Caltech Makes Flexible, 86% Efficient Solar Arrays 439
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.
I think its entirely reasonable to say... (Score:5, Insightful)
Re:I think its entirely reasonable to say... (Score:5, Interesting)
It sounds like the summary here is overstating the efficiency a bit. The numbers are for the absorption efficiency, not the overall conversion efficiency.
'The light-trapping limit of a material refers to how much sunlight it is able to absorb. The silicon-wire arrays absorb up to 96 percent of incident sunlight at a single wavelength and 85 percent of total collectible sunlight. "We've surpassed previous optical microstructures developed to trap light,"
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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."'
It looks like the overall efficiency is still very very high while using minimal resources. This is exactly the kind of innovation the U.S. needs for carbon-friendly jobs.
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This is exactly the kind of innovation the U.S. needs for carbon-friendly jobs.
Carbon friendly?! Dude, they are planning to reduce the amount of carbon being released. That's like calling Auschwitz "Jew friendly."
Re:I think its entirely reasonable to say... (Score:5, Funny)
Actually it's spot-on. See, carbon-friendly means not turning the carbon into carbon dioxide. That is, it means not gassing the carbon. I think you would call not gassing Jews Jew-friendly.
Re:Godwin's Law! (Score:5, Funny)
Talking of Nazis, did you know that every other use of an apostrophe in your first sentence was incorrect?
Re:Godwin's Law! (Score:4, Informative)
Right you are. Ugh I feel dirty. I thought only morons did that! Maybe it is still true ... maybe I am a half-wit!
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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.
Re:I think its entirely reasonable to say... (Score:5, Informative)
The title of this post and the article is incredibly misleading and very annoying/frustrating to someone who's been working on solar technologies for a while. Don't get me wrong, I think this is a very cool thing, sounds like they have to potential to make very cheap cells, but approach, let alone surpass, current multijunction cells (30-40% eff.) they will not.
Disclaimer: University of Michigan Solar Car Team alum
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Disclaimer: University of Michigan Solar Car Team alum
Cool, someone who knows this stuff (I don't). So given the following numbers 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.
and
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
and
High absorption plus good conversion makes for a high-quality solar cell
And if the current efficiency is around 40%, my two questions are:
In essence, I'm asking:
I am an
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Re:I think its entirely reasonable to say... (Score:5, Informative)
Re:I think its entirely reasonable to say... (Score:5, Insightful)
I think that even if they only last 10 years at the same price per surface-unit, they'll still be more economically viable, because payback-time gets a lot better.
Re:Plastic? 10 years under the sun? (Score:5, Interesting)
Saturn vehicles. Body panels are solid plastic, and I know Saturn has been around since the 90s.
Re:Plastic? 10 years under the sun? (Score:4, Funny)
Yeah, but it has to function after ten years too.
Re:Plastic? 10 years under the sun? (Score:4, Interesting)
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.
Re:Plastic? 10 years under the sun? (Score:4, Funny)
'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*
Re:Plastic? 10 years under the sun? (Score:4, Informative)
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.
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I'd also be very interested to know whether this can be mass produced, and for how much money. They say they are currently working on cells one square centimeter in size.
They're currently working on scaling it up, but arranging these nanowires in a large array, making the electrical connections, and filling with the polymer and scatterers sounds like it will be hard to mass-produce, even if the materials cost is not as high.
Still, good for them.
Better Article... (Score:5, Informative)
http://www.rsc.org/chemistryworld/News/2010/February/14021001.asp [rsc.org]
'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.
Re:I think its entirely reasonable to say... (Score:5, Informative)
The original article is poorly written. MIT's Technology Review has an article that includes information about efficiency of generating electricity, and it says 15%-20%. http://www.technologyreview.com/energy/24665/?a=f [technologyreview.com]
So the story is really that there might be a way to make cheaper, flexible solar panels by mixing silicon and polymers.
Re:I think its entirely reasonable to say... (Score:5, Interesting)
I saw this posted by grobbo at engadget: http://www.engadget.com/2010/02/28/caltech-gurus-whip-up-highly-efficient-low-cost-flexible-solar/#comments [engadget.com]
Turns out the only benefits to this are the flexibility and low cost (which are good, sure, but not that exciting).
According to their letter to nature.com this "also may offer increased photovoltaic efficiency", _may_ suggests to me there probably isn't any significant improvement.
For anyone wondering why high absorption and a high QE don't necessarily result in high energy conversion (like I was a few hours ago) it's because 30% of the photons have insufficient energy to free an electron in silicon, and most of the rest of the photons have more energy than needed to free an electron, so any excess energy beyond that required to free a single electron is wasted as heat.
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No, the only remaining question is: When, if at all, will it actually come to the market. Meaning when will I be able to go to an electronics shop, grab it with my own hands, buy it, and then use it?
Until then... anyone can just make up stuff, put it somewhere trustworthy, and then let the trust-relationship-machine do the rest. (Not saying this is the case here. Just opening the mind. :)
The thing is: I got absolutely zero proof that any of this is not made up. And I don‘t trust “the news”
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The lowering of cost would actually be the most important impact. Current solar panels would cost too much no matter how efficient they were.
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Fortunately electric companies are better regulated than the credit card companies. By which of course I mean, regulated at all.
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If a solar solution appear
Absorbed not necessarily equal to electricity (Score:5, Insightful)
Re:Absorbed not necessarily equal to electricity (Score:5, Insightful)
If light is absorbed but not converted to electricity, isn't the panel going to get hot?
Re:Absorbed not necessarily equal to electricity (Score:5, Funny)
Well, getting hot water out of it is a feature, not a bug.
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Hot air. Hot air. Dammit, you missed the obvious joke by 998.7 kg/m^3.
Re:Absorbed not necessarily equal to electricity (Score:5, Informative)
Yes, just like any other dark panel you leave in the sun. Except not as hot, because some of the energy is being exported as electricity. So unless they're flammable at really low temperature we'll probably be okay.
Re:Absorbed not necessarily equal to electricity (Score:5, Informative)
Re:Absorbed not necessarily equal to electricity (Score:5, Informative)
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The quantum efficiency of existing solar cells is also very high - approaching 100%. But a large fraction of those electron-hole pairs quickly recombine within the semiconductor.
Re:Absorbed not necessarily equal to electricity (Score:4, Insightful)
Re:Absorbed not necessarily equal to electricity (Score:5, Insightful)
I don't understand why the break-even time on solar has to be on the order of a handful of years for it to be economically feasible.
The break-even time for nuclear is over a decade, and it's pretty long for hydro projects too. So why do we insist that solar has to turn a profit Real Quick Now?
Re:Absorbed not necessarily equal to electricity (Score:5, Insightful)
For appeal to common users, and also for appeal to producers.
Now, solar is limited by two big things:
1. total cost (panels are expensive, so few people buy them, so few people produce them, so they are more expensive than it could be)
2. the Return on Investment is low (extreme cases - 10 years, but typically more than 20).
If a cheap production method can be devised, this will open the market to many buyers (many people don't even consider buying a $25,000 solar panel system, but will buy in a heart beat a $2,500 solar panel system).
Also, a cheap production method will allow (hopefully) a quick panel production ramp up)
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None of what you just said contributed to the conversation in anyway. All you did was repeat the GP's statement of the problem in more detail.
His point was that nuclear and hydro (and I'll add coal to that list too) power plants take longer to recoup their initial investment, so there's no reason for this to be a problem for solar power other than stupid reporters repeating the myth that it takes to long to pay for itself, and thus people actually believe it.
Re:Absorbed not necessarily equal to electricity (Score:5, Insightful)
Because unlike nuclear, solar is a system that can be deployed on decentralised on many homes. Expect most poeple dont stay in the one home for 20+ years, so it's very hard to justify the investment.
If they can get the costs down, more poeple will buy this, just like solar how water and insulation. Not to mention rural/remote and 3rd world installations. The potential market for small systems is huge.
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most poeple dont stay in the one home for 20+ years, so it's very hard to justify the investment.
Except installed solar increases the value of the house. If you live in a house a few years and have solar panels installed when you move in, when you leave it will be mostly paid for and you get more from the sell. This is even more true in California with it's high electricity costs.
If they can get the costs down, more poeple will buy this, just like solar how water and insulation.
Actually of these the first
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They've already invented inexpensive lightweight solar panals (see Nanosolar).
As a result, their entire production for the next few years has already been sold to a solar power plant in germany.
I figure I was blowing $2k for computers every 3 years. If I extend that by a year or two, I get two solar panals and support hardware with the savings. A cost turns into a profit center.
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It doesn't have to be 2-3 years, that's nuts (if it was, people would build solar until the price of energy dropped enough that the payback-time rose)
But it -does- need to be significantly less than the expected lifetime of the panels. Current ones tend to be estimated at 20 years, though local conditions influence it a lot.
With a payback of 10 years, it'd probably be interesting.
At the moment though, you typically get around 2% of the purchase-and-installation cost in payback a year, so you'd recoup in 50
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Re:Absorbed not necessarily equal to electricity (Score:5, Insightful)
Re:Absorbed not necessarily equal to electricity (Score:5, Interesting)
Because I don't pay for the nuclear plant or the hydro dam
Yes you do (if you use power from one).
However, getting the money together to buy and install the solar panels is all on me, the homeowner
No it's not. I see/hear ads from solar power rental places all the time (on local media no less, but then again it is Los Angeles). They will do the full install at no upfront, then charge you amortized payments--if the payments are less than what you save on electricity (which their ads claim will usually be the case, for what that's worth, I have no idea if that part's true) then they pay for themselves on day one.
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Hmmm.
So if financing a nuclear power plant is economically attractive, then so should financing consumer solar panels. In fact if they are lightweight an easy to install, it'd be a lot more feasible to repossess and resell them, although that means you'll probably need to insure them against theft.
That said, I'd bet the problem is with consumers rather than banks. Most houses wouldn't be able to generate enough power to go off the grid, and the payback time doesn't justify the aggravation of having another
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Because most current cells break down and become less efficient over time. eg the don't last forever!
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It's important if you want Joe Home-owner to shell out the initial investment, not so much if it's a corporation setting up a plant to generate hundereds of megawatts. That being said TFA claims this design uses 1/50th the amount of silicon crystal which is the expensive part in existing cells. Not only would it be a lot cheaper to make the new
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The break-even time for nuclear is over a decade,
And it gets worse with every plant we build.
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I buy things for my household that I expect to keep for many years, like cars and major appliances. Why can't solar power be the same way?
If a solar installation can repay itself in 15 years, then either buy one or borrow money and then buy one, just like you do with any other big residential purchase.
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The article states a quantum efficiency of %90-%100. That is the rate of photons converted to electrons. So you have a high rate of absorption and a high rate of conversion. 77% total efficiently (see below) of course they have only made them 1cm square so far.
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That’s explained trough simple quantum physics and energy preservation. It must go somewhere. It can’t just “vanish”. And since absorption means it gets an electron out of the atom and moving, it is equal to electricity.
I can only recommend to learn a bit about quantum physics. Not necessarily the math, but the rules/laws of it. Useful and fun. :)
Meh (Score:5, Funny)
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.
Re:Meh (Score:5, Insightful)
Meanwhile, Germany (where it is always cloudy, and where the government recognizes the need for renewable energy) is pushing solar like crazy, and Arizona (where it is always sunny, and where the governor has no conception of future beyond a few years) is burning coal.
wtf?
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Yeah, but try telling that to those silly Germans [wikipedia.org].
NOT incandescent light! (Score:5, Informative)
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I was about to comment on the absurdity of "single-frequency incident light" until I saw that TFA had it right. I figure this can slip as a typo or brain-o rather than something out of ignorance.
Will they float? (Score:5, Funny)
Is that the right question? (Score:2)
Will they float?
Maybe, but what I really want to know: will it blend?
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But then an oil tanker would accidentally stray off course and cut the power cable with its propellers.
In requires polymer to make... (Score:4, Interesting)
Re:In requires polymer to make... (Score:5, Insightful)
I beg to differ. This is exactly what we should be using our oil reserves for: building up a supply of renewable energy. Look at it this way: we can burn our oil; or we can use it to create systems that will generate energy for us, without needing further input of oil.
I'd dearly love to see us in a world where we no longer need to burn oil or coal for energy, or if we do need to do so, we use oil we've produced ourselves - using only water and carbon dioxide as the essential inputs. On that day, we will have overcome one of the major problems facing our society today.
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We'll never run out of plastic. Don't forget that "oil" came from biological sources. It'll be more expensive than just pumping the stuff out of the ground, but as long as there is life on Earth we'll be able to produce all the polymers we need.
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Even when there's no life on Earth we'll be able to produce all the polymers we'll need.
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But we won't nee... ohhh.
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you don't need oil to make polymers (its a lot easier though) hell you don't even need oil to make oil.
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How so? The oil isn't being burned, so it's not ending up in the atmosphere.
Or do you think oil is evil even when it's locked out of the biosphere?
Oil isn't bad. The byproducts of burning it are.
And for that matter, you can produce polymers from bio-oil just as well (though not so cheaply).
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Last time I checked you're a blithering idiot who talks out of his ass.
Does silicon grow on a beach? In a manner of speaking...
However, the factories that process raw silica into high grade silicon for semi-conductor production are in short supply, and this has driven up the price of silicon. Silica is cheap, and every where. Silicon is manufactured, and currently not cheap (enough for widespread solar panels).
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I for one hope this does maximum harm to the wallets of coal luddites such a Senator Inhofe and his corporate pay-masters.
Massive typo in summary. (Score:4, Informative)
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.
Re:Massive typo in summary. (Score:5, Funny)
You hook a lightbulb up to a solar panel, and it will keep glowing forever. Obviously this has to be done in a completely sealed box so that none of the light escapes, so you are forbidden from checking that the light is still glowing.
Some would say it's useless, but it improves the quality of life of physicists' cats quite dramatically.
So when can I buy those? (Score:2)
That's all I really want to know. If I can put them on my roof for a reasonable price, I'll be one happy wanker, but lab situations just don't necessarily translate so well into real life.
Not having read the article I don't know whether it was mentioned.
Assuiming that production of these is not too difficult, this seems like a very good way to produce power for you and at least one neighbour just by tiling one roof (I'm pulling the figures for that calculation out of my ass, so if you want to comment on tha
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Way to early to be talking mass production. But very promising science. If they are right they will be very rich little scientists.
This is way over-hyped (Score:4, Informative)
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red light (Score:4, Interesting)
i'd love cheap energy from the sun, but this won't be it.
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Predicted photovoltaic efficiency only 14.5% (Score:5, Informative)
Here's the actual scientific paper, "Predicted Efficiency of Si Wire Array Solar Cells". [caltech.edu] 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.)
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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.)
From Nanosolar's website, it sounds like they've been shipping panels commercially for the last two years, and that they have panel assemblies in both the US and Germany...
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From Nanosolar's website, it sounds like they've been shipping panels commercially for the last two years, and that they have panel assemblies in both the US and Germany...
Yes, from Nanosolar's web site, it sounds that way. But as of 2009, "not one Solarply cell has been held yet in the hands of a consumer". [buildingwithearth.com] There are no reports of actual Nanosolar installations. Supposedly they're building big solar panel installations for utility companies. So where are the announcements from those utility companies
Re:Predicted photovoltaic efficiency only 14.5% (Score:5, Informative)
The take-home message from the paper, as far as I can tell, is that the researchers showed that one can achieve performance comparable to commercial solar cells by using 1% of the expensive ultrapure silicon used in current PV's.
nice try blanco nino (Score:5, Insightful)
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.
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conversion effiency (Score:2, Informative)
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 ef
NOT 86% efficient. (Score:2, Insightful)
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
Cold fusion, Amazing solar energy, gasoline (Score:5, Insightful)
"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.
from the ignore-kdawson-the-idiot dept. (Score:4, Interesting)
Slashdot, pls think of the children. (Score:3, Funny)
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.
solar payback period (Score:3, Interesting)
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 [calfinder.com] 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 a
It's plastic ! (Score:2, Interesting)
How durable can this device be? It's made up of 98% plastic.
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Re:It's plastic ! (Score:5, Insightful)
You've never left them out in direct sun for ten to twenty years then.
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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.
Re:It's plastic ! (Score:4, Insightful)
There's plastic, and then there's plastic. Some modern plastics are quite durable.
Re:It's plastic ! (Score:5, Funny)
There's plastic, and then there's plastic. Some modern plastics are quite explosive.
Re:It's plastic ! (Score:4, Interesting)
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.
Re: (Score:3, Informative)
Re:Efficiency (Score:4, Informative)
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.