General Motors Sequel

The General Motors Sequel is the third step in the company's effort to rethink the automobile in preparation for the so-called hydrogen economy. In 2002, GM introduced the low-profile, skateboard-shaped AUTOnomy fuel-cell platform, followed by the Hy-wire, a car that added a futuristic body to form a drivable prototype. In this third concept car, GM has come down to earth by marrying a more conventional cabin to the skateboard, resulting in a five-seat "crossover" vehicle that compares with the Cadillac SRX in size.The Sequel also demonstrates the improvements in efficiency, range and acceleration that GM says will carry the company closer to its goal for 2010: a vehicle that competes with a conventional car in all ways — except affordability.GM says the improvements in the 11-inch-high, self-contained powertrain/chassis include an increase in range and acceleration. The responsible technology includes higher-capacity hydrogen tanks that hold 800 kilograms of the gas. Hidden from view in the center of the skateboard, the carbon-fiber tanks withstand 10,000 psi, twice the earlier capacity. This and a 25 percent more efficient fuel cell contribute to a range of about 300 miles, roughly 35 percent greater than that of the average fuel-cell prototype on the road.Like most fuel-cell prototypes, the Sequel includes a battery to capture electricity that's generated as the vehicle brakes, a system called regenerative braking that's used in gasoline/electric hybrids. The 65-kilowatt battery uses lithium-ion technology, which is lighter than the more common nickel-metal hydride for a total of just 143 pounds. Powered by the 73-kW fuel cell, a 60-kW motor drives the front wheels and two 25-kW "hub motors" drive each of the rear wheels. The effect is all-wheel drive and maximum power regeneration.The advantages of GM's approach ostensibly include modularity and improved ergonomics. Modularity means the skateboard is a complete unit, so different body types could be attached to the same platform — possibly even after purchase when the owner tires of the body style.The ergonomics opportunity comes from the fact that there's no conventional drivetrain around which the car must be built, and no steering column because the steering mechanism is electric and controlled by wire. GM took this idea too far in the Hy-wire and incorporated the accelerator and brake controls into the steering wheel — the solution to a problem that didn't exist.In the Sequel, the steering wheel and pedals are back, and the cabin is more what you'd expect from a conventional car. The differences include a lower dashboard and more foot- and legroom. Rather than a central control panel, GM locates the typical dashboard controls on the driver's armrest.Some of the tougher challenges remain cost, reliability and extreme-weather operation. GM says the Sequel's fuel cell generates maximum power in a 100-degree environment. Reliability is one of the major areas of study. The issue of cost is no small one in the area of fuel-cell vehicles, which is why GM now limits its goal to viability by 2010. Fuel cells are still astronomical in cost, in the six-figure range, and the mass production and distribution of hydrogen gas is just one of the many aspects of the hydrogen economy that remain a question mark.