Energy harvesters with high electromagnetic conversion efficiency through magnet and coil arrays

This paper presents a new technique of converting mechanical energy to electrical energy that can be used to harvest mW - W power level from a vibrating surface of tens - hundreds microns amplitude. The technique uses an array of alternating north- and south-orientation magnets to enhance magnetic flux change by more than an order of magnitude. Experimental results show that a microfabricated energy harvester of 20mm×5mm×0.9mm (=0.09cc) weighing 0.5 gram generates an induced electromotive force (EMF) of V_p-p =30mV with 2.6μW power output (into 10.8Ω load) when it is vibrated at 290Hz with vibration amplitude of 11μm. Its macroscale version, that is scaled up to 51mm×51mm×10mm (=26cc) weighing 90 gram, generates an EMF of V_p-p=22V with 158mW power output (into 96Ω load) when it is vibrated at 82Hz with vibration amplitude of 414μm, and lights an incandescent light bulb.