Significant optimization of active thermomagnetic generator for low-grade waste heat recovery

[Display omitted] •Active thermomagnetic generator is built for low-grade waste heat recovery.•Effects of key device and material parameters on performance are optimized.•The peak I value increases from 28.8 μA to 136.1 μA after the optimization.•The power density is one order higher than that before optimization.•The improved performance is much larger than those of other reported devices. Recently, thermomagnetic generator (TMG) based on the thermomagnetic effect is becoming a promising technology for low-grade waste heat recovery. However, poor performance still hinders the application of this novel technology. The performance of TMG is significantly affected by the key device parameters and material properties. Unfortunately, there is a lack of systematic research in this regard. In present work, for the first time, we systematically study the effects of different key device and material parameters on the TMG performance through a combination of experiment and finite element simulation. It demonstrates that the TMG performance is influenced largely by both device and material parameters, especially the cabin size and specific heat capacity. Furthermore, the key device parameters are optimized, i.e., the sample cabin size is shortened from 145 mm to 20 mm, the system temperature range is expanded from 288 ∼ 353 K to 276 ∼ 361 K, and the cycle period is reduced from 60 s to 10 s. In comparison with the non-optimized experimental peak I of 28.8 μA, the simulated peak I increases largely to 136.1 μA after the optimization. In addition, more I peaks are obtained by shortening the cycle period. The maximum power density Pd and average Pd are 3.6 mW/m3 K and 0.4 mW/m3 K, respectively, which are one order of magnitude higher than the values before optimization (0.16 mW/m3 K and 0.01 mW/m3 K), and even three orders of magnitude higher than those of other reported TMGs.