Realizing high conversion efficiency in shallow cryogenic thermoelectric module based on n-type BiSb and p-type MgAgSb materials

The thermoelectric (TE) modules have been extensively studied, which have the features of recovery of waste heat energy into electricity. At present, many TE researches focus on the materials and modules of medium and high-temperature regions and hardly report on shallow cryogenic TE modules (173–300 K) aiming for the utilization of cold energy of liquefied natural gas (LNG). In this work, the TE arms of shallow cryogenic modules are composed of p-type MgAgSb-based materials synthesized by ordinary ball milling and n-type Bi85Sb15 synthesized by melting. By optimizing the raw material ratio of MgAgSb materials and the SPS pressure, the average ZT of MgAgSb-based material was increased from 0.196 to 0.482 at the temperature range of 173–300 K. Therefore, the maximum simulation conversion efficiency of the module by the optimization of the module structure and materials can achieve 1.95% at the temperature range of 200–300 K, which is 144% higher than that of the non-optimized module. Meanwhile, the maximum measured conversion efficiency of the corresponding manufacturing module reaches 1.76%, which is 2.63 times higher than that of the non-optimized manufacturing module. This work provides a reference for improving module conversion efficiency by optimizing materials and module structure in cryogenic environment.