An electromagnetic-triboelectric hybrid generator (ETHG) for harvesting broadband and multi-directional vibration energy from transmission lines

Given the ubiquity of wind-induced vibrations on transmission lines, harvesting this energy to power wireless sensors is crucial for developing smart grids toward the electric Internet of Things (eIoT). This paper introduces a high-power electromagnetic-triboelectric hybrid generator (ETHG) as a self-powered solution for smart grid monitoring, addressing limitations of existing generators, including single-direction operation, narrow working bandwidth, and low output power. The ETHG utilizes an innovative pick-up unit featuring a multi-spring mass structure to harvest vibration energy from arbitrary directions and multiple frequencies ranging from 14 to 24 Hz. The electromagnetic generator (EMG) component adopts a multiple magnet-coil arrangement to generate high current and output power. The origami-inspired triboelectric nanogenerator (origami-TENG) component, made of folded conductive fabrics and conductive fabric/fluorinated ethylene propylene (FEP) elastic strips, offers advantages of ultralight and high voltage output. By seamlessly integrating a pickup unit with a hybrid power generation module featuring complementary signals, ETHG performance is enhanced in an aeolian vibration environment characterized by random, low-level excitations. Under a 1 g sweep excitation along the Z-axis with a 5-fold origami configuration, the EMG and TENG components achieve maximum voltage outputs of 3.28 and 523.8 V, with corresponding power outputs reaching 46.9 and 8.2 mW, respectively. Compared to relevant reported generators from transmission line vibrations, the normalized power density of 0.88 mW/cm³·g² is improved by one order of magnitude. A power management circuit (PMC) is proposed to efficiently manage the electromagnetic-triboelectric hybrid signals, increasing the EMG and TENG charging speeds by 172 and 333%, respectively, compared to a rectifier bridge scheme. A vibration energy harvesting system (VEHS) comprising multiple ETHGs and a PMC supports a wireless sensing system for online monitoring of temperature, humidity, and vibration of transmission lines. This work highlights the potential of ETHG as a sustainable power source for smart grids towards eIoT applications.