Mechanically-driven energy harvester in railway freight system: Integrated modeling and performance analysis

Vibration energy harvesters (VEHs) convert mechanical energy of unpowered freight wagons into electricity and unlock more smart devices to improve operating conditions. In this paper, the nut-screw-based mechanically-driven VEHs (MD-VEHs) along with several mechanical motion rectifiers (MMRs) are proposed and compared in nonlinear railway freight system. Firstly, the working principles of harvesters with non-MMR, half-wave and full-wave MMRs are researched, and equivalent circuit models are established to better reveal the engagement and disengagement of one-way clutches, followed by the integrated model of wagon-harvester system which studies the suspension vibration response and assesses harvester performance. The harvester equivalent circuit model is validated on a horizontal test bench, and presents a good consistency with test data. In addition, the effects of harvester equivalent damping and inertia on performance are explored systematically. The analysis results indicate that full-wave MMR presents the best power performance under the same parameter configuration. The increase of flywheel inertia will decrease the power generation capacity of non-MMR configuration, but further enhance those of half-wave and full-wave MMRs and narrow the performance gap between both. This analysis based on system coupling will be instructive for the engineering design and application of railway VEHs.