Continuous pyroelectric energy generation with cyclic magnetic phase transition for low-grade thermal energy harvesting

Waste heat harvesting is of importance to mitigate global warming so that thermoelectric devices have often been suggested; however, such approaches are challenging because of low conversion efficiency of thermoelectrics at low temperature gradient and easy thermal equilibration. In this study, a novel thermo-magneto-pyroelectric energy generator (TMPyEG) was developed to continuously harvest waste heat and convert it into electric energy without complicated electric bias field, required in typical thermodynamic cycling-based pyroelectric generators. To enable displacement reciprocation without intervention, the second-order magnetic phase transition of the soft magnet on an actuating part was repeated in the presence of a thermal gradient. We further incorporate piezoelectric material to mitigate crest factor by filling the energy gaps between pyroelectric energy outputs. Notably, the generated energy from pyroelectric conversion in TMPyEG is superior to that from the reported thermoelectric generators under the similar thermal conditions.