An innovative phase change composite with high thermal conductivity and sensitive light response rate for thermal energy storage

In recent years paraffin-based organic phase change materials have been widely employed in thermal-energy storage systems due to their relatively high latent thermal capacity. However, the risk of leaks, low thermal conductivity, and low light-to-thermal conversion capacity has, to date, limited their use in the storage of solar thermal energy. To address these issues, we have developed a novel bio-based shape-stable organic phase change composite (SSOPCC) by encapsulating paraffin C22 with the double-supporting component consisting of poly (styrene-b-ethylene-co-butylene-b-styrene) (SEBS) and expanded perlite (EP), and improving the thermal conductivity and increasing the sensitive light response rate by introducing boron nitride (BN) and a lignin biomass-derived carbon material carbonized lignin (CL). Our investigations show that, with the introduction of the BN sheets and biomass CL into the SSOPCCs, the thermal conductivity of the composites is improved (from 0.407 W/ mK to 0.596 W/mK), and the light-to-thermal conversion ability is also considerably enhanced. The obtained SSOPCCs possess not only good thermal storage performance, such as high latent heat enthalpy (as large as 185.5 J/g) and high relative enthalpy efficiency (>95%) but also exhibit excellent thermal stability and reliability after multiple heating-cooling cycles. The findings of this study will both provide a promising way for fabricating new bio-based phase change composites for real solar energy storage and conversion applications and broaden the high-value utilization of lignin-based biomass.