Complementary Electromagnetic–Triboelectric Hybrid Generator for Low-Frequency Energy Harvesting

Ocean waves are abundant but low-frequency (0.1–1 Hz) and irregular; electromagnetic generators (EMGs) deliver high current yet weaken at low velocity, whereas triboelectric nanogenerators (TENGs) sustain high voltage at microampere-level current through megohm-level internal impedance. A complementary hybrid harvester with regime-dependent dominance is presented in a 3D-printed decagon buoy, in which rocking drives a freestanding sliding-mode TENG of polytetrafluoroethylene (PTFE) plates over aluminum electrodes and heave drives a magnetically levitated NdFeB magnet assembly through copper coils. Under idealized sinusoidal excitation at 0.5 Hz and ±45°, a single TENG layer with two PTFE plates gave an open-circuit voltage of at most 15.36 V peak-to-peak, including servo noise, and 1.25 μW near 5 MΩ, a probe-limited lower bound. The EMG delivered ≈1.488 mW at 10 Ω under rocking and charged a 1000 μF capacitor to 2.693 V (≈3.6261 mJ) in 120 s of heave. With both motions applied, the separately rectified outputs stored 5.278 mJ in a single preliminary run, 45.6% more than heave alone, a gain attributed mainly to mechanical coupling; the shared store also raises the energy value of each TENG charge an estimated 288-fold. Full-stack, replicated, irregular-wave and durability tests are the next steps toward self-powered marine sensing.