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This paper introduces a passive self-tuning energy harvester by applying self-resonating behavior. Under certain operating conditions, self-resonating systems have the capability to passively adjust their dynamical characteristics until the whole system becomes resonant. A clamped-clamped beam with an attached mass sliding freely with a slight gap showed self-resonating behavior. Under a harmonic input excitation and a well-defined operating regime, the mass moved along the beam thus causing a change in the natural frequency of the structure, and then stopped at the position where the natural frequency matched the excitation frequency, resulting in a significant increase in the vibration amplitude. For harvesting energy, a piezoelectric element was glued at one end of the beam. The operating regime of the self-resonating behavior was found experimentally in the two halves of the beam. In the half containing the piezoelectric element, self-resonating behavior was achieved between 126 Hz and 143 Hz. In the other half, it was achieved between 135 Hz and 165 Hz. Maximum power output of 2.5 mW was obtained under an input excitation of 4.92 m/s2 and 148 Hz. It is to be concluded that applying self-resonating behavior on energy harvesting provides a promising broadband technique.

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Many researchers introduced an array of generators for broadband energy harvesting. The array has been studied in comparison to a single element from this array, but never compared to a single reference harvester with same volume as the whole array. This paper presents a theoretical study of evaluating the performance of the array harvester in comparison to the reference harvester. Power from the reference harvester as well as from the array is analytically calculated. The array is compared to the reference harvester when loaded by their optimal resistances which provide maximum power capability. The comparison is divided into two sections: firstly when the elements of the array are tuned to resonate at matching frequencies and secondly when they are tuned to non-matching resonance frequencies. The comparisons lead to two significant limits of the working bandwidth of the array: the lower and the upper limit. Between the two limits, the power produced from the array is less than the reference harvester, but with a small additional bandwidth. Below the lower limit, the array has no advantage over the reference harvester. Above the upper limit, output power of the array is inconsistent. Hence, design guidelines for the array are provided.

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This paper introduces a passive self-tuning energy harvester by applying self-resonating behavior. Under certain operating conditions, self-resonating systems have the capability to passively adjust their dynamical characteristics until the whole system becomes resonant. A clamped-clamped beam with an attached mass sliding freely with a slight gap showed self-resonating behavior. Under a harmonic input excitation and a well-defined operating regime, the mass moved along the beam thus causing a change in the natural frequency of the structure, and then stopped at the position where the natural frequency matched the excitation frequency, resulting in a significant increase in the vibration amplitude. For harvesting energy, a piezoelectric element was glued at one end of the beam. The operating regime of the self-resonating behavior was found experimentally in the two halves of the beam. In the half containing the piezoelectric element, self-resonating behavior was achieved between 126 Hz and 143 Hz. In the other half, it was achieved between 135 Hz and 165 Hz. Maximum power output of 2.5 mW was obtained under an input excitation of 4.92 m/s2 and 148 Hz. It is to be concluded that applying self-resonating behavior on energy harvesting provides a promising broadband technique. Users without a subscription are not able to see the full content. Please, subscribe or login to access all content.

This study presents theoretical investigations on the effectiveness criteria for piezoelectric energy harvesters (PEHs) under volume constraints. Firstly, the importance of the volume consideration is investigated. The powers of different PEHs of variant volumes are investigated under the same resonance frequency. It is found that the power output is strongly dependent on the volume of the transducer. Secondly, the impact of the mechanical damping, the electrical damping, the volume of motion, the normalized power to the volume, and the applied load resistance on the power output are investigated. The investigations are analyzed to find the optimized conditions of the applied load and the excitation frequency in order to optimize the power output under volume constraints. The proposed procedure for estimating the effectiveness is to compare the performance of the proposed PEHs to a rectangular-shaped PEH of the same volume. An optimized structure for a rectangular-shaped PEH to be used as the reference is investigated. The power output under the optimized conditions is derived. In order to estimate the effectiveness of the proposed PEHs, the average power over a band of frequencies from the proposed structure must be compared to the average power over the same band of frequencies from the optimized reference harvester.