Flexible solar panels - pros and cons?

[starman]

Ditto all those concerns. I must say it is already starting to do my head in wading through the pseudo scientific gobbledygook about panel designs - let alone find and compare sizes and prices.

I think we need a 'what solar panel?' Magazine or website.

[TheBiscuits]

One of the problems I'm facing at the moment is working out what size would fit best around the existing roof furniture. I'm also wondering what sort of total wattage would be best in the real world.

 

I think this might well be my winter project to source and cost what would be required.

 

If in doubt about wattage required, get a larger MPPT controller and less panels. If you need more solar than you had thought, you only need to add an extra panel and a bit of wire, as everything else will be installed with spare capacity.

 

My controller won't take any more than it had got attached, so any upgrade to mine will require a new controller.

 

On walking on panels: don't! The you can walk on it selling point is for access to roofs for building maintenance, not for locks on a boat.

 

If you still want flexi for the slimline appearance, get ones narrow enough that you can walk past them rather than over them. This also means you could mount them on the plastic blocks that give half an inch of air gap underneath, giving better cooling and not touching your paint.

[Richard T]

There are also aesthetic considerations - perhaps not upper most in many peoples minds - but I hate the look of solar panels sitting on poorly designed brackets or even as worse top box lids. I like our stick down panel. I doubt if there will be rust issue as before fitting the roof was repainted - 6 coats on top of the existing paint which had been rubbed down.

Another consideration is the extra height of bracket mounted panels and bridge/tunnel clearances.

A final comment and then I'll shut up is bracket mounted panels are a hazard when using ropes around the boat especially centre lines.

[frangar]

There are also aesthetic considerations - perhaps not upper most in many peoples minds - but I hate the look of solar panels sitting on poorly designed brackets or even as worse top box lids. I like our stick down panel. I doubt if there will be rust issue as before fitting the roof was repainted - 6 coats on top of the existing paint which had been rubbed down.

Another consideration is the extra height of bracket mounted panels and bridge/tunnel clearances.

A final comment and then I'll shut up is bracket mounted panels are a hazard when using ropes around the boat especially centre lines.

Couldn't agree more! One thing I forgot to mention.....I had thought of coating the roof in comastic under the panel to protect the steel from trapped moisture.

 

Cheers

 

Gareth

[Top cat]

There are also aesthetic considerations - perhaps not upper most in many peoples minds - but I hate the look of solar panels sitting on poorly designed brackets or even as worse top box lids. I like our stick down panel. I doubt if there will be rust issue as before fitting the roof was repainted - 6 coats on top of the existing paint which had been rubbed down.

Another consideration is the extra height of bracket mounted panels and bridge/tunnel clearances.

A final comment and then I'll shut up is bracket mounted panels are a hazard when using ropes around the boat especially centre lines.

We have 4 centre ropes one going to each corner, had them long before we got the panels as other things stick up to catch the ropes like boiler exhausts, plank and pole and just occasionally a load of firewood. BTW two of the ropes came free with our house (together with an anchor, chain, fenders, boarding plank, pole) but I expect that's unusual.

 

We have the triangular brackets, not the best looking things on the roof and I'm not sure if I would bother with them if I was doing it again. BUT after very careful measurement they are not the highest thing on the roof, the cratch and boiler exhaust are higher. So whether bracket mounted panels are an issue will depend on what's on your roof.

 

Going back to the original question the cons for flexible panels are:

You need more area than rigid panels for the same power output.

They cost more per sq metre than rigid

They may damage your roof unless carefully installed

They may not stand up to being walked on as well as you might hope.

 

Top Cat

[RLWP]

You seem to be a man who likes a bit of rope, Top Cat

 

Richard

[spaceyaface]

I'm also struggling with this....

[starman]

I'm still scratching my head about this one. Can anyone help on a couple of points. First, what should I regard as a maximum distance between panel and batteries? Or do I simply upgrade cabling to suit length?

Second, rigid panels shouldn't be walked on but would that prohibition also apply to our Jack Russell sized dog? I'm not sure I could explain the concept of solar no-go areas to him.

[blackrose]

I'm not sure why there is such concern about the paint under panels that are stuck down on the roof?

 

As long as the paint is in good condition and the correct PU adhesive/sealant is used (Sikaflex or Marineflex, etc) and no gaps remain under the panel for water to penetrate, then there shouldn't be an issue. No water and no air means no rust. How is it any different to bedding in any deck fitting? - ok it's a bigger area but it's the same principle.

 

It's really not that difficult to do. I'm not sure about sikaflex but if using marineflex you clean both sides with a cloth dampened with a bit of white spirit first.

 

Good flexible adhesive/sealants are designed to cope with differential thermal expansion/contraction of various materials and won't crack..

Edited September 5, 2015 by blackrose

[blackrose]

I'm still scratching my head about this one. Can anyone help on a couple of points. First, what should I regard as a maximum distance between panel and batteries? Or do I simply upgrade cabling to suit length?

Second, rigid panels shouldn't be walked on but would that prohibition also apply to our Jack Russell sized dog? I'm not sure I could explain the concept of solar no-go areas to him.

 

I think you'll have to do some cable size calculations. There is a pinned thread somewhere with a calculator. As for the animal, I think your problem is more likely to be the dog curling up and going to sleep on the panel, reducing its efficiency!

[Chewbacka]

I have a couple of Bimble used solar farm panels and would have no worries if a 15kg pet were to walk over then, though the clatter of his 'claws' on the glass would irritate me. I would not worry too much about cable lengths between the panels and the controller, just use a heavier cable, or accept a bit of loss. If you are not tracking the sun - I don't - then the losses caused by that are probably a lot more, and it does not bother me.

[MoominPapa]

I'm still scratching my head about this one. Can anyone help on a couple of points. First, what should I regard as a maximum distance between panel and batteries? Or do I simply upgrade cabling to suit length?

 

If you have a choice, minimise the length of the cables from the controller to the batteries, rather than those from the panels to the controller. In other words, put the controller close to the batteries. The reason being that the controller is also using those cables to measure battery voltage, so any significant drop will cause it to shut down early and you'll lose more energy than if the drop is in the panel cables.

 

MP.

[notts_alan]

I am more than happy with the Baird 150 watt panels I fitted , two panels and a good mppt controller and I have not had to start generator since , not sure how they will do over the winter period but definitely great for summer.

It is worth investing in a good mppt controller.

[Top cat]

If you have a choice, minimise the length of the cables from the controller to the batteries, rather than those from the panels to the controller. In other words, put the controller close to the batteries. The reason being that the controller is also using those cables to measure battery voltage, so any significant drop will cause it to shut down early and you'll lose more energy than if the drop is in the panel cables.

 

MP.

Another reason to have the controller close to the batteries is so they are at the same temperature. Most decent controllers adjust the charging voltage with temperature but sense it internally, so you want it in the same environment as your batteries.

 

Top Cat

[trackman]

We began with a 68W Unisolar peel & stick panel several years ago as a trial. I wanted one like that for all the positive reasons people have given for them.

We now have 3 of them, as RichardT has said.

People got on the roof to steal the original one and failed to even lift a corner, so they are pretty theft resistant.

I left space to walk around them but they do get walked on with no harm yet.

The makers claim that they are less sensitive to the angle of incidence of sunlight than conventional ones. I can't substantiate this but they give plenty of power early and late in the day in summer.

The roof (raddle red) gets too hot to touch in strong sun but the panels haven't shown any harm from this. They produce the specified 68W in the best sun as far as I can tell despite the heat. I suspect their rating takes the heat into account as they are designed for installation on metal roofs on buildings.

In any case, like all panels they are dark coloured, nearly black. They would therefore get pretty warm themselves through absorbing the sun's heat even were they not on a hot roof.

The big issue is the higher cost per Watt. I thought they were worth it for the benefits I expected and got, but it's a personal decision.