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Old 23-07-2019, 05:03   #1
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Why are flexible solar panels catching fire?

A friend is considering a boat that has a bimini top. He would like to install solar and the best/only option would be flexible solar panels on the bimini.

There have been a few reports of flexible solar panels burning, melting, or even catching fire. Can someone please explain from a physics or engineering standpoint how this happens? Can it be prevented or is it just an inherent tradeoff for flexibility?

Thanks.

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Old 23-07-2019, 06:07   #2
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Re: Why are flexible solar panels catching fire?

Buy high quality products like Solbian flexible panels instead of cheap junk..... and then stop worrying about the cheap junk catching fire.
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Old 23-07-2019, 06:12   #3
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Re: Why are flexible solar panels catching fire?

Cheap panels that are poorly mounted are highly susceptible to this.

Better quality panels with proper attachments that prevent flapping will cure most of these instances.
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Old 23-07-2019, 06:29   #4
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Re: Why are flexible solar panels catching fire?

Okay, so the prevention is to buy quality products and secure them with quality attachments.

But how do these cheaper panels burn or catch fire? What occurs that makes them vulnerable? Delamination, short circuit, late friday afternoon products?
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Old 23-07-2019, 06:41   #5
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Re: Why are flexible solar panels catching fire?

My understanding is that the cells, through a manufacturing or handling defect, have cracks and/or short current paths. These cracks and paths cause localized heating, that when carrying the current from the other cells creates heat. A large enough (or small enough, depending on your perspective) can cause enough local heat to melt and burn.
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Old 23-07-2019, 06:48   #6
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Re: Why are flexible solar panels catching fire?

Almost burned down my boat because I left a connection loose.

Thats one way.
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Old 23-07-2019, 06:51   #7
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Re: Why are flexible solar panels catching fire?

Ah. Gotcha. Okay. Good to know. Thanks. That helps. I will pass it on to him.

John
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Old 23-07-2019, 06:52   #8
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Why are flexible solar panels catching fire?

Google solar panel fire, do some reading, what you learn, let that guide you in choosing a mounting system.
Mostly itís about house fires, and glass panels of course. Flexible panels are far more susceptible, but solid panels are not immune, just much less likely
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Old 23-07-2019, 09:22   #9
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Re: Why are flexible solar panels catching fire?

I had some solar panels on my house made by BP which were recalled because they had poorly made internal connections between the wire leads and the panel itself. These poor connections had high resistance and some cases actually heated to the point of catching on fire. These were glass panels and I imagine it would be even more difficult to make secure connections on flexible panels.
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Old 23-07-2019, 10:07   #10
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Re: Why are flexible solar panels catching fire?

"Flexible" panels should be labelled "bendable" panels. They won't tolerate an infinite number of flexes. They can be bent over a stable rigid cambered surface, but you can't let them flap in the wind. If they are mounted on a flexing surface, the aluminum bonding wires flex, fatigue, and break. If you've found aluminum that doesn't fail from metal fatigue, please call Boeing and they'll make you a millionaire on the patent rights.

Cheap panels fail sooner - but they will all fail eventually if allowed to continually flex. Mounting those panels on a (flammable) cloth bimini or between flexing bimini mounting poles without a rigid substrate is a terrible idea. It is guaranteed to fail with time. Maybe catastrophically with a fire. Unless you want a Viking funeral, don't do it.

The bonding wires are all those thin little metallic lines between the darkly colored silicon cells. You can't access them, repair them, or detect early fatigue fractures without a microscope. They are each intended to carry only a fraction of the total current output of the panel. When they break they can short to adjacent bonding wires.

The worst design has multiple panels in an array connected in parallel -- without steering diodes on each individual panel output, where ALL the current from the entire array passes to any short circuit anywhere in any panel in the array. Always use Schottky steering diodes on the output of every panel in a parallel array! (The diodes will also stop reverse current flowing to any shaded panel.)

Flexible panels aren't. They are bendable over a rigid surface.

Sorry to burst your bubble. Maybe someday we will have solar sails that incorporate bonding wires composed of metal that tolerates flexing because it's stays in a liquid state - but we're not there yet.
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Old 23-07-2019, 10:45   #11
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Re: Why are flexible solar panels catching fire?

My panel fire started with a small black circle a short I now know and people that I talked to said it's not going to be detrimental to my system as far as the output that I get through it well I left that go on for a month or so and it got bigger and one morning I came down to the boat and it had started a fire and it had burned through the Bimini I had about a 12 inch diameter hole in the and that drop down to a pillow luckily underneath that
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Old 23-07-2019, 11:33   #12
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Re: Why are flexible solar panels catching fire?

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Originally Posted by tjandoverguy View Post
My panel fire started with a small black circle a short I now know and people that I talked to said it's not going to be detrimental to my system as far as the output that I get through it well I left that go on for a month or so and it got bigger and one morning I came down to the boat and it had started a fire and it had burned through the Bimini I had about a 12 inch diameter hole in the and that drop down to a pillow luckily underneath that
Not surprising. That's the usual failure mode. Before the bonding wires break, they develop high resistance at the partial fracture point, which causes resistance, and the current is dissipated as heat concentrated at that one point. Which causes the resistance to rise, which dissipates more heat... until you get a fire. P=I squared R.

Please don't continue with that configuration, and return the panel for warranty adjustment, or throw it out. If it developed one fatigue fracture, there are others about to fail. It's a time-bomb. tick...tick...tick

"...people that I talked to said it's not going to be detrimental to my system as far as the output." It will be detrimental -- when your boat goes up in flames. Instead of talking to those "people," you should talk to the Fire Department about their response times, your insurance company about fire coverage, and tow an inflated life raft at all times when underway.

"Quality" flexible panels only take longer to fail from metal fatigue. If they are being continually flexed (even just a little), they will all fail eventually. Mount your flexible panels on something that is truly rigid. Or use conventional framed panels that have a sheet of glass acting as a stiffener (which are also a lot less expensive).

See my post #10 above for details: Why are flexible solar panels catching fire?


I've seen the ads: a flexible panel flapping in the wind. Suspended by lines. It's false advertising. An accident waiting to happen.


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Old 23-07-2019, 13:47   #13
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Re: Why are flexible solar panels catching fire?

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Originally Posted by a64pilot View Post
Google solar panel fire, do some reading, what you learn, let that guide you in choosing a mounting system.
Mostly it’s about house fires, and glass panels of course. Flexible panels are far more susceptible, but solid panels are not immune, just much less likely
As a guess, solid panels are mounted with some ventilation below. Who knows what the flexible panels have been affixed to that cause a fire?
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Old 23-07-2019, 15:07   #14
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Re: Why are flexible solar panels catching fire?

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As a guess, solid panels are mounted with some ventilation below. Who knows what the flexible panels have been affixed to that cause a fire?
It's usually a single point on the flexible panels that catches fire. It looks like someone burned a spot by concentrating sunlight with a magnifying glass. That's where the bonding wire fractured from fatigue failure. After that, the burn spot starts to grow.


So it's not a ventilation issue, which would affect a large area of the panel.


Of course, ventilation is beneficial for all panels. The panel output decreases with rising temperature. But ventilation isn't a fire safety issue - only a performance issue.


BTW, if you want to hang a conventional framed panel, it's just as important to attach reinforcement to the back of the panel frame to prevent twisting (racking). Framed panels are also intended to be mounted on a rigid surface. I used aluminum bar stock.
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Old 23-07-2019, 18:06   #15
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Why are flexible solar panels catching fire?

Quote:
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As a guess, solid panels are mounted with some ventilation below. Who knows what the flexible panels have been affixed to that cause a fire?


With the house panels that catch fire itís almost always because there are flammable materials that build up under the panels, leaves etc.
There have been many panel failures that donít amount to anything except a failed panel because there was nothing to burn.

When I was in Georgetown last Winter there were three panel failures and small fires, and a forth the guy was sailing came up from a short break from down below and his Bimini was on fire, he lost his boat I believe.
My take is donít mount any kind of panel on something that will burn, but your boat, you do as you think best.
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