Ashwath Aravindhan1,2,Pierre Lheritier1,Alvar Torelló1,2,Tomoyasu Usui3,Youri Nouchokgwe1,2,Junning Li1,Uros Prah1,Veronika Kovacova1,Olivier Bouton1,Sakyo Hirose3,Emmanuel Defay1
Luxembourg Institute of Science and Technology1,University of Luxembourg2,Murata Manufacturing Co., Ltd.3
Ashwath Aravindhan1,2,Pierre Lheritier1,Alvar Torelló1,2,Tomoyasu Usui3,Youri Nouchokgwe1,2,Junning Li1,Uros Prah1,Veronika Kovacova1,Olivier Bouton1,Sakyo Hirose3,Emmanuel Defay1
Luxembourg Institute of Science and Technology1,University of Luxembourg2,Murata Manufacturing Co., Ltd.3
Electrocaloric (EC) materials display a reversible change in temperature with a varying electric field, which could be utilized for solid-state cooling. To enhance the performance of electrocaloric coolers, it is crucial to improve the intrinsic EC effect of the material and develop appropriate heat management strategies. Torelló et al. [1] developed a fluid-based active EC regenerator based on lead scandium tantalate (PST) multilayer capacitors (MLCs). In addition to the sharp first-order transition of PST, they also took advantage of the multilayer structure to increase the active volume of the material to obtain a temperature span of 13 K. Due to their strong electrothermal coupling, PST MLCs can also be used to convert heat into electricity for pyroelectric energy harvesting (thermodynamic converse of the EC effect). Similar ideas have also been realized in magnetocaloric materials by exploiting the change in magnetization with temperature to produce electrical energy [2]. Here we developed a macroscopic pyroelectric harvester using 42 g of active PST-MLCs, which produces 11.2 J of energy per thermodynamic cycle [3]. One PST-MLC can generate an electrical energy density of 4.4 J cm<sup>-3</sup> during one cycle. In addition, we also built an autonomous pyroelectric harvester comprising of microcontrollers, low-voltage converter, and temperature sensors which is powered by the energy harvested from 0.3 g of active PST-MLCs. Finally, we show that 40% of Carnot efficiency could be achieved in PST-MLCs for a temperature span of 10 K near their phase transition temperature.<br/><br/>[1] Torelló, A., et al. "Giant temperature span in electrocaloric regenerator." Science 370.6512 (2020): 125-129.<br/>[2] Waske, Anja, et al. "Energy harvesting near room temperature using a thermomagnetic generator with a pretzel-like magnetic flux topology." Nature Energy 4.1 (2019): 68-74.<br/>[3] Lheritier, Pierre, et al. "Large harvested energy with non-linear pyroelectric modules." Nature 609.7928 (2022): 718-721.