A Novel Centrally Symmetric Spiral-Nested Piezoelectric Energy Harvesting System and Its Management Circuit

To realize high power density, low-frequency, multi-directional energy harvesting and efficient energy storage management, a piezoelectric energy harvesting system comprising a centrally symmetric spiral-nested piezoelectric energy harvester (CSS-PEH) and an energy management circuit is proposed in this work. The harvester features a doubly clamped outer beam and a nested dual-spiral inner beam, while the management circuit integrates an SP-PSSHI rectification circuit, BQ25570 IC, and supercapacitor. A three-degree-of-freedom (3-DOF) lumped parameter model and an electromechanical coupling model are established to analyze frequency response and output characteristics. Measured results show that the CSS-PHE has resonant frequencies at 12.8 Hz and 17.2 Hz, with corresponding open-circuit voltages of 73.5 V and 38.7 V. Meanwhile, the SP-PSSHI rectified series circuit achieved maximum output powers of 6.23 mW with the normalized power density (NPD) of 32.4 μW∙g<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup>∙mm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup>; the SP-PSSHI rectified parallel circuit delivered maximum output power of 3.21 mW with the NPD of 21.6 μW∙g<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup>∙mm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup>. The energy management circuit enables supercapacitor charging up to 4.05 V while maintaining stable 3.3V DC output. Furthermore, the CSS-PEH demonstrates multi-directional energy harvesting capability. Therefore, this piezoelectric energy harvesting system provides stable power supply solutions for many fields, such as intelligent transportation energy harvesting, wireless sensor networks, and so on.