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Power Hardware Science Technology

Nanowire Forests Use Sunlight To Split Water 56

Posted by Soulskill
from the just-have-to-keep-the-nanosquirrels-away dept.
An anonymous reader sends this excerpt from IEEE Spectrum's Nanoclast blog: "One of the fundamental problems with fuel cells has been the cost of producing hydrogen. While hydrogen is, of course, the most abundant element, it attaches itself to other elements like nitrogen or fluorine, and perhaps most ubiquitously to oxygen to create the water molecule. ... Now researchers at University of California, San Diego have developed a quite different approach to mimicking photosynthesis for splitting water molecules by using a 3D branched nanowire array that looks like a forest of trees. ... The nanowire forest [uses] the process of photoelectrochemical water-splitting to produce hydrogen gas. The method used by the researchers, which was published in the journal Nanoscale (abstract), found that the forest structure of the nanowires, which has a massive amount of surface area, not only captured more light than flat planar designs, but also produced more hydrogen gas."
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Nanowire Forests Use Sunlight To Split Water

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  • Maybe this will encourage GM to bring back the Hy-Wire [howstuffworks.com] platform
  • by tp1024 (2409684) on Friday March 09, 2012 @07:01PM (#39307029)

    I hate abstracts. But I do have the abstract feeling, that the efficiency is not very high.

    • I read the full article and I still can't tell what the efficiency is.

      • by Skapare (16644)

        They did say the area is 400000 times as much. So it better be producing at least 400000 times the energy to be considered as least equally efficient as what we have now.

      • Re: (Score:2, Offtopic)

        by hairyfeet (841228)

        Besides wouldn't the smarter thing to do to be capturing all the carbon we belch out anyway and using it to make biofuels thus actually cutting down on the amount of greenhouse gasses? hell that might even stop the outsource hemorrhaging we've been having in this country where all the factories go to Asia where nobody gives a fuck about greenhouse gasses.

        While coming up with new ways to produce power is good ultimately we need to be working on ways of bring the current damage DOWN without simply moving po

        • by Anonymous Coward

          Besides wouldn't the smarter thing to do to be capturing all the carbon we belch out anyway and using it to make biofuels thus actually cutting down on the amount of greenhouse gasses?

          If you can produce enough hydrogen, cheaply enough, you should be able to use some of it to produce enough energy to synthesize hydrocarbons like methane or propane, which would at least be carbon-neutral.

          And hydrocarbons are much, much easier to store and transport than elemental hydrogen.

      • Yes, efficiency is what it's really about. At what point will the technology provide more useful energy output than is required to manufacture and maintain the system? Will it substantially reduce fossil fuel usage, or is it another ruse, like the wind farms?
        • Re:Efficiency? (Score:5, Informative)

          by Jeremi (14640) on Friday March 09, 2012 @09:31PM (#39308407) Homepage

          At what point will the technology provide more useful energy output than is required to manufacture and maintain the system? Will it substantially reduce fossil fuel usage, or is it another ruse, like the wind farms?

          Oh dear, a Slashdot poster has made what appears to be a false claim about the EROI of wind farms.

          Time to google around a bit and see if there's anything to it [academia.edu]....

          This analysis reviews and synthesizes the literature on net energy return for electric power generation by wind turbines. Energy return on investment (EROI) is the ratio of energy delivered to energy costs. [...] Our survey shows an average EROI for just the operational studies is 19.8 (n=60; std. dev=13.7) This places wind in a favorable position relative to fossil fuels, nuclear, and solar power generation technologies in terms of EROI."

          So, to sum up the above summary -- parent poster is wrong. As a matter of historical record, the average wind farm produces about 20 times more much energy than it expends on construction and maintenance.

          • Re: (Score:2, Interesting)

            At what point will the technology provide more useful energy output than is required to manufacture and maintain the system? Will it substantially reduce fossil fuel usage, or is it another ruse, like the wind farms?

            Oh dear, a Slashdot poster has made what appears to be a false claim about the EROI of wind farms.

            Time to google around a bit and see if there's anything to it [academia.edu]....

            This analysis reviews and synthesizes the literature on net energy return for electric power generation by wind turbines. Energy return on investment (EROI) is the ratio of energy delivered to energy costs. [...] Our survey shows an average EROI for just the operational studies is 19.8 (n=60; std. dev=13.7) This places wind in a favorable position relative to fossil fuels, nuclear, and solar power generation technologies in terms of EROI."

            So, to sum up the above summary -- parent poster is wrong. As a matter of historical record, the average wind farm produces about 20 times more much energy than it expends on construction and maintenance.

            Oh dear, a Slashdot poster appears to share the same opinions as the Big Energy Companies. Please google a little further and take a look at http://www.wind-watch.org/ [wind-watch.org] for a different point of view. BTW - I live in West Texas - we're surrounded by these beasts. It's all a scam foisted on us by companies like (early adopter) Enron. The winners are the developers, the losers are the customers neighbors, and wildlife. Ask the folks in North Texas, who had to deal with a brownout a few years ago when the w

            • by tragedy (27079)

              Ask Big Energy why they must build more conventional plants when they add wind to the grid, and why those conventional plants have to be running while the wind farms are generating.

              Ok, the answers to that one are so blazingly obvious I wonder why you bothered to ask. The obvious answer is that demand is increasing all the time so they need to build more plants anyway. Also the wind doesn't blow all the time, so it needs to be supplemented. As for those plants running while the wind farms are generating... Hmm, maybe because they cost a lot to build, the companies that built them want to run them as much as they can and sell the power?

              Seriously, the stuff you're saying comes off like a

              • Re: (Score:1, Interesting)

                Ask Big Energy why they must build more conventional plants when they add wind to the grid, and why those conventional plants have to be running while the wind farms are generating.

                Ok, the answers to that one are so blazingly obvious I wonder why you bothered to ask. The obvious answer is that demand is increasing all the time so they need to build more plants anyway. Also the wind doesn't blow all the time, so it needs to be supplemented. As for those plants running while the wind farms are generating... Hmm, maybe because they cost a lot to build, the companies that built them want to run them as much as they can and sell the power?

                Seriously, the stuff you're saying comes off like a bit of a crazy rant. I certainly get that some people don't like these wind farms being built next to them. How that equates into the wind farms being some giant conspiracy to erect towers that don't really generate power (which seems to be what you're implying), I have no idea.

                I apologize - perhaps this will explain my viewpoint.

                The conventional plants aren't being built to meet new demand, but as a backup to the wind farms. When a large portion of power provided on the grid is from wind, there must be an almost equivalent capacity available as spinning reserve, because the grid is a demand driven system. In other words, the reserve must be up and running, and ready to be switched onto the grid at a moment's notice if the wind dies. In Texas, that usually equates to a gas or c

            • by dbIII (701233) on Saturday March 10, 2012 @01:31AM (#39309561)
              Thinking for several seconds about windmills should have been enough to bring up some historical examples of where windmills were used, for the one and only reason that they got the job done. If they didn't provide the "return on investment" they would not have been used as widely. Move forward to today and it should also be obvious that there is more than one type/size/etc of wind turbine and more than location where they can go and the wind behaves differently in different places (average/maximum/sustained/etc), so the time for an energy return on investment is going to vary wildly enough that the question is almost irrelevant. It wouldn't be irrelevant if the answer in most cases was a long time, but if it was we wouldn't have had that historical use of wind power in the first place.
              To sum up, the EROI (energy return on investment) argument is recycled from weird US anti-solar propaganda from the 1970s which lost all credibility when silicon based integrated circuits were mass produced and photovoltaics got the benefit of the being produced out of the same wafers. I'm assuming the hope is that a younger generation will not see it as the lazy bullshit that it is and swallow the lie whole. Did you swallow the lie or do you know it is a lie but are maliciously spreading it to cheer for your political team?

              Also scammers will take anything handy to use as a tool to make money. Just because there are opportunists gouging people under the excuse of "green energy" does not mean that their tool is inherently bad.

              Wind is crap at baseload but that doesn't always matter for several reasons:
              Everything that is good at baseload has to be built at huge scales anyway, so building something small that is more expensive per MW can be a good idea if you don't need a lot of new capacity right away.
              Covering the peak loads is often the big problem on a grid and small power sources that can be switched in quickly can solve that.
              The small unit size means lower consequences of failure and makes scheduling downtime for maintainance easier, which is just as well because wind needs a lot of maintainance.
              You don't want all your energy eggs in one basket. In a drought your inland coal, oil or nuclear plants can run short on cooling water for instance. The amount of cooling water thermal power stations need is staggering, but of course usually just comes out as warmed up water not a big deal unless there isn't much coming in from upstream or a dam is drying up.

              Anyway, I'm not sure why wind has come up at all since it's about as offtopic as nuclear, which seems to get thrown up the second somebody mentions anything at all about energy. Getting back onto the point, there's no reason to limit this down to just writing about burning the stuff - it takes a vast amount of equipment to get hydrogen out of gas that is already conveniently methane/butane/etc on an industrial scale and there is a lot you can do with it. The majority of fertiliser is made from natural gas simply because that's the easiest way to get hydrogen to make ammonia. That's just one example. Hydrogen is very useful stuff in it's own right before you even think about burning it. A new way to produce hydrogen without expending a lot of energy that can be used without requiring equipment that fills a large space has a lot of potential uses.
          • Along these lines a new study adds up the return on energy for deploying sustainable power globally. It claims that "rapid deployment of low-emission energy systems can do little to diminish the climate impacts in the first half of this century. Conservation, wind, solar, nuclear power, and possibly carbon capture and storage appear to be able to achieve substantial climate benefits in the second half of this century; however, natural gas cannot." Myhrvold, N P, and K Caldeira. âoeGreenhouse Gases, Cli
    • by Dr Fro (169927)

      It's better than an article summary that tells us the ground-breaking news that hydrogen combines with oxygen to form water.

    • by Anonymous Coward

      Efficiency isn't really a useful number for a process like this, because it only tells you what percentage of incident energy is converted into your useful product. In an industrial application, the efficiency basically only determines the amount of area you would have to cover to produce your product. Given that land is very cheap in some places with abundant sunlight (say, Arizona), this isn't as big as a cost factor as the actual capital cost. The important discovery here though is that the kinetics of t

  • by Anonymous Coward

    A little misleading. Hydrogen may the most abundant element in the solar system, galaxy, or universe, but it's certainly not the most abundant on Earth. You know, where we can use it. Either way, awesome technology.

    • Re: (Score:3, Informative)

      by Anonymous Coward
      Maybe not by itself, but there's hydrogen in water, which Earth has a lot of to say the least.
  • Can a dry form of this be used to enhance solar cell efficiency?

  • Groovy (Score:5, Funny)

    by RedBear (207369) <redbear@re3.1415926dbearnet.com minus pi> on Friday March 09, 2012 @07:30PM (#39307235) Homepage

    So in the future we'll all be driving electric-hydrogen vehicles covered in a sort of shag carpet of nanowire trees?

    That...

    is...

    AWESOME!

  • by wbr1 (2538558)
    On phone so tl;dr, but how efficient, does it scale, and can it be done at an acceptable price for consumers?
  • by Anonymous Coward

    Hydrogen storage is the main obstacle to widespread adoption, not production.

    • by Skapare (16644)

      Unless you can find a way to make hydrogen as you need it, in which case storage becomes moot.

      • by tibman (623933)

        I agree but the problem then becomes.. where does the power required to split water into hydrogen (and oxygen) come from?

  • by dsgrntlxmply (610492) on Friday March 09, 2012 @09:39PM (#39308459)

    The experiment is interesting as regards the benefits of the nanostructure of the materials, but the 3.37 eV band gap of ZnO must be kicked across by a photon of no less energy (no longer wavelength) than 367 nm: ultraviolet.

    The good news is that you have plenty of energy relative to 1.25eV minimum needed to split water. The bad news is that you need high energy photons that are relatively scarce in sunlight by the time it reaches the earth's surface.

    • by spribyl (175893)

      What if they used co2 and h2o, or with some adjustment just h2o. Could this be used to build hydrocarbons? My physics and chemistry failed math.

      You have all the bits to make them and there seems to be a "simple" way of collecting energy.
      There are two ideas here. Hydrocarbons from nano-tubes and water or co2 and h2o processed via a nano tube catalyst.
      My guess is the required pressure and or reaction time will be to high to be practical.
      Joke: Gas from soda-water and a straw.

      • by dsgrntlxmply (610492) on Saturday March 10, 2012 @02:05AM (#39309711)

        Look at the carbon fixing (CO2-transforming) enzyme in nature: Rubisco. The elegance of the photon capturing and energy transport systems around it, and the machinery required to assemble the enzyme itself, will make you weep in amazement that it ever could have happened. The slow throughput of the system (molecules per second) and its bungling propensity to run backwards and re-oxidize (respiration), will make you weep in frustration.

        Some plants (the C4 plants, such as maize/corn, sugar cane, and sorghum, typically evolved in hotter climates) cheat this up some by structural improvements that increase the concentration of CO2 through an intermediate structure.

        We very likely have a lot of hard but interesting work to do, before we can design something comparable or better for human purposes.

  • by jmv (93421)

    That looks nice except for the fact that it might be a health hazard. The abstract doesn't say what the nanowires are made of, but things like carbon nanotubes are AFAIK just as bad as asbestos.

    • by dbIII (701233)
      Asbestos fibres are a problem due to the length vs width ratio so they can get into your lungs, turn sideways, then get stuck. Being effectively inert in the body means they don't break down so they are stuck there forever. Being hard and having sharp edges means they irritate the tissue and cause cancer.
      So for something to cause the same sort of problem as asbestos it has to behave the same way on all of those points. There are a lot of materials that fit those criteria (eg. some of the carbon nanotubes
      • Luckily I was upwind and a few floors above it when I saw it and there was nobody on site underneath and nothing downwind apart from a very large disused coalmine.

        Scary shit. If they were slack then, they were probably slack at other times too, and that shit has been inhaled by unsuspecting downwind folk at home or work...

        • by dbIII (701233)
          Slack to the point of being criminally negligent. Of course nothing ever happened other than a big pile of paperwork and their boss telling them to check more carefully for witnesses in the future.
  • And for renewables that are driven by sun or wind, that cost is surface area.

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