Tony Markel drives a plug-in hybrid that runs 50 miles per charge, goes 100 miles per gallon and gets power from the sun. If he has his way, you'll drive one too before long.

His 2006 Prius has a lithium-ion battery six times more powerful than the nickel-metal hydride pack Toyota put in it. But what makes the car really cool is the solar panel on the roof. It generates enough juice to go 5 miles.

Markel is a senior engineer at the National Renewable Energy Laboratory. He and his colleagues have been experimenting with the car for about a year in a quest to make lithium-ion batteries cheaper and more durable. "Those are the barriers – battery cost and battery life," he says. "That's the main thing holding the technology back."

The way he sees it, though, the barriers won't stand much longer.

Automakers are chipping away at those barriers as well, and the lab hopes its research hastens the day when electricity supplants petroleum in our cars. "The landscape is changing quickly," he says, with plug-in hybrids and electric cars from General Motors, Toyota and Nissan looming on the horizon as early as 2010. They're all working with the leading battery makers to perfect the technology, and lab is working with battery maker A123Systems to bring improved thermal management to lithium-ion batteries.

The lab, known formally as the U.S. Department of Energy's National Renewable Energy Laboratory, started working with Detroit on hybrids in 1994. Honda and Toyota beat them to the showroom, but DOE says even those vehicles benefited from its research. The lab started experimenting with lithium-ion batteries four years ago; last year it had Energy CS convert a Prius to a plug-in drivetrain at a cost of $40,000. (Another from HyMotion is on the way.) The car's got a 9 kilowatt hour li-ion battery and a rooftop solar panel that generates 165 watts.

"The vehicle is a research platform," Markel says. Much of the work has focused on improving thermal management of the battery and minimizing the losses in efficiency and energy capacity that occur as li-ion batteries age. The challenge, Markel says, is developing a battery that'll last as long as the car it's energizing. That's a tall order, given the lifespan of a car is about 15 years.

The lab also is exploring vehicle-to-grid charging – the idea that plug-in hybrids charged at night, when electricity demand is low, can return some of that power to the grid during the day. Although utilities like Pacific Gas & Electric are interested in V2G, "that's research that's outside the scope of what the auto industry is doing," Markel says.

Markel says the car will go 50 miles on a charge, which is more than adequate because 78 percent of Americans drive 40 miles or less each day. Befitting the lab's name, the car is charged at a solar charging station. Ask Markel when he last filled the tank and he needs a second to remember. "A couple of weeks ago," he says. "It's a pretty rare event."

Photos: National Renewable Energy Laboratory

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