Broadband Vibrational Energy Harvesting with a Spherical Piezoelectric Transducer Devoted to Underwater Wireless Sensor Networks

Abstract

A new sensing node container based on a spherical piezoelectric transducer is proposed. This device provides broadband vibrational energy harvesting and sensing facilities intended for underwater wireless sensor networks. The transducer is composed of two acrylic glass (PMMA) half-spherical shells and a Pz26 piezoelectric ring clamped between the two shells. A simulation model of vibrational energy harvesting has been developed with electromechanical circuits for thickness and radial vibrational modes. This approach was validated by a finite element simulation. As a result, optimal power harvesting conditions and estimated harvested voltage were defined. A prototype of 2.2 cm in diameter was realized and characterized. Analysis in air environment reveals several structural resonance modes in the 20–80 kHz frequency range. The directivity patterns corresponding to these modes was obtained using laser Doppler vibrometry. The measurements for the underwater environment show that the structural resonance modes shift down in frequency to the 10–60 kHz range, and exhibiting low directivity dependence. Power harvesting performances was measured and quantified relative to acoustical pres- sure measurements using a hydrophone. The average conversion coefficient value was found to be in the order of 3 V/MPa. In broadband excitation mode, and for an acoustic pressure of 10 kPa, the amount of harvested power out of 5 main resonance modes is 3.3 μW.

An autonomous low-power management system for energy harvesting from a miniaturized spherical piezoelectric transducer

“…More details on FEM modeling and spherical shell multimode vibrational behavior could be found in Ref. 27.…”

“…34 Also, frequency response vs the displacement of the acoustic source was characterized with a Laser Doppler Vibrometer (LDV); this technique is presented in the first part of this work. 27 The measurement points were positioned at the center of aperture. The Tonpilztype transducer has several resonance frequencies due to different vibrational modes [Fig.…”

“…The overall acoustical pressure in the 10-60 kHz frequency range was measured to be about 20 kPa, and the average conversion coefficient was estimated to be 3.3 V/MPa. 27 There exist several noise sources in underwater acoustics in the ultrasonic range of either natural or artificial origin. For example, a cargo ship emits in close zone the noise level varying from 0.6 kPa to 35.5 kPa for the frequency range from 10 Hz to 32 kHz.…”

“…In addition, this configuration of the sensor exhibited low directivity, which is advantageous for operation under random ambient conditions. 27 In the first part of this work, the essential properties of the spherical piezoelectric transducer are presented based on our work reported elsewhere. 27 These properties are relevant for interfacing the piezoelectric transducer with the power extraction circuit.…”

“…27 In the first part of this work, the essential properties of the spherical piezoelectric transducer are presented based on our work reported elsewhere. 27 These properties are relevant for interfacing the piezoelectric transducer with the power extraction circuit.…”