Re: Using nuclear power to make renewables and a hydrogen economy cost effective

From: Ian St. John (istjohn_at_noemail.usa)
Date: 10/28/04 

Date: Thu, 28 Oct 2004 14:45:06 -0400

G. R. L. Cowan wrote:
> Alex Terrell included:
>>
>>> it. I suspect, though that fuel cells are prominent because they
>>> have the *potential* for 80%+ conversion efficiencies while the ICE
>>> is limited to a much lower value by thermal laws.
>
> Fuel cells have no potential for "80%+ conversion efficiencies".

Yes, they do. Theoretically they could approach 100% but that is unlikely as
some losses must occur to drive the internal proceses. They are not
restricted to the otto/diesel cycle effiicency of the ICE engine.

> Thermal laws limit the ICE to about 80 percent.

Bull***. The otto cycle ( standard ICE ) or diesel cycle are limited to
about 65.5% by the controlling factor of compression ratio.

http://www.qrg.northwestern.edu/thermo/design-library/otto/otto.html
http://www.qrg.northwestern.edu/thermo/design-library/diesel/diesel.html

This is assuming steady loads ( feasible only in hybrids ) while actual
results are much poorer due to running in load ranges that are not optimal.
Fuel cells are always running optimally. They do not have the problems of
changing physics.

>
>>>
>>> I read pure hydrogen fuel cells can manage 80%, even today.
>
> You were deceived.

No. I wasn't. I corrected Alex's statement in my rebuttal which pointed out
that the only claims for such rates were in 'cogeneration' which used the
'waste heat' and that the current record for fuel cell conversion is 60%.

>
> A perfect hydrogen fuel cell would, by producing infinitesimal power
> at infinite cost, convert the whole delta 'G' of oxidation of
> the hydrogen fed to it to DC electrical energy.
>
> 100 percent conversion of the delta 'G' of oxidation of hydrogen
> to liquid water is equal to 83.0 percent conversion of its HHV,
> its higher heating value.

The higher vs lower heating value is immaterial to direct conversion. It is
applicable only to the limiations of Carnot cycle heat engines.

>
> Misleading discussions of fuel cell efficiency often sneak in
> a claim of attainable perfection under cover of this scale change:
> in effect, they say, stable multi-century funding for
> all the researchers in the world would never in a million years
> get you 100 percent conversion of HHV,
> unless you call it 83 percent of DG,
> in which case, success can reasonably be expected
> in 15 to 20 years. Or 10 to 15 years.

You seem to have a confusion about the whole area. There is no 'degrading'
of chemical energy to 'heating value' as the fuel cell does not work as a
heat engine. Please take some physics courses.

>
> Where a perfect, infinitely low-performance, infinitely expensive
> fuel cell could do 83 percent (of HHV), real ones top out in the low
> 30s.

No. Real ones currently have efficiencies of up to 60% but those are only
suitable for stationary applications.

> On the delta 'G' scale where perfect, infinitely low-performance,
> infinitely expensive fuel cells could do 100 percent, real ones
> top out at 41 percent or so.

You are infinitely stupid.

http://www.eere.energy.gov/hydrogenandfuelcells/fuelcells/pdfs/fc_comparison_chart.pdf
Descriptions and drawbacks.

http://www.dodfuelcell.com/fcdescriptions.html
Molten carbonate is the most natively efficient and reaches 60% so far.

>
>
> --- Graham Cowan
> http://www.eagle.ca/~gcowan/Paper_for_11th_CHC.doc --
> How individual mobility gains nuclear cachet

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