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Written on: 18 October 2008 [19:56]
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ecoadmin
Administrator
registered since: 20.07.2007
Posts: 504
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The air car...the saga continues:
I have found some interesting and reliable information which supports the claim that the air cars are not a viable alternative.
While it has been proven that compressed air can power a car, it is not certain what range can be achieved with a filled up tank of compressed air.
MDI, a company led by Guy Nègre, claims to have made the breakthrough.
The air is filled into 4 pressure cylinders at a pressure of 300bar each. The 95.000 liters of compressed air weigh 117 kg. The 18kw engine of the car achieves a range of 200km using compressed air, according to MDI.
Professor Horst Brunner from the Technical University in Dresden, Germany doubts these claims. He and his co-workers closely examined the official technical details of the aircar produced by MDI and their computations showed a much lower range.
Dietrich Hennecke from the University of Ilmenau confirms the low range. Using traditional calculation methods and diagrams, he got 60 km range. "In the compressed air is simply not enough energy", he explains. Using conventional car technology, this is what you get....
Air Pressure Specialist Erwin Ruppelt of the compressor manufacturer Kaeser in Coburg, Germany says: "To fill the four cylinders with compressed air at 300bar, an electrically powered air compressor uses approx. 65 kWh of energy".
One tank filling therefore costs about 5 Euros. Of the 65kWh, only a fraction will actually make it into the pressure tank. The compressor used to fill the tank is only running with a 20% efficiency. Of the 65kWh, only 13kWh will be stored in the tank.
The engine used in the MDI car is probably also not 100% efficient, unless the MDI engine uses a principle no-one else has discovered yet so far.
The remaining energy is simply not enough to propel the car 200km.
Lets assume the air engine has an efficiency of about 50%. This would mean that only 6.5 kWh would be available to move the car. This amount of energy is good for approx. 80km in a small city vehicle.
The eco-balance is not convincing:
65 kWh/80 km * 520 g CO2/kWh = 422 g CO2/km.
Note: A coal power station emits approx. 900g of CO2/kWh.
The above figure (520g) is an energy mix using also other resources.
Other developments using pressurized air in connection with a piston engine seem to be more promising.
ecocarforum.com - Green Car Network
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