I know a lot of you would rather drive a Yugo than ride a scooter, but what if you could fuel one with woodchips and dried banana peels? Got your attention, didn’t I?
Surprisingly, and unusually for me, I didn’t make that up. Almost 200 years ago, a Scottish minister named Robert Stirling invented a steam engine that used external (fuel burning outside the engine) combustion to drive a piston, converting heat into mechanical work in a very efficient manner. Anything combustible works as fuel, and Stirling engines are used in various industrial, military and educational applications. You’ve never heard of a Stirling engine because although efficient, they aren’t very powerful, light, or cheap. Developing a practical, cheap and powerful Stirling has been the Holy Grail for generations of engineers, a saga that sounds like the quest for perpetual motion (queue Homer Simpson shouting, “In this house, we obey the laws of thermodynamics!” as he points at Lisa’s mysteriously accelerating science project).
Don’t tell that to Dean Kamen, the brilliant inventor of the Segway two-wheeled mobility device and God of Those Who Hate Walking. He’s a fan of the Stirling engine (he has a huge one in his house), and in the last days of 2008, he patented plans for a Stirling engine/electric motor hybrid scooter (or “personal transportation device”). With a Stirling – a small, efficient one like Kamen and his team have been working on for some time – running at a constant rpm to recharge a battery, a low-speed vehicle like a scooter starts to make sense.
Kamen’s patent describes some interesting features. The engine and generator would be in a hermetically sealed container, exhaust heat would be re-circulated to generate more power, and a controller unit would manage the whole affair, controlling fuel burn and other factors to maximize efficency. Fuel could be any kind of clean-burning fluid or gas, like propane, butane, ethanol, methanol, LPG or even plain natural gas. It will run on dirtier fuels like gasoline or diesel, as well.
I am sure there are lots of engineering types out there who can pick apart Kamen’s concept, but given the success of the Segway, which went from science fiction to toy of the wealthy to cheesy annoyance in less than a decade, the appearance of Segway-branded hybrid scooters wouldn’t surprise me in the least. Okay, maybe they won’t burn banana peels, but combining the efficiency of electric drive ultimately powered by energy-dense fuels makes a lot of sense.
