[Oeva-list] Compressed air vs. Batteries?
stevel at fern.com
Sun Jul 1 10:55:49 PDT 2012
> Hello OVEA enthusiasts,
> Most of you have a lot more experience with EV's than I do, what do
> you think of compressed air cars?
> Seems like a viable method for storing and transferring potential
> energy. In a sense they are electric cars, in that electricity powers
> air compressors and lke "conventional" Battery EV's, they're
> flexible-fuel in that the electricity can be generated by a wide
> variety of sources. I'd welcome input and suggestions, I may do a
> story on them.
Compressed air has been looked at a number of times. There is actually a
few companies building them now.
They are not very efficient.
Air, when it's compressed, heats up. It must be cooled to compress it to
a fairly high pressure. The energy needed to cool the air isn't recovered.
Air, when expended, cools. If it conains any moisture it freezes. The
air needs to be dehumidified, again requiring energy.
Compressors are pretty awkward beasts. When you start out, you are trying
to move a large volume of air at lower pressures. As the tank "fills" you
are going to higher and higer pressures, requiring additional stages of
compression. A compressor that works well at low pressures won't work
at high pressures. One that works well at high pressures doesn't work
well at low pressures.
The energy "density" in a volume of compressed air isn't very large, requireing
large, heavy tanks to get much range.
Compressed air tanks are heavy, and in a crash, can be lethal.
All that being said, there are places where they might make sense. Lift
trucks and personel transport indoors, seem like a likely "win".
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