Vibration Energy Harvesting Based on Magnet and Coil Arrays for Watt-Level Handheld Power Source

Abstract

Electromagnetic energy conversion, based on Faraday's law, can deliver a relatively large, continuous power to a low impedance load from a vibrating body. However, increasing the energy-conversion efficiency and keeping it high at a relatively large vibration amplitude have been difficult, and no miniature energy harvester has shown more than tens of milliwatt power level from submillimeter vibration amplitude. Here we provide a new energy-conversion technique to convert mechanical vibration into electrical energy with unprecedented power level of more than a quarter watt out of submillimeter vibration amplitude. The technique uses an array of alternating northand south-orientation magnets to enhance magnetic flux change by more than an order of magnitude. A newly fabricated harvester occupying 51 × 51 × 10 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> (= 26 cc) and weighing 90 g generates an electromotive force (EMF) of ν <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p-p</sub> = 28.8 V with 263 mW power output (into 96-W load) when it is vibrated at 65 Hz with vibration amplitude of 660 μm. The power level is high enough to light an incandescent light bulb. Also, its microfabricated version occupying 20 × 5 × 0.9 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> (= 0.09 cc) and weighing 0.5 g generates an EMF of ν <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p-p</sub> = 30 mV with 2.6-μW power output (into 10.8-W load) when it is vibrated at 290 Hz with vibration amplitude of 11 μm.