A good idea can come from the most unexpected places. In Lei Zuo’s case, inspiration struck while looking out the window of a train.
Zuo was passing through a remote rural area when his eyes trained on an upcoming road crossing. It had neither gates nor powered signs.
While considering the danger to motorists who might not be cognizant of an oncoming train, he became aware of the vibrations passing through the railcar that were surely transferring to the rail on which it rode. “I thought, ‘Hmmm, we could make energy out here just from train-induced track vibrations. This could power lights and gates,’” the Stony Brook University mechanical engineering professor says.
He developed a mechanical motion rectifier, a device that attaches to a rail and harvests the energy transferred to it from an oncoming train. The train’s up-and-down movement sends irregular vibrations to the metal rail, which Zuo’s device converts into stable, unidirectional motion. This harvested, rectified motion runs a DC motor that generates enough electricity to power railroad signage and gates.
(A prototype mechanical motion rectifier for railroad tracks designed by Lei Zuo and colleagues at Stony Brook University. Courtesy Lei Zuo.)
“Other people’s work on this has used materials that are very expensive and inefficient at converting energy,” he says. “You could harvest small-scale energy to power sensors, but not enough to power lights. You need more energy than that.”
His team’s device, he says, is much better at harvesting energy, achieving conversion efficiency higher than 70 percent. And since its gears operate in only one direction, the machine doesn’t suffer extreme wear resulting from quick reversals in direction.
It can generate around 200 watts of power output depending on the amount of vibration, which changes significantly depending on the train’s weight. A battery stores the power until the roadside equipment needs it. “In my vision of the system, one motion rectifier and storage unit can meet most applications for signal lights, cross gates, track switches and monitoring sensors, but you could mount several along the track to increase power output,” he says.
He estimates that trackside power supply savings for railroads could amount to more than $10 million in New York alone. Cutting electricity generation and distribution to power trackside equipment could also reduce CO2 emissions by 3,000 tons per year in the state. With more than 140,000 miles of railroad tracks in the U.S., Zuo’s device could amount to significant electricity savings and emissions reductions.
The Stony Brook team is also working on a shock-absorbing regenerative device to be mounted between a railcar’s bogie and its body that would generate electricity for the train. This device can output up to 400 watts of power that it converts from the oscillating motion of the vehicle.
Top Image: Passing freight train via Shutterstock.