Symmetrically pumped charges with high confinement stiffness for boosted performance in wave energy harvesting

Enhancing the output is the most crucial challenge for developing triboelectric nanogenerators (TENGs) as an alternative technology to exploit wave energy, which is more difficult than other application scenarios due to the full-encapsulation requirement and slow agitation of practical waves. Here, we develop a symmetrical charge pumping method based on a non-contact TENG, achieving boosted performance in practical slow waves. The method allows synchronously accumulating positive and negative confinement charges to a high density under the synergistic effect of oil dielectrics. More importantly, we find a new control parameter for device performance termed as confinement stiffness, which refers to the degree of squeezing out of confined charges under Coulombic reaction force. Through enhancing the confinement stiffness, the output performance and stability of TENGs can be greatly improved. Moreover, a pre-switching power management circuit is designed which solves the inconsistency problem of traditional circuit with the charge pumping method, reaching an 874.6-fold enhancement in charging a capacitor. Meanwhile, a novel negative power phenomenon is also reported. Based on the comprehensive designs, the charge density and power output are greatly boosted, reaching 1.6 mC/m² and 1.215 W respectively in an ideal condition. While tested in a 45-meter-long wave basin, the peak power density can reach 176.15 W/m³ under 1 Hz waves, which sets a new record and is 10.37 times of the reference device. The work demonstrates comprehensive strategies for boosting TENG performance, which should represent a key step toward efficient blue energy harvesting for self-powered systems and marine clean energy.