Unless this work differs completely from Nocera's previous work, the device relies on a conventional solar cell (with sub 20% efficiency if made from silicon as suggested in the press release) to provide current for electrolysis of water. Nocera's group focuses on developing low-cost, durable catalysts for electrolysis that can work efficiently at neutral pH. This would allow electrical energy (from solar or other sources) to be stored as hydrogen gas.
However, there are other ways to store solar energy once it is converted to electrical energy or chemical energy. The bigger impediment to large scale adoption of solar is the high cost and low efficiency of initially capturing the energy in each photon. Unfortunately, Nocera's interesting work does not address this much greater challenge.
Also, why was the device tested for only 45 hours? It would have taken more than two days just to prepare the talk he gave. This almost certainly means that the efficiency started dropping and the experiment was stopped.
Anyone interested in this topic should check out the work of Michael Gratzel and others on photoelectrochemical cells, which are more deserving of the label "artificial leaf."
If this is as good as it seems to be, why is the focus purely on the third world? Unless I'm missing something, this could bring cheap and extremely environmentally friendly energy to developed countries too.
If it's purely a case of "they need this more than we do", why not either just license out the technology to companies who can use it, or develop it themselves for developed countries. Either way, they could take the money raised through that side and use it to help bring the technology to third world countries. I can't see any downside of pushing to get this kind of technology widely used everywhere.
"With a single gallon of water, Nocera says, the chip could produce enough electricity to power a house in a developing country for an entire day."
I think a house in a developing country is key. They say the chip is 10x more efficient than a natural leaf. I don't think 10 leaves produce a whole lot of power...
I'm curious how it compares to a traditional photovoltaic solar cell.
In fact, the framing of the performance characteristics of this this artificial leads me to believe that the selling point is their ease of manufacture. That is, they are less efficient than traditional solar cells, but cheaper/easier to make.
Just a guess, though. Would love to see actual figures.
I think more specifically, the battery is cheap. It's the size of a refrigerator and provides very little power (a few AA batteries?) but it uses water instead of lithium.
All that said, if they can find a comercial use for it in it's current form, they may be able to improve the standard of living for a lot of people while funding the research needed to bring it to the developed world.
Earth receives about 1.3 to 1.4 kW per square meter from the sun (and that's before the atmosphere absorbs and reflects a huge chunk of that) - which is effectively an upper bound on the energy that can be produced by any solar power source. A playing-card sized device is going to take more than a day to produce a day's worth of electricity for a current developed-world lifestyle, even if it were 100% efficient.
Solar panels are already good enough that they are used in developed countries such as USA and UK. Are they perfect? No, they cost too much, and they don't generate enough electricity, but they are used none-the-less.
By the sound of it, this new creation would be more efficient, either in price, electricity generation, or both, than traditional solar panels - if that wasn't the case, why on earth would any project use them in third world countries, when they could instead use solar panels.
So, based on those two facts, surely anyone who would be using solar panels ought to look to be using this product in the next few years? (And, depending on how much better than traditional solar panels it is, possibly more people/companies would want to use it than are willing to use solar power right now.)
I don't see, in the linked article, a comparison of the efficiency of this device to that of existing solar panels (which are quite a bit more efficient than natural leaves).
> Solar panels are already good enough that they are used in developed countries such as USA and UK. Are they perfect? No, they cost too much, and they don't generate enough electricity, but they are used none-the-less.
Subsidy and vanity explain a lot of economic activity.
Plus, energy costs are not very uniform. It's much easier/cheaper to get power to the next house in a suburb than it is to get power to a freeway sign 10 miles from the nearest town. That's why solar is cost effective in some situations even when it doesn't make sense in general.
>>Solar panels are already good enough that they are used in developed countries such as USA and UK. Are they perfect? No, they cost too much, and they don't generate enough electricity, but they are used none-the-less.
Does no one follow energy news, except for oil prices and the Polywell project?! :-)
Many estimates talk about soon reaching "grid parity" in large parts of the world. If this leaf isn't good enough, there will be some other solar variant soon.
BTW one reason that Grid Parity is a moving target is that one of the input costs to making solar power is energy. When energy (hydrocarbon fuel) becomes more expensive, instead of making solar power cheaper in comparison, it has no real effect.
Instead, regular power becomes more expensive, which makes building solar power also more expensive, and the net result is a wash.
That seems weird. That would imply that the lifetime energy capture of a solar panel is roughly equivalent to the creation and installation energy cost.
Doesn't seem weird at all, I think. Solar just barely passed breakeven in the last decade, unless you factor in subsidies. I notice that for a random zip code in Maine, http://bpsolar.cleanpowerestimator.com/bpsolar.htm shows that absent federal and state subsidies, you'll save only about $4600 over 25 years with their default settings. It's phrased as saving $36K, though, due to subsidies and interesting presentation. :) But BP Solar really wants you to buy solar panels, of course.
I believe the energy costs are now competitive (but wind still cannot serve as "base" power), but my yet-unresearched hunch is that solar is still at the same stage that wind was: only viable due to the massive tax breaks.
Breaking bonds does not release energy. Bonds are the way the are because they are (locally) the lowest-energy configuration for the atoms that are taking part. You need to put energy in to get out of a low-energy configuration.
The device appears to use water->hydrogen as an energy storage mechanism, to solve (at some efficiency cost) the issue of energy demand generally being out of sync with the supply from the sun. You put energy in to convert water into hydrogen+oxygen, and then you can get that energy back out by converting it back into water.
Since most reactions do not end up with all the constituent atoms as free ions, the real question is how the sum of bond energies of the reaction product(s) compares to the sum of bond energies of the starting molecule(s).
In the case of water, 2 H20 -> 2 H2 + O2 is endothermic, but reactions do not have to be endothermic, or else chemistry would be very boring and cold.
Pisses me off that comments like the one I'm replying to get downvoted. He expressed his understanding of the science, if he's wrong then by all means explain why and upvote those who have explained why - but don't downvote just because somebody made a mistake, it's surely better to have the discussion than for nobody to bring it up.
I won't upvote GP because it contains a factual error and you can't upvote only parts of a comment. If it was edited to include a note about the mistake, thus dismissing the error, I'm sure it'll get get some votes.
I would wager it's also an issue of corporate politics.
If these leaves are capable of creating a sustainable in-house power generator, you will have no more need to buy electricity from your local provider. (Or at least in significantly reduced quantities). This obviously won't sit well with them.
Consider then that it's these companies which have the expertise to develop and commercialize a technique like this. You need to keep them on your friendly side when you are about to market. Going for those locations which are not paying customers anyway, is a safe move from an economic p.o.v. At least until said corporation can figure out a way to monetize the new product in a way that does not reduce their profit.
A better use for this technology in the west would probably be inside of a powerplant, because generating power from hydrogen is probably cheaper in a large scale power plant than using a fuel cell.
My guess it's pretty hard to deploy new technologies inside of powerplants. It takes years of testing, larger sums of money, and very long sales cycles.
So it makes more sense to develop a grid-less version for the developing world, that would serve both as a commercial product and as a proof of concept for the technology, and would take much less time and money to deploy.
Is "photosynthesis"[1] the correct term? Seems to me that "photolysis"[2] would be closer (although readers would get the gist of the former more quickly).
> MIT's artificial leaf is ten times more efficient than the real thing
This doesn't surprise me, to be honest. Organisms have evolved to be fit enough to survive, and efficiency above a certain level might not affect an organisms fitness (or might even affect it negatively).
Was it input solar energy to O2 output? to H2 output?
Was it input solar energy to electricity output - trees doesn't directly produce it, so what thermal efficiency coefficient they applied to calculate conversion, if it is the case?
Photosynthesis stops above a certain temperature due to quantum effects anyway, so there's a natural governor. And I assume plants' vascular system also does some cooling.
Evolution "optimizes" for a lot more constraints. It needs to be self-healing, and work for a long time without any outside maintenance and monitoring. It collects its own energy, and competes with (unpredictable) other organisms for nutrients and sunlight.
Good luck engineering a system like that. Elegant mathematical solutions are great, but only exist for limited, well-defined problems.
Provide every house on the planet with an artificial
leaf and we could satisfy our 14 terrawatt need with
just one gallon of water a day.
One gallon of water a day, in case we are talking about freshwater, is waaaay to much.
In case you haven't noticed, there are regions in this world with a freshwater deficiency (precisely those third world countries which would benefit from something like this), and one gallon of water per day is enough for 3, even 4 people to drink per day.
The article doesn't make it clear if this can function with salt-water, which would be more difficult. And if it cannot, this is not bio-friendly or cheap for that matter.
The US and other western nations would make up for it quickly. According to http://www.sustainablebusiness.com/index.cfm/go/news.display... we currently use 200 Billion gallons of water per day for the current Coal/Nuclear system. There's around 115 million households in the us so one gallon per house per day would be exponentially better.
Maybe it's possible to make this a closed circuit by channeling the "burnt" water back into the solar cell. This way, the daily water consumption could be brought down to (almost) zero.
I guess that this would need distilled water anyway.
This fact concerned me, especially when they suggested using this in India. 80% of Indians currently rely on a finite subterranean water supply. When this runs out, this will pose a very serious humanitarian problem. I'm hoping the technology they mention can be used or adapted to use sea water.
"Nocera's leaf is stable -- operating continuously for at least 45 hours without a drop in activity in preliminary tests -- and made of widely available, inexpensive materials -- like silicon, electronics and chemical catalysts."
So semiconductor grade Silicon is readily available and easily manufactured in a third world country? Or will they have to buy the finished product from first world countries? If they do, where do they get the money? Unless they can build it themselves - and it doesn't sound like they can - how will it help them?
Is it my impression or this device produces energy and water? It apparently works with seawater and, since its exhaust is hydrogen and oxygen that will be recombined in a fuel cell, the end result will be solar power and desalinated water.
I believe this alone is almost more interesting than the power output.
Seemingly every other month, someone comes out with a "solar power breakthrough". This has been happening for the past 30 years and they never seem to follow through. I believe it when I see it for sale at walmart.
I'm guessing the substance he is using is Melanin.
I've already heard of something like this. Mexican scientist, Dr. Arturo Solis Herrera, when studying the properties of melanin, discovered that this substance is to the human body, what chlorophyll is to plants. He achieved alternative energy generation using self-renewing photoelectrochemical cells which separate water into hydrogen and oxygen and then bring the atoms together again. Check it out!!! http://www.energiaadebate.com/Articulos/noviembre2007/imagen...
Since you're intent on belaboring the point, it doesn't claim that one is at ~100% and the other was at 0%. More significantly, if the assertion is that one is more stable, don't you think it would be more compelling to demonstrate its operation for, say, a month? Or did they build this one leaf 45 hours before issuing a press release?
"Lifespan" implies that at the end of the period, the old leaf died. There would be no other reason to use the word. The submitted article also mentions 45 hours without a drop in activity, implying 100% at the end of 45 hours for the new leaf without any kind of assertion about a lifespan for the new leaf. The linked ACS release doesn't discuss this, either.
Grant him the point. Truthfully, you're splitting hairs, and it really isn't worth arguing about, especially since this entire thing seems dubious without proof.
Certainly not when you're trying to judge energy payback horizons for a device incorporating silicon, nickel and cobalt, all of which come with significant costs of production. What if the degradation isn't linear, as seems very likely? Obviously it's a significant improvement, but 45 hours' operation tells us virtually nothing about the device's likely practicality.
The real problem here is that, as usual, we're forced to speculate about what should be straightforward facts, because the story in the OP is based on a dumbed-down press release relating to a talk we can't see, describing research we can't freely access (http://web.mit.edu/chemistry/dgn/www/pubs/publications_2011....), and as a result contains almost no actual information. So it's grandiose claims "we could power the third world!" without any means of assessing whether they're even plausible.
None of this is to say the new cell isn't really interesting, of course. But it's just so typical of science churnalism.
However, there are other ways to store solar energy once it is converted to electrical energy or chemical energy. The bigger impediment to large scale adoption of solar is the high cost and low efficiency of initially capturing the energy in each photon. Unfortunately, Nocera's interesting work does not address this much greater challenge.
Also, why was the device tested for only 45 hours? It would have taken more than two days just to prepare the talk he gave. This almost certainly means that the efficiency started dropping and the experiment was stopped.
Anyone interested in this topic should check out the work of Michael Gratzel and others on photoelectrochemical cells, which are more deserving of the label "artificial leaf."