Acoustic energy harvesting with emphasis on low frequencies

• Κύριος συγγραφέας: Παπαδάκος, Χαράλαμπος
• Άλλοι συγγραφείς: Μουρτζόπουλος, Ιωάννης
• Μορφή: Thesis
• Γλώσσα: English
• Έκδοση: 2018
• Θέματα: Acoustic energy harvesting; Electroacoustic transducers; Piezoelectric transducers; Συλλογή ακουστικής ενέργειας; Πιεζοηλεκτρικοί μετατροπείς; Ηλεκτροακουστικοί μετατροπείς; 621.042

This work presents novel findings and results in the field of acoustic energy harvesting with emphasis on low frequencies. At the beginning of this work, ambient acoustic power density is estimated and a comparison between the potential of sound and that of other ambient energy sources exploited for energy harvesting is performed. The interest in AEH is justified and the corresponding state of the art is presented. Prior the analysis, the motivation of this work is described in detail and the main objectives are set. The analysis considers the piezoelectric transducer to be the transduction element for this study. Initially, it provides a lumped element model (LEM) for evaluating the AEH potential of such transducers directly coupled to the sound field and utilizing such a framework, it demonstrates the inefficiency of such approach for AEH of practical interest. Subsequently, a novel method and device is proposed for improving the coupling of such transducers and the sound field and enhancing the potential of AEH. For this case of indirect coupling, the analysis provides a modified LEM compared to the direct coupling case. At a next level, a novel biomimetic device that mimics the function and the structure of the human middle ear is proposed for implementing such indirect coupling of piezoelectric transducers and the sound filed for AEH. Such device can potentially ensure sufficient electric power for driving low power applications in the range nW - mW. Next, in order to provide an AEH proof - of - concept case, this study focuses on loudspeaker enclosures since the sound pressure level (SPL) therein can be significantly high during operation, as it is shown via tests performed for realistic 3D virtual prototype models, which are validated also via measurements performed inside real - life loudspeaker systems. Specific examples of 3D virtual prototype models of loudspeaker enclosures are combined with the proposed biomimetic device and a piezoelectric transducer and are tested for evaluating the in - Box AEH potential. The test results indicate that the proposed biomimetic device may operate as a harvester and the same time as a passive absorber. These test results further show that the output voltage of the proposed AEH can be adequate for charging a rechargeable battery or for driving an electronic load, while the electric power delivered to a load resistance may be up to units of mW. These results presented in this work are discussed in detail and the framework for future work and applications is presented.