Nanowire Forests Use Sunlight To Split Water 56
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."
Hy-Wire? (Score:2)
Efficiency? (Score:3)
I hate abstracts. But I do have the abstract feeling, that the efficiency is not very high.
Re: (Score:1)
I read the full article and I still can't tell what the efficiency is.
Re: (Score:1)
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)
Re: (Score:1)
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.
Re: (Score:1)
Re:Efficiency? (Score:5, Informative)
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
Re: (Score:3)
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
Re: (Score:2)
So, how do wind farms remove any carbon dioxide from electric generation, when the conventional generators have to run, even when not supplying anything to the grid?
The answer is that the convention generators don't run in that case. That's why they use natural gas or hydro for this purpose. Both of those can start and stop. Coal doesn't so it's not used for this purpose.
Re:Efficiency? (Score:4, Insightful)
Why not use the wind energy to make hydrogen, and store the hydrogen (as a gas, as a liquid, or in metal hydrides)?
http://en.wikipedia.org/wiki/Hydrogen_storage [wikipedia.org]
Or why not use the wind to make compressed air, and store the compressed air?
http://en.wikipedia.org/wiki/Compressed_air_energy_storage [wikipedia.org]
http://en.wikipedia.org/wiki/Fuel_cell [wikipedia.org]
http://en.wikipedia.org/wiki/Hydrogen_economy [wikipedia.org]
Or why not use the wind to charge batteries?
http://arpa-e.energy.gov/ProgramsProjects/GRIDS/ARobustandInexpensiveIronAirRechargeableBat.aspx [energy.gov]
Or why not use the wind to heat up molten salts, and use a steam turbine to make power? Solar does it, but so could wind:
http://grist.org/solar-power/2011-07-05-groundbreaking-solar-plant-in-spain-generates-24-hours-of-power/ [grist.org]
Or why not use the wind energy to produce liquid synthetic fuels from carbon from the air?
http://www.staxera.de/announcement.105+M5320325207d.0.html?&L=1 [staxera.de]
Or why not use the wind energy to run energy-intensive industrial processes that can run intermittently (like grinding up rocks for fertilizer or chilling nitrogen out of the air)? And so on.
http://www.remineralize.org/ [remineralize.org]
There are solutions for the lack of buffers for renewable energy. Put them all together, and you have a way to use wind.
That said, LENR and cheap solar panels seem more likely to succeed, one because it is compact (if it really works) and the other because it has now moving parts and requires little maintenance.
http://hardware.slashdot.org/story/12/01/15/0226219/can-nasa-warm-cold-fusion [slashdot.org]
http://cleantechnica.com/2011/05/29/ge-solar-power-cheaper-than-fossil-fuels-in-5-years/ [cleantechnica.com]
"A Road Not Taken: Solar Panels, Jimmy Carter, and Missed Opportunities for Change "
http://www.renewableenergyworld.com/rea/blog/post/2010/06/a-road-not-taken-solar-panels-jimmy-carter-and-missed-opportunities-for-change [renewableenergyworld.com]
http://www.renewableenergyworld.com/rea/blog/post/2010/09/obama-no-thanks-to-carter-solar-panels [renewableenergyworld.com]
The true cost of fossil fuels:
http://www.treehugger.com/energy-policy/true-cost-fossil-fuels.html [treehugger.com]
"For decades now, fossil fuel company executives and D.C. politicians have worked together to ensure that coal and oil prices stay low enough to keep the American people hooked. In his new book Greedy Bastards, Dylan Ratigan explains how "vampire industries" like oil and coal have forged "an unholy alliance with government based not just on the money that they contribute to political campaigns and spend on lobbying but on their ability to hypnotize us with false prices." Industry gets tax breaks, subsidies, military support in volatile regions, the right to use our air and water like a sewer, and assurance that the government will clean up its environmental messes. Politicians get campaign contributions, a steady flow of dirty energy, and a talking point to brandish about how they kept gas affordable. But the Ame
Re: (Score:3)
Citation needed. If people believed as you did, there would never be any innovation...
Also, you raise a false dillemma. Vast amounts of financial capital in our society have tied themselves up into energy sources they can more easily control. It's a mindset that won't invest much in alternatives, and will invest in politics to keep their control in place (like preventing laws regulating coal pollution).
Actually, I live in a fairly energy efficient house (partially passive solar), so I am practicing that I p
Re: (Score:2)
The current situation is less than ideal, I'll grant, but I find it odd that you focus your efforts into vilifying the actual power generation method rather than focusing on the energy companies and the stuff they get up to or on the problems of the antiquated grid itself. Clearly we need better ways to buffer renewable power sources and we need a smarter, more capable grid (a smart UPS/generator in every home so that the power _never_ goes out for anyone would also be nice here in the 21st century), that c
A simple answer means no attempt at a clue (Score:4, Insightful)
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.
Energy used deploying global sustainable energy (Score:1)
Re: (Score:1)
It's better than an article summary that tells us the ground-breaking news that hydrogen combines with oxygen to form water.
Re: (Score:1)
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
Abundant where? (Score:1)
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)
Solar cells? (Score:2)
Can a dry form of this be used to enhance solar cell efficiency?
Re: (Score:2)
It's probably a lot more efficient than using photoelectric cells to produce hydrogen, though.
Re:Solar cells? (Score:4, Interesting)
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.
Re: (Score:2)
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.
Without taking anything away from your statement: my Holy Grail of solar power is to initially wrap the sun (and all the stars) in Dyson Spheres, or Matrioshka Brains (the latter seems more heat-efficient), with solar collectors on the inside and batteries on the outside, so that we can capture 100% of the output of the sun into stored energy (rather than just the small fraction of the Earth covered in solar cells, which is a small fraction of the energy being beamed across Earth's radius from the sun).
Once
Re: (Score:1)
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.
I have around 30 such devices in my home. They're called windows. The IR part of the spectrum heats the house in the winter, the visible part lets me see.
Groovy (Score:5, Funny)
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!
Re: (Score:2)
Actually... we'll be saying hello in a big way. It'll just be a real drag.
Re: (Score:2)
Say hello to the SHAGMOBILE! Yeah baby!
Re: (Score:3, Funny)
Re: (Score:2)
"When the world hand you a Jeffrey, stroke the furry wall."
Wow (Score:1)
Hydrogen production is not main cost (Score:1)
Hydrogen storage is the main obstacle to widespread adoption, not production.
Re: (Score:2)
Unless you can find a way to make hydrogen as you need it, in which case storage becomes moot.
Re: (Score:2)
I agree but the problem then becomes.. where does the power required to split water into hydrogen (and oxygen) come from?
Hmmm... ZnO band gap is 3.37 eV (Score:5, Interesting)
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.
Re: (Score:2)
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.
Re:Hmmm... ZnO band gap is 3.37 eV (Score:5, Insightful)
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.
Re: (Score:2)
Visible light not only is not currently energetic enough, it is never energetic enough with ZnO, unless perhaps you do something much more complicated: heterostructures and engineered bandgaps. But that's not cheap and simply grown ZnO anymore.
Going to the Moon does not help much. Look at the Wikipedia article on Sunlight, Solar Radiation Spectrum graph. The Sun approximates a black body radiator at 5525K. Look at the solid line (theoretical black body at 5525K) at 367 nm and shorter wavelengths: com
Toxic (Score:2)
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.
Re: (Score:2)
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
Re: (Score:2)
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...
Re: (Score:3)
Re: (Score:2)
So maybe you should submit better articles to Slashdot to raise the quality level. Of course, be sure the FULL article, not just the abstract, is available free to the public (or at least to those coming to the site from Slashdot).
Everything has a cost (Score:2)
And for renewables that are driven by sun or wind, that cost is surface area.