

Sun-powered water splitter makes hydrogen tirelessly - cwan
http://www.newscientist.com/article/dn18511-sunpowered-water-splitter-makes-hydrogen-tirelessly.html

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wglb
There are major problems with hydrogen as a fuel, even presuming that this
method becomes practical. First, it is more bulky than gasoline for the same
energy value of fuel. Second, it is disastrously flammable, and you can't see
the flame. Third, it causes metals to be brittle.

These are major infrastructure and transportation issues that cast doubt on
the viability of the "hydrogen economy" even if its production can be done
without burning coal.

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pyre
Do we even know what pumping out all that water vapor will do to our
environment? Sure, "it's just water," but won't that cause a shift in climate
as well? Maybe not as severe as pumping out CO2 (since CO2 doesn't rain out of
the atmosphere), but couldn't this affect local ecologies pretty severely in
some areas (i.e. significant increases in rainfall)?

I don't pretend to be an expert on the subject, but I've never heard anyone
really comment on this other than the anti-global warming pundits spouting
catch-phrases like "water is a greenhouse gas too."

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camccann
At a global scale, the "rains out of the atmosphere" bit mostly covers it.
Condensation and evaporation processes tend to make water vapor largely self-
regulating, shifting around quantities of water that dwarf human factors.

However, where does the article mention water vapor? They're doing
_electrolysis_ , i.e., cracking water molecules apart. The desired result is
the liberated hydrogen; the waste is oxygen--hopefully O2, or if you're
unlucky O3, which is a pollutant in the lower atmosphere.

~~~
pyre
I was under the impression that when using hydrogen for fuel, the by-product
was water (at least in automobiles). The article just triggered the question,
I wasn't necessarily commenting on the technology.

> _At a global scale, the "rains out of the atmosphere" bit mostly covers it.
> Condensation and evaporation processes tend to make water vapor largely
> self-regulating, shifting around quantities of water that dwarf human
> factors._

I was thinking more on a local level. I realize that water vapor will dump out
of the atmosphere (unlike CO2) so it for the most part will not be a
greenhouse gas. My question was on whether or not large amounts of water vapor
being released from cars will cause local ecosystem changes. (i.e. If every
vehicle in NYC or Los Angeles ran on hydrogen, would it cause average rainfall
in the immediate or surrounding areas to increase? What about yearly average
ratio of cloudy vs sunny days?) Obviously people in middle-America (for
example) probably won't cause much of a local impact, but what about major
urban centers?

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wglb
Gasoline-powered ICEs also produce water vapor. One might assume that the
water vapor output produced by hydrogen-powered vehicles is on the same order
as the ICE that is replaced.

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pyre
I realize that water is produced by burning gasoline too, but since the _only_
by-product of burning hydrogen is water (IIRC) I assume that the amount is
larger.

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ars
Most of the energy from burning gasoline is from the hydrogen in the gasoline.
It's about a 1 to 2 ratio of carbon to hydrogen. (i.e. 2 hydrogens for each
carbon). So twice as much water as carbon dioxide when burning gasoline.

And on top of that the hydrogen releases more energy than the carbon (for each
atom).

So if you have no carbon, just hydrogen it might be 25% more water (just a
guess off the top of my head).

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Groxx
60% efficiency in splitting water apart? That's pretty incredible efficiency
for _anything_ solar powered. Whether or not you favor hydrogen as fuel, this
may actually make it feasible.

Heck, I wonder if this could surpass solar cells in efficiency & cost (no word
on cost in the article), by burning the H & O or using a fuel-cell method with
the hydrogen.

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ars
They say they are making electricity for electrolysis.

So why not just use that electricity directly?

This article is nonsense. What they are claiming is impossible. 60% is just
not possible with a single (i.e. non-layered) material.

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aaronbrethorst
Holy cow. can someone better educated than me comment on this? This _sounds_
like it's a tremendous supply solution for hydrogen fuel cells. Is that
accurate?

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InclinedPlane
TANSTAAFL, this is a significant improvement but the process of converting
water into a supply of Hydrogen sitting on a shelf somewhere or otherwise
readily available for use includes other costs than just the energy to
hydrolyze water (though that is a big one). For example, the costs of land,
the cost of water, the cost of the equipment and its maintenance, and
especially the cost of collecting Hydrogen and storing it (generally under
pressure). This may be a revolutionary breakthrough but until it's put into
practice and we can judge all of these factors it's probably too soon to tell
exactly how much of an impact it will have.

~~~
camccann
Right. It's just a variety of solar power, converting the energy in sunlight
into another form--in this case, chemical potential energy.

The potential value lies in weighing practical considerations between
different ways of storing solar energy--standard solar technologies tend to
produce either heat or electricity, neither of which stores well.

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lucifer
There are other considersions:

<http://en.wikipedia.org/wiki/Indium> says that Indium is "rare". (Let us all
pray that is not found only in the Middle East .. ;)

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houseabsolute
No major reason to do it on gold or platinum, so basically they used these
precious materials just for the hell of it? Odd.

~~~
camccann
Many precious metals have useful qualities in terms of resisting corrosion,
conducting heat or electricity, and such. In a lab doing this kind of work,
they are likely to have those materials just lying around.

Read it as "we used super-high-end electrode materials because we had them on
hand, but the process doesn't actually require them".

