A triboelectric–electromagnetic hybrid generator for scavenging low-frequency oscillation energy from the environment and human body

Vibrational energy can be found in the environment and the human body. Herein, we propose a compact and portable triboelectric–electromagnetic hybrid generator (TEHG) for scavenging low-frequency oscillation energy from the environment and human body. The TEHG comprises two freestanding triboelectric nanogenerators (F-TENG) and an electromagnetic generator (EMG), which uses repulsion between magnets to efficiently collect low-frequency vibration energy. After characterization, the TEHG presented high-performance output in a low-frequency environment and the maximum output power was obtained by impedance matching. We proposed ferromagnetic materials contributing higher output for TENG in the magnetic field environment of the device. The maximum open-circuit voltage of inner cylinder triboelectric nanogenerator was found to increase from 400 V to nearly 500 V after sandpaper surface treatment. The short-circuit current reached 30.6 mA by rectifying and connecting two F-TENGs in parallel. The charging effects by using a single TENG, two TENGs connected in parallel, both TENGs and EMG connected in parallel were compared. Finally, the TEHG was showed to effectively capture low-frequency portable energy in daily life, such as in human movement and automobile driving. Also, it was also found that the output of TEHG could easily light 240 white LEDs and drive small electronic sensors. This work advances the optional application of hybrid generator for harvesting low-frequency vibration energy.