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Photocatalyst Cracks Water with Sunlight
lonenut writes: "With fuel cell laptop batteries in the news lately, I thought this article on water-cracking photocatalysts would be good reading. A bit short on details, but apparently Zhigang Zou of the NIAIST in Tsukuba, Japan is working on a promising catalyst which creates hydrogen and oxygen from water and sunlight. I look forward to someday watering my laptop just like the houseplants."
No it doesn't
a) catalyssts are by definition resuable
b) there are other source of minerals than just the Earth. (There aren't any other useful sources of hydrocarbons on the other hand).
Were that I say, pancakes?
How do you convert the sunlight to electricity?
Electricity producing silicon solar-cells actually take more energy and generate more pollution during manufacture, than they will ever generate. The uninformed non-tech green set never seems to understand this point.
This leaves using an intermediary like water or sodium, to be heated by sunlight, and to generate electricity mechanically. This is highly inefficient, and/or dangerous.
The fact is, sunlight is too diffuse to be a practical large-scale energy supply without a hell of a lot of energy being put into it, by traditional means. Unless you count photosynthesis, which I give more creedence to than solar cells, the energy is just in a completely different form.
The nice thing about conversion directly to hydrogen, is that it is definetly an easier way to concentrate the energy.
Anyone who considers arithmetical methods of producing random numbers is, of course, in a state of sin.-John von Neumann
Building the solar pannel requiers more energy than you get out of it. Same as a battery. It's only "efficient" for the end user.
Petrolium is efficient because we are just harvesting millions of years of sunlight-and-plant stored energy. In real terms, it's not efficient at all. Ethanol is more efficient, brewing burnable liquid fuel out of sugar, or using lye and methanol to crack vegetable oil into "diesel" fuel. Or just burn the veggie oil directly, like Heir Diesel did in his original engines.
All of these convert sunlight into fuel, with various efficiencies and usefulness. I think the direct use of veggie oil to be the best myself, but one still has to press the oil out!
The answer, I believe, is to use them all. Bio-diesel, veggie oil, ethanol, hydrogen, tide and wave forces, wind, sunlight, petrolium.
The "scarce resource" idea is a myth. 150 years ago, whale oil was an important strategic national resource. Silica is as common as sand, and more valuable than gold when formed into a computer chip.
Bob-
The Ludwig von Mises Institute. The reasoning individuals economics
Why? When you "burn" the hydrogen to recover the
energy, guess what you get back?
Every bloody emperor has his hand up history's skirt [Peter Hammill/VdGG]
I believe that this is no longer true. The latest generations of cells are much thinner and lighter (less silicon to refine and melt so less energy) and more efficient than earlier generations.
Conversion between different forms of energy results in a low efficiency. Converting from electricity to hydrogen and back would have an efficiency of about 50% (at a guess), not including transport of the hydrogen. The electricity grid has an efficiency of about 75% (again an educated guess), and is very convenient.
;)
This is indeed true: the processes which convert energy from one form to another are rarely efficient. There is one thing which has struck me about this: we don't need to be efficient. What we need it lots of energy which we can waste.
On a day to day basis we waste more energy than could be imagined. The great fiery fusion reactor in the sky emits it whether we use it or not. Lot's of it. More energy than even a Californian household could use! In a sense, sitting on a rock and collecting what comes out way isn't very efficient. I doubt we get more than a hundred billionth of the energy that we could get. It's just difficult to it!
Imagine a process of generating hydrogen using sunlight which was commercially viable but was only 1% efficient. Is this a problem? Not if you can collect 100 times more of the free energy which is being lost from the great fusion reactor in the sky. To put it in context, use a reflector 10 times the size.
This is entirely an engineering problem, and with current technology it's solvable but expensive. The end result though, is enough energy for rock and roll for as long as the fusion reactor in the sky is pumping it out. All we have to do is enough work to collect some of what's wasted!
(yes, I know. Ultimately, you want an elipse with a collector at one focus and the sun at the other so we don't waste any of it. Dyson sphere anyone?
Ian Woods