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Quantum Dots Could Double Solar Energy Efficiency 112

Posted by kdawson
from the hot-enough-for-ya dept.
dptalia notes the recent publication in Science of research demonstrating a way to use hot electrons in solar cells, resulting in an overall energy conversion efficiency of 66%. Here is the abstract in Science; access to the full article requires a subscription. "A team of University of Minnesota-led researchers has cleared a major hurdle in the drive to build solar cells with potential efficiencies up to twice as high as current levels, which rarely exceed 30 percent. ... Tisdale and his colleagues demonstrated that quantum dots — made not of silicon but of another semiconductor called lead selenide — could indeed be made to surrender their 'hot' electrons before they cooled. The electrons were pulled away by titanium dioxide, another common inexpensive and abundant semiconductor material that behaves like a wire."
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Quantum Dots Could Double Solar Energy Efficiency

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  • But by when? (Score:4, Insightful)

    by bhagwad (1426855) on Friday June 18, 2010 @08:49AM (#32612336) Homepage
    Seems like I keep hearing of breakthroughs, but nothing ever seems to fucking change!
    • Re:But by when? (Score:4, Informative)

      by amorsen (7485) <benny+slashdot@amorsen.dk> on Friday June 18, 2010 @09:12AM (#32612584)

      Meanwhile, partially as a result of various breakthroughs in solar cell technology, solar cell prices are finally dropping despite unprecedented demand.

      • Re: (Score:3, Informative)

        by ottothecow (600101)
        Large facility demand has actually slowed due to the economy...solar is still a pretty big investment. Prices are dropping and we are seeing some good hard work out of some of the sole-purpose solar companies (First Solar, Sunpower, etc) since they can't fall back on other products like the industrial giants can when solar orders drop.

        We are also seeing some cool developments to make solar better. Not just big efficiency gains like this article mentions but also more environmentally friendly processes t

      • Re: (Score:3, Informative)

        by Lumpy (12016)

        The ones that are dropping are because of two reasons...

        1 - china made junk flooding the market. There is a metric crapload of really low grade Solar panels on the market from china. These low grade panels are also of the worst designs that are easiest to make that flat out suck in real world use.

        http://www.amazon.com/Sunforce-50044-60-Watt-Solar-Charging/dp/B000CIADLG/ref=sr_1_1?ie=UTF8&s=hi&qid=1276875660&sr=8-1 [amazon.com]

        for example is complete garbage. It's all marketing hype and they fail to tell

      • by operagost (62405)
        It still takes about 5 years to recoup the cost of a residential solar system-- even with huge government subsidies!
        • Re: (Score:3, Informative)

          by falconwolf (725481)

          It still takes about 5 years to recoup the cost of a residential solar system-- even with huge government subsidies!

          But energy is free after that whereas you have to keep paying for distributed power, even with huge government subsidies to coal, natural gas, and other fossil fuels. Solar panels are warrantied 20, 25, even 30 years. I think the shortest warranty for hardware are on batteries, yet Surrette/Rolls [wholesalesolar.com] has a 10 year warranty. On the other hand Enersys Batteries [solar-pane...energy.com] only have a 5 year warranty. Even i

        • Do you live in homes for less than five years?

        • I thought the idea behind solar was not return on capital investment but lower CO2 emissions and less reliance on fossil fuels and none recyclable / renewable (well in human time) resources.

          even if it took twice the life of the solar cells to get your money back, so long as that cost wasn't the result of energy used in production then there's a net environmental gain.

          Also energy prices are rising and will continue to rise, possibly quite steeply. Especially as were supposedly coming out of recession some ti

          • I don't know how big subsidies are but with that kind of ROI the government could probably solar up everyone for less money that they spent on the recession.

            That would also I presume result in a huge drop in fossil fuel prices too.
            Countries that were net importers on fossils would stand to gain quite a boost to their cost effectiveness etc.. and overall there should be a good reduction in poverty as a result in a good drop in the cost of living.

    • Re:But by when? (Score:4, Insightful)

      by Sockatume (732728) on Friday June 18, 2010 @09:56AM (#32613126)

      Things would go a lot faster if more people were saying "how can I make this happen?" and fewer "I was supposed to have a jetpack frownyface exclaimation mark question mark"

      • If we put 10% of what went into the bailouts into alternative energy
        this issue would solved already.

        The best minds with a good budget and a effort on par
        with the Apollo missions and this would be a done deal.

        I think Jetstream wind and Ocean current power need to
        be tapped as well as they will take up near zero land.

        1% of the World's jet streams would replace all forms of
        power on earth.

        The strongest ocean current has 125 times the flow
        of all rivers on earth combined.

    • are you referring to Solar Energy specifically, or in general?
    • Seems like I keep hearing of breakthroughs, but nothing ever seems to fucking change!

      Prices have changed. According to Solarbuzz [solarbuzz.com] per watt costs have dropped from about 5.40 euros or a little over that in US dollars in December 2001 to about 4.20 euros or a little less US dollars for June 2010. Further it says "there are now 488 solar module prices below $4.00 per watt (3.24 euros per watt)". Efficiency has also increased. In 2001 conversion efficiency pushed 12%, in 2009 SunPower [reuters.com] sold panels with conve

  • by Tekfactory (937086) on Friday June 18, 2010 @08:51AM (#32612366) Homepage

    "The next step is to construct solar cells with quantum dots and study them. But one big problem still remains: “Hot” electrons also lose their energy in titanium dioxide. New solar cell designs will be needed to eliminate this loss, the researchers said."

  • by luckytroll (68214) on Friday June 18, 2010 @08:52AM (#32612378) Homepage

    If I had a tribble for every time one of these solar energy articles came out with their pages full of nothing.... I could make a lot of fur coats.

    Could someone in the research field please hold on to their excitement until they can post a report that has words like "WILL, SHALL, DEFINITELY, HAS, IS" instead of the wimpy "could, may, might, has potential to, in 5 years if all goes well....."

    I got sucked in by one years ago and pestered the company for information about their new "product" which was due out "soon".... and that was nearly 10 years ago.

    So many advances in tiny little cells on a research bench, and so many promising advances. Yet none of them seem to show up at the local hardware store.

    I understand that advances in quantum materials science is cool, and can change everything just like the invention of the transistor did once. But seriosly folks - the number of speculative postings based on
    these barely germinated lab experiments seem a little bit like the kid who cried "Solar revolution", or was that wolf?

    • by Tekfactory (937086) on Friday June 18, 2010 @09:10AM (#32612548) Homepage

      I think you mean;

      Give me more Grant money!

      Fund my Startup company!

      You can't get the money to do the engineering to make these things a reality if nobody knows about your research in the first place. Shameless self-promotion (in this case publishing in Science) therefore becomes a necessary evil.

    • by John Hasler (414242) on Friday June 18, 2010 @09:16AM (#32612636) Homepage

      Read the damn paper, or at least the abstract, ok? The horsepucky all comes from the university PR flacks, amplified by the Slashdot editors.

      • Yeah, there's just this tiny little gap between basic science research and a complete industry based around the technology which may ultimately result.

        Sheesh, kids, the world isn't like in comic books.
    • by Sockatume (732728) on Friday June 18, 2010 @09:57AM (#32613142)

      It's a research paper, not a god-damned press release. Don't blame the scientists for publishing their awesome research in a prestigous journal, blame the journalists who treat every Friday as a chance to jizz out a couple of easy stories by rewriting articles in Science.

    • by bzipitidoo (647217) <bzipitidoo@yahoo.com> on Friday June 18, 2010 @10:17AM (#32613374) Journal

      It's messy.

      If you're lucky, you have a clear goal, and that goal is reachable though no one knew it beforehand of course. Also far from assured is that no one else has already done it. Not at all easy to find it out either, as others may have approached some problem from a completely different direction, and you will not be looking in the right places when you try to find out what others have done. And you could discover something entirely unrelated while in pursuit of your objectives, something worth taking a massive detour to pursue. Reporting on science skips over the difficulties to the point that it's like the joke about how to put an elephant in a refrigerator. You open the door, put the elephant in, and close the door, duh! Even scientific journals omit "extraneous" details about wrong turns taken, because "thinking is vulgar". Researchers naturally don't want to look dumb, and neither do journals. Plus, journals are always trying to save space and time. Streamlining articles to talk of only the successful experiments is an obvious cut to make. There's a STNG episode that touches on the problem. Lore mocks Dr. Noonien Soong, calling him "Often Wrong", but there it is clear that Lore's criticism is unfair. Science is all about doing things that will probably turn out to be mistakes, and learning from them.

      Most people think science is about finding answers. That's only half of it. More important is asking good questions. Finding out which questions to ask and hopefully answer. Yes there are bad questions, don't believe that dogma about there being no such thing as a dumb question. They're still worth asking if you don't know or can't know they're bad. What they aren't is worth answering, and discovering that is the problem. There are questions that turn out to make no sense, or are too simple, or too complicated, or pointless, or misleading, or are based upon or arise from inferior modelings or from misunderstandings, or are predicated on assumptions that actually aren't valid, or are unanswerable. Math is full of shifts in representation to avoid such problems.

      For instance, how do you deal with infinity in, say, the slope of a line? Vertical lines have infinite slope. You could pull out calculus and limits to handle these infinities, but if you do, you've just been sucked into doing things in a much harder way, been pulled down a rabbit hole to figure out all kinds of problems with working with infinities and division by 0. So much easier to use vector representations from linear algebra and avoid those infinities. All those questions about handling infinities turn out to be pointless for this problem. Mind you, infinites crop up in plenty of other places, so having ways to handle them is still useful, it just isn't necessary for this problem of representing a line. That's an old, well known problem for which we've known good answers for a long time now. There are also things like the famous Fourier Transform, and Lagrangian basis, not to mention Calculus itself to handle problems that are very nasty in classical geometry. But in new, unexplored territory it's not so easy to tell which questions will turn out to be bad.

      Most things that scientists try turn out to be wrong. History has a few famous ones, such as "Squaring the Circle". The public hears little more than the 1% that turned out right.

      • More important is asking good questions.

        Like, WTF are we going to do with all this lead and selenium waste?

    • I would totally agree with your post if it wasn't for the small detail that this was an article published in Nature by a team of university scientists. It's not supposed to be commercially available yet - indeed, no one even knows if it ever will be. They're just exploring a novel way of constructing solar cells, that's all.

    • by geekoid (135745)

      You might want to pay attention. Thing promised 10 year ago, are now rolling out in new solar technology. Plus the media reports this interesting development s as a just about ready to go to market breakthrough when they are really just studies.

      10 years ago, it was about printing solar cells, and now they can do that.

    • If I had a tribble for every time one of these solar energy articles came out with their pages full of nothing....

      Your starship would be full of tribbles. Then it's tyme to call Klingons.

      Falcon

  • by smaddox (928261) on Friday June 18, 2010 @10:16AM (#32613356)

    I wrote a paper on this idea last semester, and as interesting a find as it is, I don't think it's ever going to lead to enhanced power conversion efficiencies (PCE). The "Double Solar Energy Efficiency" is actually a theoretical doubling of the thermodynamic limit on PCE, and it doesn't take non-radiative losses into account. These losses have been minimized in the record breaking silicon and multi-junction solar cells, but quantum dots bring lots of problems with them.

    It's definitely worth further investigation, but currently I'm not convinced that it will ever bring improvements.

    • It's definitely worth further investigation, but currently I'm not convinced that it will ever bring improvements.

      Fortunately the difference between real research (like this) and not a company doing "let's find a way to modify our product and create a new revenue stream" is that even if it doesn't work it tells us something. It might simply be "this won't work", or it might lead to research in a new direction, or it might improve other processes that do work.

      Thomas Edison is quoted as saying "I have not fa

      • by smaddox (928261)

        Solar thermal isn't much different from every other thermal based energy. Steam turbines have pretty much hit a practical limit in efficiency. Scaling them down decreases the efficiency/cost ratio considerably. Thus, most interest in solar thermal is on the industrial scale and a lot of investigation is theoretical. There are plants being built, but Photovoltaics has the advantage of being relatively cheap to investigate in a lab on the small scale. In addition, the small size and lack of moving parts makes

        • Solar thermal isn't much different from every other thermal based energy. Steam turbines have pretty much hit a practical limit in efficiency.

          I'm not talking about steam turbines, I'm talking about absorption chillers. [wikipedia.org] And beyond a certain level of efficiency, efficiency no longer matters when your energy source is essentially free.

          In the US most household energy costs are heating and cooling. If you want to PV a home you are not going to build an array large enough to power the air conditioners. At leas

  • Every time one of these solar cell tech. stories come out, I look forward to digging up the specific details of the technology and am left wanting. It seems like no researchers offer any insight into the lifetime of their new, super-duper technology. They very rarely list a W/kg or W/m^2 figure. Hell, they don't even talk about the largest/smallest wafers that can be cut using the new technology. It's extremely frustrating. As an engineer that wants to look into, 'What could new solar tech actually do for m
    • by jvkjvk (102057)

      That is because this is not a "technology" yet.

      At least not the way you seem to define "technology".

      This is a discussion of research results.

      Regards.

    • come out, I look forward to digging up the specific details of the technology and am left wanting. It seems like no researchers offer any insight into the lifetime of their new, super-duper technology.

      Perhaps that's because they are research papers and the tech has not reached practical application yet. And perhaps that's the difference between scientists and engineers, scientists want to know what's possible whereas engineers want the practical application. Without the other neither one gets very far.

      F

  • Is when it matters, otherwise it's just a curiosity.

    Really, these releases of "Ahh YES! We've discovered X" is nothing more than the scientists, engineers, Universities and Labs making a press release so they can get more grant money.

    If I can't buy it then I'll spend exactly 20 seconds thinking about it.

    • by Jeremi (14640)

      Is when it matters, otherwise it's just a curiosity.

      You're absolutely right. If only there was some sort of "News for Nerds" web site where such technical curiosities could be posted...

  • by mosb1000 (710161)
    I doubt a semiconductor called "Lead Selenide" is going to go far if, as it's name implies, it is comprised of lead and selenium.
    • Re: (Score:1, Interesting)

      by Anonymous Coward

      I've got more than plenty of batteries with lead and electronics composed of parts containing much nastier chemicals. As long as it's contained and the goo or magic smoke stays inside, it's all good.

  • by lazn (202878) on Friday June 18, 2010 @11:22AM (#32614082)

    who cares about efficiency?

    If you make a solar cell that is 100% efficient but costs $10billion / watt to make, who cares?

    On the other hand if you make one that is only 1% efficient but only cost .01c / watt to make, that would change the world.

    • by smellsofbikes (890263) on Friday June 18, 2010 @11:57AM (#32614710) Journal
      You need both. It'd be great to have dirt-cheap solar cells, sure, but current 20% efficient cells can produce the amount of power a house needs, mounted on the roof of the house. If you make dirt-cheap 1% efficient cells you need 20x the space, which exceeds the entire yard space of most suburban and urban houses. Then, you have a solution that only makes sense for huge power generation companies that can afford to buy up half of Nevada to cover it with solar cells and transport the power. If we can make reasonably-priced, reasonably-efficient cells we can have microgeneration at each individual house.

      While this isn't as much the case in very rural, very poor areas, where making kilometer-square solar arrays is viable, there's at least two orders of magnitude less money to be spent in such locations, so you're back to the same problem.

      • Re: (Score:2, Insightful)

        by brbrbrad (1701932)
        Those rural/poor areas don't need the same amount of electricity as your house to make a world of difference. A roof covered with 1% effecient solar cells plus a deep cycle battery would power lights, run a radio, and charge cell phones.

        Make it cheap enough and it would be nothing short of revolutionary.
        • Totally true... for about a year. And then they'll have soaked up every watt those cells can provide and want more. (And why not? They should have as good a life as anyone else.) Nighttime illumination revolutionized industrialized nations, more than doubling their productivity and manufacturing capability, and I'd expect and hope the same thing would happen across southeast asia and africa.

          Don't get me wrong: I'm not saying that low-efficiency solar cells are useless. What I'm saying is that because

        • Those rural/poor areas don't need the same amount of electricity as your house to make a world of difference.

          Really? Homes in the city or suburbia require large screen TVs whereas homes in rural locations don't? Satellite dishes originally were used in rural locations, large analogue dishes, but now digital dishes are found in the middle of cities. Me, while the large TV would be nice, I want servers, a lab, and workshops. I also want a greenhouse.

          A roof covered with 1% effecient solar cells plus a deep

      • by danhaas (891773)
        One cool characteristic of eletric power is that you can send it through dozens of miles with a reasonable efficiency. So it's possible to generate power in rural areas and consume it in urban areas, *pretty much like we do with food*. That's where the name solar farm comes from. While a home grown garden is awesome, the bulk of the food you consume is generated or collected in extensive, mass-producing, corporate farms.
        • One cool characteristic of eletric power is that you can send it through dozens of miles with a reasonable efficiency. So it's possible to generate power in rural areas and consume it in urban areas, *pretty much like we do with food*. That's where the name solar farm comes from. While a home grown garden is awesome, the bulk of the food you consume is generated or collected in extensive, mass-producing, corporate farms.

          You choose an interesting analogy, and because I think it is an excellent analogy, let me address it first. "Transportation now major production cost for food" [findarticles.com]. When we buy food that's been raised overseas, we're paying a *lot* of money for the oil that's been used to get it to us. For well-off people, that's a reasonable tradeoff right now, although transportation costs and our cultural reliance on just-in-time manufacturing are going to be very challenging for our economy over the next decade.

          Likewise

  • By replacing benign silicone with a toxic heavy metal like lead, we're guaranteed full Republican support for a roll-out!

  • So, If I want to make my existing solor cells more efficient, I just need to stick my existing panels into a crock-pot?

  • Is there anything it CAN'T do?
  • NEED MOAR DOTS!!!
  • It must be time for me to cut back on my WoW. All I could think of when I saw the headline, was "MORE DOTS! MORE DOTS!"

  • by BlueParrot (965239) on Friday June 18, 2010 @01:51PM (#32616838)

    I seriously wonder why people keep promoting micro-generation. Electricity distribution is very efficient ( you lose maybe 10% of the electricity on average ) , and you lose a lot of economies of scale when going micro. Even assuming you'd manage to make some super cost-efficient solar cells, why would you go destroy it by putting them on poorly aligned roofs, as opposed to building a designated plant where they can be made to track the sun throughout the year?

    Seriously , for EVERY energy source centralized generation will come out on-top. It's a consequence of how easy electric power is to transport, as well as the fact that most energy generation schemes scale very well. The only real exception is where you're burning something for combined heat and power, thereby allowing you to recover the spill heat from the power-plant. However, even in that case district-heating will probably work out better, and does in many regions. We use it extensively in Sweden.

    Essentially the only way micro-generation is going to be competitive with centralized generation is if government fucks up big time to make centralized generation inefficient. Granted that is of course plausible, and I'm sure there's many people who are willing to say that it is happening many places, but this is a political problem that could just as well ( and probably will ) hit micro-generation. It does nothing to alter the fact that on technical merits, micro-generation is inferior for all places that are connected to the electric grid. It just doesn't make any sense to take technologies that scale very well and deploy them in as small units as possible.

    • "Competitive" takes many forms. Decentralized systems lose on efficiency and cost, but often win big in terms of stability and resilience. Also, depending on your political system, you may not have much trust in the politicians or the corporations who deliver your power. Or you might not trust that the national grid won't fail (temporarily or permanently). We had a massive blackout in the northeastern U.S. a few years back (arguably because our privatized energy companies tend to underinvest in the infr

    • I can think of a few reasons why people would like to microgenerate, Think outside of your own country.
      1. 1. Most countries central power supplies are inevitably unreliable due to one or more of the following,
        1. a. Weather (lightning, floods, landslides, extreme heat, bush/brush fires, cyclones/hurricanes, snow storms)
        2. b. Poor Maintenance of Polls and Wires or Trenches and Wires or outages to perform maintenance on the streets
        3. c. Poor Generation (coal shortages, strikes, fire/destruction, corru
  • by Goldsmith (561202) on Friday June 18, 2010 @02:11PM (#32617154)

    This is good, solid condensed matter physics research, and it is important. But, the 66% efficiency they're quoting comes from an old calculation of what is effectively a perfect solar thermal converter where the electrons are "hot" and the temperature of the crystal doesn't really matter because there's no interaction between the electrons (or photons) and the crystal. This theory has been the motivation for the hot electron transfer work on quantum dots, but at some point it should come up that they can't get hot electron transfer to work at much above around 100 K. That's kind-of really important (not to mention impractical). The device they're *trying* to make shouldn't need to be cooled at all. That's a giant clue that the theory they're basing this amazing 66% on is more than a little oversimplified for what they actually have. It's annoying that people are using an out of date 28 year old paper to sell the direction of their research; it makes life hard on their competition using more honest efficiencies.

  • I skipped the yearly trip to Vegas and invested some time and money in small scale solar for the house. Best 1K I ever spent. Running the entire outdoors media system and lights on solar.

    DIY Solar project.
    http://www.flickr.com/photos/nsaspook/sets/72157622934371746/show/ [flickr.com]

I've never been canoeing before, but I imagine there must be just a few simple heuristics you have to remember... Yes, don't fall out, and don't hit rocks.

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