A Magnetic-Multiplier-Enabled Hybrid Generator with Frequency Division Operation and High Energy Utilization Efficiency

Abstract

The hybrid electromagnetic-triboelectric generator (HETG) is a prevalent device for mechanical energy harvesting. However, the energy utilization efficiency of the electromagnetic generator (EMG) is inferior to that of the triboelectric nanogenerator (TENG) at low driving frequencies, which limits the overall efficacy of the HETG. To tackle this issue, a layered hybrid generator consisting of a rotating disk TENG, a magnetic multiplier, and a coil panel is proposed. The magnetic multiplier not only forms the EMG part with its high-speed rotor and the coil panel but also facilitates the EMG to operate at a higher frequency than the TENG through frequency division operation. The systematic parameter optimization of the hybrid generator reveals that the energy utilization efficiency of EMG can be elevated to that of rotating disk TENG. Incorporating a power management circuit, the HETG assumes the responsibility for monitoring the water quality and fishing conditions by collecting low-frequency mechanical energy. The magnetic- multiplier-enabled hybrid generator demonstrated in this work offers a universal frequency division approach to improve the overall outputs of any hybrid generator that collects rotational energy, expanding its practical applications in diverse multifunctional self-powered systems.

Fig. 1.

Structure and working mechanism of the MMHG. (A) Exploded view of the MMHG, including a RTENG, a magnetic multiplier, and a coil panel. (B) Working mechanism of MMHG. (C to F) Digital photographs of the 60° grating electrode, rabbit fur, magnetic multiplier with 1:4 transmission ratio, and copper coils, which works together to construct the MMHG. (G) Comparison of TENG and EMG energy utilization efficiency in hybrid generators with different operating modes.

Electrical characteristics of RTENG. (A) The test platform consisting of a sliding rail, a lifter, a motor, and the MMHG. (B) Transferred charge curves of 30°, 45°, and 60° grating electrodes cooperating with the rabbit fur, obtained in 1 cycle at 2.67 Hz. Insets are the general view of 3 kinds of electrodes. (C) Dependence of open-circuit voltage and transferred charge of 3 different electrodes on frequency. (D) Average power of 30°, 45°, and 60° grating electrodes under external load resistances at 2.67 Hz. (E) Comparison of the output energy for 3 electrodes in 1 cycle at the matched impedance (2.67 Hz). (F) Transferred charge and open-circuit voltage of 4 kinds of tribo-layers (rabbit fur, wool, spandex, and PET). (G) Durability test of RTENG with FEP film and rabbit fur. Insets are the charge waveform at the beginning (blue line) and the end (red line) of the test. (H) Photographs of the rabbit fur and SEM images of the FEP film before and after the durability test. The device is driven by a motor.

Fig. 3.

Electrical characteristics of magnetic multiplier enabled EMG. (A to C) Open-circuit voltage curves of EMG with 3 transmission ratios magnetic multipliers (1:2, 1:3, and 1:4). Insets are the schematic diagrams of low-speed rotor, modulation plate, and high-speed rotor for 3 magnetic multipliers. (D) Dependence of open-circuit voltage and short-circuit current on frequency. (E) Average power of EMG with 4 transmission ratios under external load resistances. The device is driven by a motor.

Fig. 4.

Output performance of the power-managed MMHG. (A) Current curves of rectified RTENG supplied to different external resistances (1, 10, 100, and 1,000 MΩ). (B) Average power and peak current of RTENG after rectification under external load resistances. (C) Current curves of rectified EMG with a 1:4 transmission ratio magnetic multiplier supplied to different external resistances (0.1, 1, 10, and 100 KΩ). (D) Average power of the EMG of 4 transmission ratios after rectification at external load resistance. (E) Schematic of the circuit for power-managed MMHG. (F) Charging performances of a 470-μF capacitator by the direct rectified RTENG, RTENG with PMC, direct rectified EMG, and power-managed MMHG. (G) Photograph of the powered-managed MMHG as a power source to light 416 light-emitting diodes (LEDs) in parallel connection. (H) Photograph of the lighted state. The device is driven by a motor at 2.67 Hz.

Fig. 5.

Application of the power-managed MMHG. (A) Typical application scenario of the power-managed MMHG in water quality monitoring and fishing alarm. (B) Experimental platform for simulating the scenario of harvesting wind energy to power the acidimeter. (C) Charging and discharging process of a 9.4-mF capacitor in powering the acidimeter by airflow-driven MMHG, indicating the acidimeter works 163 s after charging in 20 s. (D) Working waveform of the 9.4-mF capacitor in powering the water quality tester by airflow-driven MMHG. (E) Voltage curve of charging an 18.8-mF capacitor to power a fishing alarm by hand-driven MMHG. The respective working status is recorded in the inset.