Dean Kamen's DEKA Revolt: An Electric Car With a Stirling Engine

The Stirling heat engine was invented by a Scotsman in 1816, but that doesn't stop Dean Kamen from using this new-old technology to create a unique hybrid vehicle.

Dean Kamen is probably best known for the creation of the Segway personal transportation device. And when he talks, people tend to listen. In addition to the somewhat whimsical Segway, his New Hampshire-based company DEKA Research has invented numerous breakthrough medical devices, including the AutoSyringe (a wearable device that dispenses medications on schedule), and Hydroflex, an irrigation pump for laproscopy and other procedures. He's won numerous awards for his inventions, including the Global Humanitarian Action Award from the UN, and numerous honorary doctorates.

The Deka Revolt: Best of both worlds?

But the 2008 DEKA Revolt is something else again. The basic car is a 1999 or 2000 Think City, a plastic-bodied two-seat electric car built in Norway. The company was briefly owned by Ford (1999 to 2003), and the Kamen car dates from that era. Under the name Think Global, the now-independent company has been infused with new venture capital and is once again operating internationally from a base in Aurskog, Norway. It is now selling battery cars in Scandinavia and soon to the rest of Europe. A decision on the U.S. will be made next year.

Against this backdrop, Kamen said he contacted Think approximately a year ago with the idea of turning a small battery electric EV into a mild hybrid equipped with a rear-mounted Stirling engine. The Stirling, which works by heating and cooling pressurized gases, can run on a wide variety of fuels, including gasoline, E85 ethanol and other biofuels, propane, natural gas and methane.

The next thing he knew, Kamen says, a large crate arrived on his loading dock. Inside was a disassembled Think, which he retrofitted with a two-kilowatt Stirling engine (soon to be replaced with a much larger 10-kilowatt version), a small fuel tank, a custom-made 18.3-kilowatt-hour lithium-ion battery pack using Kokum America batteries, and a 55-horsepower Azure Dynamics electric motor.

After some head scratching at the New Hampshire Department of Motor Vehicles-was the car a 2000 or a 2008? -- the car was finally registered as a brand-new 2008 DEKA Revolt and began running around Manchester, New Hampshire. And soon it was Dean Kamen's personal transportation.

The Stirling engine does not power the wheels; instead, it provides heat and defrosting and powers accessories to avoid depleting the batteries. And, even better, it can trickle-charge the battery pack so that the driving range can be greatly extended. At speeds below 40 miles per hour, Kamen said, the Stirling should be able to recharge the batteries at the same rate as they're being depleted. Getting stranded with dead batteries won't be a problem, either, because you can run the Stirling for a short while and recharge them.

"Most of the time, for most uses, you would not need to engage the Stirling," said Kamen, from whom ideas emerge thick and fast. "It only comes into play on cold winter days when you want heat and don't want to run down the batteries. It runs accessories and extends range."

The Revolt is a running car, but Kamen says it needs two years of solid engineering to fully integrate the Stirling engine with the battery pack and the onboard charger.

Kamen proclaims it "fantastic" that GM is going out on a limb with its Chevrolet Volt, which also uses a small engine as a range extender. "But if I'd had a clean sheet of paper I wouldn't have used that architecture," he said. "Knowing the capability of the Stirling engine, I just think it's a better fundamental system."

The car of the future, Kamen says, "won't be your father's Buick." The debate on what it actually will be has two camps. "One group says we need pure electrics, that batteries will get better and performance will go up," he said. "And the other likes hybrids, but assumes the core car has to be able to run perfectly well without the electric stuff, which is why they end up with expensive, heavy and redundant systems. I look at all that and see that we're missing a big opportunity. I think what we need ought to combine the best of both worlds."

Hence the DEKA Revolt.