Housing the solar cells

[Mike Wolak]

I reciently made a solar panel with the cells adhered via a dab of silicon,  sandwiched between two plexix glass panels with silicon bead around the sandwich panel.  This sandwich panel was mounted (mistake) on painted 1/2" plywood and mounted to a pole outside.  This project worked for a year then the plywood warped and the cells cracked from the warped panel.  So I'm looking for ideas to make 3 panels.  I saw the post of cells, imursed in clear riesen, that turned white (scary).  I am thinking of the sandwich procedure and then mounting on angle iron frame welded together with angle cross supports.  I am looking for ideas to have weather proof panels to endure the 4 seasons.  This solar section of this board seems too quiet lately.  So lets fire up this solar section and run some ideas by this 5th day non smoker.  Im keeping myself busy with this solar project.  SO WHAT SAY YOU?

N8JGU

[Jeff7]

Link.

That's the process I used to make two prototype panels. As you can see from the later pages at my site, the first revision did not hold up to high heat, as the epoxy used was very inflexible.

My next version looks much the same, but with a few tweaks.

• The corners are reinforced and covered with Goop Adhesive
  
• Instead of regular epoxy, I used Devcon Metal Welder, an utterly noxious adhesive that is also reported to be exceptionally strong, yet fairly flexible.
  
• I used solid wire, rated for outdoor use, instead of stranded wire. Stranded wire allows for plenty of passageways for air and water.
  
• The ends of the solid wire are also covered in Goop to prevent moisture from getting in around the insulation
  
  

Now, I'm about 350 miles away from the panel, at college right now. I'm told though via e-mail that there is a slight bit of condensation in the panel, but since there's not a lot of it, and no evidence of leaks, I am inclined to think that the moisture was in the panel when it was sealed, despite that I blasted it out with helium. It is only cheap, Walmart-grade helium, so I don't even know for sure how pure and dry that was. It was also sealed in summer, so the humidity wasn't going to be too low, even in a dehumidified basement.

If you've read over my site there, you see I used two fairly expensive materials - aluminum and polycarbonate. Aluminum was used because it is naturally resistant to corrosion, yet is still quite rigid. Polycarbonate has good light transmission, can be made UV-resistant, and it withstands impacts very well.

These materials seem alright on a small scale, but I'm not sure how it'll do on a larger scale. Plus, it'll be expensive. Aluminum, polycarbonate, and the best-pick solar cells, and the metal welder is $11 per tube, and a large panel might take 2-3 tubes.

So it seems like a robust design, but it needs some serious work on the expenses side. I've never been good at finding connections and getting cheap materials, so I always have to buy things new.

And, I need a very dry environment to seal the panels in. I still like the helium idea - ideally, it'd be a dry, inert gas to let the cells live in for the duration.

When I get home in December, I'll check up on my panel again, and maybe give it a submersion test, and throw ice cubes at it (hailstorm simulation).

[crashk6]

Hey N8JGU,

 The method I use and love, the ease of assembly is a plus too... you'll need a peace of tempered glass to start with, it will provide the structural support for the cells so the larger the glass, the thicker it must be to avoid any flexing and support it's own weight.

Clean your glass well, use ammonia, isopropal alcohol or high proof everclear. After it's clean, lay it on a flat level surface with a cotton or other non shedding peace of protective cloth under it (old towls).

Now dawn a pair of rubber gloves give face side up on the glass one last polish to remove finger prints and start laying out your cells. How you lay them out will depend  on the voltage you want and the shape of your glass.

The way I do mine allows me to have a dual voltage panel that is also shade tolerant, the way I accomplish this is by running my series strings in a U shape the length of the panel (really need an illustration about now). You will need to bring out leads for your series strings @ 17 volts per string use bypass diodes on the physically adjacent strings on both sides of the panel but leaving two sets of leads @ 17 volts for each side of the panel, in this way they may be connected in parallel for 12 volt systems or in series for 24 volt charging... I might make a diagram of this wiring methoed if  it's requested... I realized trying to describe it is confusing.

Anyway my specialty cell wiring aside once the cells are layed out FACE UP (e.g. the glass will be on the back of the finished panel) start connecting them using conductive tape or other thin conductor that will lay flat... adhere each cell in place with a very TINY amount of silicone.. about a quarter of a pea sized dab and only one right in the center. run your flying traces to the edge of the panel for later connection.

Here comes the fun/scary part depending on your point of view.

At this point you need a dielectric (insulating), TRANSPARENT, high light transmittance epoxy. Mix and pour over the whole panel... (I told you a flat and level) let cure. Once hardened you may connect the flying leads to studs epoxied to the other side of the glass or in a connection box on the other side of the glass... I house the bypass diodes in this box as well.

Then silicone aluminum stock around the edges of the panel this gives you a frame and  something to bolt onto for mounting... This assembly method is very close in final appearance to a manufactured panel.

Sorry if anythings unclear gotta run to get to an appointment...

If you need further clarification or some illustration let me know.

--

crashK6

[DanG]

A few deep breaths, a count to 10, a short walk to get a break when the mood strikes - Thats 432000 seconds; 7200 minutes; 120 hours of a good fight fought!  Remember to save one excellent thing above the usual as reward for when everything is trying to weld a ciggarette back on your face, okay?

The epoxy that turned white was intentional, a UV blocker additive or thickener, where that project took the wrong turn was the epoxy flowed too easily and wicked in front of the cells.

If you are using mild iron or aluminum frame-brackets-runners remember your back plate can be anything - 24" wide aluminum roll stock (10 foot lengths) as used in aluminum siding for home contruction or, as I am investigating, the plastic cheap snow sleds made only of a tough sheet plastic w/ a hole cut out in the front that rolls up for storage. Just absolutly have welded frame to avoid diagonal wracking; and allow alot of room for the polycarbonate to move from thermal expansion.

If you must use polycarbonate glazing, allowing a 1-inch overhang on all four sides to slip 'loosely' into slots built into metal frame to do the work of mechanical fastening with cell laminate free and clear of frame entirely seems a straightforward way that I havent seen done yet. Also not seen are strips of cells, say 8-inch wide and 30-inch long plexiglass for a 36-cell panel that slip into cross-brace runners to provide extra support and simplicity. Strips would use the oversize glazing - smaller backplate as mentioned above..

I'm still not able to commit to custom order of tempered glass here for my cells, overrun w/ possibilities...

[Jeff7]

Just to add to what I said:

Bear in mind, nature is exceptionally harsh. These panels will have to endure great cold in winter, and very high temperatures in sunlight, especially in summer - at least 140F, probably more. Everything will expand and contract, which will strain any joints.

The air inside will want to escape, and the pressure forces can be very powerful - more joint strain.

And finally, weathering. Rain, snow, wind, hail, freezing rain (really bad if water freezes and splits a joint apart), and good old ultraviolet radiation. You'll want your panel to be able to survive all that for years on end. If not, you'll spend more building your own panels than if you'd buy a commercial panel with 25+ years of warranty. Sure, it takes the fun out of building something yourself, but at least you'll get something that is proven to be durable.

[sLaShEr]

Hey crashk6,

I have been looking for some information on wiring solar cells together - and panel design.  The cell configurations seems to be pretty straight forward - 36 cells connected in series (connecting front of cell(negative) to the back of the next cell(positive) and so on...)  Your approach seems to be a little more involved - I think I understand what you did - but I'm not 100% sure.  That diagram would be greatly appreciated !  I want to incorporate some bypass diodes in my panel - but I'm not exactly sure how to wire them in & what size diodes I need.

I am using the ebay cells 3" x 6" (3.0 amps / .55 volts etc...)

Thanks so much,

sLaShEr.

[zander1976]

Hey N8JGU,

 The method I use and love, the ease of assembly is a plus too... you'll need a peace of tempered glass to start with, it will provide the structural support for the cells so the larger the glass, the thicker it must be to avoid any flexing and support it's own weight.<p>
Clean your glass well, use ammonia, isopropal alcohol or high proof everclear. After it's clean, lay it on a flat level surface with a cotton or other non shedding peace of protective cloth under it (old towls).<p>
Now dawn a pair of rubber gloves give face side up on the glass one last polish to remove finger prints and start laying out your cells. How you lay them out will depend  on the voltage you want and the shape of your glass.<p>
The way I do mine allows me to have a dual voltage panel that is also shade tolerant, the way I accomplish this is by running my series strings in a U shape the length of the panel (really need an illustration about now). You will need to bring out leads for your series strings @ 17 volts per string use bypass diodes on the physically adjacent strings on both sides of the panel but leaving two sets of leads @ 17 volts for each side of the panel, in this way they may be connected in parallel for 12 volt systems or in series for 24 volt charging... I might make a diagram of this wiring methoed if  it's requested... I realized trying to describe it is confusing.<p>
Anyway my specialty cell wiring aside once the cells are layed out FACE UP (e.g. the glass will be on the back of the finished panel) start connecting them using conductive tape or other thin conductor that will lay flat... adhere each cell in place with a very TINY amount of silicone.. about a quarter of a pea sized dab and only one right in the center. run your flying traces to the edge of the panel for later connection.<p>
Here comes the fun/scary part depending on your point of view.

At this point you need a dielectric (insulating), TRANSPARENT, high light transmittance epoxy. Mix and pour over the whole panel... (I told you a flat and level) let cure. Once hardened you may connect the flying leads to studs epoxied to the other side of the glass or in a connection box on the other side of the glass... I house the bypass diodes in this box as well.<p>
Then silicone aluminum stock around the edges of the panel this gives you a frame and  something to bolt onto for mounting... This assembly method is very close in final appearance to a manufactured panel.<p>
Sorry if anythings unclear gotta run to get to an appointment...

If you need further clarification or some illustration let me know.

--

crashK6

Hello,

Sorry for posting on such an old post but this is a great design idea. I just needed a bit of clarification. You poor the epoxy over the face of the cells. What kind of epoxy can I use for this. Is there any recommended types.

Thanks, Ben