Naslov
Design of Miniaturized Wearable Broadband Energy Harvesters

Autori
Gljušćić, Petar

Vrsta, podvrsta i kategorija rada
Ocjenski radovi, doktorska disertacija

Fakultet
Tehnički fakultet

Mjesto
Rijeka

Datum
28.04

Godina
2022

Stranica
150

Mentor
Zelenika, Saša

Ključne riječi
piezoelectric energy harvesters ; wearables ; DoE ; frequency up-conversion ; optimized geometry ; FE numerical modelling ; experimental assessment

Sažetak
Energy harvesting (EH) is the process of collecting low-level ambient energy and converting it into electrical energy to be used for powering miniaturized autonomous devices, wearable electronics or Internet-of-Things components. The use of kinetic energy, converted into electrical energy via the piezoelectric principle, is of special interest in this frame. The main drawback of piezoelectric EH devices is the narrow area of optimal operation around the eigenfrequency of a specific device. The voltage levels achieved within this area are high, but they rapidly decrease with the variation of the excitation frequency. This is especially important in wearable applications, where the excitation frequency from human motion varies randomly. Based on a thorough analysis of the state-of-the- art in energy harvesting, with a particular focus on wearable applications, an innovative design approach, which comprises the segmentation of a conventional energy harvester into optimized segments, excited by plucking their free ends, is proposed in this work. An original method of optimization is utilized here, combining the DoE methodology and a complex experimentally validated numerical model. Several novel miniaturized energy harvesters with optimized shapes are suggested, produced and experimentally tested, while keeping in consideration, in this frame, the generally neglected fatigue strength. The experimental results have shown a good match with the numerical data. The results show that a significant increase in performance, i.e., up to ~ 500%, can be achieved by using the herein proposed design approach, compared to a conventional device. What is more, the proposed optimized devices are capable of providing enough power for a compact wearable device aimed for biomedical applications, requiring ~ 5 mW of power, also suggested in this work. An extensive DoE-based experimental study of plucking parameters is also carried out, providing a deeper insight into the complex mechanism of impact excitation, as well as valuable guidelines for plectrum design, using additive manufacturing. The concept of the design of a wearable watch-like device is also developed, capable of generating an estimated ~ 270 mW of maximum power as well as ~ 6.8 mW of average power. The performed research provides a significant scientific contribution to the field of kinetic EH by proposing an optimized solution to the aforementioned problem, based upon an original framework of application of state-of-the-art approaches. The results obtained on optimized design configurations are validated and verified by using numerical and experimental methods.

Izvorni jezik
Engleski

Znanstvena područja
Strojarstvo, Temeljne tehničke znanosti, Interdisciplinarne tehničke znanosti

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