Slashdot Mirror
Nanowire Forests Use Sunlight To Split Water
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."
Maybe this will encourage GM to bring back the Hy-Wire platform
I hate abstracts. But I do have the abstract feeling, that the efficiency is not very high.
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.
Can a dry form of this be used to enhance solar cell efficiency?
now we need to go OSS in diesel cars
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!
On phone so tl;dr, but how efficient, does it scale, and can it be done at an acceptable price for consumers?
Silence is a state of mime.
People sometimes forget that hydrogen is bad, bad, bad for the ozone. Hydrogen != Green Energy....just sayin'
Hydrogen storage is the main obstacle to widespread adoption, not production.
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.
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.
Opus: the Swiss army knife of audio codec
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.
Nate Lewis at Caltech already did this with silicon in 2007, which has a lower bandgap and is more ubiquitous and easy to process than ZnO. And they published it in Science, but Slashdot only seems to follow papers that are published in minor journals that no one has ever heard of (Nanoscale). Why is that?
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, Climate Change and the Transition from Coal to Low-carbon Electricity.â Environmental Research Letters 7.1 (2012): 014019. Web. 28 Feb. 2012.
And for renewables that are driven by sun or wind, that cost is surface area.