Thermo-mechanical energy harvesting and storage analysis in 0.6BZT-0.4BCT ceramics

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.

Giant energy harvesting potential in (100)-oriented 0.68PbMg1/3Nb2/3O3–0.32PbTiO3 with Pb(Zr0.3Ti0.7)O3/PbOx buffer layer and (001)-oriented 0.67PbMg1/3Nb2/3O3–0.33PbTiO3 thin films

This work emphasis on the competence of (100)-oriented PMN–PT buffer layered (0.68 PbMg 1/3 Nb 2/3 O 3–0.32 PbTiO 3 with Pb ( Zr 0.3 Ti 0.7) O 3/ PbO x buffer layer) and (001)-oriented PMN–PT (0.67 PbMg 1/3 Nb 2/3 O 3–0.33 PbTiO 3) for low grade thermal energy harvesting using Olsen cycle. Our analysis (based on well-reported experiments in literature) reveals that these films show colossal energy harnessing possibility. Both the films are found to have maximum harnessable energy densities (PMN–PT buffer layered: 8 MJ/m3; PMN–PT: 6.5 MJ/m3) in identical ambient conditions of 30–150°C and 0–600 kV/cm. This energy harnessing plausibility is found to be nearly five times higher than the previously reported values to date.

A Novel Procedure for Pyroelectric Energy Harvesting Using Heat Conduction and the Olsen Cycle

Waste heat can be directly converted into electrical energy by performing the Olsen cycle on pyroelectric materials. The Olsen cycle consists of two isothermal and two iso-electric field processes in the displacement versus electric field diagram. This paper reports, for the first time, a procedure to implement the Olsen cycle by alternatively placing a pyroelectric material in thermal contact with a cold and a hot source. Poly(vinylidene fluoride-trifluroethylene) [P(VDF-TrFE)] copolymer thin films with 60/40 VDF/TrFE mole fraction were used. A maximum energy density of 155 J/L per cycle was achieved at 0.066 Hz between 25 and 110°C and electric fields cycled between 200 and 350 kV/cm. This energy density was larger than that achieved by our previous prototypical device using oscillatory laminar convective heat transfer. However, it was lower than the energy density obtained in previous “dipping experiments” consisting of alternatively dipping the samples in cold and hot silicone oil baths. This was attributed to (1) the lower operating temperatures due to the slow thermal response achieved using heat conduction and (2) the smaller electric field spans imposed which was limited by the smaller dielectric strength of air. However, the proposed procedure can readily be implemented into devices.

Pyroelectric Energy Harvesting Using the Olsen Cycle on Relaxor Ferroelectric 8/65/35 PLZT

Waste heat can be directly converted into electrical energy by performing the Olsen cycle on pyroelectric materials. The Olsen cycle consists of two isothermal and two isoelectric field processes in the electric displacement versus electric field diagram. This paper reports on the energy harvested by lanthanum doped lead zirconate titanate (8/65/35 PLZT) subjected to the Olsen cycle. The material was alternatively dipped into a cold and a hot silicone oil bath under specified electric fields. A maximum energy density of 770 J/L per cycle corresponding to a power density of 9.6 W/L was obtained for temperatures between 25 and 160°C and electric fields cycled between 0.2 and 4.5 MV/m.