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."

Comments

Nice concept, but reality may be different!

[DamonHD]

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

ATS / Spheral Solar Power

[Mr. Flibble]

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

Re:ATS / Spheral Solar Power

[ahfoo]

Yep, the former darling of Slashdot submissions that disappeared off the map last year. I was a real cheerleader for their business plan so I was disappointed when they gave up. My two cents on what happened was that they decided amorphous silicon AKA thin film was going to put them out of business. Those suspicions are based partly on watching all the action around Swiss company Oerlikon. They're a turn-key provider of thin film production plants and they're making a lot of deals in Taiwan and China in the last few years. Their local sales rep is going around saying they can build you a factory that produces product at 60cents a watt in the next twenty four months.

Re:Cannonballs!

[Cutterman]

Small-shot, not cannonballs! Shot-towers were once not that uncommon to see. Given the mass of a cannonball, temperature when molten and a normal environment, you'd need a very tall shot tower to cast cannonballs! Now I suppose some slashdotter will promptly work out just how high a cannonball shot tower would have to be....(I'm too lazy). The Cutter

Re:Cannonballs!

[mishmash]

Not quite cannonballs, but shot: http://en.wikipedia.org/wiki/Shot_tower

Innovalight

[sanman2]

So nobody's been payint attention to Innovalight in the news lately?

They have the cheaper and more efficient technology:

http://www.news.com/Pour-yourself-a-silicon-solar-panel/2100-11392_3-6213132.html?tag=nefd.top

www1.eere.energy.gov/solar/solar_america/pdfs/41741.pdf

Multiple Exciton Generation is where it's at. Only nanoparticle quantum dots can achieve that, and it's the means to get the highest solar efficiency, because it 's about generating multiple electrons of current for each photon absorbed by your photovoltaic material.

Re:Cannonballs!

[Danny Rathjens]

Thanks, that gave us the correct term to look it up. :) http://en.wikipedia.org/wiki/Shot_tower

You were misled.

[Kadin2048]

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.

Re:Details needed.

[ChrisMaple]

Links in the article lead to the details you ask for. Electrical efficiency appears to be about 11% in sunlight, although this is my estimate extrapolating their graph of packing density. Flat, quality silicon cells run 15% to 23%, IIRC.

The balls are p-type silicon doped n-type on the surface. A small, flat slice is removed to expose the p-type interior. Contact to the n-type region is any convenient place on the spherical surface; contact to the p-type region is the center of the flat area.