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Testing the Sequel

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Testing GM's `Sequel'

Fuel-cell concept vehicle peppy, smooth, silent

But fuel tanks, batteries make it unusually heavy

Sep. 25, 2006. 01:00 AM



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NEW YORK—If an afternoon behind the wheel of General Motors' latest prototype hydrogen fuel-cell vehicle, the Sequel, is any indication, powertrains of the future will not feel much different from the engines that drive today's cars and trucks.

By a seat-of-the-pants evaluation, the Sequel feels reasonably peppy; acceleration is smooth and nearly silent. And it is capable of reaching 90 miles an hour, said Mohsen Shabana, chief engineer for the Sequel program and my passenger.

More important than its performance or apparent normalness, though, is its role as a development mule for future production models. Next year GM will demonstrate the real-world capabilities of the Sequel's fuel-cell technology when it begins to deploy a fleet of more than 100 fuel-cell-powered vehicles in the United States. Vehicles for this program, called Project Driveway, will be powered by the same fourth-generation fuel cell used in the Sequel I drove, but installed in a Chevrolet Equinox crossover sport wagon.

According to Larry Burns, GM's vice president for research and development and head of strategic planning, a variety of drivers — families, fleets, government and utilities — will operate and regularly refuel the fleet in three regions: California, the New York metropolitan area and Washington.

There's more: GM promised three years ago that by 2010 it would have a hydrogen fuel-cell propulsion system, fully validated for production, that would compete head-to-head with the internal combustion engine in overall performance and durability. By all indications, that fuel cell — a development of the Sequel's powertrain — will be installed in a redesigned Equinox body scheduled to makes its debut in 2009.

The Sequel is the latest milestone in GM's fuel-cell-development program, which has shown steady progress and has the support of the company's top managers, including the chairman, Rick Wagoner, despite GM's financial challenges.

Though large-scale production of fuel-cell cars faces many hurdles — high costs and the ready availability of hydrogen, to name just two — their environmental friendliness makes them attractive. Combining hydrogen and oxygen to generate electricity, fuel cells are typically made up of many small units, clustered in stacks. The car emits only trace amounts of water vapor.

The Sequel, originally shown by GM at the 2005 Detroit auto show, also compares favourably with conventional vehicles in another crucial attribute — it can travel 300 miles between refueling stops, GM says.

A 480-kilometre operating range is the current benchmark for hydrogen-fueled vehicles, because it is the minimum distance customers expect from a tank of gasoline in their current cars, explained Burns.

Range is likely to be of great interest among the test-fleet drivers. Sequel trades its 480-kilometre envelope for a curb weight of 2,100 kilograms — portly indeed for a rather small 5-metre-long sport wagon that seats four. And that's despite its weight-saving aluminum body shell and carbon-fibre front fenders.

The primary culprits in the car's extra mass are three large cylindrical tanks, made of a tough carbon fibre composite and nestled underneath the specially designed centre tunnel of the aluminum chassis (where the driveshaft would reside in a rear-wheel-drive vehicle).

Adding pounds is the rectangular pack of lithium-ion batteries under the rear seat area, a backup steering column (in case the steer-by-wire system fails) and those wheel-hub motors.

"To meet our range target, we needed to carry eight kilograms of hydrogen, which has the energy equivalent of 16 gallons of gasoline in a conventional vehicle," Shabana said. One kilogram of hydrogen is roughly equal to one gallon of gasoline in terms of energy content, GM says. Fuel cells, which work without combustion, derive about twice as much work from each unit of fuel.

Since hydrogen takes up a lot of space as a gas, it must be stored under high pressure in a car. On the 480-kilometre Sequel, that required large tanks that hold hydrogen at 10,000 pounds per square inch. They are arrayed along the centre line of the vehicle as a consideration toward meeting federal crash standards; GM has demonstrated the car's compliance by computer simulation.

Sequel's travel range, which GM promises to prove publicly early next year, is considered somewhat of a breakthrough, said Burns, whose team of engineers and scientists in the United States and Germany is working to put hydrogen fuel-cell vehicles into the transportation mainstream.

But notions that the technology has the potential to reduce transportation's dependency on petroleum fuels are rife with caveats. How will hydrogen fuel be produced? What energy is consumed in the process of producing hydrogen? How will the fuel be distributed?

Burns suggested that one solution might be nuclear reactors, situated on high-security U.S. military bases and dedicated to making the electricity needed to produce hydrogen.

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