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REVOLT: The Segway-maker’s next move

Never mind the new deal with GM. Dean Kamen reaches back to an 1800s combustion engine to fire up automotive’s electric future.

By Staff Writer for The Christian Science Monitor / April 29, 2009

Entrepreneur Dean Kamen saw limited success with his stand-up two-wheeler. But his prototype hybrid-electric car, REVOLT, could help third-world villages generate power.

Ann Hermes/The Christian Science Monitor


Manchester, N.H.

General Motors perpetually promises to deliver its Volt electric car. Tesla Motors has the wealthy and trendy anticipating its luxury electric sports car. The Chinese say they will mass produce electric cars to help clean up their choking cities.

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But none of them is committed to do what Dean Kamen hopes his prototype REVOLT hybrid-electric car will do: Bring electricity to the 1.6 billion people who still live without it.

Mr. Kamen, an inventor and entrepreneur perhaps best known for the two-wheel Segway Human Transporter, doesn’t want to get into the car business himself. He just wants to see the Stirling engine that helps power the REVOLT be mass produced for vehicles. That would drive down the price, he says, and allow it to be cost-effective in another role: as a miniature electric plant for villages in the developing world.

A Stirling can run on just about anything that creates heat, from gasoline, kerosene, and ethanol, to natural gas, propane, hydrogen, and, yes, the methane given off by animal manure.

In a recent test, two villages in Bangladesh ran Stirling engines to create electricity for 24 weeks – using only cow dung for fuel. “We’re pretty excited about that,” Kamen says.

“The little engine that could,” as Kamen calls the Stirling, was invented in 1816 by Scottish clergyman Robert Stirling. He found that alternately heating and cooling gases in a closed system could create power to do work, such as drive a piston. But steam engines soon became far superior in producing power for large applications, such as railway locomotives. Later, the diesel and gasoline internal combustion engines proved superior for mid-sized jobs, such as cars and trucks. And in the 20th century, the jet engine combined tremendous thrust and relatively light weight to rule the skies.

So the Stirling was mostly forgotten, even though its simple concept is “elegant, it’s brilliant,” Kamen says. But its time to shine might be now. All-electric cars still suffer from wimpy batteries that limit driving range and refuel slowly. “The energy you can carry around in a liter of gasoline is 100 times higher than you can carry in the same size and weight of a battery,” Kamen says. “And that’s going to be true for a long time.”

Today’s hybrid cars add a gasoline engine to both power the vehicle and recharge the battery. But the sooner cars can be weaned from fossil fuels, the better for US security and the environment.

Why not use a Stirling to charge the hybrid car’s batteries, Kamen asks. The Stirling’s waste heat could warm the car’s interior on cold days, saving even more battery power.

Outside the offices of DEKA Research & Development Corp., Kamen’s company located in a former mill along the banks of the Merrimack River in Manchester, N.H., Kamen shows off his prototype. The exterior and chassis are from a Think electric car, developed and abandoned by Ford years ago. It was shipped in a crate from a Norwegian company trying to revive the brand. Its pebbled plastic body is a little larger than the Smart ultracompact now on US roads.

Lithium-ion batteries, the current state of the art, sit under the REVOLT’s hood. Below a cover in the back is the cylindrical Stirling engine, a bit smaller than a golf bag. It’s not hooked up at the moment, Kamen says, because it’s about to be swapped out for an improved version. But the car does work. “I’ve had it up to 70” m.p.h., he says with a smile.

Does he have any automakers interested in buying his Stirling engine?

“A number of very large companies, very well recognized,” have engaged in “very serious conversations” about using his Stirling in their vehicles, he says.

In an interview in his office, the serial inventor explains why he’s involved in projects like the REVOLT and a science education project called FIRST, in which he reportedly has sunk millions of dollars of his own money. (He also has developed a robotic arm for amputees, a water purifier for the developing world, and a stair-climbing wheelchair called the iBOT.)