> On Sat, Aug 02, 2008 at 05:45:03PM -0400, cdb wrote:
>>  http://web.mit.edu/newsoffice/2008/oxygen-0731.html


> In summary it's a new process for water splitting into H2 
> and O2.
> The huge question is what is the efficiency? If you put 
> one kW of
> electricity into the process, how much energy can be 
> produced from the
> resulting hydrogen and oxygen?

I meant to post on this a few days ago but didn't.
It was an embargoed release out on 31 July so they seemed to 
think it significant.

The key issues the new process is said to address are 
covered in the press releases.

Essentially (they say), until now electrolysis had good 
efficiency as far as the Hydrogen side of the cell as the 
available catalysts worked well BUT the Oxygen generation 
was inefficient due to the cell potential needed being 
higher than the theoretical half-cell potential.

What they have done is come up with an Oxygen generation 
catalyst which allopws nearly 100% of theoretical efficincy 
so that Hydrogen generation is now very close to 100% 
efficient. This is a very timely response to the issue that 
I addressed recently - I noted that there was no theoretical 
reason that conversion could not be almost 100% but that 
this had not yet been achieved in practice. Apparently it 
now has, so we can (perhaps) move on to the other issues.

> Also there's still issues on hydrogen storage to be 
> addressed.
> You can't
> just contain it like air.

True. But air is harder to burn :-).

> Waiting for more data.

Granted -

Storage is being addressed extensively and intensively as 
per other recent posts.
US energy department Hydrogen "storage in a solid" targets 
were 6.5% by mass.

That's a pathetic 1.6 kWh/kg.
But about 5 times (falling with new developments) the mass 
density of Lithium Ion batteries.
IF you eg used the Hydrogen to run a heat engine (IC or 
Stirling or ...) you'd likely still be noticeably ahead of 
Li Ion overall on energy mass density.


>From before:

"For now" here is an article by people who think that
Hydrogen may be a potentially viable energy transfer media.

    http://www.rsc.org/Education/EiC/issues/2007Nov/FuellingFutureSolidPhaseHydrogenStorage.asp

They point out the difficulties and the storage goal - which
is modest if achieved and may not be achievable. ie 6.5%
Hydrogen storage by mass in "solid phase" storage (hydrides
or nanotubes ??? ...).

AND:

These people are claiming a quantum leap to 720 W/kg (they
asy 720W/kg but I'll assume that's just a typo and not
ignorance)

        http://www.everspring.net/txt/product-battery.htm?gclid=CPT0463h6ZQCFRIuagod1yigQQ


AND


Note that LiPo here is only talking about around 200 Wh/kg.
    http://en.wikipedia.org/wiki/Lithium-polymer
LiIon with < 200 here
    http://www.batteryuniversity.com/partone-3.htm



        Russell

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