If you inflate a balloon and place it on a little toy car frame and then release it, it will race across the room until the balloon deflates. That is essentially the idea of engineer Guy Negre of MDI in . Popular Science magazine reports he is working with an Indian company to put about 6000 Air Cars on Indian streets by August 2008.

In case you've missed the previous stories (see below), Mr. Negre is using a piston-type engine to extract the stored energy in the compressed air to drive the wheels. This makes elegant sense. Why do we combust air with fuel in an engine? To get high pressure, of course! Compressed air at 4350 psi is powerful! And it takes energy to raise air to that pressure level with is actually 290 bar (290 times higher) than atmospheric pressure. Stored gas pressure is like stored energy in a battery. You put it in at one time, and you take it out later. Gasoline and diesel engines put energy in (the fuel) and take it out at the same time.

Compressing air to 290 bar is a relatively straightforward task. Take a reciprocal compressor, power it up, fill the Air Car's tanks in a few minutes, and then drive away. That takes energy, probably electric energy, to get that done. Petroleum use can be avoided but electric use is still needed. The car will even come with it's own on-board compressor. Refilling that way should take about 4 hours.

The range of the vehicle is said to be 125 miles and it has a top speed of 68 mph. I haven't gone through the thermodynamics of the full process but I gotta admit this is a pretty nifty way of circumventing petroleum use. If the compressor is green-powered (solar, water, wind, etc.), the Air Car will be too. And vice versa.


[Source: Popular Science, MDI]

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