Nanostructured thermoelectric composites for efficient energy harvesting in infrastructure construction applications

Although numerous investigations have been performed on thermoelectric (TE) fields, no notable studies have been conducted on TE structural materials. In this study, the electrical characteristics of cement were induced by incorporating carbon nanotubes (CNTs). Although cement can serve as a TE material owing to its low thermal conductivity, its extremely low electrical conductivity hinders its feasible application. The introduction of cement composites containing small amounts of CNTs is suggested as a solution. CNTs can improve the TE performance of cement-based composites because they exhibit superior electrical conductivity and are suitable as additives for carbon isotope-based composites. Such composite materials can be used as TE structural materials for energy harvesting in buildings. Therefore, to analyze the feasibility of the cement/CNT composites, the electrical conductivity, Seebeck coefficient, and thermal conductivity were measured by varying the CNT concentration using 4-probe measurement and ASTM D5470 methods. The electrical conductivity was improved by approximately 104 times as the CNT concentration increased from 0.0625 to 0.25 wt% while maintaining a relatively stable Seebeck coefficient, whereas the thermal conductivity remained in the insulating material region. The results showed that the critical CNT concentration associated with the percolation threshold was relatively low (similar to 0.1 wt%). This study may contribute to the development of self-powered sensor systems in buildings based on structural temperature differences.