[opendtv] Re: GM exec: Time to reinvent the automobile
- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Thu, 7 Jun 2007 12:20:19 -0400
Barry Wilkins wrote:
> As Aluminium has a similar energy to weight ratio as petrol
> when oxidized (burnt) it would appear to be a very stable
> and practical alternative to fossil fuel.
>
> Of course the original energy is derived from the
> electrolysis of aluminium oxide to the metal and this
> process has its losses and requires electrical energy which
> may perhaps be derived from an original fossil source.
Interesting. Sort of similar to the H2 proposal, where the aluminum,
like the hydrogen, is only used as a means to transfer energy. Both
start and end in their original state (aluminum oxide in this case, or
water in the case of H2 fuels), and the problem becomes one of purifying
the stuff efficiently, and then transporting it to the consumer
efficiently.
How would you deliver and then load this purified aluminum into
vehicles? Pellets?
> Problem is, you have already lost some energy in the
> splitting process and internal combustion engines run on
> hydrogen run so hot that valves and pistons are destroyed.
> So for these reasons an external combustion process (which
> is cleaner burning) and makes use of the heat of reaction
> would be preferred. The electric cell/motors are required
> for instant demand as a turbine has a slow acceleration
> rate and should be operated at optimum revs continually.
As long as you're going to do external combustion, my preference is also
electric motors. They are clever and simple, as opposed to rube goldberg
contraptions like engines. However, one of the really cool things about
internal combustion engines is that they can operate at a much higher
temperature, therefore higher Carnot efficiency, than external
combustion engines. Because there is no barrier that has to survive the
high temperatures.
In a piston engine, the peak temperatures at top dead center are much
higher than the metal could survive, and the only reason it works is
that the piston quickly moves down, expands the volume, and therefore
cools the mixture. Somehow, I don't see that basic advantage to be easy
to beat. What you have to do here is bank on some sort of renewable
energy or really cheap energy source, in the purifying process.
Bert
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