Optimized Electromagnetic Harvester with a Non-Magnetic Inertial Mass

This paper presents an optimization study to decrease the operation frequency and increase the output power of a miniature electromagnetic (EM) energy harvester, by incorporating a non-magnetic inertial mass together with the moving magnet. The harvester coil position has been optimized through FEM, and validated through tests. Experimental studies on the inertial mass showed that increasing the magnet size further increases the resonance frequency due to the increased magnetic forces. Conversely, using a non-magnetic mass over the magnet effectively decreases the resonance frequency (27Hz to 15Hz), and increases the generated output power. The power output during operation at even lower frequencies is also improved by adding the non-magnetic mass. The optimized 6 cm3 harvester generates 0.45 Vrms and 110 μWrms output power at 15Hz and 0.7g peak acceleration.