Triboelectric energy harvester with large bandwidth under harmonic and random excitations

This paper investigates an approach to impact vibration energy harvesting using a triboelectric mechanism under harmonic and random excitation. The harvester consists of a clamped–clamped beam with a stiff plate in the middle to realize the impact electrification process when subjected to external vibrations. The harvester uses stiffening in the clamped–clamped beam introduced by the impact between two triboelectric layers to increase the frequency bandwidth. A piecewise theoretical model is used to model the harvester for two scenarios of motions, before and after impact. The harvester is tested experimentally under different harmonic excitation to validate the theoretical model. The outcomes show a good agreement between both experimental and theoretical results. Higher bandwidth is achieved at a lower gap separation distance. The operating bandwidth of the energy harvester increased from 4.4 Hz to 17.8 Hz with an RMS output voltage level of 7 V and an output power density of 7mW∕m² at 1.4 g excitation level and 100μm gap. The model is extended and validated experimentally under random excitation. The simulated power spectral densities are in good agreement with the experimental results.