High Tech Shocks Turn Bumps Into Power

Students at the Massachusetts Institute of Technology have developed a shock absorber that harnesses energy as it smooths your ride, and they say it can improve fuel efficiency by as much as 10 percent.

The regenerative shock absorber uses the oscillations of a vehicle's suspension to generate electricity. Its inventors claim a heavy-duty truck using six of their GenShock shock absorbers can produce enough power to displace the alternator, thereby increasing engine efficiency and fuel economy. The students have attracted the attention of AM General, the company behind the military Humvee, and believe future iterations of GenShock could improve the fuel economy of passenger cars and extend the range of electric vehicles.

"I want this to be a standard feature on heavy vehicles and eventually hybrid consumer vehicles and electric vehicles," Shakeel Avadhany, who led the GenShock team, told Wired.com.

The power-producing shock is the latest example of the push to recapture energy from automobiles that is otherwise wasted. Turbochargers are the most obvious — and oldest — example, but more recent developments include the regenerative braking systems used in hybrids and electric cars. The quest to increase efficiency also has automakers increasingly replacing mechanical components like air conditioning and power-steering pumps with electric ones to ease the load on the engine and save fuel. These technologies will grow more common as automakers strive to increase fuel efficiency and extend battery range.

"You main losses are friction, braking and heat," says Spencer Quong, senior vehicles analyst with the Union of Concerned Scientists. "Anything you can do to regain energy there will improve efficiency."

Avadhany, a senior studying materials engineering, started toying with the idea of a wasted energy in August 2007. He and classmate Paul Abel set out to identify where energy leaks from vehicles and figure out how to reclaim it.

It wasn't long before they focused on shock absorbers, which expand and compress countless times over their lifetimes. The kinetic energy is lost as heat. They figured there had to be some way of capturing that energy, which their tests show can be "a significant amount" — especially in heavy-duty vehicles.

"The amount of energy available in the suspension is on par with the energy coming out of the alternator," Avadhany said. "It's 6 to 10 kilowatts for a heavy truck and 3 to 4 kilowatts for a passenger car."

The students developed a shock absorber that forces hydraulic fluid through a turbine attached to a generator. It is controlled by an active electronic system that optimizes damping to provide a smoother ride while generating electricity to recharge the battery or operate electrical equipment. Should the electronics fail for any reason, GenShock works just like a regular shock absorber.

Avadhany says tests have shown a heavy-duty truck outfitted with six GenShocks can generate an average of 6 kilowatts of electricity on a typical road. That is enough to displace the alternator load, allowing the alternator to freewheel and eliminate parasitic drag on the engine.

Whether it is enough to significantly increase the fuel economy in passenger cars is another story. Simply put, heavier vehicles on rough terrain will generate more electricity than smaller cars on smoother roads, said Tom Turrentine, director of the Plug-In Hybrid and Electric Vehicle Research Center at University of California at Davis.

Still, any improvement is an improvement, and the students founded Levant Power Corp. about a year ago to develop and commercialize the technology.

They're being advised by Yet-Ming Chiang, an MIT professor and founder of batterymaker A123 Systems, and Avadhany says Levant is talking to outside investors and VC firms.

Perhaps more impressive, AM General is interested enough that it sent the students a military Humvee to use as a test mule. Company executives want the students to give them a full-scale demonstration in July.

Photos: MIT

The regenerative shock absorbers are made of steel and force hydraulic fluid through a turbine that is attached to a generator. Shock absorbers take a tremendous amount of abuse — especially those installed on heavy trucks and military vehicles — but Avadhany says that won't be an issue with GenShock, which they've tested on a military Humvee. "We beat the piss out of this thing and it did just fine," he said.

As the shock absorbers compress and expand, they push hydraulic fluid through a turbine attached to a generator. The system is controlled electronically to optimize damping, something Avadhany says provides a smoother ride than conventional shock absorbers. That increases safety, he says, because "if it's a smoother ride, you can go over the terrain faster."

Although heavy-duty trucks and military vehicles like the Humvee are the initial market for GenShock, Avadhany says the goal is to develop the technology for passenger cars and hybrids.

By Chuck Squatriglia