Present work shows waste energy (thermal/mechanical) harvesting and storage capacity in bulk lead-free ferroelectric 0.6Ba(Zr0.2Ti0.8)O3-0.4(Ba0.7Ca0.3)TiO3 (0.6BZT-0.4BCT) ceramics. The thermal energy harvesting is obtained by employing the Olsen cycle under different stress biasing, whereas mechanical energy harvesting calculated using the thermo-mechanical cycle at various temperature biasing. To estimate the energy harvesting polarization-electric field loops were measured as a function of stress and temperatures. The maximum thermal energy harvesting is obtained equal to 158 kJ/m3 when the Olsen cycle operated as 25-81 °C (at contact stress of 5 MPa) and 0.25-2 kV/mm. On the other hand, maximum mechanical energy harvesting is calculated as 158 kJ/m3 when the cycle operated as 5-160 MPa (at a constant temperature of 25 °C) and 0.25-2 kV/mm. It is found that the stress and temperature biasing are not beneficial for thermal and mechanical energy harvesting. Further, a hybrid cycle, where both stress and temperature are varied, is also studied to obtain enhanced energy harvesting. The improved energy conversion potential is found as 221 kJ/m3 when the cycle operated as 25-81 °C, 5-160 MPa and 0.25-2 kV/mm. The energy storage density varies from 43 to 66 kJ/m3 (increase in temperature: 25-81 °C) and 43 to 80 kJ/m3 (increase in stress: 5 to 160 MPa). Also, the pre-stress can be easily implemented on the materials, which improve energy storage density almost 100% by domain pining and ferroelastic switching. The results show that stress confinement can be an effective way to enhance energy storage.
Efficient Power Management Circuit: Thermal Energy Harvesting to Above-IC Microbattery Energy Storage
