A cam-booster-based hybrid harvester for efficient ultra-low-frequency wave energy conversion

Intelligent ocean buoys are indispensable for environmental monitoring and marine scientific research. However, their long-term and large-scale deployment is constrained by insufficient energy autonomy. This study proposes a cam-booster-based hybrid wave energy harvester (CB-WEH) that effectively converts low-frequency wave energy into high-power electrical output to supplement ocean platforms. Ocean waves exhibit ultra-low frequencies and randomness. In the CB-WEH, the wave-induced sway is converted by a planar pendulum into low-frequency oscillations or rotations, which are further transformed by the sinusoidal cam booster into high-frequency reciprocating slider motions, driving electromagnetic generators (EMGs) and triboelectric nanogenerators (TENGs) for electricity generation. At 1 Hz and 20° excitation, the CB-WEH achieved a peak power of 369.44 mW and an average power of 66.57 mW. Through power management, 137 mWh of energy can be stored in the battery within 3 h, ensuring stable operation of the pose and temperature–humidity (T&H) sensors. Field tests in the Yellow Sea demonstrated that the cam booster achieved a maximum frequency up-conversion of 30 × , enabling the TENG and EMG to generate peak voltages of 50 V and 7.2 V even under small platform inclinations of about 3.5°, highlighting the strong potential of the system for ocean applications.