A nonlinear hybrid energy harvester with high ultralow-frequency energy harvesting performance

The exploration of renewable energy technology is increasingly important owing to depletion of fossil fuels and the environmental pollution caused by the use of fossil fuels. Converting mechanical energy to electrical energy is one approach to developing renewable energy. However, the harvesting of ultralow-frequency mechanical energy is a challenge that limits the development of energy harvesting technology. To address this difficult problem, this paper proposes a nonlinear hybrid energy harvester in which an electromagnetic generator (EMG) and a triboelectric generator (TEG) are coupled to harvest the mechanical energy from ambient vibrations at ultralow frequencies. The energy harvester is combined with a quasi-zero-stiffness (QZS) mechanism composed of four QZS springs and a linear spring to produce a large-amplitude response and improve the energy harvesting performance. The effect of the mechanical condition (linear, quasi-zero-stiffness and bistable) on the efficiency of energy harvesting is analysed analytically and verified by theoretical and numerical analyses. The dynamics responses of the nonlinear energy harvester influenced by systematic parameters are also dissected. This work provides a guideline for improving the ultralow frequency ambient vibration energy harvesting performance of a TEG through nonlinearity.