According to a team of mechanical engineers from Stony Brook University, only 10-16 percent of the fuel energy is used to drive the car during everyday usage – that is, to overcome the resistance from road friction and air drag and actually transport the vehicle forward. That amounts to a lot of energy being wasted. Hybrid cars recapture some of the energy usually lost in braking but the dissipation of vibration energy by shock absorbers in the vehicle suspension remains an untapped source of potential energy. To harvest this lost energy the researchers have designed and tested a shock absorber that can be retrofitted to cars to convert the kinetic energy of suspension vibration between the wheel and sprung mass into useful electrical power.
Unlike the regenerative shock absorber system designed by MIT researchers that uses the up and down movement of the suspension to drive an external hydraulic motor the mechanical engineers built and tested a 1:2 scale prototype that relies on magnetic flux to generate power, much like the Etive concept we looked at last year, which uses kinetic energy to charge mobile devices.
In the new regenerative shock absorber, rare-earth permanent magnets and high permeable magnetic loops are used to harvest energy and could help increase fuel efficiency and help cut pollution.
The magnet assembly is made of ring-shaped permanent magnets and ring-shaped high magnetically permeable spacers stacked on a rod of high reluctance material. The magnets are arranged with like-poles of adjacent magnets facing each other to help push the magnetic flux outward. The magnetic assembly is encased in an outer cylinder made of high magnetically permeable material to further increase magnetic flux density in the coils.
The coil assembly is made of copper coils wound on a delrin tube. The coils were designed to align with the magnet stack and are connected to a rectifier set-up so, as the copper coils move inside the magnetic field, a voltage will be generated.
Many hybrid vehicles harvest energy from braking to enhance the efficiency of the vehicle, but this is only intermittent. A system that captures energy through a vehicle’s suspension would be able to do so much more consistently resulting in greater fuel efficiency and reduced pollution. It might also means that cars will soon be swerving to hit potholes instead of avoid them.
The team is working to further improve the energy density and efficiency of the device. Their research appears in the paper, Design and characterization of an electromagnetic energy harvester for vehicle suspensions, which appears on IOP Science.
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