I know what you're thinking. It's written all over your face. You're all, "awww, man! I'm sitting here, ready to make a solar panel, and I've got my silicon cells and EVA all ready and waiting, but my dang kid just threw my soldering iron at the glass I was going to use for the frontsheet, and now the iron and the glass are shattered and on fire, respectively. How am I ever going to make a solar panel now? The only other things I've got in the house are a couple transparency sheets and an office laminator. This mad sucks, yo"
Well, solar friend, don't you worry. I'm here to tell you about a sweet technique to make waterproof solar panels out of silicon cells with NO soldering, NO glass, and NO money down. All you need a cheapo Staples laminator (got mine for $15 from the Chinese version of Staples down the street in Hong Kong, ??!), a few simple materials and an iron will.
It takes about five minutes to make a small panel, and they're delightfully sturdy, waterproof and easy. Ready? Once more into that shiny solar breach!
(no, not that one)
p.s. My boy Chill Solar Dude is coming along on this instructable hayride to drop some ill narration on us. How's it hanging, CSD?
Step 1: A little background on solar
This instructable is all about making solar panels. Solar panels are different than solar cells--a solar cell is a single piece of silicon. Typically, solar cells are low-voltage, high-current devices, putting out about half a volt, with a current proportional to the cell's area and the intensity of the light. A modern 6" x 6" cell puts out about 7A of max-power current, at 0.5V*
Electrically, there's not much you can do with 0.5V and 7A. So we combine solar cells in series and parallel to get to a useful voltage and current. If we combine ten solettes in series, we get five volts at the max power point, which is a generally useful voltage for powering small electronics.
The other tricky part about making solar panels is protecting the delicate silicon cells. These cells are very thin--0.2mm, and they're susceptible to every evil the world has to offer--vibration, humidity, moisture, flexing, heat, cold, bad feelings and hurtful statements. Once the cells are electrically connected, you have to find some way to wrap them up in a powerful, strong sleeping bag that keeps the warm feelings in and the bad, harmful things on the outside. This process is called encapsulation.
There's lots of ways to encapsulate solar panels--you can cover them in plastic resin, use huge presses with heaters and vacuums to fix glass and plastic to the front of the panel, and all other kinds of neat tricks to keep the silicon safe and dry. This instructable is all about a new trick that a friend and I came up with that lets you electrically connect the cells and physically protect them, all using a standard office laminator and a few cents of plastic film.
That's all there is to making solar panels--combine pieces of silicon together, protect them from the harsh outside world, and then ride the solar wave into the glorious sunset. It's actually quite easy to do. Read on!
* If terms like 'max power' and 'short-circuit current' are unfamiliar, check out the other images. Homey Chill Solar Dude put together some quick tutorials explaining how it all works.
Step 2: Get what you need
There is one very special thing about this method of making solar panels, and that's that it's very cheap and simple. The cheapest commercial solar panels sell for $.68/W, and homemade solar panels often run higher, because they use very expensive encapsulants. These panels won't last as long as a glass-laminated panel, but they're made with scrap silicon and some plastic film, making them, to my knowledge, the cheapest, simplest microsolar panels in the world. The raw material cost for the panels is about $.50/W, a minute to get a good lamination, and you're ready to go! It's pretty awesome, if I do say so myself.
SO, you'll need some materials. Here's what you need and some places to get it:
Shameless plug: we went ahead and packaged all of these materials up in a kit for hacking your own solar panels, and you can get it here. You can get the materials other places, too, and I'm listing those sources, but we put a lot of effort into sourcing high-quality materials that work right. Also, each kit comes with ten microliters of Love.
PET lamination film -- This film will make the front and back of your solar panel. You can get this in your local office supply store for laminating papers and ID badges and the like, or there's plenty of places online that sell PET film specifically for solar. The solar film is UV-stabilized and will last longer outdoors.
EVA film -- EVA is a rubbery plastic that's very similar to hot glue. This goes in between the PET film and the solettes, and when heated, forms a perfectly clear, index-matched layer bonding the solettes to the PET. Mechanically, it also cushions the delicate solettes and forms a moisture barrier, waterproofing the panel. This is a pretty specialized material, so you're unlikely to find a local source, but you can buy big rolls of it on ebay for pretty cheap.
Copper Tape -- this stuff is awesome. Shiny, real copper with an adhesive backing! You'll use it to make electrical contact with the enapsulated panel and make a nice connection that you can solder or alligator-clip onto. You can pick it up at craft stores like Michaels, or there are plenty of cheap sources on ebay.
Doublestick Tape -- you use this to hold the solar cells in place while they're being laminated. The plastic gets all melty and skooshy, and it tends to push the cells around unless they're taped down. The best stuff is very thin, very strong tape. Get it at any stationary store.
Solettes -- This is where the solar magic happens. These are silicon cells cut to whatever size you want. The size determines the current of the solar cell--in this instructable, I'm using 52mm x 13mm cells, which put out about 200mA Isc. You can get these from us or from ebay. If you do buy from ebay, be sure not to get cells with tabbing--you want just the bare solar cell.
A laminator -- Any desktop laminator will do. Use one you've got lying around, or pick one up from an office supply store.
A note for the true solar hounddog -- you can get particularly beautiful laminations if you do a simple mod to your laminator to slow it down, so if this project excites you, you might consider dedicating a laminator to the pursuit of solar glory. I'll go into details of the laminator mods in another instructable.
Step 3: An overview of the underbite
I'm going to make this panel with what we call a "shingled solette" technique. The solettes are held down to a PET backing using double--stick tape, and they overlap one another slightly, so the negative top of one solette is in electrical contact with the positive bottom of the next solette, making a series connection that adds the solettes' voltages.
What's wonderful about this technique is that you don't have to solder anything. Just lay the solettes on top of one another, laminate the solettes inside plastic, and the lamination holds the solettes in solid electrical contact.
This video is a good overview of the process--it's a sped-up video of me making a solar panel from start to finish using this technique.
Step 4: Step 1: It starts with a backing
The first thing you'll need is a PET backing. I really recommend using solar PET rather than the lamination sheets--it's a bit thicker and it doesn't get as floppy when you melt it in the laminator. You can get working panels either way (I used lamination sheets in the video), but the panels come out cleaner with solar PET film.
Decide what voltage panel you want to make. This will determine how many solettes you have in your panel, and how long your panel will end up. If your panel is voltage V, you'll have V/2 + 1 solettes, i.e. if you're making a 5V panel, that panel will have 11 solettes. The shingled solettes should have about 1mm of overlap with their neighbors.
I'm attaching a template for a 5.5V panel that uses 52x13mm solettes. This makes a ~5.5V, 170mA panel that's good for charging 5V electronics, like phones, cameras, and other devices. You can print the template directly onto the rough side of the PET backing, which is quite handy. If you use it, print it out at 1:1 scale on A4 paper.
If you want to make a different size or voltage solar panel, that's fine. Figure out how many solettes you're using and how large your backing needs to be to accommodate them. You can as large a margin as you like around your solettes.
Cut your backing out of PET and you're on your way!
Step 5: Step 2: Ze copper tape
The next thing to do is place the copper tape on your backing. This tape will bring out the electrical contacts from the panel and let you connect to the panel after it's laminated.
You'll notice the two sides of the PET have different textures--there's a smooth side and a rough side. The rough side is coated to make it stick better in a lamination. You're going to place the solettes on that side.
Cut two pieces of copper tape and stick them on either end of the PET. Leave a bit of the tape hanging over the end of the PET piece, and wrap that around to stick on the other side. Remember, everything on the rough side of the PET is going to be laminated, so you won't be able to get to it. Wrapping the tape around to the other side lets you access the electrical contacts after the panel is laminated.
Step 6: Step 3--Doublestick
Place a line of doublestick tape on either side of the copper tape and peel back the protective backing. This tape will hold the solettes in place during the lamination.
Step 7: Step 5--place the solettes
Whichever piece of copper tape you place your first solette on will be the positive contact of your panel. Choose with care, and you might want to make a mark to remind yourself later (although you'll be able to look at the solettes and figure it out, too)
Place the solette so it's centered on the PET and is overlapping the copper tape by several millimeters. Be delicate with the solettes--they are quite fragile, and it's easy to crack them. Press the solette down onto the doublestick tape, and thar she goes.
One by one, add the rest of the solettes. Doublestick tape holds the solettes pretty permanently, so make sure you like how the solette looks before you press it down into the tape. If you do misplace a solette, it's not the end of the world. It'll probably break, but try to twist it, rather than peel it away from the tape. It it does break, just pull the pieces from the tape and put down a fresh one.
When you get to the last solette, take a moment to look at what it's doing, electrically. The bottom of the last solette contacts both the previous solette and the copper tape. It's a funny trick that we call the "false solette" trick--we're just using the conductive bottom of the solette like a wire to connect the top of the previous solette with the copper tape on the backing.
Once you've finished placing all your solettes, kick back in your chair and take a deep breath. Relish this moment. One minute from now, you'll be the proud owner of a finished solar panel, and everything will change.
Step 8: Step 6--sudo make me a sandwich
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Now is a good time to preheat your laminator.
First up, make a lamination sandwich. Take a piece of EVA and lay it on top of the solettes, and then take another piece of PET and lay it, rough side-down, on top of the EVA. Your baby is ready for the hot rollers!
The doublestick tape should keep everything in place, but all the same, be gentle with the unlaminated panel. Pick it up and feed one end into the laminator. It's important to laminate the panel along the length of the panel--feeding it in a different way may crack your solettes. Chill Solar Dude made a drawing for you, for clarification.
The laminator will pick it up and start pulling it through. On the other side of the laminator, you'll see a beautiful panel emerge like a dhota from an air chrysalis.
You may notice that my laminator looks like the terminator while he's being lowered down into the pool of molten steel. Yours doesn't have to look like that. I've been tinkering with my laminator so frequently that I've wised up and stopped putting the cover back on, but you just do this with a normal, off-the-shelf laminator, and it'll work just fine.
Most desktop laminators run too cold and fast to fully melt a panel. The easiest way to handle this is to pass your panel through the laminator several times, and each time, it'll melt a little more. This is a dirt-simple method, and it makes panels that work fine, but it leaves small bubbles inside a panel where the EVA didn't fully melt.
The best way I've found to make good-looking panels is to slow it down by stopping the laminator every ~10mm or so and waiting a few seconds for the panel to melt, then advancing it another 10mm. This lets the panel spend more time under the hot rollers, melting the plastic more thoroughly, and then the laminator's rollers can completely squeeze out any bubbles in the plastic, giving a perfectly clear, smooth panel.
When you're feeding the panel into the laminator, you might get your plastic layers slightly misaligned. That's fine. Once your panel is laminated, you can trim down any sloppy edges with scissors and get a nice clean edge.
Well there you go. Ain't nothing left to do but test 'er out.
Step 9: Well? Did it work?
I made a nine-solette panel. One of those solettes is a false solette and doesn't add voltage to the panel, but each of the other solettes adds half a volt at the max power point, so I should see 4 volts at the max power point.
I plugged it into our little solar testbed, and lo and behold, the panel's putting out 208mA at 3.7V at the max power point, or .75W. Pretty good, ain't that right, Chill Solar Dude?
Step 10: Wellsir, I reckon it's time to hit the ol' dusty trail
Well, that's about it I reckon. Go forth and build cool stuff. Show everybody what you make in the comments!
If you think this is neat, well, my amigo Shawn and I do this all the time, and we're busy making lovely tiny little machines that make solar panels. Read more about our project, our story, get materials for your own DIY solar projects and join the microsolar lovefest at solarpocketfactory.com