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Solar Cells Crystallized Out of Molten Silicon
Hot Toddy sends in a link to a story up on Digital World Tokyo about a more efficient process for manufacturing solar cells. It involves dropping molten silicon from a height of 14 m; surface tension causes tiny spheres 1 mm in diameter to form; the silicon crystallizes in the 1.5 seconds of free-fall. The spheres can be mounted on surfaces of any shape. They capture light from many directions, increasing their solar efficiency. Kyosemi is the company behind the Sphelar technology. Some of the pages on this site date to 2003 and the status of most listed Sphelar products is either "under development" or "engineering sample is available."
For example, the statement about solar panels not having to be flat already applies: there are flexible, stickable (see the UniSolar laminate for example) ones now, with Fresnel lenses etc.
In fact, for many uses, solar is easily laid on an existing flat surface such as a roof. Flat is very often convenient.
The issue about capturing light from any angle is only valid if the individual cells/balls and their connectors (and any surrounding obstacles such as walls and trees) don't get in the way. Multi-layer cells and mechanical trackers and even mirrors mitigate these problems in existing systems: http://www.earth.org.uk/note-on-solar-PV-for-diffuse-light.html
Anyway, interesting, and it would be good to test some in places like the tops of walls, roof ridges, pathways, etc.
Rgds
Damon
http://m.earth.org.uk/
Uh, this looks like the same thing that came out from Spheral Solar Power, that was bought (and later divested) by Automation Tooling Systems:
http://environment.newscientist.com/article/dn3380
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Neat! This is the same method that was used to make cannonballs during the US Civil War.
I can't find any references to cannon ball manufacture on Wikipedia, but my high school had a cannon forming tower (it was originally a civil war arsenal).
Outside of that, the more techniques the merrier! I'm somewhat curious how they create a PN junction out of a homogenous liquid of silicon, but I suppose that can be done afterwards. I'd also be a bit curious if it's single crystalline. I very much doubt it, as there is no seed crystal to nucleate on, so there should be a lot of independent surface nucleation sites (IAAMS).
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Sounds like one of those accidental discoveries...
"Ah crap, I just knocked over the vat of molten silicon we had sitting on the roof ledge!! My boss is gonna be super mad at.... oh hey, look at all these little balls! Weeee, silicon balls!"
Yeah, but pointing down.
Bert
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Missing from the story are important and obvious details.
1. Electrical output efficiency compared to a correctly aimed flat solar panel.
2. How are tiny silicon balls connected to produce electricity?
Any other questions, please chip in.
Thanks, Jim
Hot liquid metal inside an aircraft - what fun! Look up "liquid metal embrittlement" to see why this would have to be done very carefully and why you currently cannot take mercury on an aircraft. In short the liquid metal gets into any small flaws, dissolves it into a sharp crack quickly, and then after a short time the crack gets long enough that it goes at the speed of sound in the material - more than 4miles/second (6.6km/s) in steel.
... hopefully it'll have legs, too.
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Someone misled you. Shot (for shotguns) is made in freefall using a tower. And it basically does work the way you're thinking: it doesn't necessarily solidify all the way, but the outside does, and that's enough for it to retain its shape when it hits the water at the bottom of the tower.
Cannonballs were generally made out of cast iron. If you look at an authentic one that's in good shape, you can usually see the mold lines and sprue marks where it was poured. They were usually poured into sand molds that were then knocked away after they cooled.
Some very old cannon balls (prior to the 18th century at least) were cast bronze or cut stone rather than iron, but most people switched to iron as soon as they were able to because it's a harder, cheaper material than bronze, and easier to work with and more effective than stone. (Bronze remained as a material for the cannons themselves well into the 19th century, though, since it has greater tensile strength than cast iron and is less likely to shatter.)
Also, if you think about pouring large quantities of viscous liquid, you'd realize that "dropping" a cannonball wouldn't work; rather than forming a sphere, you'd probably form a teardrop or ellipsoidal shape* due to the air resistance. Forming spheres via freefall cooling is only practical (in normal Earth gravity) for rather small parts, where the surface area to mass ratio is low.
* I'm told that if you look at the shot produced in a shot tower closely enough, all of it is really ellipsoidal rather than truly spherical, but it's such a small difference that it's normally ignored.
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