Researchers Improve Solar Cell Performance 292
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."
from the FAQ (Score:5, Informative)
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.
4 vs 40. (Score:4, Informative)
FYi, its 40 time better than standard solar cells and 4 times better than their previous results.
The reference from the FAQ
1. Currie, M. J., Mapel, J. K., Heidel, T. D., Goffri, S. & Baldo, M. A. High-efficiency Organic Solar Concentrators for Photovoltaics. Science. In Press.
Re:Factor (Score:5, Informative)
The quoted factor of 40 improvement is a comparison against unconcentrated solar cells, which nobody uses. At present, all the solar generating plants in the world use mirrors to concentrate the sunlight on the solar cells, thereby greatly increasing performance.
The "factor of 4" improvement refers to how much they've improved over their previous results; it does not refer to an improvement over currently-deployed technology.
But the question is, how much does this technology improve performance relative to currently-deployed mirror concentration? And, what is the cost relative to currently-deployed mirror concentration?
If you want a more detailed description (Score:4, Informative)
http://www.sciencemag.org/cgi/content/short/321/5886/226 [sciencemag.org]
Re:Oh, Is It That Time Again? (Score:3, Informative)
Expensive stuff (Score:3, Informative)
This article [venturebeat.com] says the window treatment for the dye alone would run around $300-$400 per square meter of glass. The solar cells would cost extra. The process requires vapor deposition which adds to the cost and it alters the light color passing through the window which may or may not be acceptable to the end user. And then there's this:
Oddly enough, a number of reports appearing today (for example, in the Associated Press) suggested that Covalent's concentrators would be of use in actual windows, but cofounder John Mapel made no mention of that possibility when we talked last week. That's no great surprise -- it would be difficult to get high-intensity light into vertically-positioned windows, much less windows placed on the wrong side of a building.
As a number of other posters have pointed out - wait for an actual product to see what it actually is and what it's capable of.
Re:4 vs 40. (Score:3, Informative)
Actually, yes... but they are collecting more sunlight for each cell, not making the cells more efficient :)
The concept is not new, but apparently the dies are better and more stable now.
Re:Bullshit numbers, no facts to be found... (Score:3, Informative)
Re:Oh, Is It That Time Again? (Score:5, Informative)
Re:Oh, Is It That Time Again? (Score:3, Informative)
Re:You need to increase them by three times that (Score:5, Informative)
Meanwhile passive solar continues worldwide (Score:4, Informative)
While it's great that we have an improved solar cell film, the reality is that, for the most part, the most efficient method used on a practical worldwide scale involves passive solar heating, especially for providing heating and hot water.
Part of the problem is that the manufacturing process - such as that used by Sony in cranking out OLEDs (which they build at the same plant as their photovoltaic solar cells) - causes a fair bit of pollution, both thru film extrusion, bonding, and the doping process.
By 2020 we may see some useful scaled implementation of photovoltaics, but it's still projected that the vast and overwhelming majority of growth in solar will be it's use in passive solar heating (and cooling, using heat exchangers) and in passive solar water heaters, as both such uses have little in the way of pollution in the manufacturing process and have an easier permitting process for factories, installation, and residential and commercial use, and easier to develop tax incentives for on the local and national scales worldwide.
Re:Factor (Score:5, Informative)
Right, most of the trucks driving around in a Solar Farm aren't replacing hydraulic pistons (which operate at one cycle per day).
The trucks are cleaning the surfaces. This technology won't require cleaning because why?
They have achieved 40x concentration; but there is no cell currently manufactured which is cost competitive at 40 suns. If you find one - there are hundreds of ways to concentrate light to 40x.
The reason concentrators are 1000x is because that is precisely where III-V cells are most economic.
Also no discussion of module efficiency. This puts the tech in a class with nanotech, which are equally quiet about their efficiency.
Indeed the disturbingly inaccurate use of the term effeciency by the author suggests a weak grasp of the subject.
Re:Call me when 1000 sq ft = 5kw (Score:4, Informative)
BP sells 200 watt panels that are 14.85 sq ft each. 1000/15 = 66.67 x 200watt = 13.3kw
Of course, that is under ideal generating circumstances.
http://www.bp.com/sectiongenericarticle.do?categoryId=9019633&contentId=7036926 [bp.com]
Re:Oh, Is It That Time Again? (Score:5, Informative)
If oil were free, then all electrical power would be generated from oil. If electricity were free, then oil use would be near-zero because people would be cracking H2 in their homes to fill their hydrogen powered vehicles. That there is a current situation where a small amount of electricity is powered from oil (I'm in Alaska and the vast majority of area covered by power lines is powered by oil, but we are an exception) is mainly because of the economics where oil is a better mobile fuel than coal, and coal is cheaper for generating electricity. If all oil were gone tomorrow, we'd be generating gasoline or diesel type liquids from coal, and coal prices would jump and so would electricity because of it. They aren't linked in that oil goes up $1 and so does electricity. But large changes in price either way will change the demand for the other (with significant market delay when it comes to getting electric or plugable hybrids, but it is happening now none the less).
No, you don't have to track the sun. (Score:5, Informative)
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
Concentration (Score:2, Informative)
Re:4 vs 40. (Score:2, Informative)
Sorry to pick your post to rag on, but literally hundreds of people had a hard time interpreting the article.
Re:Factor (Score:3, Informative)
In their defense, I don't think that they are claiming that this will replace the big solar farms. I think that they are envisioning this tech being used where windows currently are installed, or where solar was only worth installing with tracking collectors - so basically you get feasible solar installations where it wasn't feasible before.
They did nothing to improve solar cells themselves, and thus the efficiency is not touched upon - these guys are just getting light to the edge of a piece of glass.
This is very old tech (Score:3, Informative)
A. Goetzberger et al., "Solar Energy Conversion with Fluorescent Collectors", Applied Physics 14, 1977, pp. 123-139.
Yes 1977!!!
I was also playing with this using plastic from TAP plastics (in the SF Bay Area) http://www.tapplastics.com/ [tapplastics.com] in the late 80's.
Works ok.
See:
Patent 4149902
Patent 5227773
Patent 5816238
Patent 7316497
Mobay Chemical Corporation make a fluorescent called LISA. "fluorescent dye-doped edge-illuminating emitter panels" Technically.
There were some articles.
"A Little Light Goes a Long Way with Lisa", Mobay Corp. Marketing Document.
"Light-Collecting Plastics-A Brilliant Idea", Provisional Information Sheet, Mobay Corp.
Steven Ashley, "Razzle-Dazzle Plastic", Popular Science, pp. 100-101. Sorry can't find the year, (any one can you help here)
CA deregulated electricity? (Score:5, Informative)
California has struggled with an unregulated power supply industry. [spur.org]
CA didn't really deregulate electricity, power, they shifted the regulations. Before, the same company could own both power generation and power transmission. but when the so called deregulation came it split generation and transmission, a company wasn't allowed to do both [wikipedia.org]. Then transmitters were barred from raising rates but generators weren't.
Falcon
Re:Oh, Is It That Time Again? (Score:5, Informative)
"The plants get the orange light and the coating takes the rest."
Most of the photosynthetic response curve is in the blue and red areas, orange is actually pretty low in the curve and thus many plants do not use that wavelength.
Nit pick time... (Score:3, Informative)
I know we will all nit pick this to death so here is mine...
From the FAQ:
"The sun is an inexhaustible source of clean power."
Well, not quite. I know that we cannot exhaust it just by using it's normal emissions as we would place no additional drain on the sun's resources by using solar power than if we didn't exist, however, the suns normal processes will eventual exhaust even it's vast resources of Hydrogen and then start "burning" (there you go, nit pick me now) hydrogen which will drastically change its characteristics. I do however agree that we (everyone alive today and probably the human race in general) won't really care by that time because, hopefully, everyone alive today will be long dead by then and, again hopefully, the human race will have moved on to the rest of the galaxy (galaxies?) by then and look back at "the birth place of mankind" with fond memories but the loss of the Earth due to the sun running out of Hydrogen will be a fairly minor news item.
Re:No, you don't have to track the sun. (Score:3, Informative)
Well no, the angle doesn't change the amount of energy hitting the panel.
Not true. One square foot of light hitting a surface perpendicularly imparts its energy to one square foot of surface. If you increase the angle of incidence the square foot of light spreads its energy out over a larger area and the original square foot of surface area now receives much less energy. It's the reason we have seasons.
You had a very long post, but after that first sentence I didn't bother to read the rest of it - I guess first impressions ARE important.
Re:This is very old tech (Score:3, Informative)