**4. Remarks and Conclusions**

Between 2010 and 2020, there have been few studies concerning thermoelectric generator (TEG) modules that examine the larger holistic picture from mass manufacturing, profitability (from the economic point of view), efficiency, life cycle, and competitiveness to final disposal. Despite this, in the systematic search, an approach towards circular economy and sustainability has been considered indirectly since the articles analyzed covered topics ranging from raw thermoelectric TE materials, manufacturing of TEG modules, energy efficiency, and also the applicability and recycling of materials and modules.

The cost of manufacturing the modules is a little explored topic since in most works, only the relationships concerning the cost of the constituent TE materials are analyzed, and other factors that contribute to the high commercial cost of these modules are not examined.

In the present review it is highlighted that the efficiency of TEG modules depends, in addition to the TE materials, on external agents such as refrigeration systems, connections between the TEG modules, and the environment in which they will be operated. Therefore, these are important research topics to improve the cost-efficiency ratio of TEG systems.

Modeling is a valuable tool in predicting the efficiency of TEG modules at different stages of their development and implementation.

Additionally, the present research evidences the lack of work oriented towards the circular economy and sustainability of TEG modules, highlighting this aspect as an extremely important area for the development of TEG systems.

Taking into account the limitations that current TEG modules present in relation to the efficiency-cost relationship and the lack of research from circular economy and sustainability perspectives, this review proposes an approach for new studies that would allow an improved understanding of the processes used and their useful life. The research approach would aim to balance the cost-efficiency ratio from a sustainability perspective, not only addressing the base material, but also provide a more general approach to understanding the entire life-cycle of the modules from their manufacture to their final disposal. This would provide more information on the economic viability and sustainability of TE materials and modules.
