Experimental car is powered by air
French developer works on making it practical for real-world driving
March 18, 2004
BY WILLIAM DIEM
CARROS, France -- In an industrial park a few miles from Nice on the French Riviera, Guy Negre has developed an environmentalist's dream car.
Compressed air is the fuel, cold air is the only exhaust. A prototype van called CityCAT -- the sixth made by his company, Motor Developpement International s.a. -- tools around the parked cars of his staff of about 30 just as any small van might, except that the power is coming from three long black tanks in the back, full of air compressed to 5,000 pounds per square inch.
No powertrain could be more environmentally attractive. It requires some up-front electric energy to compress the air, and that's all. Like an electric car recharging its batteries, you could plug it somewhere when the air pressure has fallen too low and have the on-board compressor refill the tanks.
The car and Negre's invention have been on television on every continent. More than a dozen investors from Mexico, France and elsewhere have invested $13 million for 35 franchises on a future mini-factory and sales territory.
The only problem is, it won't work in real life.
"The clean engine is insufficient to be sold," he says, after seven years of development. The air-powered car has too little power and too little range. Negre's son Cyril, an engineer at MDI, said that the CityCAT prototype goes about 37 miles on the test track before it runs out of air.
However, Negre is not waving a white flag. He is simply returning to an engine he started designing in 1992 after a career designing Formula 1 engines.
The air car engine, he said, will now get a clean-burning external combustion chamber so that the CityCAT can operate as a hybrid with two energy sources: running on compressed air from the tanks or burning fuel to expand ambient air, which powers the pistons. "All motors are essentially compressed air motors," he said in an interview at his company headquarters. Internal combustion in a standard diesel or gasoline engine simply heats and expands air.
He would not describe in detail the changes he expects to make for his new engine, except to say that the external combustion would produce tiny amounts of exhaust pollution. As for fuel economy, he said, "On an early engine, we achieved 2.5l/100km (94 m.p.g.), and this one will do better than that."
Negre doesn't dream small. Starting with his compressed air engine in 1997, he developed the idea of a Green Taxi for city centers. That has evolved into two cars, the three-seat MiniCAT and a five-seat CityCAT. He has an idea for a compressed air bus. To build the MiniCAT and the CityCAT, he has designed a small factory with a capacity of two cars an hour -- about 7,000 cars a year -- where workers would manufacture engines and body panels and assemble the finished product. In six to 10 years he hopes to have 400 factories around the world, 20 of them in France.
"In the concept, MDI will deliver the raw materials to the factories, to assure the same quality everywhere," said Negre.
His dream doesn't really match the reality of industrialization, validation and government approvals. Negre's new engine with the external combustion chamber is still in the design stage. It isn't expected to reach the prototype stage until the end of this month, yet Negre is confident he can validate it and sell his first MiniCATs by the end of the year.
That is unlikely. Automakers with huge resources take years to validate an engine and test its durability. Negre has a small staff and is operating on a shoestring, without enough money to return to the Paris auto show this fall.
His dream has some credibility, because his air car works. Compressed air gives an adequate performance in city driving for a limited time. But MDI is a long way from taking on the big automakers.
March 18, 2004
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