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Page 4 of 17 Lekbir et al. Energy Mater. 2025, 5, 500101 https://dx.doi.org/10.20517/energymater.2025.46

state technologies.

4. It is assumed that the TEG system experiences no significant performance degradation over its lifespan.
Minor degradation from oxidation or thermal cycling is estimated to occur in real-world scenarios, but its
impact is minimal for encapsulated modules under stable thermal gradients.

5. The estimated environmental impact is primarily attributed to the embodied energy associated with the
raw materials used in the TEG module. Variations in processing techniques and energy inputs across
different stages of the TEG lifespan lead to non-generalizable outcomes, complicating direct comparisons
and limiting the practicality of broader studies.

System geometry
A TEG module is a solid-state device that converts heat into electricity through the Seebeck effect. It
consists of multiple thermoelectric couples, typically made from semiconductor materials, arranged in a
series of p-type and n-type legs connected by a conductive electrode. These legs are sandwiched between
two ceramic plates, which provide mechanical support, facilitate heat transfer, and ensure electrical
insulation. When a temperature difference is applied, charge carriers move from the hot to the cold side,
generating electricity. The schematic 3D geometry of TEG module is presented in Figure 1. TEG efficiency
is fundamentally influenced by material properties, the temperature gradient, and the system design. For
instance, the design factors play a pivotal role in determining the overall performance of the module.
Specifically, the arrangement of thermocouples directly influences internal resistance and voltage output,
while the selection of electrode materials governs electrical conductivity and thermal stability. Additionally,
the ceramic plates are crucial for ensuring effective thermal insulation and heat transfer. Consequently,
optimizing the geometry of the TEG module, with careful consideration of these factors, is essential for
maximizing its thermoelectric performance and overall operational efficiency.

Commercial TEG modules are available in various system geometries, sizes, material compositions, and
power ratings. This study considers different types of TEG materials to evaluate the performance of TEG
modules with a standardized geometry. The dimensions of the various components in these TEG modules
are equivalent to those of the most common commercial TEG module. The detailed dimensions of
commercial TEG components are presented in Table 1.

Performances calculation
The output of a TEG module depends on several factors, including the temperature gradient (ΔT), the
Seebeck coefficient (S), internal resistance (R s,TEG ), and the number of thermocouples (n). This study uses
different materials for various types of TEGs. Since different materials have varying Seebeck coefficients and
electrical resistivities, material selection plays a crucial role in performance. Ideally, materials used in TEG
applications should exhibit a high Seebeck coefficient, high electrical conductivity, and low thermal
conductivity to maximize electrical performance. The equivalent Seebeck coefficient for each TEG module
is summarized in Table 2.

Once the equivalent Seebeck coefficient (S) for each TEG module is determined, the open-circuit voltage
[42]
can be evaluated using :

V = n × S × ∆T (1)
oc