[opendtv] Re: GM exec: Time to reinvent the automobile

  • From: "Albert Manfredi" <bert22306@xxxxxxxxxxx>
  • To: opendtv@xxxxxxxxxxxxx
  • Date: Thu, 07 Jun 2007 21:22:26 -0400

Bob Miller wrote:

Air power is another solution. It could rely solely on the
electric grid where we can more efficiently control
emissions and work toward centralized power sources
that are renewable.

http://www.theaircar.com/

Ironically air conditioning is no problem but heating is.

I'm not sure that I buy the hype.

I have no big problem believing that air can be compressed at high enough pressure to run a small car, and that the energy required to compress that air is similar to the energy required to make H2 and run a similar sized H2 engine for the same car and distance. And I can believe that air flasks may be lighter than batteries, although probably more voluminous, for equal energy content.

I have a much bigger problem believing that it takes less time to fill tanks with the required compressed air, for x miles of range, than for the amount of H2 fuel required for that same range.

I would have guessed that storing as much PSI of H2 in an x-gallon tank as PSI of air in an x-gallon tank results in a lot more energy in that high pressure H2 tank. Because the H2 is burned, which releases all that energy given off when H2 becomes H2O. And the O2 required for the process is not in the tank! Whereas the compressed air only contains the energy inherent in the delta P with atmospheric pressure. So it seems it should take longer to store the required amount of air than the required H2, for the same energy content.

One advantage air has is that the molecules are bigger than H2, being mostly N2, O2, and CO2. There ain't much smaller molecules than H2. Should be a little easier to build the high pressure system. As to where you do the pressurizing, that's not so different from the H2 case.

Something doesn't jive. I think we aren't being told the whole story (hardly surprising). In fact, those air engine ranges were not so impressive. I'd ask for a direct comparison with H2 engines or fuel cells.

Bert

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