PERFORMANCE ENHANCEMENT OF VIBRATION-BASED ELECTROMAGNETIC ENERGY HARVESTER DUE TO REDUCED AIR DAMPING
Farid Ullah Khan·
ABSTRACT
This work presents on the performance enhancement ofvibration-based electromagnetic energy harvesters (EMEHs) due to reduced air damping. Fabrication and characterization of Copper foil-type EMEH-l and polydimethylsiloxane (PDMS) membrane type EMEH-2 under vacuum and without vacuum pressures are reported. The harvesters are subjected to harmonic excitation with constant acceleration frequency-sweeps. In the developed energy harvesters, the air damping is decreased by generating vacuum pressure in the cavity where the magnets are oscillating. Under a pressure of-93 kPa and when excited at an acceleration of 13.5 g and resonant frequency of371 Hz, in EMEH-l, the load voltage and load power delivered to a load resistance of 1000 increases from 46.3 to 79.4 mV and from 10.9 to 24.1 fJ-W respectively. However, at optimum load condition (7.5 0) and at resonant frequency, 48.6 % and 122 % improvement in load voltage and load power respectively is obtained. With and without vacuum pressures, EMEH-2 exhibits nonlinear behaviour at 3 g acceleration level. When connected to 1000 load and excited at 3 g acceleration, under vacuum pressure the EMEH-2 produces 37.6 mV more load voltage and 39 fJ-W more load power. Moreover, at optimum load condition (10.1 0) and under vacuum pressure, the harvester produces a maximum load voltage of 68 mV and load power of231 fJ-w: The reduced air damping provides a maximum improvement of 124 % and 107.6 % in power densities for EMEH-l and EMEH-2 respectively.
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