Three-dimensional montmorillonite/Ag nanowire aerogel supported stearic acid as composite phase change materials for superior solar-thermal energy harvesting and storage

Abstract

Phase change materials (PCMs) which can harvest regenerative solar energy and convert into storable thermal energy are supposed to be advanced energy storage mediums. Stearic acid (SA) with suitable phase change temperature, large latent heat and negligible supercooling is considered to be promising organic PCMs in solar thermal energy harvesting and storage. However, the low thermal conductivity and poor shape stability of SA inevitably inhibited the energy storage and practical applications. Herein, Montmorillonite nanosheets and silver nanowires (AgNW) have been self-assembled to three-dimensional network structural aerogel and used as supporting matrix for PCMs. Then, novel form-stable composite PCMs have been prepared by impregnating SA into the porous aerogel matrix. The porous matrix can support SA and prevent leakage effectively by the strong surface tension and capillary forces during solid-liquid phase transition. The composite PCMs with more than 94 wt% SA loadings has a specific phase change enthalpy large than 196.48 J/g. Besides, the matrix provided cross-linked thermal conductive fillers and heat transfer path to greatly enhance heat transfer ability, which contributes to the outstanding solar energy harvesting performances. Moreover, the structural, thermal and cycling stability of the composite PCMs are very well under the protection of three-dimensional aerogel structure. Phase separation and sedimentation of thermal conductive fillers during solid-liquid phase transition has also been solved because the AgNW fillers were fixed by the matrix. With excellent thermal energy storage capacity, good shape-stability and superior heat transfer ability, the prepared composite PCMs show considerable potential in solar-thermal applications and sustainable development.