Finite element modelling and optimization of Ge/SiGe superlattice based thermoelectric generators

Abstract

The study presents the development of a 3D Finite Element modelling (FEM) technique for a uni-coupled Ge/SiGe superlattice-based module configuration. The methodological approach involved the development of the geometrical design of the Ge/SiGe – based Thermoelectric generator (TEG), defining the thermoelectric material properties and boundary conditions and then implementation of the governing equations to obtain an approximate solution via meshing of the TEG module. The developed FEM was then used to optimize the geometry of the TEG with the aim of reducing the contact resistance for improved performances. One way to achieve this is to reduce the thickness of the silicon substrate. Thus by reducing the thickness of the substrate, the thermal losses in the system will be minimized. Secondly, by increasing the superlattice heights, the output voltage also increased and given the anisotropic nature of the superlattice, it was inferred that the optimal voltage measurements can be obtained at the surface of the superlattice which yields the maximum leg height. The relevance of this study is that the FEM allows the simulation of the TEG module for different real-world conditions that would otherwise be expensive and time-consuming to investigate experimentally. It also gives insight to the temperature and voltage distribution of the TEG module under varying operating conditions.

On the thermoelectric alloy SixGe1-x

“…SixGe1-x composites are wiedly used in thermogenerators, coolers, sensors, 1,2 thin-film transistors, 3 batteries, 4 solar cells, 5,6 photodetectors 7,8 and others. These alloys are good high-temperature materials for the temperature range up to 1200℃.…”

“…In Ref. 11 the concept of electronic quality factor (B E ) of thermoelectric was introduced: B E =(ћN V C l /3π 2 m*ξ 2 )(kB/q) 2 , where ћ is reduced Planck's constant, Cl is a combination of elastic constants, 𝜉 -deformation potential coefficient , m* -electron rest mass, N Vband degeneracy, k B -Boltzmann's constant, q -elementary charge. To calculate B E , based on experimental data (Seebeck coefficient -S, specific electrical conductivity -σ), the formula is used:…”