Tumbler-inspired electromagnetic generator for low-frequency ocean wave energy harvesting

Ocean wave is considered as one of most promising renewable energy sources due to the merits of wide distribution and high energy density. However, the low-frequency and large randomness characteristics make it hard to harvest. Here we report a tumbler-inspired electromagnetic generator (T-EMG) with a Halbach array to improve the low-frequency ocean wave energy harvesting performance. The theoretical model of the T-EMG is established. The amplitude-frequency relationship is derived. The simulations and experimental investigation are carried out. The maximum harvested voltage of 3 V with a lower frequency of 2.6 Hz is obtained, and the maximum average output power can reach 65 mW through adjusting the load and tumbler parameters. More significantly, the offshore tests in the East China sea were carried out and the experimental results showed that T-EMG can work effectively under ultra-low frequency (<1Hz) real ocean wave environments and achieve a maximum peak power of 120 mW, which could meet the requirement of low-power wireless sensors. In addition, the offshore tests also demonstrate the strong frequency adaptability of T-TMG that enables it to harvest random and low-frequency ocean waves efficiently. This work provides an effective solution to harvest low-frequency and random ocean wave energy and can be easily adapted to mechanical or aerospace engineering, etc.