Compressed Air Car

[materia3]

Has anyone in the UK seen or examined this automobile? It allegedly can run for 124 miles on one tank of 90 cubic meters of air but needs an oil change every 31K miles. If this is for real, I want one. No, I want a franchise.


http://www.theaircar.com/aboutmdi.html

http://www.theaircar.com/UKPressrelease.html

On the 20th September a car with an air-compressed engine, invented by the Frenchman Guy Nègre, will be presented in London. The presentation will take place at 10 am in the Millennium Hotel (17 Sloane Street, Knightsbridge, London SW1). The aim of the event is to present MDI´s technology to the public before its imminent arrival on the market and to offer to businessmen and institutions the chance to take part in establishing the factories in the UK.

 

[toddjh]

This was discussed a few months ago. The consensus seems to be that it's mostly woo.

Jeremy

 

[materia3]

Thanks for tipping me to the previous thread. Apparently now, however, the car was unveiled in London as per the press release cited above. Many interesting points were brought up on the previous thread and I appreciate hearing about these as I am no expert on engines. The company has pubished a brief description with diagrams of the engine at:

http://www.theaircar.com/howitworks.html

so if anyone has any further comments it would be appreciated.
.

 

[Bikewer]

Years ago (10 or more, anyway) the local paper ran an article on a Missouri inventor who had built a prototype of such a vehicle. The thing (they had pictures of him tooling around in it) looked like a sort of dune-buggy frame with three commercial-sized compressed air tanks hooked up to the motor he'd invented.

Never heard any more about it, and always wondered about the possiblilities. Supposedly, when you figured in the costs to compress the air, the thing ran very cheaply compared to an internal combustion engine.

 

[Zombified]

It doesn't seem like this would be able to store enough energy. The web site says 60 cubic meters of air compressed to 300 bar (pretty close to 300 atmospheres).

If you picture a 60m long cylinder of air with a cross section of one meter, and you calculate how much energy you need to compress it to 300 atm, you're going to compress it to 1/300 of its original volume, or 20cm (still one meter-square cross-section).

Work to compress a little ways is

dQ = F*dx = P*A*dq

P = P₀V₀/V

V = Ax

so

dQ = P₀V₀/x dx

The total work is

Q = P₀V₀ ln (60/.2)

P₀ is 1 atm or about 10⁵ N/m², V₀ is 1m³ so

Q = 60 * 10⁵ ln 300 J = 3.4 x 10⁷ J

However, one gallon of gasoline contains about 1.3 x 10⁸ joules (according to random site from Google). So this is about a quarter of a gallon of gas.

'course, they do claim to get 13% back from regenerative braking.

So how far do you think you can get on a quarter gallon of gas? I suppose if you have a very light, perhaps single occupant car, you might get a decent distance out of this. To go 142 miles, you'd effectively be getting about 500 miles/gallon, including the regenerative braking.

Edit to add: even if you could get that mileage going straight out, with 13% regeneration you're not going to get very far in the city...

 

[DangerousBeliefs]

They have to demonstrate a working prototype before I'll get excited... so far all we've seen are pretty pictures and claims of greatness