Legs Geometry Influence on the Performance of the Thermoelectric Module

Abstract

The performance of the thermoelectric module highly depends on the geometry of the legs, the module area, and implicitly on the number of the pairs, besides the properties of the materials. The geometry of the legs consists of the shape, the dimensions on three axes, and whether the legs are filled or are hollow. The legs can have one hollow or more, the hole can be from the top to bottom or not. This paper studies and compares the performance of different thermoelectric modules in function of the shape: square, triangular, trapezoid, reverse trapezoid, hourglass, inverse hourglass (filled and with the hollow from the top to the bottom or not), and with different dimensions of the length and width. The simulations are performed using the COMSOL Multiphysics software, where 3D numerical models are developed and solved using the finite element method. The results are compared with others from the specialized literature for a one pair square shape. The current-voltage and power-voltage characteristics have a good matching, which proves the simulations are good and the model can be used for other shapes. A steady-state heating condition is applied to the hot side of the thermoelectric generators, while the cold side is subjected to steady state, natural convection, and forced convection heating conditions. The square shape with an internal hollow is studied first. The best performance when the length and width are 1 mm × 1 mm, 1.5 mm × 1.5 mm, and 2 mm × 2 mm is obtained for the thermoelectric generator with filled square legs. The highest maximum power is obtained for thermoelectric generator with the sizes 2 mm × 2 mm. The gain in power for the square shape in comparison with the worst value of the TEG (Inverse Hourglass for filled and Triangular for hollow) for the three dimensions considered is for those filled 199%, 202%, and 204%, respectively, and for those that are hollow 198%, 232%, and 243%, respectively. The reduction in maximum power is 5%, for the thermoelectric generator with square legs (2 mm × 2 mm) and with hollow legs, in comparison with one filled. The maximum power increases for the thermoelectric generator with square legs which have a hollow interior, in this case 2 mm × 2 mm, with 0.2% and 1% for the thermoelectric generator with sizes of 1 mm × 1 mm. Additionally, the results obtained for the square filled shape are compared with the real ones obtained for a thermoelectric generator with sizes 40 mm × 40 mm × 4 mm. The matching is very good, which confirms that the model can be used for different geometry of the thermoelectric generators in order to help the manufacturers improve their performance.