A multi-unit miniature thermomagnetic generator using half-Heusler (MnNiSi)_1−x(Fe₂Ge)_x alloy for harvesting low-grade waste heat

Abstract This study focuses on designing and analyzing a series of thermomagnetic generators for efficient low-grade waste heat energy harvesting, addressing the challenge of bulky thermal harvesters that cannot be integrated into small mechanical structures. A miniature harvester with a total height of 16 mm and a diameter of 8 mm was designed. Using a single heat source at a maximum temperature of 450 K, the system drives multiple thermomagnetic generator units connected in series. Each unit utilizes thermomagnetic material with (MnNiSi) 1-x (Fe 2 Ge) x compositions with x values of 0.3, 0.32, 0.33, and 0.34. These materials operate within a Curie temperature range of 300 K to 420 K, enabling continuous operation as the heat transfers between units. Finite element analysis, conducted through COMSOL Multiphysics, was employed for numerical simulation to study the system’s performance. Results show that the three-unit series configuration achieved a peak voltage of 0.2 V per oscillation and 200 oscillations within 60 s. The sequential arrangement of units maximizes residual heat utilization and offers practical applications in industrial waste heat recovery, automotive heat management, and renewable energy systems.