Thermal energy storage characteristics of carbon-based phase change composites for photo-thermal conversion

Abstract

Capture and utilization of solar energy using phase change materials (PCMs) can effectively answer the challenge of solar intermittency. However, the flaws of low thermal conductivity and poor thermal stability of PCMs limit their practical applications, and the selective absorption of solar energy also hinders it to achieve high photo-thermal conversion. In this work, a novel PCM was synthesized by adding expanded graphite and olefin block copolymers blended within paraffin wax. Enhanced thermal conductivities were realized that a 17.12 W/(m·K) in the vertical compression direction and 4.71 W/(m·K) in the parallel compression direction, which were 68.48 and 18.84 times in contrast to that of raw paraffin wax. A maximum solar absorptance of 97.47 % was achieved, and the photo-thermal conversion and energy storage capacity in the vertical compression direction were superior using the novel PCM. With the increase in light intensity, this PCM completed phase transition faster, reached a higher equilibrium temperature, and exhibited an outstanding thermal stability and cyclic stability within the assisted electron conductivity. Additionally, commercial software was also used to simulate thermoelectric applications of the PCM in real-world settings. This study provides new ideas for preparation and solar-thermal applications of anisotropic carbon-based PCMs.