Sustainable geopolymer concrete for thermoelectric energy harvesting

Concrete is a widely used material that presents vast opportunities for energy harvesting applications. Among these, thermoelectric concrete shows promising potential for harvesting waste heat generated in urban and industrial environments. However, the development of thermoelectric concrete poses several challenges that need to be addressed, such as the need to accurately account for the intrinsic voltage. This factor is frequently disregarded, but it has a significant impact on the measurement of thermoelectric properties in improving the intrinsically low electrical conductivity and Seebeck coefficient. In this context, this study evaluates the performance of industrially scalable geopolymer-based concrete that incorporates recycled aggregates as low-cost and environmentally friendly additives for thermoelectric energy harvesting applications. The concrete exhibited an intrinsic voltage of 15 mV, and a new test protocol was proposed to exclude its impact on thermoelectric measurements. The geopolymer concrete demonstrated a significantly high Seebeck coefficient of 570 µV/k, surpassing all previously reported values for geopolymer-based materials. Furthermore, it was discovered that the thermoelectric behavior of geopolymer-based concrete is of ionic origin, indicating that further improvements can be made by adjusting the pore solution chemistry. This finding suggests that there is ample opportunity for innovation and optimization in the development of thermoelectric concrete.