A Novel Heaving Ocean Wave Energy Harvester with a Frequency Tuning Capability

This study introduces a novel wave energy harvester (WEH) with frequency conversion capability to convert the ocean wave energy to usable electricity based on the piezoelectric effect. The presented WEH is with characteristics of space saving and minimized component quantities and is made of a cylindrical case reciprocally moving with respect to the fixed core shaft attached to identical magnetic bars. The cylindrical case contains four magnetic bar-mass-spring-lever-piezoelectric systems arranged symmetrically each other to the fixed shaft. By this smart design, the WEH is capable of converting the low frequency of ocean waves to a higher excitation frequency of motions on the piezoelectric transducer to harness higher electric power and reduce electrical leakage. A mathematical model of the WEH considering the wave–structure interaction is developed to evaluate the effectiveness of the converter. The simulation results reveal that the occurrence of resonance can lead to an outstanding power output via adjusting the distance between two adjacent magnetic bars. The power output is realized up to 750 W with the converter height and diameter, ocean wave height, and wave period being 1 m, 1 m, 1.5 m and 8 s, respectively.