The Piezoelectric Energy-Harvesting Ceiling: A Bound from Coupling, Stress, and Dielectric Breakdown

The maximum electrical energy convertible per mechanical cycle per unit volume of a piezoelectric material is derived from the linear constitutive equations as u_max = (1/2) d g sigma_allow^2, with sigma_allow set by the smaller of the usable stress limit and the stress generating a breakdown field. Evaluated from published constants, the ceilings are 40.66 kJ/m3 per cycle for PMN-PT, 33.73 kJ/m3 for PZT-5H, 12.30 kJ/m3 for PVDF and 0.66 kJ/m3 for quartz. For all four classes the mechanical stress limit binds first and dielectric breakdown is redundant, by a factor of 5.20 to 16.77 in stress.