Optimized piezoelectric energy harvester for hydrogen generation from automotive vibration

Abstract

Abstract This study presents the design and optimization of a piezoelectric vibration energy harvesting system integrated with electrolysis-based hydrogen production. The suggested harvester is integrated into an automotive engine block and designed as a bimorph cantilever beam, experiencing authentic low-frequency vibrations from the engine at primary working frequencies of 37 Hz and 52 Hz. Finite element analysis (FEA) is performed in COMSOL Multiphysics 6.1 to assess the electromechanical response of the system under dynamic excitation conditions. Three piezoelectric materials PZT-5 H, PVDF, and improved PVDF (PVDF-E) are comparably analyzed under uniform working circumstances to assess their viability for automobile vibration energy harvesting applications. Structural optimization is conducted with BOBYQA and Monte Carlo techniques to enhance harvested electrical output while adhering to geometric and frequency limitations. The numerical model is evaluated against experimental data from the literature, exhibiting a maximum error of 4.47%, hence affirming its trustworthiness. The results suggest that both material characteristics and frequency adjustment substantially influence electromechanical performance. Among the examined materials, PZT-5H obtains the maximum output power of 1.2507 mW at an ideal load resistance of 10 kΩ due to its better piezoelectric coupling coefficient. PVDF and PVDF-E demonstrate reduced power output but greater mechanical flexibility and durability, making them more appropriate for high-stress and flexible applications, whereas PZT-5 H is chosen for low-stress, high-power-density systems. The captured electrical energy is immediately utilized for hydrogen synthesis using a simplified post-processing electrochemical estimate derived from Faraday’s law, as opposed to a fully integrated Multiphysics electrochemical simulation. Over an operational duration of 600 s, the system generates roughly $$\:1.5123\times\:{10}^{-6}\:\:$$ mol of hydrogen, equating to an energy content of 0.363 J and an equivalent gasoline volume of $$\:1.134\times\:10{-}^{11}$$ L. This study reveals a unique hybrid piezoelectric–electrochemical energy conversion framework that permits direct translation of ambient vibration energy into storable chemical energy, giving a scalable approach for self-powered automobile and hybrid energy systems.