A teeterboard-like hybrid nanogenerator for efficient harvesting of low-frequency ocean wave energy

Recently, a large number of triboelectric nanogenerators (TENGs) have been explored to harvest blue energy from the ocean. In this work, a teeterboard-like hybrid nanogenerator (named as THNG) is fabricated for harvesting the widely distributed low-frequency ocean wave energy. The unique design includes a multi-layered TENG at one end of the teeterboard and an electromagnetic generator (EMG) at the other end. Benefiting from the novel design, the TENG unit can realize a full-packaged and light-weight structure that can be easily triggered by ocean waves with a low-frequency and it demonstrates desirable performance without environmental impact. The motion amplitude of EMG unit can be easily adjusted by changing the fulcrum position between the TENG and EMG. Even in a slight wave state, the EMG can still move with a reasonable amplitude to generate an ideal electrical output, which overcomes the problem of low efficiency of EMG when working at low frequency. Moreover, because of the innovative design, the THNG can automatically adjust the direction to match the incident wave and consequently capture wave energy from any directions. The impact of wave frequency, pitch angle and fulcrum position to the performance of THNG have been systematically investigated, and the maximum voltage of TENG and maximum current of EMG reach 760 V and 10 mA respectively at the optimum working condition. Moreover, the as-fabricated THNG is capable of charging commercial capacitors, lighting more than 200 LEDs and driving a rain-drop senor directly under simulated tide flow. This work presents an innovative and reliable approach towards large-scale low-frequency (<0.8 Hz) blue energy harvesting and applications.