Experimental Study on the Optical Properties and Photothermal Conversion of Biomass Composite Phase Change Materials

Abstract Solar energy is a renewable source of energy. The advantages of solar energy include its wide distribution, short cycle, high power, easy availability, and no pollution. As solar energy is seriously affected by changing weather, large-scale utilization of solar energy is restricted. Organic phase change materials (PCMs) are an ideal thermal energy storage medium, and the development of solar-thermal energy conversion technology requires materials to effectively capture and store solar energy. However, PCMs have some characteristics that need improvement, such as low light-to-heat conversion rates. Therefore, this article added biomass porous carbon (BPC) to improve the thermal conductivity and optical properties of PCMs. The experimentally determined thermal conductivity of 70% paraffin wax (PA)-(BPC) composite PCM (CPCM) was 3.18 times higher than that of pure PA. In addition, the average absorbance in the range of 190–2000 nm was approximately 1.3, and approximately 95% of solar radiation was absorbed by the CPCM and stored as thermal energy. The photothermal conversion efficiency of the CPCM was as high as 89.6%, thus infrared thermal image analysis was used to discover the positive effects of biomass porous materials on solar light capture and heat transfer. Therefore, composite BPC-based PCMs have broad application prospects in light-to-heat conversion and energy storage.