Bandwidth widening of piezoelectric energy harvester by free moving cylinders in liquid medium

Ambient vibrations are one of the promising sources of energy harvesting to power up IoT and WSN nodes. Harvesting random vibrations requires the energy harvester to dynamically tune to the dominant vibration over large frequency band. The tuning is achieved with the help of auto/self-tunable, wideband or broadband energy harvesters. The reported cantilever based harvester is a wideband energy harvester which increases the bandwidth by immersing the moving mass in liquid medium. Splashing of liquid, viscous resistance offered to the moving mass, and the self weight of the liquid contributes to the improved performance over the moving mass based PEH reported earlier. Increased bandwidth is observed for system with two moving cylinders immersed in different liquids. Harvester’s proof-mass height is another constraint used to observe the bandwidth change. Effect of viscosity of liquid, liquid filled percentage and amplitude of vibration are reported. The device with increased height of proof-mass and liquid filled for 50% volume shows 63.75% increase in bandwidth compared to the standard device without liquid.