Isogeometric design optimization of multi-piezoelectric harvester arrays: A critical analysis of bandwidth vs. energy maximization

Piezoelectric energy harvesters (PEHs) offer a promising solution for converting ambient vibrations into usable electrical energy; however, their narrow operational bandwidth remains a major limitation under variable excitation conditions. This study introduces a comprehensive optimization framework for multi-piezoelectric energy harvester (MPEH) arrays designed to enhance both energy output and adaptability across diverse environments. Leveraging isogeometric analysis (IGA), we accurately model the mechanical-electrical coupling in both isolated and interconnected PEHs under various circuit configurations. Two key optimization objectives are explored: maximizing harvested energy and maximizing effective bandwidth. The framework is tested using both idealized inputs and real- world vibration data collected from bridges. The results provide consistent evidence that, under the studied conditions, broader bandwidth, while extending the resonance range, does not necessarily lead to improved energy harvesting. Instead, energy-maximizing designs tend to converge toward unified resonance tuning across the array, suggesting that synchronized dynamics are more effective in matching the dominant excitation frequencies. Although this behavior cannot be generalized to all scenarios, the findings challenge the conventional assumption that wider bandwidth inherently equates to better performance, and emphasize the importance of tailoring harvester designs to the spectral characteristics of specific excitation environments.