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Topic ClosedSolar wiring, chase through to roof?

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podwerkz View Drop Down
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Direct Link To This Post Topic: Solar wiring, chase through to roof?
    Posted: 20 Jul 2019 at 3:02pm
Yep, I consider flexible panels as disposable...my experience and other's experience, back this up.

I have one that failed a couple of years ago, after less than 2 years of intermittent use, and I have begun to slice it up to see if I can use a few of the individual cells in a small project un-related to camping or RVing. The thin conductors between cells are a bit of a puzzle...but I'll figure it out. 

At any rate, the life and health of the flexible panel is quite secondary, in my opinion, to the life and integrity of the r-pod roof and the foam underneath the outer skin...so I would gladly let the panel destroy itself in thermal run-away to save the r-pod roof, if it came to that.  

The only panel I have secured to my r-pod roof is a small 50w rigid glass panel with an air-gap under it. Otherwise I have portable and truck-mounted rigid glass panels that should last for many years, without damaging anything or self-destructing.
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Motor7 View Drop Down
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Direct Link To This Post Posted: 20 Jul 2019 at 3:15pm
That's odd, in all my research on the flex panels I never ran across anything about excessive heat. It's too late now since I installed the panel right on the roof yesterday evening. I have an ir thermometer, so I Wil do some spot checking on those temps.

I have not been to Steamboats gig, but we have skied there.
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Direct Link To This Post Posted: 20 Jul 2019 at 3:52pm
Originally posted by Motor7

That's odd, in all my research on the flex panels I never ran across anything about excessive heat. It's too late now since I installed the panel right on the roof yesterday evening. I have an ir thermometer, so I Wil do some spot checking on those temps. 

I have not been to Steamboats gig, but we have skied there.

Oh yeah, that's one of the biggest issues with them: cell breakage, overheating,  cupping, scratching, dirt adhesion. Those are the main issues in what I think are probably the order of importance. Add hail damage toward the top of the list if you live or camp in a place that gets serious hail. I did a post on this back around the beginning of the year, and there's lots of comments on it on the internet. 

To see what you have temp wise, measure with the suns rays falling perpendicular to the solar module surface, cloudless sky, no or slight wind at most, wait for at least 60 minutes of sun exposure to get things stabilized. You don't really need to do the measurement on a hot day, just measure the difference between the module and ambient temp. You should see something like 100F plus above ambient temp. That will track whatever ambient temp you see later.  In the east you're not likely going to see 200F module temps, you have to go to the western deserts to get that. 

Assuming you're charging, check out several solar cells, the temp will probably vary slightly from one to the next due to electrical variations, and if you find one that's broken the unbroken part will be hotter than the rest. 

If you're careful measuring you can even see the temp difference when the module is charging compared to when its not. If you connect the module the temp goes down around 10F because some of the solar energy is being converted to electricity so doesn't show up as heat. There is no other electrical device that when you turn it on the temp drops (a fridge doesn't count because the condenser coil heats up when you turn it on). 


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Direct Link To This Post Posted: 20 Jul 2019 at 4:05pm
Originally posted by podwerkz

 

I have one that failed a couple of years ago, after less than 2 years of intermittent use, and I have begun to slice it up to see if I can use a few of the individual cells in a small project un-related to camping or RVing. The thin conductors between cells are a bit of a puzzle...but I'll figure it out. 



The cell interconnect tabs run from the front of one cell to the back of the next, which is what creates the series string of cells. Depending on what you have they are usually solder coated copper ribbon. Google "solar cell tabbing ribbon", it is available on ebay if you want more. 

The tabs can be a real PITA to work with especially on the cell fronts because they are machine soldered to the cell metallization layer, which is very thin. Try removing the tabs from the backs of the cells rather than the fronts, there is more metallization on the cell backs to re-solder to.  There should be visible spots where the tabbing machine attached the ribbons to the cells, if you place your soldering iron on those spots while gently pulling the tabs they should come off, one spot at a time. 
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Direct Link To This Post Posted: 20 Jul 2019 at 5:21pm
lol....wishful thinking.

The cells are imbedded in the PET or ETFE or XYZ or whatever the plastic polymer is.

Do you remember when we were kids and you would see those clear acrylic paper weights with a scorpion embedded inside?
 
Imagine trying to extract that scorpion without damaging it. Chisels, dremels, utility knives, micro torches, scrapers, nippers, cutters, surgical tweezers, files etc.......I have all kinds of tools available but my eyes and hands just dont work like they did when I was 25 years old. I managed to uncover some of the copper and do some voltage tests in full sunlight but the results are inconclusive...so far.

And, there seems to be a parallel pair and a series pair of ribbon conductors sandwiched on each edge of each cell. A total of 8 connections PER CELL. Who knew? Or possibly some of those ribbons are embedded between the cell and the polymer with no electrical connection....its really hard to tell, and you cant see it without an x-ray machine....and mine is, wouldn't you know, at the repair shop. Wink

The conductors are so thin they get mangled when I get close to them with any of the tools I've tried...maybe some kind of solvent that would dissolve the plastic but leave the copper, silver, and silicon un touched...of course, whatever that gallon of miracle chemical costs I could simply buy whatever small cells I want from the ebay store.

No, these were designed to stay put. But....the panel is junk anyway, so I'm having fun with it. Learning is a lifelong passion for me. 






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Direct Link To This Post Posted: 21 Jul 2019 at 5:18am
Ha Ha you must be a glutton for punishment as they say.... I assumed from your description that you had a delaminated module to begin with or you wouldn't be trying to do what you're trying to do. That's not uncommon for many poorly made products, some of them look ok at first but just peel right apart. 

ETFE (Tefzel) is the front superstrate material in most "flexible" modules.  The encapsulant is usually EVA (ethylene vinyl acetate) in any module. In the layup there is the superstrate, an EVA sheet, the cell circuit, another EVA sheet, then the backsheet, usually PVF (Tedlar). The layup is placed in a laminator which de-airs the assembly, then cures the EVA under heat and pressure. Once heated properly long enough the EVA becomes highly cross linked so a really tough material. IOW, you're not getting that module apart without destroying the cells. If you want to try anything at all try a heat gun. If the module wasn't properly laminated and the EVA cross linked to begin with it remains soft and flexible and will peel off.  It will drip and burn though if you get it hot enough.

There won't be both series and parallel connections between the same cells, that would just short them out, so I'm curious what module you're working on.  Some module designs use separate conductors concealed behind the cells to return the cell row output back to one end of the module, but usually there is a bus bar that connects one row to the next which is reversed so the series string can just continue on back and forth along the module. They're not Sunpower cells with all the contracts on the back are they? 

If you want to make your own custom modules buy a stack of cells and some interconnect ribbon and bus bar material. Its really pretty cheap nowadays. That part is pretty straightforward DIY, fun to come up with a design that fits where you want it to go. and has the voltage you want.  You just need a good soldering station and some jigs and fixtures.   Its the encapsulation that's hard to do in your garage, unless you want to build a laminator, you'd need a vacuum pump and bag and silicone heating blanket. Or you could go for poured urethane. 

None of this will save any money over just buying off the shelf of course. 
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Direct Link To This Post Posted: 21 Jul 2019 at 11:38am
Ah, you miss the point, grasshoppah...

I will figure this out, make a video of it, upload it to youtube and make MILLIONS of dollars in micro-payments.

THEN I can buy that fifth wheel r-pod in the year 3535....

Tongue
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Direct Link To This Post Posted: 21 Jul 2019 at 12:15pm
So, side by side, what the surface temp difference between a flex and a traditional panel at say 100f ?
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Direct Link To This Post Posted: 21 Jul 2019 at 12:43pm
Originally posted by podwerkz

Ah, you miss the point, grasshoppah...

I will figure this out, make a video of it, upload it to youtube and make MILLIONS of dollars in micro-payments.

THEN I can buy that fifth wheel r-pod in the year 3535....

Tongue 
I need to introduce you to my friend, the Nigerian prince.
bp
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Direct Link To This Post Posted: 21 Jul 2019 at 12:46pm
Originally posted by Motor7

So, side by side, what the surface temp difference between a flex and a traditional panel at say 100f ?
The surface temperatures will be similar. Any difference will largely due to the ventilation, or lack thereof.
bp
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