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'[TECH]Solar energy news from MIT'
2008\08\02@174450 by cdb

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web.mit.edu/newsoffice/2008/oxygen-0731.html
--
cdb,   3/08/2008

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spam_OUTcolinTakeThisOuTspambtech-online.co.uk

2008\08\02@181046 by Byron Jeff

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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?

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

Waiting for more data.

BAJ

2008\08\02@222430 by Apptech

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> 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

2008\08\03@031020 by Cedric Chang

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That was one of the most poorly written releases I have seen.  And  
where do they come up with those silly, " it will take 10 years to  
commercialize".  As if they have any idea whatsoever.
cc



2008\08\04@125328 by piclist

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On Sun, 3 Aug 2008, Apptech wrote:
> 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.

Still not good enough for a car.. but what this is really going to do is
make solar and wind much more viable.

If you can cover your roof with solar, and have a washing machine sized
box in your basement that converts spare power in the day into hydrogen
and oxygen, then burns it later when it's needed.  Or a much larger
version for huge solar arrays that can provide power on demand at night.

--
Ian Smith
http://www.ian.org

2008\08\04@132357 by Apptech

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>> US energy department Hydrogen "storage in a solid"
>> targets
>> were 6.5% by mass.

> Still not good enough for a car.

Maybe not. But Lotus will sell you a Li Ion battery powered
car with even lower mass energy density and a $100,000 price
tag, and tell you how wonderful it is.

{Quote hidden}

Or a larger water gasometer at near atmospheric pressure
that uses off peak mains from whatever source to do water
electrolysis at near 100% efficiency, and the hydrogen is
burned next day.


   R


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