Open-book-like triboelectric nanogenerators based on low-frequency roll–swing oscillators for wave energy harvesting

The invention of triboelectric nanogenerators (TENGs) provides a great opportunity for large-scale harvesting of water wave energy, which is both clean and renewable. To realize this prospect, devices with high power density and low-frequency response capability are highly desired. Here, an open-book-like triboelectric nanogenerator with enhanced power density and high responsivity to wave agitations is presented. The device efficiently integrates a large number of TENG units into an open-book-like structure in a limited space, greatly improving the volume density of the microstructured contact interface. A mechanism of force conduction chain is proposed for the first time to effectively drive multiple stacked TENG units. For a device with 50 units, the transferred charges can reach 26 μC and the short-circuit current is 0.45 mA, which should set new records among similar devices. The design of the roll-swing oscillator demonstrates a nonlinear feature in the elasticity with double energy minima, enabling a wide frequency response at low frequencies which is crucial for harvesting wave energy. When agitated by water waves, the roll-swing oscillator can respond effectively to the excitation and drive the stacked TENG units with the assistance of the force conduction chain. A high peak power density of 7.45 W m-3 and an average power density of 0.335 W m-3 in water were obtained. Such high performance of the device makes it an excellent candidate for constructing self-powered marine systems or large-scale wave energy harvesting farms to realize the blue energy dream.