
Artificial Leaf Harnesses Sunlight for Efficient Fuel Production - zw123456
http://www.caltech.edu/news/artificial-leaf-harnesses-sunlight-efficient-fuel-production-47635?utm_source=Elektor+United+States+%28English%29&utm_campaign=79c067ec54-140EN9_17_2015&utm_medium=email&utm_term=0_8b7374950c-79c067ec54-234904333&mc_cid=79c067ec54&mc_eid=7fba0d115c
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woofuls
Have they made a cheap device entirely out of sustainable materials? No. The
photoactive GaAs/InGaP would be extremely expensive to fabricate. Have they
tested it for commercially relevant timescales? 40 hours is hardly close,
realistically they need to do stability testing for thousands of hours. They
did use non-precious materials to protect the semiconductors from the
corrosive solution and inexpensive catalysts, but this is a very long ways
from practical. Further, they didn't even hit the 10% efficiency mark which
has long been heralded as starting point for these devices.

It is not clear to me that this approach could ever be economically viable
even with the right semiconductors. H2 just doesn't provide enough bang for
your buck.

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avmich
> H2 just doesn't provide enough bang for your buck.

This seems to be a stretched generalization. You do need energy accumulator to
use it in transport systems, and H2 is pretty efficient by mass. It's not
without problems of course, but dismissing it as a whole...

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woofuls
Absolutely not. H2 gives 5.6 MJ/L @ 700 psi, which is too weak compared to
diesel which gives 35.8 MJ/L @ 1 atm. Also, compressed H2 is considerably more
difficult to work with than diesel.

The Department of Energy mandated that these same researchers pursue liquid
fuels in the future (note, they do not mean H2) from the reduction of carbon
dioxide, because they do not think H2 stands a chance.

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zw123456
Right but the advantage of H2 using a system like this could make solar a
viable round the clock energy source. If one could run on conventional solar
cells during daylight hours whilst also using another array of these to
stockpile H2 for use in a fuel cell at night, then it could provide 24hr power
vs. Lion batteries with .6MJ/kg. Clearly they have a lot more work to do
before it would be viable, but I think it has interesting possibilities.

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woofuls
Right now every solar hydrogen production technology is an order of magnitude
more expensive than steam reforming with little opportunity of ever becoming
competitive.

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WalterBright
I know scientists have been working on this problem since decades before 2010.
Have these guys really solved it?

If so, it's absolutely huge news, not the little footnote this is getting so
far.

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Teodolfo
They haven't resolved all the practical problems, they just seem to have made
some incremental progress.

