Abstract
This paper deals with analytical modelling of piezoelectric energy harvesting systems for generating useful electricity from ambient vibrations and comparing the usefulness of materials commonly used in designing such harvesters for energy harvesting applications. The kinetic energy harvesters have the potential to be used as an autonomous source of energy for wireless applications. Here in this paper, the considered energy harvesting device is designed as a piezoelectric cantilever beam with different piezoelectric materials in both bimorph and unimorph configurations. For both these configurations a single degree-of-freedom model of a kinematically excited cantilever with a full and partial electrode length respecting the dimensions of added tip mass is derived. The analytical model is based on Euler-Bernoulli beam theory and its output is successfully verified with available experimental results of piezoelectric energy harvesters in three different configurations. The electrical output of the derived model for the three different materials (PZT-5A, PZZN-PLZT and PVDF) and design configurations is in accordance with lab measurements which are presented in the paper. Therefore, this model can be used for predicting the amount of harvested power in a particular vibratory environment. Finally, the derived analytical model was used to compare the energy harvesting effectiveness of the three considered materials for both simple harmonic excitation and random vibrations of the corresponding harvesters. The comparison revealed that both PZT-5A and PZZN-PLZT are an excellent choice for energy harvesting purposes thanks to high electrical power output, whereas PVDF should be used only for sensing applications due to low harvested electrical power output.
Highlights
Energy harvesting is more than 20 years a hot topic in the field of wireless sensing [1]since it allows for converting various energy types from ambient sources into an electrical one
Piezoelectric kinetic energy harvesters in the form of a vibrating multilayer structure with piezoelectric layers [3] are commonly used in vibration energy harvesting applications, where the structure is excited by an ambient source of vibrations
The derivation of a coupled electromechanical model was published several times, e.g., [19,20,21,22,23], here, we show the effect of chosen mode shape function which is used in reducing the beam model into single DOF model
Summary
Energy harvesting is more than 20 years a hot topic in the field of wireless sensing [1]. As a non-toxic alternative, new lead-free piezoceramic materials have been developed which are based on multifunctional Perovskite [13] or structured layers made of Barium and Titanate [14] Besides these piezoceramic materials which are inherently very brittle and stiff, there are more flexible materials such as macro-fiber composites which are very promising in the area of strain energy harvesting [15] and piezopolymers which are summarized in review paper [16]. Derivation of an analytical beam model of a kinematically excited piezoelectric cantilever in both bimorph/unimorph configurations which respects the dimensions of used tip mass This beam model is subsequently reduced to a single degree-of-freedom (DOF) system using the first mode shape function. The main aim of this paper is to provide a methodology based on a verified model that can be used to compare the effectivity of materials commonly used in energy harvesting applications
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