Piezoelectric materials and its flexible composite have garnered interest owing to their straightforward synthesis, mechanical flexibility, and ease of customization, hence can be for utilized in energy applications such as energy storage and energy harvesting. Herein, the paper projects the aspects of lead-free ternary piezoelectric Barium Calcium Tin Titanate (BCST) as a future of energy storage materials. BCST synthesis involves by yocto energy () sintering. The Retiveld refinement studies confirms tetragonal structure and an average grain size of 0.95 µm is found by SEM. XPS verifies the presence of Ca and Sn within BT matrix. A colossal dielectric constant of 35,291 at Curie temperature is noted. The ferroelectricity of BCST ceramic is confirmed by polarization versus electric field hysteresis loops. The BCST demonstrated a promising energy storage efficiency of 70.2 %. For energy harvesting application, the PVDF/BCST flexible piezoelectric nanogenerator (PENG) is fabricated. The Fourier Transform Infrared analysis reveals that the flexible composite demonstrates an elevated β-fraction (79.02 %) in comparison to the pure PVDF (23.2 %). The flexible PENGs exhibited an open-circuit voltage of 5.5Vpp and a short-circuit current of 0.6 µA at a force of 3 N. Thus, BCST and its composite is future material to be utilized in energy related applications.