piclist 2002\09\18\195758a >
Thread: hydrogen/aluminium
face BY : Russell McMahon email (remove spam text)

> > The energy used to make pure Al from the naturally
> > occuring oxide form is heat energy bought generally
> > as coal or natural gas, whatever is mega-cheap in
> > that area and bought under bulk contracts by large
> > corporations. Hence this energy is bought much cheaper
> > than what an end user would pay for household
> > electricity etc. There is a margin that makes aluminium
> > a viable fuel if the alternatives are expensive.
> > What wrecks the idea is the low efficiency of
> > converting the heat energy released on Al oxidation
> > to usable energy.
> > -Roman
> Are you sure about this? Do you have a reference? I thought you could only
> reduce Al using electrolysis.

You are correct about the electrolysis.

What he means (I think) is that energy is "stored in Aluminium" by reducing
it from it's oxide and recovered by re-oxidising it (with liberation of
Hydrogen which is then also available for oxidation) BUT that the resultant
heat is not a high grade energy source.

The patent being discussed is intended to overcome the normal problems with
the oxide layer on Aluminium. The rotating drum and spark presumably
disperse fine Aluminium particles into the water where they react to form
Hydrogen. IF it works well this does appear to be a good way of getting the
energy of reaction out in a useful form.

The British mad a torpedo at one stage that was powered by reacting Al with
seawater. I believe there was a mechanical scraper that removed the surface
oxide layer.

Overall TANSTAAFL applies. (There aint no such thing as a free lunch?)
This is just one way of TRYING to exploit the Al / water reaction. It would
be simpler to use Calcium or Sodium or Potassium, and more fun in the latter
two cases :-),  but Al is more available and safer until used.

I have my doubts about the original BMW letter.

       Russell McMahon.

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