Research on preparation and thermal performance of carbon sphere-modified PCM perlite-paraffin composite

• A low-cost, eco-friendly functional brick for agricultural applications was developed, utilizing graphene-modified paraffin as the core material, a mixture of cement and fly ash as the wall material, and a coating composed of resin blended with micron-sized carbon spheres. • Surface modification enhances carrier performance: Chemical functionalization of perlite with sodium carboxymethyl cellulose (CMC-Na) significantly improves the substrate characteristics, achieving enhanced paraffin loading capacity. • Micro-nano structured carbon spheres were synthesized using tea waste biomass as the carbon source, which were then composited with epoxy resin via a sol-gel method to form a high-efficiency photothermal conversion coating. • The semi-industrial validation experiments conducted in high-latitude winter conditions demonstrated the practical feasibility of phase change materials (PCMs) in real-world applications. A carbon sphere modification approach was developed to construct a perlite/paraffin composite phase change material (CS-PCM) with both high photothermal conversion efficiency and stable thermal energy storage capability. The surface of the perlite matrix was modified using sodium carboxymethyl cellulose (CMC-Na), increasing the water contact angle from 0° to 67°. Micro/nanoscale carbon spheres (0.1–20 μm) derived from tea waste were embedded into a resin matrix, demonstrating superior performance compared to conventional carbon-based additives. The CS-PCM was incorporated into thermal storage walls through a scalable manufacturing process, with phase change materials comprising 30% of the system. Experimental application in high-latitude greenhouses during winter confirmed that the integrated system maintained an internal crop environment at 13.6 ± 4 °C. This composite material features both low cost and reduced carbon emissions. The results offer a promising solution for thermal management in protected agriculture in cold regions and provide a theoretical and technical reference for the design of multifunctional phase change materials.