Output Performance Of Energy Harvester Research Articles

Piezoelectric energy harvesting systems using mechanical tuning techniques.

In this review, we review the recent research progress and results of piezoelectric energy harvesters applying mechanical tuning techniques in terms of literature background, methods of mechanical tuning, and practical applications. In the past few decades, piezoelectric energy harvesting techniques and mechanical tuning techniques have received increasing attention and made significant progress. Mechanical-tuning techniques are those that allow the resonant vibration energy harvesters the mechanical resonant frequency values to be adjusted to coincide with the excitation frequency. According to the different tuning methods, this review classifies mechanical-tuning techniques based on magnetic action, different piezoelectric materials, axial load, the variable center of gravity, various stresses, and self-tuning and summarizes the corresponding research results, comparing the differences between the same methods. In addition, the current application of the mechanical-tuning techniques is introduced, and the future development of mechanical tuning techniques is analyzed, facilitating the reader to better understand how mechanical-tuning techniques can improve the output performance of energy harvesters.

Energy harvesting from gravity-induced deformation of rotating shaft for long-term monitoring of rotating machinery

Energy harvesting from rotating machines for self-powered sensor networks has attracted increasing attentions in the last decade. In this work, an energy harvester employing piezoelectric stacks for rotating machinery is proposed, which cannot only harvest kinetic energy from bending deformation of rotating shaft but also has the capability of rotor fault detection. The structure and working concept of the energy harvester are initially presented. Afterward, a theoretical model for the energy harvester is established to clarify its output characteristics. Then, vibration tests under different rotating speeds are carried out with a prototype mounted on a rotor test rig. The effects of electrical connections of piezoelectric stacks, rotor geometry, energy harvester location, and fastener preload on the output performance of energy harvester are evaluated. Finally, the applications of powering a scientific calculator and detecting typical faults of rotor systems including rotor crack and rub impact faults are demonstrated. Apart from fault detection capability, the proposed energy harvester has the advantages of long lifespan and causing little interference with the rotational motion, which overcomes the inherent deficiencies of commonly studied beam-type energy harvesters and manifest the potential of proposed energy harvester for the long-term condition monitoring of rotating machines.

Piezoelectric energy harvester for rolling bearings with capability of self-powered condition monitoring

Rotational energy harvesting for powering low-power electronic devices and wireless sensors has attracted increasing attention in recent years. This paper proposes an energy harvester to scavenge rotational energy from rotating machines by installing an arc-shaped piezoelectric sheet between the outer race of rolling bearing and bearing pedestal. The proposed piezoelectric energy harvester cannot only supply power to sensors but also has the capability of bearing fault detection. The structural design and working principle are initially demonstrated, where an electromechanical coupling model is developed to explain the working principle of energy harvester. Then, a prototype of the energy harvester is fabricated and mounted on a rotor test rig, on which experiments are carried out to evaluate the output performance of energy harvester. The effects of rotating speed, rotor weight, shaft span and matched resistances on energy harvester performance are comprehensively evaluated. It is revealed that a single piezoelectric section of the energy harvester can generate RMS voltage of 25 V, and RMS power of 60–131 μW under the rotating speed range from 600 to 1200 r/min. Finally, the applications of the proposed energy harvester for bearing fault detection and self-powered wireless sensing are demonstrated to manifest its capability of bearing condition monitoring.

Impacts of stopper type and material on the broadband characteristics and performance of energy harvesters

Exploiting nonlinear impact force induced by a stopper has been widely proposed to broaden the bandwidth of energy harvesters from mechanical vibrations, but the previous studies just directly employed the stopper and did not consider the effect of inherent factors of the stopper like its type and material. This letter devotes to efficiently utilize the stopper to broaden the resonance region of the energy harvester mainly from perspective of stopper type and material. Four stopper types are taken into account including the stopper with rigid and soft materials and the spring stopper. Experimental results show that two sides followed stopper type can greatly increase the bandwidth which is much better than other considered types. Importantly, using the stopper with soft materials or the spring stopper is followed by a wider resonance region and a higher output voltage of the energy harvester compared to that with rigid materials. Moreover, agreements between theoretical predictions and experimental measurements indicate the feasibility of using the trilinear spring model to describe the nonlinear impact force which is determined by stopper type and material. The present study delivers to essentially improve the output performance of energy harvesters by selecting the efficient stopper.

Motion characteristics and output voltage analysis of micro-vibration energy harvester based on diamagnetic levitation

In this paper, the force analysis and output performance of the micro-vibration energy harvester are elaborated. The force of the floating magnet in the magnetic field of the lifting magnet is firstly analyzed. Using COMSOL™, the change of magnetic force exerted on the floating magnet versus the vertical distance and the horizontal eccentric distance is obtained for different lifting magnets of a cylinder, a ring and an inner cylinder plus an outer ring, respectively. When the distance between the lifting and floating magnets ranges from 7.3 to 8.1 mm, the change rate of the magnetic force versus the vertical distance for the inner cylinder plus outer ring structure is the smallest, whose value is 619 µN/mm. In other words, if the inner cylinder plus outer ring structure is used as the lifting magnet, the vibration space of the floating magnet is the largest, which is 8 and 7.6 % larger than the cylinder and ring lifting magnets, respectively. The horizontal restoring forces of the three structures are substantially equal to each other at the horizontal eccentric distance of 4 mm, which is around 860 µN. Then the equilibrium position change of the floating magnet is discussed when the energy harvester is in an inclined position. Finally, by the analysis of the vibration model, the output performances of the energy harvester are comparatively calculated under the vertical and inclined positions. At the natural frequency of 6.93 Hz, the maximum power of 66.7 µW is generated.

Analysis of Output Performance for Piezoelectric Double Mode Energy Harvester

The output performance of piezoelectric double mode energy harvester is studied, which is provided with a dynamic magnifier consisting of a spring-mass system placed between the piezoelectric element and the moving base. The theory governing the operation of the energy harvester with dynamic magnifier is developed using the Lagrangian dynamic approach, Numerical examples are presented to illustrate the output performance of the energy harvester in comparison with the conventional energy harvester, the results show that with proper selection of the design parameters of the magnifier, the harvested power can be dramatically enhanced and the effective bandwidth of the harvester can be improved.