Synchronicity and pure bending of bimorphs: a new approach to piezoelectric energy harvesting

Abstract

Kinetic energy harvesting with piezoelectric bimorphs has attracted considerable research interest in recent years. Many works have been dedicated to the modelling and optimisation of the cantilevered geometry to increase power density, bandwidth, etc. The increased efficiency coming from the use of trapezoidal beams has been recognised, but little has been done to produce the same uniform strain within the most commonly available rectangular beams. This work proposes a new approach via a smart compliant structure which permits to deform a set of bimorphs in pure bending. Furthermore, since the deflections are synchronous, the power signals produced are in phase and power conditioning is simplified and made more efficient. The kinematic requirements for uniform strain are discussed, the novel structure is proposed and modelled with finite elements, a prototype is presented and characterised to support the modelling. The proposed structure induces almost perfectly uniform strain in the piezoelectric beams for all useful rotation angles, demonstrating that, compared to a traditional cantilever, twice as many charges can be produced when the same maximum strain is applied to the material. Synchronicity is also experimentally verified for the prototype, as power signals resulting from impact excitation are observed to be in phase. The principle of synchronous pure bending via helper structures can be applied in general to increase the performance of piezoelectric energy harvesters.

Harvesting Energy from Planetary Gear Using Piezoelectric Material

“…The principle of rotational piezoelectric energy harvesting operation is based on the PZT plucking for excitation, which results in PZT bending, vibration, or pressing, and thus voltage is generated. Researchers have used different excitation elements in rotational piezoelectric energy harvestings, such as mass [28,31], magnetic [33][34][35] centrifugal force [36,37], gravitational force [38][39][40], and gear teeth force [41,42] or a compilation of these elements [26,43,44]. They have also applied these elements to widen the broadband range [14,45,46] or for frequency up-conversion [6,43,47] and rotational frequency, which is considered to be low in some cases compared to piezoelectric resonant frequency.…”

Nonlinear Dynamic Analysis of a Piezoelectric Energy Harvester with Mechanical Plucking Mechanism

“…Subsequently, the oscillator undergoes free vibrations, which are then converted into electrical energy. The main challenges in designing such mechanical plucking energy harvesters arise from the contact mechanism between the energy-harvesting oscillator and the external plectrum, involving complex dynamic interactions [31][32][33][34][35][36][37]. Mathematical models based on Hertzian contact theory [36][37][38][39] and methodologies utilizing finite element analysis or other numerical methods have been employed to predict the complex dynamic behaviors of the mechanical plucking energy harvesters, including strong dynamic interferences and multiple or periodic plucking effects.…”

Global optimisation approach for designing high-efficiency piezoelectric beam-based energy harvesting devices

“…This paper proposes a new general global multidimensional optimisation algorithm for optimising the performance of a PE multi-beam gravity-based device for EH in wind applications for powering wireless sensors and data transmission. While arrays adopting plucking mechanisms have been addressed in the literature [29,40] this device adopts a piezoelectric array structure along with a plucking mechanism to illustrate how a new algorithm improves the response of well-known energy harvesting designs. Section 2 describes the framework of the proposed optimisation algorithm.…”