Regenerative braking systems are an essential part of any electric/hybrid car, making it more efficient by taking advantage that energy can be relatively easy-recoverable when converted to electricity. Regenerative suspension systems are yet another approach to this class of mechanisms, continuously recovering the vibrational energy that occurs due to road irregularities, vehicle acceleration and braking.
A team of researchers from the State University of New York at Stony Brook, designed and tested a shock absorber that can harvest vibrational energy. Their prototype, at a scale of 1:2 is a retrofit shock absorber able to harvest 2-8 watts during typical driving conditions at 45 mph. The scientists predicted that such a system, fully scaled, could recover up to 256 watts if mounted on a four-wheel car, under the same driving conditions.
“For typical driving conditions, we are predicting the ability to harvest approximately 64 watts per wheel, for a total of approximately 256 watts,” Professor Lei Zuo, one of the researchers, told PhysOrg.com. “This value increases considerably when the system is used on irregular roads.”
The retrofit prototype shock absorber consisted of two tubular pieces: a hollow coil tube having a smaller magnetic one inside (the principle of an alternator). he coil component is made of copper coils wound around a plastic delrin tube, while 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 high magnetically permeable material in order to further “pull” the magnetic flux outward. As Zuo explained, having a high magnetic flux is key to the design.
“Regenerative braking harvests large amount of power in a very short time, in an intermittent manner,” Zuo said. “However, the regenerative shock absorbers can harvest the power in a continuous way. On the smooth highway road, the regenerative shock absorbers can improve the fuel efficiency by 2%, and on bumpy roads up to 10% increase can be expected.”
A year and a month ago, a team from MIT built a similar device that could harvest the energy out of bumpy roads. If there’s any connection between MIT and the researchers mentioned herein, I don’t know, but it’s for sure we’re going to see these energy recovery systems on future electric or hybrid cars.