Re: nuclear separation of hydrogen from water vs. electrolysis
From: Baby Elian (SPAM)_at_virgilio.it)
Date: 06/14/04
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Date: Mon, 14 Jun 2004 17:46:33 GMT
"brianb" <bri1600bv@hotmail.com> ha scritto nel messaggio
news:68a6629.0406140533.2aa15757@posting.google.com...
> "Baby Elian" <sandrino77(NO SPAM)@virgilio.it> wrote in message
news:<1pezc.325823$hc5.14179792@news3.tin.it>...
> > "brianb" <bri1600bv@hotmail.com> ha scritto nel messaggio
> > news:68a6629.0406131917.181b24a5@posting.google.com...
> > > Someone mentioned there is a process to split or "crack" hydrogen from
> > > water using heat, I guess, instead of a electrolysis. Which is more
> > > efficient?
> >
> > The efficiency depends from the temperatures the reactor works. For a
range
> > of 850-950 °C (today achievable in a htgr nuclear reactor) the
efficiency is
> > 45-52% or more
> > http://anes.fiu.edu/Pro/s10Sc.pdf
> >
http://www.min.uc.edu/nuclear/prezen/HydrogenEconomySeminarByBillSummers.pdf
>
>
> Thanks, I browsed them quickly. I'll read more later.
>
> But my question about efficiency isn't "energy in uranium ->
> hydrogen", it's really "energy realized in nuclear output ie 1000MW
> hours (per hour) for nuclear plant for example" -> "energy of
> hydrogen".
It's this second one.The efficiencies you read in the pdf 's are "energy
coming from the full combustion of the hydrogen /waste heat of the nuclear
reactor".It take 40 MWh (thermal) to produce one tonn of hydrogen.But,as I
mentioned before the efficiency depends from the temperature range (40-50%
is for 850-950 °C).This means that a gt-mhr module working at 80% of
capacity factor can produce about 115 tonn per day of hydrogen,assuming an
efficiency of 40% if the max outlet temperature core is 850 °C (and using
only the waste heat reactor without depauperate electric energy produce in
the plant,instead electrolisys!)
>
> Does your 50% figure count the uranium->energy efficiency also? IF
> so, I think it would be double counting for my purposes.
>
> My question is more, if you have a 1000MW plant and run it for 1 hour
> what is the amount of energy in the hydrogen you can create? I'm
> trying to figure roughly how many 1000MW plants you'd need to create
> 6.5 billion barrels of oil energy...6.1 GJ/barrel * 6.5 billion
> barrels = 40*1e18.
>
> Using 100% efficiency 1 plant =
>
> 1000MW * 9,000 H / year * 3.6 e9 J / mwh = 3.24e13 Joules/ plant
>
> barrels / plant = 3.24 e 16 / 6.1 e 9 = 5.3 e6 barrels.
>
> Or 5.3 million barrels per plant.
>
> So about 1000 plants at 1000MW hours using 100% efficiency would
> produce 5.3 billion barrels, which should be enough for the US.
> Current consumption is 6.5 billion barrels or so.
>
> The missing piece is the efficiency of nuclear power output to
> hydrogen.
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