Re: What about producing water?



"G. R. L. Cowan" wrote:

hhc314@xxxxxxxxx wrote:

G. R. L. Cowan wrote:
(2) the hydrogen would be coming from water in the first place.

Why do you assume that. Virtually no hydrogen produced today comes from
water, and hasn't been since the "water gas" or "producer's gas"
process was obsoleted when most municipal "illuminating gas" plants
shut-down during the early 1950s with the availability of natural gas.

Also, recall that the source of energy for the above hydrogen
production processes employed the combusion of coke and coal, which
produced a mixture of H2 and CO. (As in "go and stick your head in the
oven".)

Today, essentialy no commercial quantites of hydrogen are produced from
water, but are produced from the reformation of methane and various
other hydrocarbons.

So the remaining question is: If you're going to produce your hydrogen
from water, what is the energy source used to accomplish this
decomposition? Nuclear? Oil? Coal? (The order of magnitude energy
required to produce a useful quantity of hydrogen to support realistic
transportation needs is clearly far beyond the practical capabilities
of photo-voltaic hydrolysis.) Also, what happens to the carbon?

Should I guess that considerations such as the above are the same
things that tempered you faith in hydrogen?

No, carbon-free energy obviously is very abundant.
It was more a matter of noticing that hydrogen plus containment
is a lot heavier per kWh than, say, aluminum plus containment.

A hypothetical aluminum-burning vehicle drive with a bicameral fuel tank
so as to save the Al2O3 for sending back to the aluminum plant
is at its heaviest when the car will no longer go,
but that tank then is *still* lighter tank an equivalent hydrogen tank,
because it is so much smaller.

That, and aluminum doesn't tend to mix with air and blow up
upon escaping containment. If you frequent grocery stores,
you'll know aluminum containment can be a thin cardboard box.

The fly in the ointment is that turning Al2O3 back into Al is hopelessy energy
inefficient.

Graham

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