Experimental and Theoretical Optimization of Wearable Thermoelectric Generators Based on Fill Factor and Leg Geometry

Conventional thermoelectric generators (TEGs) often exhibit low energy conversion efficiency, attributed to the subpar performance of thermoelectric (TE) materials and elevated contact resistance. Furthermore, structural inconsistencies may contribute to the diminished output performance. This report presents a theoretical analysis of wearable thermoelectric generators (TEGs), with experimental validation. Key findings include the necessity of electrical impedance matching to achieve maximum output power in a TEG. The open-circuit voltage of a TEG exhibits an increase with the number of thermocouples/fill factor, impacting the output power, which, in turn, depends on internal resistance and thermal resistance. Experimental results revealed the optimal leg lengths of 1.5 and 3 mm for TE modules with 31-pair and 40-pair at a fixed temperature gradient. At a 9 K temperature gradient for the 31-pair TE module, maximum output powers of 1596, 1382, and 932 μW were obtained when the leg lengths were 1.5, 2, and 3 mm, respectively. The report also highlights the influence of leg length on output power for both flat and curved heat sources (50 °C), with the highest output powers recorded at 313.9 and 331.9 μW for the TE module with 31-pair and L = 3 mm. These insights contribute to the understanding and optimization of wearable TEGs for enhanced performance.