What is unusual about this car is how the hydrogen is stored. ECD Ovonics, the company that invented nickel-metal-hydride batteries, focused its expertise on carrying hydrogen in solid form in tanks filled with powdered metal. Two tanks fitted under the Prius' floor are filled with hydrogen by connecting a hose to a standard fitting. The tank capacity is 3.6kg, enough for nearly 322km.
Robert Stempel, the former GM chairman who now heads ECD Ovonics, points out that this storage system's lower hydrogen pressure is much less expensive than the 5,000psi or 10,000psi pressure necessary with compressed-gas storage. One negative the company is striving to improve is the 249kg weight of the Prius' fuel system.
Except for a few turbo whistles and whirs, the car sounds and performs exactly the same as a standard Toyota Prius. Tests showed reductions in all tailpipe emissions except oxides of nitrogen.
In addition to the vehicles brought to the base, here are three other hydrogen vehicles I have driven:
BMW HYDROGEN 7
BMW, which began studying the use of hydrogen in piston engines 25 years ago, is building a fleet of 100 demonstration vehicles on a regular assembly line. The Hydrogen 7 combines BMW's flagship sedan, a modified 6-liter V-12 and a superinsulated storage tank to provide dual-fuel mobility.
The liquid hydrogen offers a 200km driving range; when that is consumed, a button on the steering wheel switches the engine over to run on gasoline for 500km from the standard 74-liter gas tank. The engine is tuned to deliver nearly the same power on either fuel.
The detuned engine and 227kg added to carry hydrogen safely result in slightly impaired performance, but the Hydrogen 7's 230kph top speed and 644km range easily surpass existing fuel-cell vehicles. And while running on hydrogen, the only traces of carbon compounds in the exhaust come from engine oil consumed during combustion.
While driving a Hydrogen 7, I listened intently for changes in engine operation when the fuel supply was switched. In the hydrogen mode, there is a sharper and more metallic noise during acceleration, but most drivers would never notice that subtle difference. The beauty of the Hydrogen 7 is that it exploits hydrogen's benefits without making existing powertrains obsolete.
MERCEDES-BENZ F-CELL
Since it began hydrogen experiments in 1994, DaimlerChrysler has invested more than US$1 billion and built more than 100 fuel-cell vehicles. A fleet of 30 buses has been carrying passengers daily in 10 European cities. Sixty Mercedes-Benz A-Class sedans converted from conventional gasoline powertrains to a more futuristic F-Cell configuration have logged 3.2 million kilometers. DaimlerChrysler and Ford have made large investments in Ballard Power Systems, a leading fuel-cell developer.
In the tall four-seat A-class, passengers sit above the drivetrain, tucked beneath the floor. This arrangement is also a handy way to package the bulky storage tanks and control electronics necessary to make a fuel cell operate.
The 20-second start-up ritual is accompanied by a chorus of clicks, whirs and buzzes. Steering, shifter, accelerator and brake controls are identical to the A-Class; an electronic display on the center console tracks electricity flow.
Even though it rides tall, the F-Cell corners securely thanks to a low center of gravity. With only 87 horsepower to move 1.5 tonnes, acceleration is sluggish. According to the factory, the run to 96.5kph takes 15 seconds and a governor limits top speed to 140kph. Michelin radial tires inflated to 38psi delivered a rocky ride over the poorly maintained roads I drove.
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