Anisotropic and shape-stable sugarcane-based phase change composites in the application of solar thermal energy storage

The study of anisotropically thermal conductive phase change composites (PCCs) with shape-stability is of great importance to improve the intermittent issues in solar thermal utilization, while some drawbacks like the high cost, low thermal conductivity, and poor durability of current PCCs restrains their practical applications. Herein, a cheap and scalable biomass-based PCC containing carbonized sugarcane (CSC), polyethylene glycol (PEG), and graphene (GF) is proposed. The abundant vessels inside CSC result in a high PEG loading rate of 82.48 %. The naturally occurring anisotropic structure inside CSC can drive GF to be oriented along the lengthwise direction, which gives PCC a high thermal conductivity anisotropy degree of 1.45. The prominent anisotropy improves the lengthwise thermal diffusion and restrains the transverse heat leakage to the environment. Besides, the loaded GF can further enhance the light absorption of PCC to 98 %. As a result, the prepared PCC can achieve high solar-thermal energy storage efficiencies of 79.3–91.7 % with variable solar intensity from 1 to 2 suns. Meanwhile, good anti-leakage and durability performances promote the practical utilization of PCCs. The present work paves a promising road for manufacturing biomass-based anisotropic PCCs in efficient solar thermal energy storage. • A novel biomass-based PCC with anisotropic structures was fabricated. • The PCC has excellent directional heat conduction and storage performance. • An ultra-high loading capacity was achieved owing to the vessels in sugarcane. • Solar thermal energy storage efficiency of 91.7 % are achieved under 2 suns.