of those and mounted each two side by side with a plastic T strip down the full length. Bolts through loosely then tightened when strip right. Does not leak a drop.
Strip I got is a rubbery type 2 inches by one inch in gap. Had it for years in a roll.
I put an extra dob of silicon under T strip where it crosses over joins.
Edited 2020-03-20 13:16 by bob.steel
 
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