Charging supercapacitors by nanofibrous and ceramic piezoelectric harvesters: experimental and modeling analysis

Piezoelectric materials enable the transformation of mechanical stress into electrical energy. The most widely used piezoelectric technology is lead zirconate titanate (PZT), which provides good performance but suffers from flexibility due to its brittleness. Recently, polymer-based piezoelectric matrices, such as nanofibrous (NF) electrospun poly(vinylidene fluoride), have gained attention because they enable integration into wearable devices thanks to their flexibility. Piezoelectric nanogenerators (PENGs) can be assembled using both PZT and NF technologies to harvest energy that can be stored in an Energy Storage System (ESS). Owing to their rapid response and long lifetime, supercapacitors (SCs) represent a suitable ESS to collect the energy from PENGs. The aim of this work is to compare the results from two PENG–SC systems, one featuring a PZT device and the other incorporating an assembled NF device, both of which charge the SC with the energy generated under PENG compression. The NF–SC system stored about 210 mJ and delivered 19 mW in comparison with the 110 mJ and 17 mW of the PZT–SC system. In addition, we present and validate a newly developed model to facilitate PENG-SC design for scale-up studies.