Artificial Leaf Could Provide Cheap Energy

sciencehabit was one of several readers to tip news of a sunlight-harvesting artificial leaf, writing: "Nearly all the energy we use on this planet starts out as sunlight that plants use to knit chemical bonds. Now, for the first time, researchers at the Massachusetts Institute of Technology have created a potentially cheap, practical artificial leaf that does much the same thing—providing a vast source of energy that's easy to tap. The new device is a silicon wafer about the shape and size of a playing card coated on either side with two different catalysts. The silicon absorbs sunlight and passes that energy to the catalysts to split water into molecules of hydrogen and oxygen. Hydrogen is a fuel that can be either burned or used in a fuel cell to create electricity, reforming water in either case. This means that in theory, anyone with access to water can use it to create a cheap, clean, and available source of fuel."

MIT invents everything

[RabidRabbit23]

I saw a presentation on exactly this technology a few years ago at a conference, not from an MIT researcher. It's a strange phenomena, but within science MIT is just one of many research institutions doing great work, but to the public it has the most significant and frequent press releases. I mean, this isn't even a leaf, it's a silicon wafer which happens to be green and splitting water using catalysts is very old. The only innovation I'm seeing here is a new catalyst, which is pretty common in these fields. I also like the token quote from Bob Grubbs who won a Nobel prize in catalyst research and thus is interviewed in every catalyst article.

Re:10x more efficient than photosynthesis?!

[loshwomp]

I'm amazed that the foundation of life on earth is so inefficient (one tenth of 5.5% is only .55%!). Is this right?

Somewhere on that order, yes.

Also, if this is true, then isn't this a major reason against using biofuels?

Exactly. Plants are ~1% efficient at harvesting solar energy, and we have much better collectors (photovoltaics) that are much more efficient (15-20% in mass production) and generate energy in a more versatile form (electricity).

Re:Isn't it better with traditional electrolysis?

[im_thatoneguy]

It's made from copper and cobalt instead of a lot of the more exotic materials used in standard photo-voltaic cells.

Re:10x more efficient than photosynthesis?!

[Anonymous Coward]

Plants limit their photosynthetic efficiency largely because raising it too high starts raising the internal temperature, which raises the rate at which they lose water. Basically, they are tuned to gather 'enough' energy without wasting water (which is rarer for them than sunlight) rather than extracting as much energy from the sun as they can. Biofuels are usually suggested not because they are efficient, but because they are cheap and work fairly well with our existing infrastructure.

Re:no free energy

[Black Gold Alchemist]

If you have solar panels capture the energy, they simply suck the energy up, store it, and when it returns as heat in the friction of the objects it moves, the lights it powers, etc. Without the solar panels, the light would just be heat. So it is free.

Re:So it's a solar cell....

[rubycodez]

Actually, the deuterium in the oceans would provide fusion energy sufficient for billions of years, the sun would scorch the earth to by expansion first before we ran out. And there is lithium and boron, and we can make tritium. Fusion really is the holy grail of power generation if we can't make solar power work. http://www.engineeringchallenges.org/cms/8996/9079.aspx [engineerin...lenges.org]

Re:So it's a solar cell....

[sunzoomspark]

The big question I see with this is just how clean does the water going in have to be?

The article said they'd been running it on water from the Charles River, so it doesn't have to be very clean.

Re:So it's a solar cell....

[rubycodez]

Deuterium is much more abundant than gold and far easier to extract from water (of any source, fresh or ocean doesn't matter). We've been producing and using deuterium for decades, for example as moderator in heavy water reactor. The energy cost is negligible even for fission reactor moderator, for fusion energy even smaller cost compared to yield.

Re:What about night and bad weather?

[LBU.Zorro]

Ok, so I found 3 Humboldt Countys in California, Iowa and Nevada, but based on size it appears you mean the CA one, of course it only really has 2.2million acres of land, the rest is water.

According to this report (http://postcarboncities.net/humboldt-county-ca-energy-element-background-technical-report) Humboldt county (apologies if I got the wrong one or anything) used 940 GWh of electricity alone in 2003, which comes out to around 2500MWH averaged daily - that is a heck of a jump from your 100MWH, 25 times as much. And that doesn't count usage growth over the last 8 years, nor the natural gas heating, cooking and hot water (about 45million therms) nor transportation energy costs.

I'm pretty concerned by your numbers now, but even taking your 25 acre 5MW station at face value, and even allowing that it's a molten salt plant and stores enough energy to provide that 5MW continuously day and night with backup storage to last several weeks and to provide that 5MW during the local solar minimum you would need 12500 acres to provide just the electrical energy. 10 cubic meters of molten salt can provide 1MWH of storage, since you'd need 2500MWH of storage for a single day, and several weeks of storage you're talking about 350k cubic meters of molten salt, a heck of a lot.

Sure all of this is relatively minor compared to the actual size of Humboldt county but I'd guess the cost of manufacture of a 5MW plant to be around the $20million mark (unaccurately based on http://www.power-technology.com/projects/Seville-Solar-Tower/ [power-technology.com] and scaling down), so if you have to build 500 of them just to handle the electrical load you're talking about $10billion to manufacture (and remember this is for purely the electrical generation of 2003, not transport or natural gas). The population of 2008 is estimated at about 130k (http://mapzones.org/Humboldt_County_California.html) meaning that would cost about $77k per resident. The same report shows that the average per-capita income of Humboldt county residents is $17k annually - or 4.5 times the cost.

I don't know about you but I'm a little puzzled as to how you're going to pay for all of this? Not to mention over doubling it for powering hydrogen/electrical vehicles and replacing natural gas completely - something you'll have to do to have this green revolution of yours.

What you, and everyone who thinks that "popular pundit b.s." is just "b.s." seem to fail to understand is that this is a huge engineering, financial and technological issue to overcome. There are many reasons why it hasn't happened already, and aside from energy density and reliability the biggest reason is cost, are you really willing to have an additional 50% tax on all income in your state for the next 10 years to pay for constructing the plants necessary? Think of what that would mean, can you cope with 50% less money every payday?

Just as a comparison a 320MW natural gas power station costs about $150million dollars (http://www.power-technology.com/projects/laverton/), so you're looking at about the equivalent of 8 of them, or $1.2billion dollars - your solar plan is an order of magnitude more expensive. If you're saying that they should be built with loans and then amortised over the lifetime of the plant with the cost being the energy, you're still looking at about 5 times more expensive electricity (yes I know the fuel costs are minimal - mirror maintenance is a pain but you don't have to buy gas) unless you subsidise it somehow (in which case it's still 5 times as expensive but you're pretending it's not).

If you're going to have statements like "Now you see where the science behind green makes sense, and the popular pundit b.s. that is constantly echoed is just exaggerated doubt and nonsense claims." then you had really better match that with actual verifiable numbers and facts. Rather than just repeating what you've heard without really understanding it - it is completely possible, but then again so