Enhanced thermal properties of stearic acid/carbonized maize straw composite phase change material for thermal energy storage in buildings

The application of organic phase change material (PCM) using in thermal energy storage system was limited by low thermal conductivity and leakage problem. In this paper, we reported a low-cost supporting material with good thermal conductivity by carboning the biomass of maize straw. The composite PCM of stearic acid (SA)/carbonized maize straw (CMS) was prepared via vacuum impregnation process and characterized by XRD, FT-IR, SEM. The results show that SA/CMS has good chemical compatibility. DSC, TGA as well as thermal conductivity and thermal history method were used to evaluate the thermal properties of SA/CMS. The DSC result reveals that the composite SA/CMS melted at 67.62 degrees C with the latent heat of 160.74 J/g and freezed at 65.28 degrees C with the latent heat of 160.47 J/g. The maximum loading capacity of SA in composite of SA/CMS reached 77.22%. TGA and DTG results show SA/CMS have good thermal stability. Thermal conductivity of SA/CMS reached 0.30 W/(m.K), which was 87.5% higher than that of the pure SA. Compared with SA, the melting time of SA/CMS reduced 50% and the freezing time reduced 73%. 200 thermal cycling test shows the SA/CMS exhibits excellent thermal reliability. Based on all results, it can be expected that the form-stable composite PCM of SA/CMS has good potential application in solar heat energy storage system and energy-efficient buildings.

Automated summary

This study successfully prepared a composite phase change material of stearic acid/carbonized maize straw with good thermal properties and stability, using carbonized maize straw as a supporting material with excellent thermal conductivity. The composite PCM showed enhanced thermal conductivity and stability, with significant improvements in melting and freezing times compared to pure stearic acid.