While the Japanese are trying to produce electricity from train station gates (!?), entrepreneur Terry Kenney is going after a bigger target: Trucks.
It took him eight years to get a working prototype, but now there's one working at the Port of Oakland which Kenney calls the "Dragon Power Station". Special plates are set on the road, and as big trucks drive over them (about 2,500 of them per day at the port), they compress a tank of hydraulic fluid under the road, which in turn creates a series of pumping actions that turns a generator to produce electricity.
By June, the Dragon should generate about 5,000 to 7,000 kilowatt-hours of electricity each day, or enough to power up to 1,750 homes. Not bad for a prototype.
The plates Kenney developed for trucks are wide and sturdy. They were designed to weather the crushing force of trucks weighing up to 180,000 lbs. He developed a smaller version of the road plate for sedans and other passenger cars, which he hopes to one day see installed at high-traffic theme parks and toll bridges.
Of course there's no such thing as a free lunch. That energy actually comes from the fossil fuels burned by the trucks. The benefits of that system is that they are harnessing energy that would otherwise be lost, and doing so in a way that isn't noticeable in practice to the thousands of trucks.
Update: For more on this, see ::Further Thoughts on Turning Road Traffic into Electricity.