Studies regarding concurrent wind-flow and base-motion energy harvesting have drawn increasing attention in recent years. However, for conventional wind energy harvesters under such dual excitations, the base-excited inertial vibration and flow-induced aeroelastic vibration supplement with each other only within a narrow range of frequency near the resonance. Within this range, aeroelastic vibration frequency is locked into the base vibration frequency where the two sources are concurrently contributing to power generation; while the concurrent feature is lost outside this range. Internal resonance in multimodal systems has been utilized in recent years for efficiency improvement in pure base vibration energy harvesters. The merit comes from the fact that energy can be pumped from other modes to the power generation bandwidth, broadening the bandwidth toward both lower and higher frequency regions. In this paper, a broadband galloping-based aeroelastic energy harvester with internal resonance is proposed for the purpose of efficiency enhancement in concurrent wind and base vibration energy harvesting. Two-to-one internal resonance is aroused by arranging two sets of magnets symmetrically at the beam connection. Numerical solutions are calculated for the fully coupled aero-electro-mechanical model. A significantly widened lock-in bandwidth with multiple power peaks is achieved for effective concurrent wind and vibration energy harvesting.
A compact bistable galloping oscillator is proposed for enhanced power generation from concurrent wind and base vibration. The harvester consists of a D-shaped bluff body attached to a piezoelectric cantilever. Repulsive magnetic interaction is introduced between the bluff body and a fixed windward support to bring nonlinear bistability. An aeroelectro- mechanically coupled model is established and experimentally validated. Both experimental measurements and model predictions demonstrate that the synchronization bandwidth for efficient energy harvesting from concurrent wind and base vibration can be substantially extended.
Concurrent energy harvesting by simultaneously harvesting wind and base vibration energy has received very little attention until recently. Yet a major problem with a traditional wind energy harvester under concurrent loadings is the dramatically reduced efficiency when the base vibration frequency deviates from the resonance. This paper investigates a novel design to enhance concurrent energy harvesting from concurrent base vibrations and wind flows. A piecewiselinear aeroelastic energy harvester is integrated with a stopper which can also work as a complementary generator. In order to fast and accurately characterize the response of the harvester, exact analytical solutions are derived based on the harmonic balance analysis and method of averaging. The interaction of the two coexisting excitation frequencies as well as the impact effects between the aeroelastic energy harvester and the stopper are fully considered. Closed-form expressions for both mechanical and electrical responses are presented and validated numerically. Results show that a greatly widened bandwidth is achieved with the proposed design where both aeroelastic and base vibratory energy are effectively harnessed. The analytical solutions are essential to fully understand the characteristics of this new kind of broadband concurrent energy harvester, and serve as a guideline for efficient performance evaluation and parameter optimization.
Galloping phenomenon has attracted extensive research attention for small-scale wind energy harvesting. In the reported literature, the dynamics and harvested power of a galloping-based energy harvesting system are usually evaluated with a resistive AC load; these characteristics might shift when a practical harvesting interface circuit is connected for extracting useful DC power. In the family of piezoelectric energy harvesting interface circuits, synchronized switching harvesting on inductor (SSHI) has demonstrated its advantage for enhancing the harvested power from existing base vibrations. This paper investigates the harvesting capability of a galloping-based wind energy harvester using SSHI interfaces, with a focus on comparing the performances of Series SSHI (S-SSHI) and Parallel SSHI (P-SSHI) with that of a standard DC interface, in terms of power at various wind speeds. The prototyped galloping-based piezoelectric energy harvester (GPEH) comprises a piezoelectric cantilever attached with a square-sectioned bluff body made of foam. Equivalent circuit model (ECM) of the GPEH is established and system-level circuit simulations with SSHI and standard interfaces are performed and validated with wind tunnel tests. The benefits of SSHI compared to standard circuit become more significant when the wind speed gets higher; while SSHI circuits lose the benefits at small wind speeds. In both experiment and simulation, the superiority of P-SSHI is confirmed while S-SSHI demands further investigation. The power output is increased by 43.75% with P-SSHI compared to the standard circuit at a wind speed of 6m/s.
Aeroelastic instabilities have been frequently exploited for energy harvesting purpose to power standalone electronic systems, such as wireless sensors. Meanwhile, various energy harvesting interface circuits, such as synchronized charge extraction (SCE) and synchronized switching harvesting on inductor (SSHI), have been widely pursued in the literature for efficiency enhancement of energy harvesting from existing base vibrations. These interfaces, however, have not been applied for aeroelastic energy harvesting. This paper investigates the feasibility of the SCE interface in galloping-based piezoelectric energy harvesting, with a focus on its benefit for performance improvement and influence on the galloping dynamics in different electromechanical coupling regimes. A galloping-based piezoelectric energy harvester (GPEH) is prototyped with an aluminum cantilever bonded with a piezoelectric sheet. Wind tunnel test is conducted with a simple electrical interface composed of a resistive load. Circuit simulation is performed with equivalent circuit representation of the GPEH system and confirmed by experimental results. Consequently, a self-powered SCE interface is implemented with the capability of self peak-detecting and switching. Circuit simulation for various electromechanical coupling cases shows that the harvested power with SCE interface for GPEH is independent of the electrical load, similar to that for a vibration-based piezoelectric energy harvester (VPEH). The SCE interface outperforms the standard interface if the electromechanical coupling is weak, and requires much less piezoelectric material to achieve the maximum power output. Moreover, influence of electromechanical coupling on the dynamics of GPEH with SCE is found sensitive to the wind speed.