Given the wealth of knowledge in this place, what flexible panels should I be using on a slightly curved fiber glass roof and any tips for installation (heat) would be a appreciated.  Thanks

There maybe some quick answers to get you going:

Advanced Search: "Installing flexible solar panels" brings up 9 threads.

Thanks, so leaning to these due to a Will Prowse test..https://au.renogy.com/products/solar-panels/flexible-solar-panels/

Actually I was a bit surprised that you selected flexible based on a Prowse video. Was it this one https://youtu.be/onMZ_dRSFUs

He sells both types but was very scathing about the flexibles

Looking at the claimed efficiency. That's a lot better than a proper glass panel!

A glass panel at best is around 170 watts per square metre, but typically around 150 watts per square metre.

My small glass panels with an extremely efficient system where I am getting blood out of a stone, Victron MPPT controller, 6 & 4awg wiring, produce less than this.

If a flexible solar panel is stating more than 150 watts per square metre I would suggest they are using a rubber ruler & sky hooks!

Yes Will did not think much of them but does like Renogy, others on the diy forum seem to think there Ok. I have to go Flexible, curved roof....

Weven wrote:

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Yes Will did not think much of them but does like Renogy, others on the diy forum seem to think there Ok. I have to go Flexible, curved roof....

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 Hi Weven 

I have not used them myself, but a person who fits solar panels on vans for a living, did report he had stopped using them because of the very high failure rate. He went back to using smaller normal panels to accomodate any curvature. He got sick of replacing various brands of flexible panels. 

But your choice !

Jaahn

solar4rv, not cheap but good gear.

Also look at the cell interconnections as they are one of the main points of fail. The panels move/expand and this puts pressure on the interconnections and they can fail.
There's a new type of panel out now that instead of having a few interconnections they have many for each cell, more interconnections more redundancy.

You also need good advice on how to mount them if your going for a fixed installation, I was passed by a car the other day that had a flexible mounted between
to roof rack bars, it was flapping up and down in the middle of the panel at a great rate, it would not last long, no doubt he will be saying flexibles aren't any good or blaming the panel supplier
for selling him a dud panel. Panels need to be mounted securely to preventing them vibrating as continual flexing will fracture the interconnections between the cells but the mounting medium must also have enough give in it to let the panels expanded and contact with out bulging or again the flexing will eventually cause fatigue cracks in the interconnections.

It is interesting that caravanner's seem to have some many problems with flexibles but yachties  don't. Probably due to most yacth panels being secured with adhesive to the fibre glass. I have read of some who have had issues blaming the panels but then admitting they didn't fit them as advised as they new better. I was also following a caravan the other day and you could see the aluminum skin on the back of it moving, again gluing panels to a aluminum roof that has give in it would not be a good idea. 

-- Edited by LeighW on Thursday 7th of January 2021 10:36:20 AM

-- Edited by LeighW on Thursday 7th of January 2021 10:37:07 AM

There are not many yachts doing thousands of km at 100kph, let alone with a headwind.

Looking out our window, of the few hundred yachts they appear to all be using solid panels.

You don't see many cars surfing down 30 foot waves either, boats have to contend with rough weather rough seas and and it does get windy in storms unless they are only fair weather sailors:)

The yacht pictured is a typical example, I wouldn't install flexibles where they have the panels either as you would need to make up frames etc to mount them and you would still get flexing due to the awning tubing, easier to use glass panels in that instance.

I know of those with flexibles on a crossover units that have done 1000's of Km on tracks that are called roads that most on this forum wouldn't even dream of taking a supposed off road caravan, they have no issues with them.
I have just installed two on my cross over unit and don't expect any problems either as considerable thought and effort has gone in to the way they have been mounted.

-- Edited by LeighW on Saturday 9th of January 2021 12:50:31 PM

-- Edited by LeighW on Saturday 9th of January 2021 12:51:49 PM

185 watts / 1.520 x 0.68  = 180W/m², I would question that.

Is your roof a simple curve or complex curve (2 directions).

Have you thought about redundancy if one panel fails.

Also wiring 2 panels in series using a MPPT controller so you have power earlier in the morning.

A dark surface will warm up the caravan more than if there is an air gap.

Weven wrote:

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Have been told by a person that has some experience in the Solar game to do this, sounds like it could work. Using Core Flute with this tape, tapesonline.com.au/products/double-sided-white-butyl-tape to Fibre glass, then same tape, panel to Core Flute. Thoughts?

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 Core flute is recommended for some panels especially if the panel requires ventilation, other panels come with their own frames and some have an adhesive backing.

What you need to consider is the material you are mounting then on, if the substrate your mounting them on has a different rate of expansion to the panel then I would not be using adhesive backed panels unless they have been expressly designed for the purpose.

The idea of the core flute is it has a similar expansion rate to the panels and also spaces them for ventilation, as the panels expand so does the core flute, the channels in the core flute allow the the two sides of the core flute to expand at different rates so if the mounting surfaces does not expand as fast as the panel there is some give in the core flute to absorb the stress, this together with the give in the double side tape keeps stress in the panel to a minimum. I have seen pictures where panels have been installed on a flat surface and the edges sealed, the heat from the panels has caused the air under them to expand and cause bubbles to form in the panel putting consider stress on the panel. Same with panels glued directly to aluminum skins, the aluminum does not expand as much as the panels so they buckle and again stress cracks form.

Even when mounting with core flute you need to consider the lenght of the core flute strips, they should be not longer than the width of the panel, if panels are mounted across the van then the core should be cut into reasonable size strips and have a small gap between them. For normal sealed road use strips should be positioned under the centre of the solar cells. If you intended to travel on rough roads then the strips should be positioned directly under the centre of each row of cells and also under the interconnections of the cells ie where one cell touches the next cell which will be in the middle of the other strips. Strips should run opposite to the direction og travel to prevent peeling. 

The leading edges of the panels facing the oncoming airstream should be secured to prevent peeling and lifting of the leading edge, whatever you use to secure the edge should not prevent the panel being able to expand and contract and should not put stress on the panel. In my case I decided to use sail track, the edge of the panel sits in the sail track slot with the top edge of the track just resting on the panel, this allows the panel to expand and contract and prevents the edge lifting.

How much do the panels expand, think of poly carbonate roof sheeting, they should be mounted on foam sheets to allow the to move, the fixing screws for each sheet cut a considerably bigger hole in the sheet than is required for the screw. If you try to just screw them down using ordinary screws the sheets will buckle as they get hot.

Mounting flexible's with screws using the eyelets provide on some panels is also not a good idea unless there is considerable looseness to allow the panels to expand and contract.

I have a Renogy 100watt flexible, that I have owned for 3 months, I went with it, after a very concerted use and review, from an trusted source, on W...camps( I cannot name the forum properly here as when ever I do, it, the comment gets deleted). It has been outside on the roof on my landing, to charge a 20ah lithium battery, that runs my security lights. But I bought it to put on my bicycle camper, as where it has to go, the roof of the camper is curved there. I get nearly 6amps an hour, and am very happy with it. It doesn't seem to worry about the 70 degree temps up there. I am sure you could walk on it as well. They do also recommend them for boating.

Weven wrote:

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The roof is a simple curve, thank heavens.

"Also wiring 2 panels in series using a MPPT controller so you have power earlier in the morning."

Yes, MPPT and series is my thoughts.

_____________________________________________________________________

Well I have taken the plunge X 5......

solarcampingaustralia.com.au/product/solar-panels/semi-flexible-solar-panels/100w-semi-flexible-shingle-solar-panel/

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Hi Weven 

Noteing you bought x5 then I guess you will run them in one string of 5 into a MPPT controller. You will have to be selective on the brand and specs of the controller  as the OCV voltage will be over 100V. I hope it works out well for you. At $ 1375 for 5 panels that is a substantial investment. 

Jaahn

'x5' is a good idea, you can keep a spare panel as back up & wire the other 4 panels as 2 x 2 (2 series then in parallel).

Otherwise it's 5 in parallel so you won't get the best low light feature out of the MPPT.

5 in series & you will kill the MPPT with over voltage.

Most DC-DC chargers are dumb chargers, maybe the redarc is different, but I do not know. A quality solar controller has a smart charging output so you will not kill your batteries. I am actually looking at feeding a 12 to 24v DC-DC charger into my solar controller.

Let's put aside the odd number of panels for the moment (another safety issue is too many panels in series is simply dangerous voltage territory, you do not want to go there)

185 watts / 12v = 15.4amps x 5 = 107.8amps. you could parallel wire a handful or Victron DC-DC chargers to get to your amperage. I have 2 in parallel.

A MPPT solar controller will adjust the voltage to get the maximum amps to charge the batteries (I can get up to 11.3amps out of my 120 watts of panels, why I upgraded from a 10amp to 20amp controller).

But the controller can't push out any more amps. Ideally you want your controller to have some headroom. Under load & in hot weather they will throttle down, lower output so they don't overheat (you can add passive or active cooling to help, I've added a pile of additional heat sinks front & back).

So you are looking at a controller of 150amps output. The largest output Victron do is 100amps. This should be ok as I doubt 5 panels are capable of over 100amps out of the controller. To be safe reduce by 1 panel until you have some satisfactory measurements.

So I think you should go with 4 Panels in parallel (or 2 in series x 2 in parallel), into a 150/100 controller, as least to start with.

One more issue if you have 4 or more panels in parallel you will need some serious wiring to the controller (resistance is the total length of + & -) & the controller should be as close as possible to the batteries.

If you haven't already got a quality DC clamp meter, get one so you can safely measure your system, otherwise it is the blind leading the blind!

Just realised you have gone with a 100 watt panel instead of a 185 watt panel.

So a 150/70 controller will be ok.

Weven wrote:

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J, hope I am correct here. Redarc Bcdc 12v 25a Voc 17.5-28v, panels wired in parallel Voc=21.4.

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Hi Weven 

This is a quote from Redarc "For most applications, the BCDC1225D is suitable for battery bank sizes of 75-200AH. For higher capacity needs of over 200AH, REDARC recommends the BCDC1240D." What battery capacity do you have ?

Hmm might not be most suitable ! Your 5 panels of 500w in parallel could put out about 26+up to 30A. I have no experience of Redarc gear too XXy for me. The specs do not specify if the 25 or 40A rating is into or out of the controller ? But it could mean that controller will be limiting the current in some conditions. I guess it should do that to protect itself.  

But note the other comments about the size of the solar connections and in particular of the controller to battery as it will pass even more current than the panels in MPPT mode !

Jaahn

My setup. I just did not have any room as we are only in a car. So panels, controller, wiring are each the best I could build.

I didn't want to nobble the setup with an under performing link in the chain.

You have invested a lot or money on panels so there is no point throwing away 10 - 20% of their output on an underperforming controller & being a cheap skate on the wiring.

MPPT controllers are "rock stretchers", they do seem to find every last amp, more so early in the morning, but you do need 2 panels in series to get the best out of the controller.

I have just looked at the 100w solar panel link. It only has solar cells in strings of 33.

36 cells is what you really want, so your voltage is going to be at 91.6% of what's is generally considered the standard. So you are off to a less than idea start with 33 cells.

You do not want to loose any more voltage in your setup.

With MPPT you need 5 volts above the battery voltage for the controller to fire up in the morning. So it will be more difficult if you use these panels in parallel.

At least with a MPPT putting 2 panels in series your voltage will be 91.6% of 2 panels so that will ok.

So now it is 2 in series & then in parallel so a 100/50 controller will be ok. 100w / 12v = 8.3amps x 4 = 33.2amps MPPT controller output.

There are plenty of fake MPPT controllers out there so be very careful what you buy.

Looking at the size of the panel at 1.070 x 0.510 = 0.545m²

At 150 watts per square metre I think one would expect to get 81.4 watts out of the panel.

81.4 watts x 4 = 327 watts for a 4 panel setup. Realistically expect about a maximum of 27amps out of the controller.

A 100/30 controller does not have enough headroom.

Newer solar panels are now more efficient  and 200 Watt panels of good quality run about 1.1 Sq Mt area.

Alan