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

["Barry Wilkins" <barry.barrywilkins@xxxxxxxxx>]

On 6/8/07, Jeroen Stessen <jeroen.stessen@xxxxxxxxxxx> wrote:
> Hi,
>
> Barry Wilkins wrote about The Air Car:
> > Furthermore , it would appear that people loose track of the origination
> of the energy source
> > and the losses involved in the storage process. Much heat is generated
> in the compression of
> > air and this is simply waste energy that cannot be extracted by the
> vehicle.
>
> Not true ! As the air expands in the engine, it cools down.
> It is reheated between cylinders from warm ambient air.
> This extracts energy from the ambient (and provides for free
> air conditioning). Thus the car uses some energy from the
> ambient that it does not have to carry with it. You could
> say that some of the heat from the compressor travels to
> the car through the air and is used by the expander...

I do not understand your comment. The loss in energy occurs as heat when the
compressor powered by an electric motor external to the vehicle compresses
the air to start with. Some of the radiated heat is from the latent heat of
the air but a proportion is from the work expended in compressing it. Have
you ever tried pumping up a tire on a bicycle. You will note the pump gets
warm in the hand as you do it. Though there is heat in the air initially,
you are providing the added energy to raise its temperature and pressure.
You can work up quite a sweat doing it! Now, if you could re-release the
pressure back expanding into the pump cyclically, you will find you can do
nowhere near the amount of work that you expended in the pumping up.

> A vehicle that needs to operate for 4 hours per day at an average 20KW
> work load
>
> You are completely missing the point. A lot of cars are used
> less than 30 minutes per day. Air would be the perfect solution,
> also because there are no self-discharge losses like in
> batteries and cryogenic hydrogen tanks. You can leave such car
> parked with a full tank for years, and it should still be full.

Yes, a sitting time bomb!


I do not suppose you have considered what an enormous risk a large storage
tank at a  filling station would pose. It would be far worse than a liquid
propane tank if it exploded. The shock wave would demolish huge areas around
it. The alternative rapid charge via huge electric motor/compressors would
not be practical.

> requires double this energy from the electricity supply to compress the
> air in the first place.
>
> So what ? The alternatives are not that much more efficient !
>
> > As a 50KW 3 phase induction motor would be required to operate over at
> least
> > 4 hours to compress this air I do not believe it is a very practical
> solution in general.
>
> You could connect the air compressor directly to a steam
> turbine and install a compressed air network. But I think that
> in order to fill an empty tank efficiently you need multiple
> sources of compressed air at different pressures. You should
> probably not fully empty the tank in the first place, or the
> power output from the engine would be insufficient.
>
> Let's also not forget that a simple flame under the heat
> exchanger for this Air Car engine serves as a range extender.
> This flame can be from any source, even burning old newspapers.
>
> I think I might buy one, if they ever start making them... !
>
> Best,
> -- Jeroen
>
>
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