Compressed Air Car: Too Good to be True??

[Joe Blake]

http://www.gizmag.com.au/compressed-air-car-set-for-us-launch-in-2010/8896/


I think I'd have grave reservations about some of the figures given. Range of "up to" 1000 miles? It'll cost next to nothing to run??

This link goes into a bit more detail on how the engine works.

http://www.gizmag.com/go/3523/

I've got no difficulties with the concept of the engine, seems a very slick piece of engineering, but I'm wondering about the "hidden costs". Compressing a gas does take a lot of energy, and unless one is very cunning about such things as recycling the waste heat, I would have thought it wouldn't be too efficient.

But on the other hand it's claimed it's only going to run at 35 mph, which would make a big difference.

Anyway, I think this'll be one of the things I'll keep an eye on.

Hoping not to appear too cynical, I would imagine that any country which is population rich might be able to use a degree of manual labour to compress the air as a last resort. (Would be like my using my pedal powered 12 volt generator to charge the batteries on my electric trike while I'm watching television - sort of "pedal now, drive later".)

Joe

[Mark Parsons]

Greetings Joe,

Like you, I am also a bit cynical about the efficiency of producing the compressed air.

All shops that run air compressor(s) for shop tools and machines know that compressed air is the most expensive resource. A significant amount of energy is wasted in heat that warms the ambient area around the compressor or goes into the cooling water stream. I know the air engine runs the pressure to below atmospheric to try and re-capture some of this wasted energy but not sure how efficient that is.

To get any sort of range from a storage tank of compressed air will require astronomical pressures. The higher the pressure, the more lost heat energy not too mention danger of explosion in an accident. In Ontario we tried for years to get range from Natural Gas. Tank pressures in vehicles exceeded 3,000PSI. With 2 of these tanks (size of large cutting torch cylinders) on board still provided a very short range in an ICE powered vehicle - under 150km. And Natural Gas has 1,000btu per ft^3. Compressed air has only instrinsic adiabatic btu plus the expansion factor to provide propulsion. Even a small handheld die grinder shop tool will use a couple of CFM (cubic feet per minute) during use.

I would need to see more validated test data to satisfy my internal skeptic on this propulsion technology.

Best regards,
Mark