Preparation and performance of lauric acid phase change material with the double-layer structure for solar energy storage

Abstract

The use of phase change materials (PCM) to absorb and store solar energy is one of the ways to solve the problem of increasing energy consumption in buildings. However, most of the PCM has low thermal conductivity and poor photothermal conversion performance, which limits their application in the building. In this study, it was proposed that a lauric acid-based bilayer material with good thermal conductivity and photothermal conversion performance. Specifically, sodium dodecyl sulfate (SDS) was used to combine carbon black (CB) and lauric acid (LA) in the upper layer to enhance photothermal conversion, and expanded graphite (EG) was added in lauric acid in the lower layer to enhance heat transfer. The synthesis ratio, thermal conductivity, latent heat, and heating rate of the LA/CB-LA/EG were tested. This study concluded that the preferred ratio of the photothermal conversion material in the upper layer is 100:5:1 (LA: CB: SDS), and the preferred ratio of the lower layer material is 100:1.4 (LA: EG). In addition, the addition of carbon material has only a small effect on the latent heat properties of the whole material. To verify the physical properties of the bilayer material, we tested the surface heating rate of the material and the inner material during the photothermal conversion of the material. The experimental results show that the surface temperature rise rate of LA/CB-LA/EG is 217 % of that of LA and 109 % of that of LA/EG in the time range of 30 min. The internal temperature rise rate of LA/CB-LA/EG is 226 % of LA and 136 % of LA/EG, respectively. Finally, we build the model in the numerical study and test it after inputting the physical parameters. The results show that the heating hours can be reduced by more than 50 % in winter using the above scheme, so this work achieves the purpose of energy saving and emission reduction.