Integrated design for underwater thermoelectric generator (TEG) based on fully coupled multiphysics fields analysis method

Based on the compact and quiet operation characteristics of TEG systems, this study proposes its application in power supply for underwater equipment, utilizing the stable temperature difference between the seawater cold source and the lead‑bismuth fluid heat source to generate electricity. First, three basic integrated structures are designed and compared in terms of temperature uniformity and electrical performance under the same operating conditions to select the most suitable structure for this application. The results show that the sandwich structure has the best temperature uniformity with a coefficient exceeding 0.95, the highest output power of 524.7 W and a medium power density. Therefore, the sandwich structure is selected as the applicable structure. Additionally, a fully coupled multiphysics calculation method is proposed, which comprehensively considers thermoelectric conversion and thermo-mechanical reliability. Using this method, an analysis of the fluid-thermal-electric-mechanical and off-design condition characteristics of the structure revealed that: under the same temperature difference, reducing the cold-side temperature can improve power generation performance more effectively than increasing the hot-side temperature. For every 15 °C decrease in the cold-side temperature, the conversion efficiency increases by approximately 5 %, while the maximum stress on the structure is reduced. Furthermore, all structures have an optimal external load that maximizes the output power, power density, and conversion efficiency. Finally, the accuracy of this fully coupled calculation method is verified through experiments. This study provides important insights into the expanded application of TEG systems in underwater equipment, as well as for performance analysis and optimization under multiphysics coupling conditions.