Evaluation of thermomagnetic generation performance of classic magnetocaloric materials for harvesting low-grade waste heat

Nowadays, the thermomagnetic generators (TMGs) based on thermomagnetic effect have been considered as a promising technology for harvesting low-grade waste heat. However, so far, most works are mainly focused on the design and optimization of these devices, while only a few studies have systematically investigated the TMG materials; moreover, evaluating the performance of different TMG materials is quite difficult. This paper reports the fabrication of an active thermomagnetic device for harvesting low-grade waste heat and, for the first time, a systematical performance evaluation of classic magnetocaloric materials (Gd, Gd₅(Si, Ge)₄, NiMn-based Heusler alloy, and La(Fe, Si)₁₃H_y/In composite). Alternating current (I) was obtained via thermally induced, reversible magnetic transition during the heating and cooling cycles, achieving the harvest of low-grade waste heat; besides, the results showed that the induced I depended not only on dM/dT but also on dT/dt. The intrinsic TMG performance of all the target materials were compared comprehensively by eliminating the influence of different T_C locations. Among them, the La(Fe, Si)₁₃H_y/In composite exhibited the highest induced current I (9.12 μA g⁻¹) and power density (0.47 mW m⁻³); in particular, its investment cost index was 1–2 orders of magnitude higher than those of the other materials. Thus, this work demonstrates that the La(Fe, Si)₁₃H_y/In composite is a promising TMG material for harvesting low-grade waste heat.