Impact-release enhanced piezoelectric wave energy harvester for self-powered water quality monitoring

To achieve a sustainable energy supply for massive distributed water quality sensors, efficient energy harvesting from water environments is crucial. This paper proposes an impact-release enhanced piezoelectric wave energy harvester (IR-PWEH) for self-powered water quality monitoring. By accumulating the slow wave energy into mechanical springs, the elastic potential energy can be automatically released as impact kinetic energy with simple magnet-spring triggering, which is then delivered to the vibration energy of the piezoelectric vibrator with strong magnetic plucking. The proposed impact-release mechanism (IRM) can effectively transform a cycle of low-frequency wave motion into high-frequency piezoelectric vibration with enhanced electric power output. An electromechanical coupling model of the system was established, a prototype was fabricated, and experimental tests along with power supply demonstrations were conducted. Testing results demonstrate that the optimal output voltage of the IR-PWEH increases by 59% to 106% compared with the conventional magnetic plucking method. Under 0.1 m wave excitation at 1 Hz, the IR-PWEH generates electric power of 33.32 mW, achieving a peak power density of 36.11 W/m3. Through the voltage regulator module, the IR-PWEH can successfully drive a wireless water quality sensor once per hour with transmission of full water quality data. This study presents an excellent approach to the development of efficient low-frequency wave energy harvesting technology for self-powered water quality monitoring.