Development and analysis of a non-resonant wide-band tri-axial electromagnetic energy harvester

This manuscript introduces a non-resonant, wide-band, tri-axial vibration-based electromagnetic energy harvester (VEMEH) with a cylindrical permanent magnet that freely moves over silicone micro beads in a Teflon casing. The micro beads operate as anti-friction micro bearings between the magnet's bottom surface and the double-sided planar coil, smoothing in-plan motion and moreover, also act as micro-springs during out-of-plan vibration. Besides two double-sided planar coils, the harvester has a wound coil to boost energy conversion. The harvester's tri-axial ability, lower frequency response, and larger frequency bandwidth are due to the freely moving magnet without the suspension spring. Furthermore, the harvester’s simple architecture allows the harvester to seamlessly integrate with vibration source equipment, thus easily converting the real tri-axial excitation into electrical power. Additionally, experimental results show that the developed harvester can generate much more power than single-coil energy harvesters. The developed harvester is also integrated with a low-power wireless monitoring system for remote equipment condition monitoring in order to demonstrate its practical utility. The VEMEH exhibits remarkable performance, featuring an open-circuit RMS voltage of 367.3 mV at 40 Hz and 3 g acceleration during in plan vibrations. Under these excitation conditions, at an optimal load resistance of 149.8 Ω, the harvester attains an RMS load voltage of 174.9 mV and a peak output power of 204.2 μW. The device produces an increased open-circuit voltage of 547.5 mV at 20 Hz and 3 g when exposed to vertical vibrations, yielding a load voltage of 272.3 mV and a power output of 495 μW. The harvester functions well throughout an extensive frequency spectrum, ranging from 10 Hz to 120 Hz horizontally and from 10 Hz to 200 Hz vertically, offering versatility for diverse applications. The devised VEMEH prototype, rectification circuitry, and rechargeable system are integrated with a wireless sensor node for real-time monitoring of a car engine compartment. Furthermore, the device is evaluated for wearable applications by placing the harvester in a trouser pocket and measuring output values while running. Moreover, the harvester is utilized with various other home appliances, including washing machine, kitchen blender, and domestic water pump. The open circuit AC output voltage for washing machine is measured at 92.6 mV with an acceleration of 0.31 g and a frequency of 35 Hz, whereas the kitchen blender exhibits an open circuit AC output voltage of 112.5 mV at an acceleration of 0.65 g and a frequency of 60 Hz. The output voltage of a home water pump is recorded at 92.1 mV with an acceleration of 0.9 g and a frequency of 100 Hz. Similarly, the developed harvester is positioned on the car dashboard and evaluated for output voltage on both smooth and rough roads.