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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."
I hate abstracts. But I do have the abstract feeling, that the efficiency is not very high.
Maybe not by itself, but there's hydrogen in water, which Earth has a lot of to say the least.
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!
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.
I've heard that concentrating light on a solar cell increases the efficiency. So if a concentrator captures 4x light from a 4x aperture onto the same size solar cell surface, you get more electrical energy than just 4 like surfaces. If that's true, the intensity is doing something to avoid the losses, which I assume are heat losses, which should normally be higher with a concentration due to the higher temperature. Any truth or applicability to that?
The Holy Grail of solar power is, of course, to turn 100% of sunlight energy (across a huge spectrum) into an energy form that can be directly used. So I'm looking for that (without all that science background to know the details about things that can really work. My last look into this was trying to find if anyone was building nano Sterling Engines.
now we need to go OSS in diesel cars
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.
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.