Shock Absorbers That Generate Electricity
MIT Students See Bumps in the Road as a Power Source
Jul 3, 2009
As is so often the case in science, some discoveries are serendipitous (lucky accidents). A team of MIT engineering students lead by senior Zack Anderson was initially investigating where energy was being wasted in a vehicle. This total vehicle search quickly narrowed focus to the suspension system, which in turn unexpectedly led to the invention of an energy – harvesting (regenerative) shock absorber.
The Development of the GenShock Energy-Harvesting Shock Absorber
The team began by renting a variety of different car models, outfitting the suspension with sensors to determine the energy potential, and driving around with a laptop computer recording the sensor data. Their tests showed "a significant amount of energy" was being wasted in conventional suspension systems, Anderson says, "especially in heavy trucks."
Quickly realizing the possibilities, the team set about building a prototype system to harness the wasted power. Their prototype shock absorbers, called GenShock, use a hydraulic system that forces fluid through a turbine attached to a generator. The system is controlled by an active electronic system that optimizes the damping, providing a smoother ride than conventional shocks while generating electricity to recharge the batteries or operate electrical equipment.
GenShock Does More than Recover Energy
Testing has found that in a 6-shock heavy truck, each shock absorber could generate up to an average of 1 kW on a standard road – enough power to completely displace the large alternator load in heavy trucks and military vehicles, and in some cases even run accessory devices such as hybrid trailer refrigeration units.
Removing the alternator and its belt – driven drag on the engine in turn improves the fuel economy of the vehicle, potentially as much as 10 percent. The team has calculated that a company such as Wal-Mart with a large fleet of heavy trucks could save $13 million a year in fuel costs.
Drivers, passengers, and cargo will also benefit from a smoother and more controlled ride due to an electronic system that monitors and responds to stress on the shocks. This in turn will improve handling and stability allowing for a safer and faster ride, especially over the rough terrain traversed by military vehicles.
The new shocks also have a fail – safe feature: If the electronics fail for any reason, the system simply acts like a regular shock absorber.
Moving GenShock from Prototype to Production
The group filed for a patent on their device and formed a company, called Levant Power Corp., to develop and commercialize the product. The company that produces Humvees for the military, and is currently working on development of the next – generation version of the all-purpose vehicle, is interested enough to have loaned them a vehicle for testing purposes.
The converted Humvee is currently being used in a series of tests to optimize the system’s efficiency. The plan is to have a final, fine-tuned version of the device ready by late summer 2009.
Although GenShock is not yet cost – effective to produce for smaller cars, Anderson says he hopes to combine it with other energy-harvesting (regenerative) systems to dramatically increase the energy efficiency of private automobiles. Regenerative technology of this sort is already being used in hybrids: Regenerative braking, for example, converts the car’s motion into electricity as the vehicle comes to a stop.
"This is a disruptive technology," Anderson says. "It's a game – changer." His statement seems verified by the fact that the military and several truck manufacturers have expressed a high level of interest in the device.
References:
Chandler, David. More Powe from Bumps in the Road. MIT News. February 9, 2009
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