Creating Electric Power From Light Using Gold Nanoparticles 77
cyberfringe writes "Professor of Materials Science Dawn Bonnell and colleagues at the University of Pennsylvania have discovered a way to turn optical radiation into electrical current that could lead to self-powering molecular circuits and efficient data storage. They create surface plasmons that ride the surface of gold nanoparticles on a glass substrate. Surface plasmons were found to increase the efficiency of current production by a factor of four to 20, and with many independent parameters to optimize, enhancement factors could reach into the thousands. 'If the efficiency of the system could be scaled up without any additional, unforeseen limitations, we could conceivably manufacture a 1A, 1V sample the diameter of a human hair and an inch long,' Prof. Bonnell explained. The academic paper was published in the current issue of ACS Nano. (Abstract available for free.) The significance? This may allow the creation of nano-sized circuits that can power themselves through sunlight (or another directed light source). Delivery of power to nanodevices is one of the big challenges in the field."
"Self-powering" (Score:2, Insightful)
If they're powered by light then they aren't really "self-powered", are they?
Re:"Self-powering" (Score:4, Insightful)
Although it is misleading, I think they meant that the actual structure of the circuit (the leads that run between devices) could actually generate the power, as opposed to having a PV cell somewhere to generate it and then carry it to the load through conventional means. The thought that you can get a watt (1A @ 1V) from a one inch piece of this stuff is really stunning. Considering how many useful things can run on a watt or less, it seems like an absolutely trivial physical package for providing power, the comparable PV cell would be a thousand times larger/heavier, if not more.
Re:"Self-powering" (Score:5, Interesting)
Still, it's a cool concept...
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No. Any reasonably focused laser would achieve such density, but over a much smaller area.
You'd need to focus one of those 50mW laser beam pointers to something like a 150um diameter round spot. Not that hard, even givem the bad mode these lasers have.
--
lalalalala
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Surely not a weapon.
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From the look of it, they are using a laser to arrive at the 1W/inch of material. Sunlight produces approx 1 watt for a 1" x 12" area, so their claims certainly need adjusting if they are going to use these in normal sunlight.
This is probably why they are currently not looking into PV applications, the device is much better at turning laser light into an electrical signal with transistor-like precision than it is anything else (like gathering sunlight).
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Sunlight striking the earth's surface has about 1.353 kW per square meter. Therefore,
So the
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This could be an interesting part of a remotely powered space craft. If we could park a large solar array out at a Lagrange point, and have a laser that could send out a concentrated beam to one of these micro-hair receivers on a space craft, that could really reduce fuel requirements and allow for some decent speed (continual acceleration).
This isn't my idea; Robert L. Forward [wikipedia.org] came up with it back in the '60's and used it in some of his books [wikipedia.org].
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I'm guessing that it's a mistake or that it doesn't scale well or that if you try it they melt but if you could build some ultra efficient collector like that then even if it was expensive it would mean cheap PV by means of a big cheap mirror and a small expensive panel.
yep, too hot (Score:1)
That's the problem with all the various solar concentrators, they tend to concentrate the heat range of the spectrum as well as the light range they need. Figure out a cheap and easy way to beat that, and you might get rich. Practical solar concentrators exist, so that isn't a problem then, for the ones that are designed for that, as thermal concentrators [wikipedia.org]. PV does not like excessive heat, it runs better cooler.
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That kind of density is amazing. So, that means one of four things.
My bet is Gross Exaggeration.
First, TFA sort of glosses over the fact that a red laser was needed to achieve even the meager results demonstrated at this point. They specifically say solar is not the direction of their research, and employ the weasel phrase "without any additional unforeseen limitations".
I suspect this is a case where the power needed to induce a current was grossly out of proportion to the achieved results. Of course this is not unusual in the discovery phase.
Remove the laser, set it in t
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It's this one. Or rather, they say nothing about efficiency or the intensity of the incident required for their 1 watt per inch 'solar hair'. At, say, 150uM diameter, an inch of this solar hair has an area of 12mm^2 and so a power density of 0.0835 W/mm^2. That's 83.5 kW per square meter, while sunlight maxes out at around only 1kW / square meter. Assuming 30% efficiency, you'd need a light amplification factor of around 240 to get this sort of power out of sunlight. I don't know of any solid material that
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Re:"Self-powering" (Score:4, Insightful)
They have their own on-board power generation. Ergo, self-powered.
Any other definition means that nothing was self-powered except possibly and extremely hypothetically the Big Bang.
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No (Score:4, Funny)
If the efficiency of the system could be scaled up without any additional, unforeseen limitations
No
I can do it too! (Score:2, Informative)
Yes
Get with the program, editors! (Score:3, Funny)
It's been a whole month [slashdot.org] since the last amazing-solar-tech-real-soon-now article. I expect to be entertained by visions of our solar-powered utopian future on at least a weekly basis.
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I prefer resonant induction stories, for the zaniness quotient.
Here ya go (Score:1)
Sorry to disappoint, I only do journal entries, not front page submissions. You would have gotten your fix sooner. This link for yet another amazing solar breakthrough that will get buried like the rest of them [caltech.edu] was from a few days ago.
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Journals (Score:1)
You need to make use of the slashdot journal system, and friend's lists. The front page here is not the total scene, there is quite a robust community of writers here going way back, and although there was the "great exodus" of journalists some years ago, it is building back up. I get a lot of interesting things to read and engage in "spirited debates" with other hard core journalists here, heh, from guys here who like to write, plus I write. I do a lot on geoeconomics and alt energy (I think I have the mos
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And meanwhile, consumer solar tech *does* continue to advance. Have you priced solar panels lately? Solarbuzz [solarbuzz.com] lists:
Lowest Mono-crystalline Module Price: $2.37/Wp
Lowest Multi-crystalline Module Price: $1.98/Wp
Lowest Thin Film Module price: $1.76/Wp
You always see this: in any field where there's lots of announcements about new tech, people berating them for that tech not showing up instantly on the consumer market... while meanwhile, the consumer market *does* continue to advance behind the scenes.
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The true irony is that we already can build large-scale efficient solar power stations. They use the amazing cutting-edge technology called "mirrors" to concentrate sunlight to heat water and drive turbines. Unfortunately, even this supertech can't get around cloudy days or nighttime.
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that's b/c they're putting the "mirrors" in the wrong place [newscientist.com]. :) (not that i really find the idea practicable, but if one had to...)
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Actually, it hasn't.
I submitted this story [slashdot.org]
on February 17, but no /. editor seemed to think it worthy of publication.
Frankly, I think they're all do-do heads ...
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That’s only reserved for sneaky Apple Slashvertisements! ^^
(Seriously, go search for articles containing “Apple”, “iPhone” or “iPad” on Slashdot. You won’t find a week without at least one, and up to 7 of ’em.)
WOW! (Score:3, Interesting)
TFA isn't particularly enlightning, but the news is indeed slashdot worthy but raises many questions.
While not currently aimed at solar panel technology
Why not?
their research has uncovered a way to turn optical radiation into electrical current that could lead to self-powering molecular circuits
Battery-free gizmos? It doesn't say, but it seems like the photons wouldn't have to be optical wavelengths. However, how much current does this tech produce? "we could conceivably manufacture a 1A, 1V sample the diameter of a human hair and an inch long"
WOW, that's a lot of power from a tinty surface. 1 amp at one volt is one watt; a device using this tech the size of a phone battery could run an air conditioner if there were any way to keep the thing from melting.
At the end of TFA it links the study [acs.org].
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One watt from an inch-long and hair-thin area? How freaking intense would that light source have to be? Pretty hard to believe.
Okay so the big stumbling block in this method of powering nano-scale devices is the macro-scale Fresnel lens you need to focus sunlight on it. But other than that it's perfect!
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Like lasers?
Yes I do like lasers, thanks for asking.
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One watt from an inch-long and hair-thin area? How freaking intense would that light source have to be? Pretty hard to believe.
Twice as bright as the sun with 100% energy-conversion efficiency, as the solar constant is roughly half a watt per square inch.
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Wrong.
An inch-long hair is only 90 micrometers wide. So that is 0.00354330709 square inches, so you would need something 282 times as bright as the sun.
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282 times as bright as the sun
I suddenly see a use for all of those nuclear weapons various countries have been hoarding...
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Wrong.
An inch-long hair is only 90 micrometers wide. So that is 0.00354330709 square inches, so you would need something 282 times as bright as the sun.
Ah, I interpreted the hair-width as the thickness of the film, and an inch to be the characteristic dimension of the area. But maybe you're right.
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Hmmm, good point. I wouuld have to re-read the article to see exactly what they meant.
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150 watts per square-inch (call it about 150 human hairs per-inch) is not in the realm of reality. That would vaporize you. The sun produces 1,353 watts per square meter on earth, discounting the atmosphere. One square meter = 1,550 square inches. So the sun produces less than 1 watt per square inch. Imagine if the sun were 150x hotter. It would not be pleasant.
not a problem (Score:2)
big fucking deal, commercial CPV, concentrating photovoltiac systems, already work with lenses or mirrors to go 400 to 100x, your 150x is puny.
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hah, typo, that's 400x to 1000x not 100. A done deal, increased efficiency is the only new thing here.
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1 amp at one volt is one watt; a device using this tech the size of a phone battery could run an air conditioner if there were any way to keep the thing from melting.
That’s what the (huge) air conditioner is for! ;)
Plasmons Surfing ... (Score:4, Funny)
They create surface plasmons that ride the surface of gold nanoparticles on a glass substrate.
Boy, does that take me back to my days in the college dorms ... good times.
Old News (Score:2, Interesting)
Nature loves expensive metals (Score:2)
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"Nanotech" always seems to require expensive metals, and it almost always require
more science PR nonsense (Score:5, Informative)
I know Dawn, and I have no idea if the reporter is taking statements out of context or what...
1) This isn't photovoltaic (power generating), and nothing like photovoltaics was demonstrated. Instead, what they showed was that the resistance of a film of gold nanoparticles can be modulated by shining light on it. This isn't overstated in the actual paper, and the explanation they give is good (surface plasmons creating excited states in the polymer between the particles, in the case of red and green light). They used low power diode lasers to see the photoresponse.
2) Scaling of the system: in the paper, they tried a few different sized devices, and say they saw the same response from each of them. This is actually really bad, as you would hope to get more of this kind of response from a larger system.
3) The 1V, 1A comment: Totally crazy. They're seeing less than 1pA at 1V right now, and as they pointed out, are not seeing any scaling behavior, let alone good scaling. It's irresponsible to make (or print) this comment. If doubling the size of the device doesn't change the photoresponse, you should not assume a device 1000 times as big gives 1000 times more response.
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Simple Maths Are Hard (Score:1)
current production by a factor of four to 20,
AKA: One to five.
And while I am being pedantic, let's discuss consistency. Proper grammar, so far as I recall, requests that you use a consistent numerical format when writing. If you want to say 20, say 4 as well. If you want to say four, say twenty as well. "Four to 20," just looks like some kind of bastardized wretch that a high school student coughed up on a rushed writing assignment.
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Actually, I believe they mean "a factor somewhere between 4:1 and 20:1". It's a much less precise statement, but given the wording it makes a lot more sense than interpreting it as a single ratio.
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TFA uses Bad Math! (Score:3, Interesting)
Consider the article's quoted claim of a 1A, 1V sample 1 inch long and the diameter of a human hair. This is plainly ridiculous.
Solar radiation intensity in near-Earth space is 1353 W/m^2 (on Earth, under all that atmosphere, it's more like 120 W/m^2). This represents the maximum possible energy input to a solar cell, of whatever design.
A human hair is about 0.001 inch in diameter, so a 1-inch piece held lengthwise covers an area of 0.001 in^2, or 6.45E-7 m^2. At the stated solar irradiance, that area will receive 873 uW of solar irradiance at MOST, in orbit, and rather less on Earth. Unless their solar cell has a 120,000% efficiency, they'll come up rather short on the 1-watt claim (1 V * 1 A = 1 W) in TFA.
I call Fuzzy Math, at least on that particular claim. The rest of their idea may well be good; let's hope the fellow who said this was misquoted, though...
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The researchers also applied for a patent on an intriguing device which takes advantage of silicon dioxide's curious ability to reduce the speed of light as photons pass through it, and can, in certain configurations, be exploited to redirect light or even concentrate it in a small area.
nope, guess again (Score:2)
Existing commercial concentrating photovoltaic systems already work in the 400 to 1,000 times concentration range. Care to do your math again?
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Sun's output is nearly identical to blackbody at 5800 degrees C. In atmosphere near ground, about half the energy is in visible light spectrum, half in near-infrared. Energy falls quickly from peak in yellow-green to essentially zero at 280 nm (ultraviolet C) and shorter wavelengths. Energy slopes gently to zero from peak in yellow to nearly zero at 3000 nm (which is infrared C). Anyway, parent post neglects fact that concentration by lenses or mirrors is common practice, typical CPV setup easily works
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yes