Vibrations can drive your watch and other small appliances more easily, as one researcher from the Kanazawa University in Japan has developed a possible replacement for button batteries. His device works on vibrations and could one day power even bigger stuff, if put to series.
Toshiyuki Ueno‘s generator has an energy density of about 22 mW/cm3, 20 times higher than the energy density of other vibration-driven generators, made with piezoelectric materials, which only feature 1 mW/cm3.
Ueno uses “Galfenol,” an alloy of iron and gallium with magnetostrictive properties. Just like piezoelectric materials react when stretched mechanically, magnetostrictive materials react when a certain magnetic field is applied to them, and change their shape in response to that. First used in 1998, magnetostrictive materials are only used for the first time in a vibration-driven generator.
Ueno has created his magnetostrictive structure to be small but to be able to generate large amounts of electricity. He used Galfenol’s ductility by fixing together two long and thin magnetostrictive elements, while he added weights to their other ends.
For electricity to come out of this contraption, he then only added coils around the elements for physical stress and hence magnetization to produce electric current, like in a classic alternator.
The researcher also said that Galfenol can be used in harsh environments, where changes are fast and temperatures can reach 700 degrees Celsius. “Because Galfenol is a ductile material, even the thin rod-shaped structure does not easily break,” he said.
Because of its resistance to physical stress and high temperatures, Galfenol-based generators could be used in the pavement of electricity-generating highways, that could recover the otherwise destructive vibrations produced by cars and transform them into something useful, such as lighting the billboards or even producing electricity for the grid.