Investigation on the Thermoelectric Energy Harvesting Using Cement Composites Incorporating the Ceramic-Type Carbon Material as Fine Aggregate

Abstract

The worldwide focus on carbon neutrality aims not only at carbon capture methods but also at reducing carbon emissions associated with energy consumption and production. In the field of civil engineering and construction, infrastructure expansion significantly contributes to environmental issues like the urban heat island effect, accounting for a substantial portion of energy consumption. To address this, utilizing waste heat energy from the urban heat island effect has gained attention, with thermoelectric effects being considered an efficient approach. Materials with thermoelectric properties, when integrated with cement, can provide energy harvesting capabilities to infrastructural elements. In this study, cement composites with Silicon carbide as fine aggregate were investigated as a foundation for thermoelectric energy utilization technology through the Seebeck effect, contributing to carbon neutrality by harnessing waste heat energy and integrating industrial waste with the construction industry. Silicon carbide, with its appropriate particle size, high hardness, chemical stability, excellent electrical conductivity, and thermal conductivity, serves as a functional material that can replace fine aggregates. Various analysis and tests were conducted to evaluate the thermoelectric properties of cement composites containing SiC. When 25% of fine aggregates were replaced with SiC, a reduction in porosity due to the formation of an appropriate particle size distribution within the cement was confirmed. CT analysis revealed that an increased SiC content resulted in a more even and widespread distribution of SiC, forming a denser network for electrical and thermal conduction, thus enhancing the electrical conductivity and thermal conductivity of the composite. Furthermore, SiC integration successfully improved the thermoelectric properties from the standpoint of the Seebeck effect. At a temperature difference of 60°C, the specimen with 25% fine aggregates composed of SiC showed the highest increase gradient in Seebeck coefficient and PF at 914.81 μV/K and 0.00469 μm-1K-2, respectively. As the SiC integration ratio increased, the Seebeck coefficient and PF gradually increased, reaching the highest values of 1971.69 μV/K and 0.03269 μm-1K-2, respectively, in a specimen with 100% SiC as fine aggregates. To evaluate the size effect on thermoelectric properties, beam and cubic mortars with SiC were compared. In a temperature difference of 60°C, the size effect comparison revealed that cubic mortars exhibited higher values for all SiC integration ratios compared to beam mortars. The cubic mortar with 100% SiC recorded the maximum Seebeck coefficient and PF at 3042.48 μV/K and 0.08053 μm-1K-2, respectively. These results emphasize the enhanced thermoelectric properties of cement composite materials with SiC as fine aggregates, showcasing the potential for energy harvesting and storage applications.|본 연구에서는 태양열 및 반도체 산업 부산물인 탄화규소를 잔골재로서 시멘트 복합체에 통합하여 미 활용 열에너지로부터 열전효과를 활용한 에너지 하베스팅으로 탄소중립에 기여하고자 하였다. 탄화규소가 통합된 시멘트 복합체의 열전 특성 평가를 위해 다양한 실험 및 분석을 수행하였다. 미세골재의 25%를 탄화규소로 치환하였을 때 시멘트 내에 적절한 입도 분포 형성으로 인한 공극률 감소를 확인할 수 있었다. CT분석 결과, 탄화규소함량이 증가할수록 균일하고 넓게 분포되어 치밀한 네트워크를 형성하고, 시멘트 복합체의 전기전도도와 열전도도가 향상되었다. 특히, 25%의 탄화규소 투입 시 터널링 효과 및 공극률감소로 인해 전기전도도가 급격히 향상되었다. 또한, 탄화규소는 시멘트 복합체의 열전 효과 향상에 성공적으로 기여하였다. 60°C의 온도차이에서 탄화규소가 25% 투입된 공시체에서 제백계수 및 PowerFatcor 가 914.81μV/K 와 0.00469μm-1K-2 로 가장 큰 증가폭을 보였다. 탄화규소 함량이 증가할수록 제백계수와 PowerFactor가 점차 증가하여 잔골재의 100%가 탄화규소로 치환된 공시체에서 제백계수 및 PowerFactor가 1971.69μV/K, 0.03269μm-1K-2으로 가장 높은 값을 나타내었다. 열전특성에 대한 크기효과를 비교하기 위하여 빔 및 큐브 모르타르 공시체가 사용되었으며, 60°C의 온도차에서 진행되었다. 큐브 모르타르에서 빔 모르타르보다 더 높은 열전효과를 얻어내었다. 이러한 현상의 원인은 큐브의 낮은 저항 값과 더 효율적인 열 에너지 전달로 해석되었다. 탄화규소를 잔골재로서 100% 사용한 큐브 모르타르에서 제백계수 및 PowerFactor 값은 3042.48μV/K, 0.08053μm-1K-2으로 측정되었다. 이러한 결과는 탄화규소를 잔골재로 사용함으로써 시멘트 복합재의 향상된 열전효과와 에너지 하베스팅 및 활용 가능성을 보여주었다.