A high-efficiency bioinspired photoelectric-electromechanical integrated nanogenerator

Currently, the key challenge in triboelectric nanogenerators (TENGs) is how to efficiently enhance the surface charge density. Here, a new strategy is proposed to increase the surface charge density by comprehensively utilizing solar energy and tidal energy, and a bioinspired photoelectric-electromechanical integrated TENG (Pem-iTENG) is developed. This enhancement of output performance is greatly attributed to the accumulation of photoelectrons from photocatalysis and the triboelectric negative charges from contact electrification. Pem-iTENG shows a maximal open-circuit voltage of 124.2 V and a maximal short-circuit current density of 221.6 μA cm−2 under tidal wave and sunlight, an improvement by nearly a factor of 10 over that of reported TENGs based on solid-liquid contact electrification. More importantly, it exhibits a high energy conversion efficiency according to the evaluation method for solar cells. This work provides insights into development of high-performance TENGs by using different natural energy sources.

Analytical calculation and analysis of air gap magnetic field for electromechanical integrated toroidal drive

This article introduces the operating principle and structural characteristics of the electromechanical integrated toroidal drive system. For its inner and outer toroidal double-stator structure, the equivalent current method is applied to calculate its spatial magnetic field, which is produced by the sector cylindrical magnetic teeth and the helical variable cross-section magnetic beam. For the application of the equivalent current method in the modeling of the magnetic field, an effective correction method is proposed. The flux density calculation models for the main magnetic field in the inner and outer air gaps are established under the unified coordinate system, and the analytical expression of magnetic field distribution in spatial air gap is deduced. Finally, the feasibility of the mathematical analytical model is verified by comparing the analytical calculation results with the finite element simulation results. The influences of the main structural parameters on the distribution of the air gap magnetic field and the torque are analyzed, which lay a theoretical foundation for the optimal design of the electromechanical integrated toroidal drive system.

Nonlinear Resonance Responses of Electromechanical Integrated Magnetic Gear System

Nonlinear differential equations for an electromechanical integrated magnetic gear (EIMG) system are developed by considering the nonlinearity in the magnetic force of the system components. Expressions for the main resonances and superharmonic resonances are obtained for output wave frequencies close to the natural frequency and half the natural frequency of the derived EIMG system. The response laws are discussed in detail. The magnetic coupling stiffness among the components is found to exhibit distinct nonlinearity, leading to strong main resonances and superharmonic resonances. Smaller values of the magnetic coupling stiffness and damping result in larger response amplitudes and transient responses that slowly decay to zero. When the main resonances and superharmonic resonances occur, the dominant frequency of the response is the natural frequency of the derived EIMG system, and the amplitudes of different components of the resonance display large differences.