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Nanowire Forests Use Sunlight To Split Water

Soulskill posted more than 2 years ago | from the just-have-to-keep-the-nanosquirrels-away dept.

Power 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."

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Hy-Wire? (1)

phaggood (690955) | more than 2 years ago | (#39307023)

Maybe this will encourage GM to bring back the Hy-Wire [howstuffworks.com] platform

Efficiency? (2)

tp1024 (2409684) | more than 2 years ago | (#39307029)

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

Re:Efficiency? (1)

Unoriginal_Nickname (1248894) | more than 2 years ago | (#39307131)

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

Re:Efficiency? (0)

Skapare (16644) | more than 2 years ago | (#39307183)

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:Efficiency? (1, Offtopic)

hairyfeet (841228) | more than 2 years ago | (#39307365)

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 pollution to the left as we have been doing. Lets face it folks our 40 plus years of environmental regulations has done fuck all except kill our economy because thanks to globalism the corps can simply go poison the third world while still having access to first world markets. look at how over 10% of China's farmland is now toxic from heavy metals and other pollution. I'd say the best bet I've seen so far is biodiesel farms set up next to factories. This way we can keep the factories going while turning what would have been pollution into something we can actually use.

Re:Efficiency? (1)

Anonymous Coward | more than 2 years ago | (#39308583)

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:Efficiency? (1)

redneckmother (1664119) | more than 2 years ago | (#39307623)

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? (4, Informative)

Jeremi (14640) | more than 2 years ago | (#39308407)

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:Efficiency? (2, Interesting)

redneckmother (1664119) | more than 2 years ago | (#39308747)

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 winds died. 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. Ask the residents of Great Britain and Europe how wonderful wind is. Ask how much carbon does wind energy eliminate from overall emissions. (/soapbox)

Re:Efficiency? (2)

tragedy (27079) | more than 2 years ago | (#39309319)

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.

Re:Efficiency? (1, Interesting)

redneckmother (1664119) | more than 2 years ago | (#39309591)

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 coal fired generator. 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? Why not just build the conventional plants, and forget about the wind?

The reason the developers build wind farms is that the Gum'mit makes it highly profitable to do so. Besides the Feds supplying almost all of the funds, there's also accelerated depreciation, carbon credits, local goverment tax abatements, and so forth. One of the first guys to jump on the wind farm bandwagon was Ken Lay, of Enron infamy.

I advocated wind generation for nearly forty years. When I took a serious look at it, I found that it makes no sense in a grid system. The entire "wind" movement is a method of moving tax dollars into the pockets of companies who don't need them.

Here is one (of many) links which may help explain: http://www.wind-watch.org/news/2011/11/22/wind-energy-realities/ [wind-watch.org]

Re:Efficiency? (1)

khallow (566160) | more than 2 years ago | (#39309655)

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? (3, Insightful)

Paul Fernhout (109597) | more than 2 years ago | (#39310645)

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 American public just gets screwed. We get stuck with a dirty, polluting energy regime; one that enriches a few one percenters while making the public sick and hobbling American innovation. As Ratigan puts it in his book, a handful of greedy bastards are fleecing Americans with a "Very Bad Deal". Fossil fuels seem cheap and convenient now, but when we get hit with the true costs -- of a spoiled environment, of missing out on vital future industries like clean energy, of a mounting public health burden, of possible war -- we'll see we were had."

Also:
http://en.wikipedia.org/wiki/Externality [wikipedia.org]

Here is Bill Clinton saying that too (though others disagree):
http://www.politifact.com/truth-o-meter/statements/2011/nov/11/bill-clinton/bill-clinton-says-wind-solar-are-already-cheaper-n/ [politifact.com]
"Solar energy and wind energy ... would already be competitive with coal if you had to pay the extraneous costs of coal -- the health care costs and other things. And ... wind within two years and solar within five will be competitive in price with coal. They're both cheaper than nuclear right now."

Anyway, don't give up on your initial optimism, which was well placed. Just try harder and in new ways. No one said it was going to be easy -- and the biggest issue (after decades of alternative energy progress by many people who kept at it despite repeated discouragement) are now socio-economic, not technological:
"Economics for the Rest of Us: Debunking the Science that Makes Life Dismal"
http://www.amazon.com/Economics-Rest-Us-Debunking-Science/dp/1595581014 [amazon.com]

But it is true that even better energy storage systems would help.

Re:Efficiency? (0)

Anonymous Coward | more than 2 years ago | (#39313415)

Because none of your "solutions" are actually practical, and depend entirely on a massive fossil-fuel powered infrastructure already in place. If they did work, we'd already be doing them. Don't believe me? Then invest your own time and money. You seem convinced it's easy, so show me.

Re:Efficiency? (2)

Paul Fernhout (109597) | more than 2 years ago | (#39314785)

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 preach to some extent (not perfectly). The state of the art in home construction these days in cold climates is to have lots of efficiency and no furnace:
http://www.nytimes.com/2008/12/27/world/europe/27house.html?_r=1 [nytimes.com]
"DARMSTADT, Germany â" From the outside, there is nothing unusual about the stylish new gray and orange row houses in the Kranichstein District, with wreaths on the doors and Christmas lights twinkling through a freezing drizzle. But these houses are part of a revolution in building design: There are no drafts, no cold tile floors, no snuggling under blankets until the furnace kicks in. There is, in fact, no furnace."

I also eat pretty low on the food chain, that saves lots of energy and water and medical costs and pollution and animal suffering and so on.
http://www.westernwatersheds.org/watmess/watmess_2002/2002html_summer/article6.htm [westernwatersheds.org]

I provided lots of links to people putting time and money into alternatives, and they just continue to improve. The fact that GE is predicting solar will be cheaper that coal in five years despite how coal is subsidized so much (including by not having to pay for the health costs or environment destruction costs) just shows how good renewables are.
http://cleantechnica.com/2011/05/29/ge-solar-power-cheaper-than-fossil-fuels-in-5-years/ [cleantechnica.com]

Coal did not pay its true cost in 1993:
http://www.theatlantic.com/magazine/archive/1993/12/the-true-cost-of-coal/4566/ [theatlantic.com]

Coal does not pay its true cost now (perhaps half a trillion dollars a year):
http://www.skepticalscience.com/true-cost-of-coal-power.html [skepticalscience.com]
http://www.desmogblog.com/true-cost-coal-half-trillion-dollars-year [desmogblog.com]

And that is what makes it so hard "economically" to sell alternatives.

So, it is indeed hard to compete against such a tilted playing field, true. That is a missing issue in your comment about "so you do it", unpaid externalities.

In fact, if you reread my comment, you will see I said "No one said it was going to be easy"... That is why it is now a socio-economic issue more than a technical issue. We have plenty of technology if we wanted to use it. And it would overall be cheaper to use it overall across our society, and then alternatives would be adopted faster when gasoline was $20 a gallon with externalities priced in (we'd all drive electric cars pretty fast) or when coal electricity was $0.50 a kilowatt-hour (we'd all switch to wind and other renewables plus energy efficiency real fast). But that does not happen because we don't pay up front. Instead we pay on our health insurance bills, or in national debt to fund a war machine, or future environmental destruction that needs to be fixed, and so on...

Re:Efficiency? (1)

tragedy (27079) | more than 2 years ago | (#39313195)

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 can deal with the ups and downs of renewable power generation would be balanced out smoothly.

A simple answer means no attempt at a clue (3, Insightful)

dbIII (701233) | more than 2 years ago | (#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.

Energy used deploying global sustainable energy (1)

bd580slashdot (1948328) | more than 2 years ago | (#39313799)

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.

Re:Efficiency? (1)

Dr Fro (169927) | more than 2 years ago | (#39307603)

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

Re:Efficiency? (1)

Anonymous Coward | more than 2 years ago | (#39307929)

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 the process are vastly improved, which almost certainly improves efficiency, but is far more important. If you had a process that could convert all of 10 incident photons per second into 10 molecules of split water, you'd have 100% (quantum) efficiency. Your actual energy efficiency depends on the wavelength of the light, but if it's exactly equal to the heat of formation of water, you'd also have 100% energy efficiency. However, this is incredibly useless, as you're only making 10 molecules of water per second. So the kinetics, or the rate at which you can produce gas using this technology, are vastly improved due to surface area. Consider that plants have an energy conversion efficiency of only about 6%. The other upside of this technology is that it is based on wafer processing techniques, so it is very cheap and the technology already exists industrially to mass produce these sort of structures.

Abundant where? (1)

Anonymous Coward | more than 2 years ago | (#39307035)

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:Abundant where? (3, Informative)

Anonymous Coward | more than 2 years ago | (#39307101)

Maybe not by itself, but there's hydrogen in water, which Earth has a lot of to say the least.

Re:Abundant where? (0)

Anonymous Coward | more than 2 years ago | (#39307549)

A lot is very relative. The oceans only comprise about 0.023 percent of Earth's mass. Hydrogen accounts for 10% of that.

Re:Abundant where? (0)

Anonymous Coward | more than 2 years ago | (#39307943)

Yeah, but there are twice as many hydrogen atoms in the ocean. Just because some atoms have more mass doesn't mean they're more important.

Solar cells? (1)

Skapare (16644) | more than 2 years ago | (#39307191)

Can a dry form of this be used to enhance solar cell efficiency?

Re:Solar cells? (0)

Anonymous Coward | more than 2 years ago | (#39307721)

Unlikely, as solar cells already have an external quantum efficiency that approaches unity (some quantum dot solar cells have an EQE above unity), which means that the extra surface area of the branching nanowires doesn't help a solar cell because it already absorbs nearly 100% of incident photons for conversion. The losses in solar cells are those that are out of band, shunting losses, Auger losses, etc. Also, it seems that the heat of formation of water is about -3 eV per molecule or so, which exceeds silicon's bandgap of 1.1 eV, meaning that more incident photons are actually out of band, so for electrical generation, it probably isn't a more efficient process that the photoelectric effect.

Re:Solar cells? (1)

Fned (43219) | more than 2 years ago | (#39308259)

It's probably a lot more efficient than using photoelectric cells to produce hydrogen, though.

Re:Solar cells? (3, Interesting)

Skapare (16644) | more than 2 years ago | (#39308789)

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:Solar cells? (1)

Thing 1 (178996) | more than 2 years ago | (#39318003)

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 we're doing that we can work on the much harder problem of turning the star off, to conserve the energy further -- achieving the Holy Grail, that being to turn the stars into batteries to be used for our purposes, and consumed at the slowest possible rate.

Re:Solar cells? (1)

someoneOtherThanMe (1387847) | more than 2 years ago | (#39323981)

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 (4, Funny)

RedBear (207369) | more than 2 years ago | (#39307235)

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:Groovy (0)

Anonymous Coward | more than 2 years ago | (#39307259)

Say goodbye to aerodynamics.

Re:Groovy (1)

binary paladin (684759) | more than 2 years ago | (#39307269)

Actually... we'll be saying hello in a big way. It'll just be a real drag.

Re:Groovy (1)

Ihmhi (1206036) | more than 2 years ago | (#39308705)

Say hello to the SHAGMOBILE! Yeah baby!

Wow (0)

wbr1 (2538558) | more than 2 years ago | (#39307527)

On phone so tl;dr, but how efficient, does it scale, and can it be done at an acceptable price for consumers?

!Green (0)

Anonymous Coward | more than 2 years ago | (#39307685)

People sometimes forget that hydrogen is bad, bad, bad for the ozone. Hydrogen != Green Energy....just sayin'

Hydrogen production is not main cost (1)

Anonymous Coward | more than 2 years ago | (#39308215)

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

Re:Hydrogen production is not main cost (1)

Skapare (16644) | more than 2 years ago | (#39308799)

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

Re:Hydrogen production is not main cost (1)

tibman (623933) | more than 2 years ago | (#39316247)

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 (4, Interesting)

dsgrntlxmply (610492) | more than 2 years ago | (#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.

Re:Hmmm... ZnO band gap is 3.37 eV (1)

spribyl (175893) | more than 2 years ago | (#39308821)

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 (4, Insightful)

dsgrntlxmply (610492) | more than 2 years ago | (#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.

Re:Hmmm... ZnO band gap is 3.37 eV (0)

Anonymous Coward | more than 2 years ago | (#39308895)

If I just ignore the first half of what you said as being completely opaque to me, the second but would make it seem that this would be a very efficient way to get hydrogen from ice on the moon -- possibly asteroids if the distance from the sun isn't so great as to diminish the value.

Also, if understand you at all, visible light is currently not energetic enough for the reaction. Given that this is a new idea, we can hope that it can be advanced through better materials or finer control of the process or some such thing.

Re:Hmmm... ZnO band gap is 3.37 eV (1)

dsgrntlxmply (610492) | more than 2 years ago | (#39309659)

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: comparatively little UV. Going to the Moon helps only the gap (absorption and scattering) between the yellow curve (sunlight at the top of Earth's atmosphere) and the red curve (sunlight at ground level).

Re:Hmmm... ZnO band gap is 3.37 eV (0)

Anonymous Coward | more than 2 years ago | (#39309137)

Could be interesting for space travel. Even on Mars it could be more interesting. There ay be less overall sunlight but Mars lacks the filtering that the Earth has so more of the actual high energy photons may reach the surface. Stored hydrogen could help a probe survive the Martian winter. Extracting water from the soil should be easy enough.

Re:Hmmm... ZnO band gap is 3.37 eV (0)

Anonymous Coward | more than 2 years ago | (#39309239)

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.

But the second good news is that thanks to what we're doing to the ozone layer, that shouldn't be a problem in the long term. :P

Toxic (1)

jmv (93421) | more than 2 years ago | (#39309143)

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:Toxic (1)

dbIII (701233) | more than 2 years ago | (#39309641)

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) but I doubt that there is anybody doing serious work on them at even an undergraduate level that doesn't know the example of asbestos and how their material relates to it. It's been a couple of decades since I was working with anything resembling nanotechnology (sub-micron metal powder), but EVERYONE had asbestos on their mind back then when dealing with any powder or short fibre.
A fun thing I've observed since then is asbestos fibres blowing in the breeze on a sunny day look just like a Disney sparkly impression of fairy dust. Some people really cut corners on asbestos removal a few years ago. 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.

Re:Toxic (1)

FreakyGreenLeaky (1536953) | more than 2 years ago | (#39309893)

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:Toxic (2)

dbIII (701233) | more than 2 years ago | (#39310163)

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.

Old news in a subpar journal (0)

Anonymous Coward | more than 2 years ago | (#39309669)

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?

Re:Old news in a subpar journal (1)

Skapare (16644) | more than 2 years ago | (#39310375)

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 (1)

fozzy1015 (264592) | more than 2 years ago | (#39315501)

And for renewables that are driven by sun or wind, that cost is surface area.

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