Hybrids are now an accepted part of our vehicle landscape, with electric cars powered by lithium-ion batteries on the horizon. But General Motors and other manufacturers are also looking much further ahead, toward a future where our personal transport--what we might call ”a car”--is powered exclusively by hydrogen fuel cells.

GM has spent a decade working on fuel-cell cars, with several concept vehicles along the way: the HydroGen1 of 2000, and the AUTOnomy and HyWire concepts revealed in 2002. The most recent push came five years ago from CEO Rick Wagoner’s challenge to Larry Burns, GM’s global head of research and development: Completely reinvent the automobile for the 21st century, unburdened by any legacy technologies.

In Burn’s words, GM wants to ”take the automobile out of the environmental debate.” With emissions of nothing more than water vapor, hydrogen fuel cells eliminate carbon fuels altogether. That is, they eliminate them from the vehicle. Instead, the debate over the types of energy used to generate hydrogen shifts from GM and other carmakers to the natural resources and power industries.

GM’s latest fuel-cell car, the Sequel concept, was unveiled at Detroit’s January 2005 North American International Auto Show. Less than two years later, it’s a drivable prototype (two of them, actually), now called the Chevrolet Sequel. Last week, GM let selected journalists—among them this Spectrum reporter—drive it within the guarded confines of the U.S. Marine Corps' Camp Pendleton in California.

Tanks: A Lot

Outside, the Sequel is a sleek, stylish SUV. You wouldn’t give it a second glance at the mall parking lot. But underneath, it has little in common with today’s cars beyond wheels and tires. Its ”skateboard” aluminum chassis is built around three long, heavily reinforced canisters that hold 8 kg of hydrogen. That mass of hydrogen contains the same energy as 8 gallons of gasoline, though GM’s latest fuel cell uses energy twice as efficiently as a gas engine.

PHOTO: JOHN VOELCKER

The Sequel's power electronics are mounted in a package with the front electric motor; "productionizing" fuel-cell vehicles will require major reductions in the size and weight of these components

The 73-kW fuel cell in the Sequel is a sealed box in which hydrogen passes through a membrane to react with oxygen, producing water and giving off energy. It’s that energy that powers the three electric motors that move the vehicle: One 65-kW motor in the front, plus individual 3-phase permanent-magnet 25-kW wheel motors at the rear. Total traction power is thus 115 kW. Those rear motors also act as generators, so when a driver hits the brakes, energy that would have been lost is used to recharge a 65-kW lithium-ion battery pack stored within the ”skateboard” between the rear wheels.

The steering wheel, accelerator, and brake pedal aren’t mechanically connected to the wheels or powertrain. Instead, a set of computer processors evaluates what you asked for--and then tells the car how to do it most efficiently. This ”by wire” control technology not only reduces weight by eliminating mechanical components, it also maximizes safety by letting the car weigh what it’s being asked to do against external factors (such as traffic, weather, vehicle proximity, etc.).

Behind the Wheel

Having drive-by-wire controls means driving the Sequel runs the risk of feeling like a video game--compelling but not quite ”real.” But in fact, GM’s engineers (spread across Warren, Mich.; Honeyoye Falls, N.Y.; Torrance, Calif.; and Mainz Kastel, Germany) did so much simulation work to make it feel real that … it actually does.

Behind the wheel, it drives and steers like a heavy SUV: Press the accelerator, and it accelerates. Turn the wheel, and it changes direction. The only difference is that the slight whine of the electric motors increases continuously--there’s no change in engine note as the transmission shifts, because there’s no transmission. And the brake-pedal feel is so natural that I completely forgot I wasn’t getting feedback through a hydraulic system but an electric simulation using pistons and quite a lot of software.

PHOTO: JOHN VOELCKER

Integrated rear-wheel motors allow regenerative braking on the Sequel, and the suspension arm includes a steering knuckle for up to 5 degrees of rear-wheel steering

The Sequel weighs 2170 kg (4774 lb), at the high end of the range for a 4-to-5-seat SUV. It will do the 0-to-60-mph sprint in less than 10 seconds, with a top speed of 145 km/h (90 mph). Most important is its range of 300 miles (480 km)--like a normal car--meaning that the Sequel travels roughly twice as far on the same energy content as a conventionally powered SUV.

We won’t see Sequels at our dealerships any time soon, though. Each of these concept cars probably costs one million dollars or more, although ”productionizing”--figuring out how to lower weight, reduce complexity, cut costs, and improve reliability--is a standard part of technology innovation. As the shape of the world’s hydrogen infrastructure becomes clearer over the next decade, the component costs will fall and carmakers will know more about how fuel cells perform in the real world.