A Gd‐Film Thermomagnetic Generator in Resonant Self‐Actuation Mode

Abstract

AbstractThermomagnetic generation is a promising technology for conversion of low‐grade waste heat into electricity. Key requirements for the development of efficient thermomagnetic generators (TMGs) are tailored thermomagnetic materials as well as innovative designs enabling fast heat transfer. Recently, film‐based thermomagnetic generators are developed that operate in the mode of resonant self‐actuation enabling high frequency and stroke of a movable cantilever and, thus, efficient conversion of thermal energy into electrical energy. Here, the performance of a Gadolinium (Gd)‐film‐based TMG that is optimized for resonant self‐actuation near room temperature is reported. The Gd‐film TMG exhibits large oscillation frequencies up to 106 Hz and large strokes up to 2 mm corresponding to 38% of the oscillating cantilever's length. This performance occurs in a sharply bound range of ambient temperatures with an upper limit near the film's ferromagnetic to paramagnetic transition temperature Tc of 20 °C and of heat source temperatures ranging between 40 and 75 °C. The maximum power per footprint is 23.8 µWcm−2, at which the Gd film undergoes a temperature change of only 0.9 °C at ≈10 °C above Tc.