Wake galloping piezoelectric-electromagnetic hybrid ocean wave energy harvesting with oscillating water column

On-site continuous and energy-autonomous wireless sensor nodes are highly desirable for the sustainable monitoring of the ocean environment. In this work, a wake galloping piezoelectric-electromagnetic hybrid energy harvesting technique is developed to take off electric power from ocean wave energy. This mechanism is composed of an air chamber intake for the oscillating water column (OWC) and a piezoelectric-electromagnetic hybrid wave energy harvester in a vortex tunnel. Theoretical models and multi-physics coupled simulations are derived and established to systematically investigate the performance of the proposed harvester and the feasibility of harvesting wave energy is verified with a series of wave flume and wind vortex tunnel experiments. The results show that when the wave frequency is 0.4 Hz (the period is 2.5 s), the air pressure of the chamber is 140.12 Pa. Hence, the air is exhaled with the maximal flowing speed of 17.85 m/s in the wind vortex tunnel. For comparison, It is evaluated by the simulation model with air pressure results of 142.86 Pa and wind speed at 18.36 m/s which agree well with the theoretical values. The output voltages of the piezoelectric and electromagnetic parts are calculated with the theory and simulation as 20.34 V and 0.258 V, respectively. Furthermore, the power of the fabricated prototype piezoelectric-electromagnetic hybrid energy harvester achieves 3.76 mW and 1.33 mW, respectively, at the wind speed of 18 m/s while it is set up from the downstream of the bluff body with a windward width of 34 mm, and the space distance ratio is about 4.5. Therefore, the test and computed results provide the wave-WG-PEEH for ocean wave energy harvesting to supply the perspective of maritime low-power wireless sensors.