Energy harvesting and electricity production through dissolved carbon dioxide by connecting two form-stable phase change materials

Abstract

Herein, we report a new solar energy harvesting approach by connecting two form-stable phase change materials in a moist environment with dissolved carbon dioxide (CO₂). Recently, a smart and creative energy harvesting concept has emerged by using form-stable phase change material (PCM) composites without any thermoelectric device. In that approach, the two form-stable PCM composites must have different electrical resistivities and phase transition temperatures based on the Seebeck effect. In this study, there is no need to make the PCM composite an electrical conductor. Instead, we propose the usage of different relative humidities on the surfaces of the two connected PCM composites and dissolved carbon dioxide as the moving ions to produce electricity. For this purpose, we synthesized and 3D printed a hydrophilic shape memory vitrimer (SMV) container as the supporting material. By infiltrating two types of PCMs into the SMV supporting container, two types of PCM composites were obtained. By changing the surface moisture content and the concentration of dissolved CO₂, PCM composites with different electrical resistivities were realized. Comprehensive characterization studies were conducted on the synthesized SMV, PCMs, and PCM composites. The effect of the relative humidity and CO₂ concentrations on the electrical energy outputs was investigated. Several groups or assembly were further investigated. It was found that an assembly made of SMV supported 1-tetradecanol with 70% relative humidity and SMV supported polyethylene glycol with 90% relative humidity at 700 ppm and 1200 ppm CO₂ concentrations preformed the best. The voltage and current outputs were about 2.73 mV and 500 nA during the light-on/off process, respectively. Numerical simulation was also conducted, which largely confirmed the experimental results. This study shows that greenhouse gases can be effectively employed to harvest energy. It is believed that this study provided new opportunities for clean energy harvesting.