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Caltech Makes Flexible, 86% Efficient Solar Arrays
strredwolf writes "Caltech has released a flexible solar array that converts 95% of single-wavelength incandescent light and 86% of all sunlight into electricity. Instead of being flat-panel, they stand thin silicon wires in a plastic substrate that scatters the light onto them. The total composition is 98% plastic, 2% wire — the amount of silicon used is 1/50th that of ordinary panels. So as soon as they can get these to market, solar could be very viable and cheap to produce." Update: 03/01 21:02 GMT by KD : Reader axelrosen points out evidence that the 80%+ efficiency figure is wrong. MIT's Tech Review, in covering the Caltech announcement, says that the new panel's efficiency is in the 15%-20% range — which is competitive with the current state of the art. And the Caltech panel should be far cheaper to manufacture.
Holy balls. If this article is spot on, they've doubled the efficiency of the current technology (which converts at about 40%) AND done it in such a way that the stuff is cheaper to manufacture AND made it flexible. This is the sort of thing that can have a real (and probably positive) impact on the world we know. Amazing. The only remaining question (I didn't see anything about it in TFA) is how durable this stuff is compared to the current panels.
As far as I can figure from the article what is says is 95/86 of the light is absorbed, it doesn't say that all of this light is converted into electricity as is stated here on Slashdot. That is also impressive numbers and very interesting, but my guess is that the efficiency of the solar panel is going to be a lot lower than those numbers posted on the parent, most likely at least a factor 2 lower.
All these idiots working on solar panels when what is really needed is overcast panels to get power from gloomy days when you use more light bulbs.
They whose government reduces their essential liberties for temporary security, receive neither liberty nor security.
It's not incandescent light, it's incident light. sigh.
If we set up solar devices so that they can float in water and function as an interconnected grid, we could drape a network of them over the Pacific Garbage Patch so no one would notice it.
so it is still tied to oil. Becoming cheap and widely popular may do more harm than good I fear.
From TFA:
The silicon-wire arrays absorb up to 96 percent of incident sunlight at a single wavelength and 85 percent of total collectible sunlight.
http://www.rsc.org/chemistryworld/News/2010/February/14021001.asp
'We have shown the optical absorption efficiency and charge carrier collection efficiency of a silicon wire array cell is comparable to a conventional silicon cell, but a wire array cell uses up to 100 times less silicon due to enhanced light-trapping effects,' says Atwater. Significantly, the wire arrays absorb infrared light more efficiently that conventional silicon surfaces, further improving the performance of the new device.
So the gist is that it's more efficient because it converts infrared, uses some type of clear polymer with alumina "reflector particles" in place of 99% of the expensive (doped) silicon, and is flexible and therefore easier to manufacture.
"I assumed blithely that there were no elves out there in the darkness"
Collection efficiency (which is what TFA is claiming to be 86%) vs. conversion efficiency (that 40% number you remember) is what you're missing, but from other articles on the technology it appears that the conversion efficiency for these cells should be higher than existing designs:
The silicon wire arrays created by Atwater and his colleagues are able to convert between 90 and 100 percent of the photons they absorb into electrons--in technical terms, the wires have a near-perfect internal quantum efficiency. "High absorption plus good conversion makes for a high-quality solar cell," says Atwater. "It's an important advance."'
Which could give them ~78% conversion efficiency, still nearly double over the best cells currently.
I've never had problems with soda bottles...and thats 100% plastic
All your 09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0 are belong to us
This is interesting work, but it is in a very immature stage of development. They seem to be no where near demonstrating a practical solar cell, and speculated conversion efficiency numbers like 86% are laughable. One of the fundamental limitations of a cell based on Si wires is that the higher a photon's energy is over the bandgap of Si, the more energy is lost as heat. I believe the theoretical maximum conversion efficiency for a Si solar cell is around 30%, and commercially viable cells are limited to around 20% because of practical issues in creating solid state cells such as making electrical contacts to the device, the high cost of making higher efficency (20+%) Si cells. This work doesn't begin to address such issues. I think it is unfortunate that over-hype like this can take luster off of progress in photovoltaics that seems less spectacular but is much closer to practical realization.
Saturn vehicles. Body panels are solid plastic, and I know Saturn has been around since the 90s.
Still waiting on Serviscope_minor to wake up to fucking reality and realize that Jessica Price isn't going to fuck him.
You've never left them out in direct sun for ten to twenty years then.
Yeah, but it has to function after ten years too.
Seconded. I sold a '94 Saturn last year that had been parked in the Arizona sun for many years. (Got rid of it due to multiple electronics failures and an engine oil leak that'd not be worth it to fix). Survived the sunlight just fine.
And the plastic body panels were GREAT. Lightweight and dent-proof.
There's plastic, and then there's plastic. Some modern plastics are quite durable.
i'd love cheap energy from the sun, but this won't be it.
If you mod me down, I will become more powerful than you can imagine....
Here's the actual scientific paper, "Predicted Efficiency of Si Wire Array Solar Cells". That's by the same authors mentioned in the press release. While the thing does trap most of the light hitting it, only a fraction of the energy in that light is converted to electricity. In fact, this thing is currently less efficient than the better commercial solar cells.
From the paper: ... simulated photovoltaic efficency of 14.5%. ... Conclusion: ... "Si wire array solar cells have the potential to reach efficiencies competitive with traditional Si crystalline solar cells."
So, an interesting development, but no big breakthrough. There's a claim that it might be a cheaper way to make solar cells, but everybody who comes up with a new design makes that claim. (Nanosolar comes to mind; their technology is supposed to be cheaper, but so far they've spent half a billion dollars and apparently have only produced sample panels.)
'94 Saturn ... parked in the Arizona sun for many years ... multiple electronics failures ... engine oil leak
Survived the sunlight just fine
It sure sounds it.
*ducks*
PhD candidate doing my research in new materials for photovoltaics here.
I'm sick and tired of all this mis-reporting. These are NOT 86% efficient cells. If they were, (and they were inexpensive) it would be the greatest discovery in 50 years and it would have been all over every newspaper in the world 2 weeks ago when this paper was published.
They simply absorb 86% of light that hits them. When you say a cell is X% efficient without qualifying it, it's taken to mean power conversion efficiency [PCE] (optical power in/ electrical power out) That and dollars per watt are the numbers that really matter. Read the Nature Materials paper that drove this and you'll see that theory says this design could be up to 17% efficient. That compares unfavorably to mid to high-end commercial cells on the market today.
I'm not saying that this research is a worthless endeavor, maybe they can hit the maximum theoretically possible PCE and keep the cost down. That might have real-world impact.
The caltech news brief quotes Atwater (the PI for this research) as saying that the photons are not only absorbed, but they're also convertedto charge carriers (which is a good step). The problem he doesn't mention here is, these charge carriers loose all their energy (voltage) before they exit the cell. Solve that problem and we've got a winner.
The fundamental issue with nano-structured designs like this is the surface area of the P-N junctions in them. Large surface area means high dark current which means low voltage output. Low voltage output means low PCE. Unfortunately, nothing in this research solves that problem.
reading these slashdot comments reveals a whole lot of confusion about solar cell efficiency.
photons with energy less than the bandgap of the conversion material will not be converted to electrons. photons with energy greater than the bandgap will only convert at the bandgap energy. the high effieincy multijunction cells attempt to address this. multi-exciton generation can happen if the photon is several times the bandgap energy, and there is some hope that quantom dot cells will be able to achieve high efficiency this way though the most effienct qd cells currently get like 5% effiency.
electron-hole recombination happening within the material instead of through the cathode and anode will cause a photon to be released. the higher absorption of the cells in TFA will help keep this photon trapped in the cell, but if it loses energy, it will be less than the bandgap and not be converted again. multijunctions can address this effect somewhat by absorbing the new lower energy photon. high temparature operation also helps increase the likelihood of the electron-hole pair making it to the cathode-anode. the highest effiency cells so far have been achieved by concentrating the lightbeams and then splitting the beams into different colors to be absorbed by different sections.
if you put panels on your roof and you live in a place with cloud cover then it won't be worth using a heliostat system to track the sun so you will suffer loss of the cosine of the angle between your panel and the sun. without tracking the sun you aren't going to be using rainbox concentrators either so you are necessarily using lower efficiency cells too.
"When was the last time you find any plastic that can last 10 years under the sun?"
My plastic garbage bins have spent at least a decade out in the Aussie sun. A lot of plastic that you find in throw away stuff these days has been deliberately engineered to be bio-degradeable due to pollution concerns in the 80's. The older non-biodegradable stuff has formed a large "islands" in the North Pacific and North Atlantic.
And did you exchange a walk on part in the war for a lead role in a cage? - Pink Floyd.
It's EQE is 77-85% (above the band-gap).
It's IQE is 90-100% (above the band-gap).
But it's energy conversion is similar to other commercial panels; about 20%.
High absorption and high QE is not enough to get high conversion rates.
You still have the band-gap (the minimum frequency which a photon needs to be able to free an electron from silicon) which excludes up to 30% of all photons, and almost all photons above the band-gap which do free an electron have more energy than is necessary to do so, so the excess is wasted as heat.
Unfortunately the only things to get excited about here are the low cost and flexibility.
You mean like vinyl siding? We also clad window and skylight frames with it. And then there's acrylic and lexan, visible at any general aviation airport, sitting in the sun.
The problem with plastic is perception. It can be designed to do a whole lot of things really well. Problem is, part of what that means is it can be used to make really cheap shit well, and people start to think plastic means cheap shit.
There's plastic, and then there's plastic. Some modern plastics are quite explosive.
45 5F E1 04 22 CA 29 C4 93 3F 95 05 2B 79 2A B2
Ever heard of polycarbonate? They use it to produce composite bulletproof window panes, safety shields for industrial machinery, impact-resistant safety glasses, underwater portholes, etc. It does degrade somewhat under UV light, but then, you can just put an UV filter on top of it, it's not going to be a problem for the panel itself. And there are other transparent plastics with very good properities for this application.
This is Slashdot. Common sense is futile. You will be modded down.
"as soon as they can get these to market, solar could be very viable and cheap to produce." And if a frog had wings his ass wouldn't bump the ground when he hops.
I appreciate Slashdot acting like an old Popular Mechanics here, but I wouldn't get too excited just yet. As somebody pointed out in another forum, when you compare ethanol with gasoline in terms of efficiency, if all we had was ethanol primarily from "corn" (U.S. term, UK term is "maize") and then someone invented gasoline, we would be raving about the improvement in efficiency and economy. IOW, I will believe cheap, efficient solar power when I see it on the neighbor's roof. Until then, this is one more expensive quest for a pot of gold at the end of a rainbow. In the meantime, we could be practicing more energy efficiency.
FWIW, I knew W was full of crap with that whole "hydrogen economy" nonsense back around 2005. That was an absurd sop to deflect a little criticism that he was as much a tool of Big Oil as his Old Man. Make note that I served in Iraq during Operation Desert Storm and when it was over, George H.W. Bush was sitting on a 91 percent approval rating based on a war we had to fight to maintain a steady supply of petroleum for the Western Powers and Japan. From the desert, I wrote my Senators and lobbied them to get a bill going to get us to start weaning off Mideast Oil. That S.O.B. Bush didn't raise a finger, nor did our Congress and eventually Western wealth transfer begat Osama Bin Laden, 9/11, Iraq War II, and Afghanistan. Wouldn't you think a 91 percent approval rating might have been enough political capital to change things a little? It may even have made Bush the Elder seem like the President of the U.S.A. instead of President of the New World Order since he rightfully earned a reputation for being allergic to domestic policy. His detachment had a lot to do with getting booted in '92. A review of the stock market back in '90 - '91 reveals that Big Oil shot up and helped a lot of folks in that business recover from the very hard times they went through in the late '80's. Though I was a conservative and a combat veteran, I campaigned for Bill Clinton in '92 as I was so disgusted with Bush the Elder. Still am. God save us from another Bush.
Most of us know in our heart of hearts that our troops are in Iraq and Afghanistan because of the continued grip the Mideast has on Western economies. In World War II, the U.S. national speed limit was 35 mph and gasoline was rationed with coupons. This was done to make sure the military had plenty of fuel. If some shared sacrifice was called for now, I think most Americans would grumble, but go along with it for the sake of untangling from the Iraq and Afghan Wars. How about bringing back the 55 mph speed limit of the '70's and '80's? What about a tax based on the weight of a vehicle? If we cut back on petroleum use, we help our independence and the environment at the same time. Now that's what I call "conserve-atism".
If you want to see what needs to be done about our dependence on petroleum, just look for the occasional Charles Krauthammer piece on it. He makes the same recommendations about every 5 years, the centerpiece of which is a flexible tax on gasoline that seeks to wean us off cheap oil while keeping the price of gasoline fairly steady.
In principio erat Verbum.
Talking of Nazis, did you know that every other use of an apostrophe in your first sentence was incorrect?
Automatic transmissions can be put into Neutral with a small move of the shifter, even while accelerating. This would have the same effect as pressing a clutch in a manual.
http://www.mhall119.com
Yes and no. Yes, UV is the most energetic light, but there isn't much of it in sunlight at the earth's surface. Most of it has been lost to ozone, Rayleigh scattering, etc. There's enough to give you a sunburn, but no, in terms of the actual amount of power in sunlight at the earth's surface, it's less than 5%. Filtering it to zero to obtain much longer PV panel lifetime is generally a net economic benefit in terms of TCO.
The original article is poorly written (no, not even close to 86% you stupid twats) and kdawson is equally foolish for echoing this garbage. This is why this site sucks. Brain-dead slashdot editors, time and time again, post shitty articles that make extraordinary claims which end up being completely false or misleading.
Slashdot, please think of the children that will be disappointed by this article.
Us grownups can see through the PR-speak, but kids can't.
We can see that this loose talk of high efficiencies is just that-- only part of the story.
It's swell that these gizmos have a 97% absorption efficiency, but that's only the front end.
The actual cell, which converts the light to electricity, is no different-- about 16% efficient, due
to the many mismatches in energy levels and the unavoidable phonon products.
Plus the business about needing less silicon is not spreadsheet-worthy. The actual bulk silicon is not a large part of the cost.
Even if they got the silicon usage down to 0%, the cost would not come down very much if at all.
Also the economic predictions are unrealistic. Nothing that's better has ever sold for less than 5% under the price of the competition. No company can afford to leave money on the table.
Right you are. Ugh I feel dirty. I thought only morons did that! Maybe it is still true ... maybe I am a half-wit!
Infuriate left and right
Let's get this over with:
As any discussion grows longer, the probability of anything being mentioned or pointed out approaches 1. The exception being Soviet Russia, where 1 approaches you.
Entomologically speaking, the spider is not a bug, it's a feature.
Right now, solar cells are so expensive, they take something like 15 or 20 years to pay for themselves, so most property owners don't see a big incentive. Lower that price to 10 years or 8 years, or even lower, and suddenly the demand for these things will skyrocket.
The payback period for solar is already under 10 years. New Jersey has a payback period of 1.5 years, "New York and Delaware are next in line with payback in 3-6 years, and California, Maryland, Massachusetts and Wisconsin all tied for fourth at seven years." Of course, if because of this everybody went out and started buying solar energy systems, the cost could go up, higher demand drive prices up. Then again because of economy of scale and competition prices could go down even more.
Falcon
Should there be a Law?