PHOTO: Jeffrey Sauger/General Motors

GM Vice-Chairman Bob Lutz shows off the Chevrolet Volt concept car, a so-called series hybrid, in which the batteries do all the work and the gasoline engine merely recharges them.

Detroit in January is cloudy and cold. But the city’s annual North American International Auto Show is still the only place to be for car buffs, people who know it as an excellent showcase for new auto technology.

This year some 7000 journalists came to the show, and there was a lot for us to cover. For instance, Audi, BMW, and Volkswagen said they will sell vehicles using Mercedes-Benz’s Bluetec system for reducing emissions from diesel engines. And by 2008, the carmakers expect to offer “50-state” diesels that meet even the limits that California has set (and that several Northeastern states have adopted).

But what stole the show was General Motors’ announcement that it will build cars that can accept a new kind of hybrid electric drive, starting in 2010. The news gave a much-needed shot in the arm to a company that for the first time in 70 years is expected to sell fewer cars than one of its rivals—Toyota.

Embodying the plan is the Chevrolet Volt, the first “serial hybrid” concept car shown by a major manufacturer. In a serial design, the engine has no connection to the wheels at all. Instead, it turns a generator that charges batteries, the batteries power a motor, and the motor drives the car. The Volt is designed to go about 64 kilometers (40 miles) on a single charge, enough to cover many drivers’ daily requirements without ever engaging the tiny, 1.0-liter engine, whose only purpose is to serve as what GM calls a “range extender.” Most of the time, the car would recharge on wall current back in the garage—hence the term “plug-in hybrid.”

Its 64-km range sets the Volt apart from today’s hybrids. They run mainly on gasoline, or on gasoline with an assist from electricity, and are capable of only a few minutes of pure electric operation. That’s because they rely on nickel-metal hydride batteries designed for high peak power rather than for maximum energy storage. The Volt, on the other hand, is designed for lithium-ion batteries, the kind in laptops.

To make the concept into a production car, GM will need something that it admits isn’t yet commercially available: automotive-strength lithium-ion batteries. Dozens of companies are working hard to design and test them, but cars turn out to be demanding customers, compared to consumer electronics. Laptops and mobile phones don’t have to survive 64-km side impacts, or work in temperatures from –30 °C to 249 °C (–22 °F to 480 °F) or during heavy dust storms. Worse yet, lithium-ion batteries for autos must last 10 years, through 4000 deep-discharge cycles—and when’s the last time your laptop battery (or your laptop, for that matter) lasted 10 years?

GM did say that it has signed R&D contracts with two battery groups, and that it planned to design small cars starting around 2010 to accept elements of the drivetrain architecture outlined in the Volt. To find out how serious the company is, just wait a year and see whether it is testing a running version of the Volt (right now, the concept can do little more than sit on its pedestal).

One thing is clear: GM is not thinking of this technology as a niche product. Unlike the EV1 two-seater, its all-electric production car of 10 years ago, the Volt is a four-seat, four-door sedan—the “sweet spot” of the small-car market—and its electric motor produces 120 kilowatts of peak power and 320 newton-meters of peak torque, powered by a 16-kilowatt-hour lithium-ion battery pack.

It was ironic that GM staked so big a claim in the “green” car game at the same show where Toyota—known for its hybrids—launched the dual-cab CrewMax version of its new Tundra full-size pickup truck, perhaps the heaviest, thirstiest vehicle it has ever sold.

Ford, too, unveiled a serial hybrid concept at Detroit, but instead of using an engine and a generator as a range extender, it chose a Ballard hydrogen fuel cell. The concept is called the Airstream, after the iconic streamlined silver travel trailers, which it resembles. Featuring asymmetric windows and an entire body side that lifts up—from white plastic seats to a so-called modern lava lamp the size of a fire hydrant, which showed soothing flame images on a circular LCD—this hyper-mod minivan has a radical style and interior décor that largely overshadows its power train. Ford did not announce plans to produce any of the Airstream’s technologies, however.