Fire / Feu


Véhicules efficaces: meilleurs, plus propres et sécuritaires

Les nouvelles technologies produisent des automobiles qui sont plus économiques en essence, plus légères et plus écologiques. Parmi les autres

avantages, ces autos à "systèmes électricité/ hydrogène" sont alimentées par des cellules électrochimiques.

On discute des avantages de cette nouvelle technologie tout en jetant un coup d’oeil à la recherche effectuée au Hypercar Center du Rocky Mountain Institute.





Efficient Vehicles:
Cleaner, Safer, Better

Dave Reed
Rocky Mountain Institute
July 1999


ood news: in the next decade or so, automobiles are probably going to get a lot more efficient, significantly reducing pollution, greenhouse-gas emissions and other related environmental problems.


Toyota Prius


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(photo: Unofficial Toyota Website)

Environmentalists might have a hard time getting their heads around this development, though, because it’s not being driven by tightened regulations, fuel taxes, an energy crisis or any other drastic measures that are usually assumed to be necessary to force car companies to get serious about efficiency.

No, it all comes down to new technology. Technology that will make vehicles not only more fuel-efficient and cleaner, but just plain better. In fact, it’s the better part, far more than the environmental benefits, that will appeal to most consumers. And consumer appeal is what is going to get these new cars onto the road and old, polluting cars off in sufficient numbers to make a difference to the environment.

Yes, these new vehicles are only a techno-fix, and like all techno-fixes, they won’t really address the deeper problems associated with driving. But they’re a step in the right direction, and will probably serve as a stepping-stone to still better solutions.


New Technologies

Today’s automobile is a sophisticated, mature technology. Despite many incremental improvements during a century of evolution, however, its design remains fundamentally unchanged. But dramatic advances in many related fields have set the stage for a new kind of car, a fundamentally digital creation that improves on its analog predecessors the way CDs trumped vinyl, and computers displaced typewriters.

The first signs of this revolution are already apparent. Most major automakers are now readying vehicles with hybrid-electric drive, and several are developing models powered by fuel cells. These technologies, along with microelectronics, software controls, and ultra-lightweight materials, are the enablers of what may prove to be the biggest thing to hit the auto industry since the assembly line.

Hybrid-electric vehicles combine the best aspects of both conventional and electric cars. Like a conventional car, a hybrid-electric car has a power plant (engine); like an electric car, its wheels are driven by electric motors. It’s a hybrid of the two because its engine generates electricity to drive the wheels.

Energy from the power plant is therefore sent to the wheels electrically, via wires, instead of mechanically, via a driveshaft and other moving parts. (Some hybrids incorporate both types of drive systems, using them separately or together at different times.)

That overcomes many of the inefficiencies inherent in conventional cars, and it eliminates the heavy batteries and limited range of battery-electric cars. In addition, the electric motors can also act as brakes, recovering much of the energy that’s otherwise lost in braking. Electric drive also opens the door to even more efficient power sources, such as fuel cells. Developed in the 1960s for the space program, fuel cells flamelessly combine stored hydrogen with oxygen from the air to produce electricity. Unlike the combustion engine in a conventional car, a fuel cell is more like a battery that, rather than needing recharging, is supplied with fresh reactants when you step on the gas pedal.

Fuel cells convert fuel into electricity two or three times more efficiently than combustion engines, and produce no emissions (except water). And because they permit the storage of energy in the form of hydrogen, fuel cells are an integral part of the long-term transition that society must inevitably make from fossil fuels to renewable energy sources. Toyota has led the rush to hybrids with its Prius sedan, which it launched in Japan in 1997. The Prius won’t be available in the United States until next year, but Honda plans to start selling its Insight hybrid in the States in December of this year. Nissan, Volvo, Audi, Volkswagen, and the U.S. Big Three all say they’re developing commercial hybrids. Meanwhile, Daimler Chrysler has invested $350 million in an effort to mass-market fuel-cell cars by 2005, with Ford and others in hot pursuit.

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(photo: Rocky Mountain Institute)



This new generation of vehicles will be much more fuel-efficient than today’s cars. Toyota’s Prius, for example, gets 66 miles per gallon, without any compromise in performance, comfort, or size. Moreover, electric drive typically provides sportier acceleration, and, combined with integrated electronic components and software, it makes possible many new or improved electronic controls and features.

Like computers on wheels, hybrid-electric vehicles, hardware and software can be made to be upgradable. Has the manufacturer come out with a more sophisticated computer-controlled suspension? Have a technician load in the new card, or upgrade the software. Replacing complex mechanical systems with solid-state electronics and software can eliminate many causes of breakdowns, and enable remote diagnostics and repairs of many problems that would send a conventional car to the shop. The dashboard could be replaced by a user-friendly interface; why have gauges when you can have a flat-screen display that’s almost infinitely customizable? In time, fuel-cell-powered vehicles could actually operate as a small mobile power plants, generating electricity cheaply enough to sell it back to the grid at a net profit.


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Automakers have been slower to embrace another emerging technology: ultra-lightweight materials. According the Hypercar Center at Rocky Mountain Institute, a resource-efficiency think tank, making auto bodies out of advanced composite materials instead of heavy steel can radically improve the efficiency, capabilities, and economics of hybrid-electric vehicles.

Hybrid-electric drive and ultralight, low-drag design are both worth doing in their own right, Hypercar Center researchers claim, but combining the two yields synergies compounding weight savings and recovered braking energy that are just too good to pass up. Thanks to mechanical simplification, indirect weight savings snowball faster in ultralights than in heavy cars, faster in hybrids than in nonhybrids, and fastest of all in optimized combinations of the two. The Center calls its optimized concept a Hypercar.

And contrary to popular perception, cars made of lightweight materials won’t be more dangerous. In fact, the Hypercar Center has done extensive research showing that they’d probably be safer. Polymer composites, materials now used everywhere from rockets to golf shafts absorb five times more energy per pound than steel. We’ve all seen Indy cars crash and burn at fantastic speeds, only to watch the driver limp away, those are composite cars. Special designs can make the most of composites strength and stiffness, while the significantly smaller propulsion system of efficient new cars would leave room for extra crush zones. This should enable cars made of composites to match or exceed the safety of a heavier car, even if the two collide head-on and note that a lightweight car fares substantially better than a heavy one in a collision with a stationary object.

These consumer advantages are only part of the story of the transition to more efficient cars. The planet and its inhabitants will also benefit from cleaner air, fewer greenhouse-gas emissions, and a reduced dependence on oil imported from politically unstable parts of the globe. And if auto makers stand to make a buck from the transition, so much the better it’ll happen that much sooner.


More on this subject:
Rethinking Automobility...