Energy harvesting based on Ericsson pyroelectric cycles in a relaxor ferroelectric ceramic

This work deals with energy harvesting from temperature variations. It is shown here that direct pyroelectric energy harvesting (connecting an adapted resistance, for example) is not effective, whereas Ericsson-based cycles give energy 100 times higher. The principle and experimental validation of the Ericsson cycle are shown with the example of 0.90Pb(Mg_1/3Nb_2/3)O₃–0.10PbTiO₃ ceramic. Harvested energy reached 186 mJ cm⁻³ for 50 °C temperature variation and electric field cycle of 3.5 kV mm⁻¹. A correlation between the electrocaloric effect and pyroelectric energy harvesting is then shown. Harvested electric energy with Ericsson cycles can be simply expressed as electrocaloric heat multiplied by Carnot efficiency. Several examples are then given from materials with the highest known electrocaloric effect. This leads to energies of hundreds of mJ cm⁻³ for a limited 10 °C temperature variation. Compared to Carnot's efficiency, this is much higher than the best thermoelectric materials based on the Seebeck effect.