A Bumpy Road to Efficiency

Imagine how you’d feel about driving if the sight of a giant pothole up ahead made you think, “Yay, more power!”

A team of MIT undergraduates has patented a new kind of shock absorber, called GenShock, that harnesses energy from even the tiny bumps on a seemingly smooth ride, while cushioning the jolts more effectively than conventional shocks. The students hope to find their first customers among companies that operate large fleets of heavy vehicles; they’ve already drawn interest from the U.S. military and some truck manufacturers.

Shakeel Avadhany ‘09 and teammates say that vehicles using the regenerative shock absorbers can be up to 10 percent more fuel efficient. The company that produces Humvees for the army is interested enough to have loaned them a vehicle for testing purposes.

The project started because “we wanted to figure out where energy is being wasted in a vehicle,” senior Zack Anderson explains. Just as some hybrid cars recover energy from braking instead of dissipating it as heat, the team’s invention captures energy from the up-and-down motions of the suspension–energy that’s also normally lost as heat.

The students began by renting a variety of car models and outfitting their shock absorbers with sensors to measure the vertical movement of the suspension in a drive on a typical road. Then they drove around with a laptop computer, recording the sensor data. Especially in heavy vehicles, Anderson says, a significant amount of energy turned out to be available that was not being harnessed in cars with conventional suspension systems.

The students built a prototype suspension using a hydraulic system controlled through a microprocessor that optimizes the damping (the resistance to the vehicle’s oscillating motion) 1,000 times per second. That helps the system provide a smoother ride than conventional shocks. The hydraulic fluid from each shock absorber is forced through a turbine attached to a generator, converting the ups and the downs into uniform rotation to produce electricity.

So far, the students’ tests have shown that in a heavy truck, each shock absorber could generate an average of up to one kilowatt on a standard road–enough power to ease the load on the alternator in heavy trucks and military vehicles, allowing the engine to run more efficiently. In some cases, power from the suspension could even run attached devices such as refrigeration units.

The inventors have also prepared for the worst: if any part of the hydraulic generating system fails, the suspension still smooths the ride. “Its broken state is a regular shock absorber,” Avadhany says.