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Researchers Improve Solar Cell Performance
Vegematic writes "Researchers at MIT have improved solar collectors using dyes. They just increased their performance results by a factor of 4. These paint-on materials can increase the power obtained from existing solar cells by a factor of over 40 without needing to track the sun. 'By collecting light over their full surface and concentrating it at their edges, these devices reduce the required area of solar cells and consequently, the cost of solar power. Stacking multiple concentrators allows the optimization of solar cells at each wavelength, increasing the overall power output.' There is also a shorter FAQ available."
You know, when they post another story about the incredible discoveries in solar power that seem to never actually make it to those of us who would be interested if it was cheaper and more efficient..... Show me a company that is already selling this stuff and then I'll be interested.
RTFG - Read The F#$%ing Google!
Why did LSCs fail in the 1970's? Two reasons: the collected light was absorbed before it reached the edges of the glass or plastic plates, and the dyes were unstable.
What about stability? We tested one of our devices and found that it was stable (to 92 percent of initial performance) for three months. This isn't good enough yet for products but we are confident that the technology developed for organic light emitting devices (OLEDs) in televisions will be portable to this application.
once we reach peak solar in 2015.
http://twitter.com/OLDTELEGRAM
If solar cell efficiency actually increased a mere 1% for each story slashdot has posted regarding solar cell improvement, then panels would be generating electricity in complete darkness by now.
Better known as 318230.
Well no, the angle doesn't change the amount of energy hitting the panel. What it changes is how well the semiconductor solar cells can convert that energy. You don't have to track with these panels because the organic film absorbs, then re-emits the light, and due to the nature of the molecules, it always re-emits the light in the same direction, regardless of the incoming angle. The classic semiconductor solar cells themselves, attached all the way around the edges, are the devices that are sensitive about angle. They receive light at their optimal angle always, emitted from the organic film on the plates, rather than directly from the sunlight.
You lose efficiency in the absorption and re-emission process, but that loss is apparently worth the cost of admission, if these guys have done their math right. Being from MIT, we can hope they can do math.
This technique has a whole host of advantages over classic off-the-shelf panels you can buy today, which the article didn't go into.
The panels you can buy today are very sensitive to shadows. Each cell produces only so much voltage. To get a useful voltage out of them, you have to wire them up in series. If some percentage (50%) of a row is shadowed, the panel will actually effectively shut itself down, and produce no power at all, because of the non-participating cells. (The shutdown is accomplished with passive circuitry, not some sort of machine or processor.) This means that in a typical residential situation, you can't have so much as a chimney on your roof, or your panels could become very expensive powerless decorations. You certainly can't have any trees that could even partially shade your roof. This concept eliminates that problem. The organic molecules in question are very egalitarian about how they re-emit what they absorb. It gets spread out evenly, all the way around. This means that if any portion of the panel is shaded, all of the semiconductor cells still get a lot of (concentrated) light, and it takes a lot more shadow to shut them down.
Another issue with modern panels is the fact that a classic semiconductor solar cell is useful only through a very narrow band of wavelengths. Sunlight is very broad band light. (No jokes about bitrates, thank you.) It shows up at your roof in all kinds of frequencies. The panels you can buy today ignore a large fraction of those frequencies, since they only work at what they're tuned for. However, in the process of ignoring the other frequencies, your standard cell also blocks them entirely. So even though you can manufacture semiconductor cells with different bandgaps that will absorb different sunlight frequencies, you can't stack them directly on top of each other and gain anything. The uppermost in the stack shadows all those beneath, so they're pointless. An older slashdot story about how to manufacture a multi-bandgap semiconductor cell was posted a while ago, but that's still in early research stages too, and it apparently involves fairly difficult semiconductor manufacturing techniques. These panels do an end-run around that problem. Different dye coatings absorb different frequencies of sunlight and DON'T block the remaining frequencies. They pass through. So you can stack concentrator panels, up to some limit, and each one has semiconductor solar cells around the edges specially tuned to utilize the light frequency the dye emits. This is the big win, and the cause for the whopping efficiency claims. The transmissiveness of these concentrators for frequencies they're not tuned for means you can make a sandwich out of them and the resulting panel can use many more frequencies out of the same square meter. There's probably still some limit to how many layers you can stack before you're wasting your efforts, but it's enough to be worth the trouble.
Lastly, classic semiconductor cells can be manufactured specifically to operate efficiently in concentrated light vs standard out-of-the-sky sunlight. That's the reason for the Fresnel lens panels that have