SMARTER STRATEGIES

A Shocking Way for Electric Cars to Get Energy from Bumpy Roads

Salvatore Salamone | Date: 04-12-10 | Comments

Experimental regenerative auto shock absorbers use an internal magnetic coil to produce small amounts of electricity when a car brakes or goes over a bump in the road. This energy potentially could improve electric car fuel efficiency by an estimated 2 to 10 percent.

Who knew that driving the pothole-ridden streets of New York City (or other places) might actually improve a car�s mileage? That might be the case if experimental shock absorber technology under development at the State University of New York at Stony Brook makes it from the lab into our cars.

Similar to the benefits of regenerative braking systems, the new shock absorbers would convert the vibrational energy of a bump into energy. Specifically, the new auto shock absorber would use an internal magnetic coil to generate small amounts of electricity when you brake or go over a bump in the road.

Work in this area has been going on for years. Past efforts have focused on recovering vibrational energy using different magnetic devices. Typically, these systems work by first absorbing the kinetic energy of the vibration and then converting that energy into electric power.

At the heart of the Stony Brook effort is a new approach to capturing the energy imparted to a car when driving over bumps in the road. The Stony Brook work is in the very early research stage, but it just got funding from the New York State Energy Research and Development Authority.

Stony Brook�s approach uses a shock absorber that consists of two tubelike components: A smaller magnetic tube slides inside a larger, hollow coil tube. The coil component is made of copper coils wound around a plastic tube. The magnetic component is made of ring-shaped magnets separated by ring-shaped magnetically permeable spacers. The magnets are aligned with like poles facing each other to produce a radially emitted magnetic flux.

The magnetic tube is also surrounded by a highly magnetically permeable material in order to further �pull� the magnetic flux outward. The researchers note that having a high magnetic flux is the key to the design. (The power regenerated is proportional to the square of the magnetic flux across the coils.)

Experimental regenerative shock absorber converts vibrational energy into electricity. Source: State University of New York at Stony Brook

When placed in the vehicle suspension, vibrations cause the coil tube to move relative to the magnetic tube. As the copper coils move inside this magnetic field, a voltage is generated. The electricity can then be used to recharge the vehicle�s battery.

The researchers believe that in normal driving conditions, the shock absorbers will generate about 64 watts per wheel, for a total of approximately 256 watts. This energy would then be used to complement the onboard power in an electric car�s battery. This would mean that less gasoline would be used than without this technology, and you could improve fuel efficiency by an estimated 2 to 10 percent.

The Stony Brook researchers recently published these findings in the Institute of Physics� journal Smarter Materials and Structures. Their paper, titled �Design and characterization of an electromagnetic energy harvester for vehicle suspensions,�can be found here.