Development of "Transpiration-Type Thermoelectric Power Generating Paper" using Carbon-Nanotube-Composite Papers Without Need for Heat Source

We propose a unique thermoelectric power generating device using carbon nanotube (CNT) composite paper, "transpiration-type thermoelectric power generating paper."<br/>In recent years, thermoelectric power generation has been attracting attention because of its ability to effectively utilize heat that tends to be disposed of. However, the problem is that many of the thermoelectric materials currently in use are rare metals. Therefore, we focused on CNT, which has been shown to have high electrical conductivity and a high Seebeck coefficient. However, CNT is difficult to handle because they exist in powder form. For this, we have solved by developing CNT composite paper by combining paper and CNT. In this study, we are developing thermoelectric power generating devices based on the CNT composite papers.<br/>Conventional thermoelectric power generating devices require a heat source to generate electricity. This research focuses on the capillary phenomenon of paper and aims to develop a new type of thermoelectric power generating paper that does not require a heat source and generates a temperature difference using the heat of vaporization when liquid evaporates from the CNT composite paper containing liquid.<br/>The CNT composite paper is made using the modified Japanese washi paper making process. Specifically, a CNT dispersion consisting of single-walled CNT and SDS (sodium dodecyl sulfate) as dispersant dispersed ultrasonically in pure water is mixed with a pulp dispersion consisting of pulp, the raw material of paper, dispersed in pure water. Next, the water is removed from this mixed dispersion with a fine mesh. Finally, it is dried and molded to complete the process.<br/>To conduct thermoelectric power generation without heat source, one end of this transpiration-type thermoelectric power generating paper is dipped in pure water filled in a container, and the other end is fixed from the top. At the top, the temperature is lower than at the bottom, which is immersed in water, due to the heat of vaporization caused by the evaporation of water lifted by capillary action. The difference in temperature causes the Seebeck effect. In the fabricated paper, a temperature difference of 0.9K was spontaneously generated, resulting in an electromotive force of 22μV.<br/>As the next step in this research, we aim to further improve the output by changing the amount of material and the structure of the paper. Since our transpiration-type thermoelectric power generating paper obtained in this study does not require a heat source, we believe that it can be used as an environmental power generator in rivers and oceans in the near future.