Intro: SPF DIY: the Fanned Light : a Solar Light From Scratch in 10 Minutes Flat
Haddock Invention (the company I work with) and partner lab Mantis Shrimp Invention are working on something called the Solar Pocket Factory (SPF), a tabletop factory that can make small-scale solar panels from raw cells at 25% lower cost than can be done today in China. We are aiming to create a new local-cleantech with thousands of little Solar Pocket Factories spread around the world, churning out locally-made picosolar in cities and towns near you.
Since it will be a while before the Solar Pocket Factory is in full operation, we decided to share some of what we're learning about picosolar in the meantime. Over the next few months, Alex (with Mantis Shrimp Invention) and I will be posting a new DIY picosolar project every week or so, using raw crystalline PV cells. The flexibility enabled by using raw solar cells (as opposed to the mounted and encapsulated cells available at Ratshack or on Digikey) is powerful, and we hope to share a little bit of what we are learning through these instructables.
Here's an easy one to kick things off -- the Fanned Light. A fanned arrangement of tiny solar cells (solettes) held together with super glue. No soldering is necessary for this project. It should take you about 10 minutes to complete. And by the end, you will have a solar light that works in the day (which is neat, but useless) or night (by adding a battery pack), from raw picosolar cells. RAW!
p.s. Where can you get the small bits of solar cells -- the solettes -- needed for these Instructables? Well, it's a pain right now. You can track these puppies down from suppliers in China, but they aren't easy to pin down: http://manilamantis.wordpress.com/2012/04/25/the-dark-side-2/
So, to make this easier, we just launched a Kickstarter campaign for all your DIY solar needs (Aug 15 - Sept 14): http://www.kickstarter.com/projects/alex9000/the-solar-pocket-factory-an-invention-adventure
Step 1: Materials and Tools
++ 4 to 8 solettes (those small pieces of raw cells), depending on the LED you want to light up
++ One or more LEDs: these can be any color, and the number of solettes will just need to be adjusted accordingly
++ Superglue (also known as cyanoacrylate, or Krazyglue): must be the liquid, thin stuff.
++ (Optional) 3.6V NiMH battery pack: this can be three AAA NiMH rechargeable batteries in series, or you can find thin 3.6V NiMH battery packs in some cordless phones
++ (Optional) Some resistors, if your solettes are not matched well to your LEDs and/or if you want to control the brightness of the LEDs
++ A LDPE folder or container cover for a super-glue resistant working surface
++ A steady hand that can right the mast of a ship-in-a-bottle
Step 2: Shingle and Glue the Solettes
The Fanned Light is a quick way to essentially do one thing -- combine solettes in series. Each solette, or any chunk of mono or polycrystalline PV silicon for that matter, outputs around 0.5 - 0.6VDC, which is not enough voltage to do very many useful things. So, we need to combine enough of these solettes together in series so that their voltage outputs add up.
In order to power a white LED, we will need a minimum of 6 solettes, and 7 series-connected solettes is a better bet to ensure your white LED will flash on in low light. If you want to tack on a 3.6V NiMH rechargeable battery so that your Fanned Light will work at night, you'll need upwards of 8-9 series-connected solettes.
The (+) output is the grey underbelly of the first solette in your shingled fan-stack. The (-) output of the series connected fan can ba accessed either at the bus bar or white silver ink runners on the blue top surface of the final solette in your stack, or by using a "false" solette that doesn't produce electricity but just serves to bring do the top surface connections to a solette underbelly. Watch the video for more info.
What to do:
A few dabs of superglue (again, the very thin clear liquid stuff -- also known as cyanoacrylate), a few seconds of pressure, and you've got yourself a solar series connection!
Step 3: Repeat!
Repeat until you've reached your target voltage for the fanned stack. For red LEDs, 4-5 solettes; for white LEDs, 6-8 solettes; for USB charging (through a battery buffer) 10-12 solettes, perhaps with a voltage regulator if you are using a sensitive battery pack.
Step 4: Finished!
If you broke any solettes, don't be discouraged. After one or maybe two more tries, you will get the hang of handling the thin silicon without causing (too many) breaks.
Even so, the Fanned Light is delicate. You can add a backing and then encapsulate with 5-minute epoxy (or you can get creative with molten sugar, lamination sheet...) for a more durable and weatherproof light.
Next week, how to transform a deck of cards into the most radical of solar chargers, made from scratch without soldering....