Multi-directional Energy Harvesting Research Articles

Complex nonlinear dynamics of a multidirectional energy harvester with hybrid transduction

Abstract Mechanical energy harvesting has increasing scientific and technological interests due to novel energetic challenges. A critical issue in classical cantilever-based mechanical energy harvesting systems is the lack of multidirectional energy conversion capabilities and, due to that, deviations from the excitation source can drastically reduce their performance. This limitation has led to the development of energy harvesters with attached pendula, serving as a direction coupling mechanism. Nevertheless, the pendulum structure itself can act as an energy absorber, drastically reducing the harvester performance in certain scenarios. In order to overcome this issue, a hybrid transduction multidirectional pendulum-based energy harvester is proposed integrating a piezoelectric element, to capture energy from the principal direction, and an electromagnetic transducer, to harness rotational energy from the pendulum. This paper presents an in-depth analysis of the hybrid multidirectional pendulum-based energy harvester using a nonlinear dynamics perspective to evaluate the energy harvesting performance. A reduced-order model is proposed to represent the essential characteristics of such systems. A parametric analysis using a nonlinear dynamics perspective is carried out to map the system dynamics and performance. The emergence of complex and rich dynamics is observed, including chaos and hyperchaos. Results reveal the most and least effective combinations of structural parameters in terms of energy conversion. Additionally, the dynamical responses and patterns associated with high performance are identified. These responses are often characterized by a blend of irregular complex behaviors, coupled with a mix of oscillatory and rotational patterns of motion, resulting in wider bandwidth systems.

Pendulum-based hybrid system for multidirectional energy harvesting

Pendulum-based hybrid system for multidirectional energy harvesting

A piezoelectric cantilever-beam-spring-pendulum oscillator for multi-directional vibration energy harvesting

Harvesting energy from environmental vibrations holds significance for powering wireless sensors and transducers. However, the current vibration energy harvesting methods still have room for improvement, especially in the field of low-frequency vibration, where the performance of output voltage is relatively insufficient. This paper proposes a novel piezoelectric energy harvester consisting of a piezoelectric cantilever beam and a spring pendulum in order to address this challenge. Under external excitation, energy exchange is generated between the internal parts of the system, so that the swinging of the pendulum is interchanged with the extension and contraction motion of the spring and the bending motion of the cantilever beam to realize multidirectional energy harvesting. Firstly, the energy equation of system is obtained and the dynamics model of system is derived based on Lagrange's theorem. In addition, the response characteristics of system under harmonic excitation and the effects of different parameters on the system performance are investigated by simulation. With proper parameter selection, the system can produce higher output voltages. Compared to a piezoelectric cantilever-single-pendulum, the proposed structure demonstrates superior performance, especially in low-frequency vibration. The maximum voltage amplitudes in the x- and z-directions were 106.6% and 187.3% of those of the piezoelectric cantilever-single-pendulum, respectively. This paper proves the superior energy harvesting performance of the proposed structure.

Research on the Directional Adaptability of a Self-Adaptive Energy Harvester.

With the continuous development of wireless sensor networks (WSNs), multi-directional energy harvesting technology has received widespread attention from scholars. In order to evaluate the performance of multi-directional energy harvesters, this paper uses a directional self-adaptive piezoelectric energy harvester (DSPEH) as an example, defines the direction of the excitation in three-dimensional space, and studies the influence of excitations on the key parameters of the DSPEH. The rolling angle and pitch angle are used to define complex excitations in three-dimensional space, and the dynamic response of the excitation changes in a single direction and multiple directions is discussed. It is noteworthy that this work presents the concept of "Energy Harvesting Workspace" to describe the working ability of a multi-directional energy harvesting system. The workspace is expressed by the excitation angle and voltage amplitude, and energy harvesting performance is evaluated by the volume-wrapping method and area-covering method. The DSPEH exhibits good directional adaptability in two-dimensional space (rolling direction); in particular, when the mass eccentricity coefficient is r = 0 mm, 100% of the workspace in two-dimensional space is obtained. The total workspace in three-dimensional space depends entirely on the energy output in the pitch direction.

Design and Experimental Investigation of an Ultra-Low Frequency, Low-Intensity, and Multidirectional Piezoelectric Energy Harvester with Liquid as the Energy-Capture Medium

Traditional piezoelectric vibration energy harvesters (PVEHs) usually adopt a rigid energy-capture structure, which can achieve efficient energy harvesting in single-directional, high-frequency, and high-intensity vibration environments. However, efficient harvesting with the use of low-frequency, low-intensity, and multidirectional vibration energy remains a challenge for existing harvesters. To tackle this problem, we proposed a PVEH with liquid as the energy-capture medium. Our previous research verified that this set up can show a good energy harvesting performance under low-frequency, low-intensity, and horizontal multidirectional vibration excitation. In this paper, we further studied the possibility of vertical multidirectional energy harvesting using this device, as well as the influence of several important parameters (rope margin, liquid level height, and floating block shape) on the output performance. The results showed that the proposed PVEH can realize energy harvesting in three-dimensional space and that the output characteristic is adjustable.

Global optimization of excitation directions for scavenging energy based on a cross-jointed L-shape multidirectional piezoelectric energy harvester

Energy harvesting technology can collect energy from environmental vibrations, but it is still challenging because the vibration from an environment is random and the directions vary. In this study, a novel cross-coupled L-shaped vibration piezoelectric energy harvester (CL-VPEH) was proposed to collect energy from different environmental vibration directions. This CL-VPEH consists of a vertical beam and a horizontal beam joint crosswise with two laminated piezoelectric layers. Finite element analysis was performed to study the voltage output and resonant frequency. A simplified lumped mass model of CL-VPEH under excitation from an arbitrary direction was built to describe its working principle and multi-directional energy-harvesting ability. The experimental results demonstrate that the CL-VPEH shows good agreement with the numerical and analytical solutions. The experimental results validate the CL-VPEH’s multidirectional energy harvesting ability. Using the lumped mass model, the performance of the CL-VPEH under every single-direction excitation is investigated. A weak power output area is found with a frequency range of 10 Hz − 25 Hz, which should be avoided in future applications of this kind of multiple-directional excitation energy harvesting.

A Multi-Modal Energy Harvesting Device for Multi-Directional and Low-Frequency Wave Energy

As a kind of sustainable energy source, ocean wave energy has always attracted attention. Because of the characteristics of multi-directions and low-bandwidth, the harvesting of wave energy has always been difficult. To harvest broadband wave energy in multiple directions and improve power generation efficiency, we present a multi-modal energy harvesting device by using a cross beam structure. In this device, the efficient harvesting of multi-frequency vibration energy in multiple directions has been achieved by using the multi-modal characteristics of the structure and the high power generation efficiency of the electric device based on liquid metal. Contrast experiments in multiple directions show that the device not only has the capability of multi-directional energy harvesting but also can work in the sweep range of the full band. Under horizontal excitation, compared with traditional single cantilever structure, the peak power density increased to 2227% and the working frequency band increased to 6.25 times. The experimental results show that the device significantly improves the efficiency of low-bandwidth multi-directional energy harvesting, providing a new method for vibration energy harvesting.

A mosquito-inspired self-adaptive energy harvester for multi-directional vibrations

In this paper, a new concept of direction self-adaptive energy harvesting is put forward for multi-directional vibrations, and a novel direction self-adaptive piezoelectric energy harvester (DSPEH) is explored by introducing a self-adaptive rotation mechanism into the cantilever beam inspired by mosquito wings to validate the new concept. Different from the conventional piezoelectric energy harvester (PEH), the proposed DSPEH has an additional rotation degree of freedom obtained by the rotation unit to realize self-adaptive rotation passively without any manual intervention or power supply. Working principle and theoretical analysis of the proposed DSPEH are conducted and a prototype is fabricated to demonstrate the concept. The energy harvesting performance of the proposed DSPEH is investigated under sweeping frequency and harmonic excitation, and the key parameters affecting the energy harvesting efficiency, such as damping parameters and mass eccentricity coefficient, are analyzed in detail. Simulation and experimental results are in good agreement. Owning to the characteristic of self-adaptive rotation, the most attractive feature of the proposed DSPEH is not simply the ability to realize multi-directional vibration energy harvesting, but the capability of achieving stable and high voltage output levels in multi directions, which is fundamentally distinct from the conventional PEH and other multi-directional energy harvesters. The average output voltage is 30% higher than that of the conventional PEH. Compared with other multi-directional energy harvesters, the proposed DSPEH also has higher energy harvesting efficiency.

Gyroscope-Structured Triboelectric Nanogenerator for Harvesting Multidirectional Ocean Wave Energy.

Wave motion in the ocean can generate plentiful energy, but it is difficult to harvest wave energy for practical use because of the low frequency and random directional characteristics of wave motion. In this paper, a gyroscope-structured triboelectric nanogenerator (GS-TENG) is proposed for harvesting multidirectional ocean wave energy. Its inner and outer generation units can operate independently in different directions, and they all adopt the friction mode of surface contact. While realizing noninterference multidirectional energy harvesting, the power generation area is increased. In the experiments, under acceleration of 6 m/s2 with variations in excitation angle, the GS-TENG can output direct currents of 0.8-3.2 μA, and the open-circuit voltages of the inner and outer generation units can reach 730 and 160 V, respectively. When the devices are networked and placed in the water, the electrical energy generated by the GS-TENGs can enable commercial thermometers to operate normally. The attenuation of direct-current output by the GS-TENG in the experiment of 30 days in water is about 8%, which verifies the good durability of the device in the water environment. Therefore, the GS-TENG has excellent application prospects in the wave energy harvesting field.

A 3D multidirectional piezoelectric energy harvester using rope-driven mechanism for low frequency and ultralow intensity vibration environment

Though numerous piezoelectric vibration energy harvesters (PVEHs) have been designed and investigated to provide power supply for wireless sensors or wearable devices, it remains a challenge for traditional PVEHs to work effectively in an environment of low frequency, low acceleration and multidirectional vibrations. This work presents a PVEH using a low-frequency energy-capturing resonant system formed by a rolling ball in a hemispherical shell and driven by a rope. Due to the symmetry of the sphere, the ball can be excited at multiple directions in 3D space, and the piezoelectric beam can be pulled by the ball through a rope in multiple directions. Thus, the efficient multidirectional energy harvesting under low frequency (<10 Hz) and ultralow intensity (<0.1 g) vibrations could be realized. A mass-spring-damper equivalent model was built to understand the operation mechanism of the proposed PVEH. The results show that the proposed PVEH has a potential to collect energy in any direction in 3D space, and could achieve a good angle bandwidth with 360° for ϕ and 240° for β under the excitation of a = 0.04 g, f = 6.8 Hz with the acceleration defined in the spherical coordinate system. The developed PVEH can generate 6.5 μW under a low-intensity excitation (0.03 g), and the normalized power density can reach 22.63 μW/(cm3 g 2Hz). Moreover, the minimum start-up acceleration analysis of the proposed PVEH indicates that the PVEH can capture multidirectional energy from vibrations as low as 0.01 g. In addition, both simulation and experimental study on rope redundancy and ball mass show that they can be used to adjust the device performance easily without structure re-fabrication. Overall, this study demonstrates a new mechanism that could effectively harvest low frequency, ultralow intensity and multidirectional vibration energy.

Interplay between internal resonance and nonlinear magnetic interaction for multi-directional energy harvesting

To investigate the coupling effects between the internal resonance and nonlinear magnetic interaction for multi-directional energy harvesting, this study proposed a single piezoelectric cantilever–nonlinear magnetic pendulum structure. The proposed structure was mainly composed of a piezoelectric cantilever beam, a magnetic pendulum fixed at the free end of the beam, and a base permanent magnet below the pendulum. Internal resonance was induced by the nonlinear coupling between the pendulum motion in the two-dimensional space and the beam bending vibration at resonance. The magnetic interactions between the magnetic pendulum and the base magnet introduced nonlinearity. The proposed structure was theoretically modeled and experimentally realized to demonstrate its energy harvesting capabilities. Owing to the positive coupling effects between the internal resonance and nonlinearity in the proposed structure under the properly chosen parameters, the experimental results showed that the internal resonance bandwidth of the proposed structure for the x-direction energy harvesting was three times wider than that of the traditional piezoelectric cantilever-pendulum system. Meanwhile, the proposed structure also achieved an additional internal resonant frequency range (3.4 Hz–4.3 Hz) for improving the z-direction energy harvesting performance. The experimental maximum power output of the proposed structure achieved 0.64 mW at 7.5 Hz in the investigated frequency domain.

A twist piezoelectric beam for multi-directional energy harvesting

This paper develops a twist beam for multi-directional energy harvesting using piezoelectric transduction. The working principle of the multi-directional ability is explained by the theory of a pre-twisted beam. A simulation study is performed for concept verification and revealing the potential advantages of the proposed twist-beam vibration energy harvester (VEH). A physical prototype is fabricated and an experimental study is conducted to evaluate the actual performance of the proposed twist-beam VEH for validation. The results show that for the excitation comes from any direction in the plane in parallel with the beam cross-section, the proposed twist-beam VEH can produce a substantial amount of power. The optimal resistance is independent of the excitation direction. Moreover, it is found that the relationships between the output voltage amplitude and the excitation direction are different for the cases around the first and second resonances of the twist-beam VEH. The underlying physics behind this phenomenon is that the dominant motion of the two resonant modes are contrarily different. In addition, the experimental study shows that the first two natural frequencies of the prototyped twist-beam VEH are 22.37 and 41.47 Hz, respectively, which are much closer to each other as compared with those of a conventional plain beam. This feature benefits multi-modal energy harvesting within a targeted frequency range. The prospects regarding further optimization of the proposed twist-beam VEH are discussed.

A novel multimodal and multidirectional energy harvester by asymmetric 3D skeletal frame structures

Designing multimodal and multidirectional energy harvester (EH) topologies with high-strain areas is among the most demanding and critical obstacles encountered in powering small electronics and wireless sensor networks. These deficiencies are highly considerable by utilizing the conventional cantilever beam EHs. In order to overcome these challenges, effective structural design is required. In this paper, two different 3D asymmetric skeletal frame topologies are designed and introduced for energy harvesters. The vibrational behaviors of the proposed structures are investigated using finite element method and compared to corresponding 1D beam and 3D symmetric frame topologies. Furthermore, the electromechanical responses of the aforementioned EHs are obtained showing the advantages in more detail. The results imply that the asymmetric frames can simultaneously solve the main problems of EHs in a successful manner.

Comprehensive Review on Effective Strategies and Key Factors for High Performance Piezoelectric Energy Harvester at Low Frequency

In the past decade, there has been rapid development in piezoelectric energy harvester due to its limited application and low output power. This paper critically reviews the strategies implemented to improve the power density for low-frequency applications. These strategies include piezoelectric material selection as well as optimisations of shape, size and structure. The review also focuses on the recent advances in multi-modal, nonlinear and multi-directional energy harvesting. Based on the comprehensive summary of the normalised power density at 1g acceleration, it was found that most works fell in the second quadrant of low frequency and high power density. The maximum value was around 1mW/mm3 /g. Adding an extension of beam or spring to the conventional piezoelectric beam could enhance the normalised power density dramatically. Additionally, the multi-modal energy harvester exhibits broader bandwidth when its multiple resonance peaks get closer. The findings indicate that the anticipated performance of a piezoelectric harvester can be attained by achieving the trade-off between output power and bandwidth. To achieve high performance at low frequency, the following factors are essential: excellent material characteristics optimised geometry for high strain energy density, excellent flexibility, high excitation amplitude and broad bandwidth.

A cross-coupled dual-beam for multi-directional energy harvesting from vortex induced vibrations

This study proposes a cross-coupled dual-beam structure for energy harvesting from vortex-induced vibrations (VIV) induced by wind flows in different directions. A series of wind tunnel tests are conducted to investigate the performance of the proposed energy harvester subjected to the wind load with various speeds and directions. The upper and bottom piezoelectric beams can generate a maximum power output of 6.77 μW and 56.64 μW, respectively. The dominant operation frequencies in different directions are different which indicates a potential broadband capability. A parametric study is performed to reveal the effect of the dimension of the bluff body on the performance of the proposed energy harvester.

Vibration of mechanically-assembled 3D microstructures formed by compressive buckling

Micro-electromechanical systems (MEMS) that rely on structural vibrations have many important applications, ranging from oscillators and actuators, to energy harvesters and vehicles for measurement of mechanical properties. Conventional MEMS, however, mostly utilize two-dimensional (2D) vibrational modes, thereby imposing certain limitations that are not present in 3D designs (e.g., multi-directional energy harvesting). 3D vibrational micro-platforms assembled through the techniques of controlled compressive buckling are promising because of their complex 3D architectures and the ability to tune their vibrational behavior (e.g., natural frequencies and modes) by reversibly changing their dimensions by deforming their soft, elastomeric substrates. A clear understanding of such strain-dependent vibration behavior is essential for their practical applications. Here, we present a study on the linear and nonlinear vibration of such 3D mesostructures through analytical modeling, finite element analysis (FEA) and experiment. An analytical solution is obtained for the vibration mode and linear natural frequency of a buckled ribbon, indicating a mode change as the static deflection amplitude increases. The model also yields a scaling law for linear natural frequency that can be extended to general, complex 3D geometries, as validated by FEA and experiment. In the regime of nonlinear vibration, FEA suggests that an increase of amplitude of external loading represents an effective means to enhance the bandwidth. The results also uncover a reduced nonlinearity of vibration as the static deflection amplitude of the 3D structures increases. The developed analytical model can be used in the development of new 3D vibrational micro-platforms, for example, to enable simultaneous measurement of diverse mechanical properties (density, modulus, viscosity etc.) of thin films and biomaterials.

Analytical and experimental investigation of flexible longitudinal zigzag structures for enhanced multi-directional energy harvesting

This paper makes a complete investigation of flexible longitudinal zigzag (FLZ) energy harvesters for the purpose of enhancing energy harvesting from low-frequency and low-amplitude excitation. A general theoretical model of the FLZ energy harvesters with large joint block mass is proposed. In order to verify the accuracy of the theoretical model, both experimental results and finite element analysis via ANSYS software are presented. Results show that the theoretical model can successfully predict the dynamic response and the output power of the FLZ energy harvesters. Both theoretical and experimental results demonstrate that the proposed energy harvesters can effectively harvest vibration energy even when the direction of excitation relative to the harvester varies from 0° to 90°. Under the low excitation level of 0.18 m s−2, the experimental maximum output power of a FLZ energy harvester with five beams was found to be 1.016 mW. Finally, the results indicate that the proposed structure is capable of effective energy conversion across a large range of excitation angles at low-frequency and low-amplitude excitations, which makes it suitable for a wide range of working conditions.

Modeling and analysis of piezoelectric cantilever-pendulum system for multi-directional energy harvesting

Piezoelectric cantilevers are widely used in vibration energy harvesting. Simple cantilever-based harvesters are mostly unidirectional. In this article, we develop a cantilever-pendulum system that can harvest vibratory energy of excitations from an arbitrary direction. The new design consists of a traditional piezoelectric cantilever with a pendulum attached to the tip. It is shown analytically and experimentally that with proper parametric combination this system can induce modal energy interchange between beam vibration and pendulum motions due to 1:2 internal resonance, which ultimately yields multi-directional energy harvesting by a single cantilever. The underlying mechanisms of this design are analyzed in detail.

Multi-directional energy harvesting by piezoelectric cantilever-pendulum with internal resonance

This letter reports a piezoelectric cantilever-pendulum design for multi-directional energy harvesting. A pendulum is attached to the tip of a piezoelectric cantilever-type energy harvester. This design aims at taking advantage of the nonlinear coupling between the pendulum motion in 3-dimensional space and the beam bending vibration at resonances. Experimental studies indicate that, under properly chosen parameters, 1:2 internal resonance can be induced, which enables the multi-directional energy harvesting with a single cantilever. The advantages of the design with respect to traditional piezoelectric cantilever are examined.

A Novel Soft Metal‐Polymer Composite for Multidirectional Pressure Energy Harvesting

DOI: 10.1002/aenm.201400024 bubbles remain trapped inside the sponge by means of solving sacrifi cing particles. The triboelectric phenomenon is promoted by periodic contact between miniature pieces of copper microwires encapsulated in a polydimethylsiloxane (PDMS) sponge. The strong advantages of this work are its simplicity and the cost effectiveness of the process, which makes it suitable for mass manufacturing and fabrication with easy-access facilities. Moreover, because the prototypes are made out of a mixture, the building process can be integrated with other fabrication methods in a broad range of scales. The possibility of trapping conductive wires in rubber opens the way to a new generation of energy harvesting devices, targeting all application fi elds where a fl exible and soft material is used and/or needed. Moreover the fabrication process is not constrained to planar technology but fully 3D shapes can be built. The wired-sponge polymer could be tailored for consumer goods used in everyday life, for which energy harvesting mechanisms have not been considered to date, such as some parts of wheels, mattresses, toys and playgrounds, dance fl oors, etc. It is noteworthy that this approach could be addressed in advanced robotic systems where the body of the robot is built with soft materials via a bioinspired design paradigm. [ 10 ]