A Funnel Type PVDF Underwater Energy Harvester with Spiral Structure Mounted on the Harvester Support

Abstract

For the purpose of stably supplying electric power to the underwater wireless sensor, the energy harvesting technology in which a voltage is obtained by generating displacement in a piezoelectric material using flow-induced vibration is one of the most attractive research fields. The funnel type energy harvester (FTEH) with PVDF proposed in this study is an energy harvester in which the inlet has a larger cross-sectional area than the outlet and a spiral structure is inserted to generate a vortex flow at the inlet. Based on numerical analysis, when PVDF with L = 100 mm and t = 1 mm was used, the electric power of 39 μW was generated at flow velocity of 0.25 m/s. In experiment the average RMS voltage of FTEH increased by 0.0209 V when the flow velocity increased by 1 m/s. When measured at 0.25 m/s flow velocity for 25 s, it was shown that voltage doubler rectifier (VDR) generated a voltage of 133.4 mV, 2.25 times larger than that of full bridge rectifier (FBR), and the energy charged in the capacitor was 44.3 nJ, 14% higher in VDR than that of the FBR. In addition, the VDR can deliver power of 17.75 μW for 1 k load. It is shown that if the voltage generated by the FTEH using the flow velocity is stored using the VDR electric circuit, it will greatly contribute to the stable power supply of the underwater wireless sensor.

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“…Figure 4 shows the generated signal and frequency spectrum of the PVDF energy harvester measured at 10 MΩ with an oscilloscope (DSO7052B, Agilent Technologies, Santa Clara, CA, USA). The PVDF generates unstable velocity distribution by vortex flow and increases directional deformation proportional to fluid velocity [ 22 ]. Therefore the PVDF energy harvester generates a high voltage proportional to the wind speed and includes a fundamental frequency of 2.9 Hz to 3.7 Hz and frequency components of 12 Hz and 35 Hz.…”

“…The PVDF energy harvester is equivalent to a circuit model of internal capacitance and source voltage , connected in series [ 22 ]. The determined internal capacitance using an LCR meter, , is found to be 10.26 nF.…”

“…The is similar to the nominal capacitance of 11 nF of the used PVDF (LDT1-028K, TE Connectivity, Schaffhausen, Switzerland). The source voltage, , can be estimated using a first-order Butterworth inverse filter at the measured voltage at 10 MΩ [ 22 ]. Figure 5 shows the estimated source using the measured voltage at 8 m/s wind speed.…”

“…Conventional bridge diode rectifier circuits, voltage doubler rectifiers, and charge pump rectifier circuits are used for energy harvesting [ 22 , 32 , 33 ]. Half wave rectifier, bridge diode rectifier, voltage doubler, and charge pump rectifier circuits were considered as shown in Figure 6 and their average powers according to load were compared with the IC-VBC via SPICE simulation.…”

“…A voltage multiplier circuit and voltage-controlled switch were used for efficient power transfer of the PVDF energy harvester [ 22 ]. This method has practical limitations in that power cannot be continuously transferred and additional power is consumed for switching operation.…”