Characterization of Fly Ash Cenosphere – Capric acid composite as phase change material for thermal energy storage in buildings

Energy demand in buildings has been steadily increasing in the recent past. The majority of energy is used to heat and cool the building envelope to maintain a conducive thermal environment for habitation. Integration of Phase Change Materials (PCM) in buildings has improved the structure’s energy efficiency by absorbing and discharging energy as latent heat. In this work, Cenosphere–Capric Acid (CeCA) composite PCM was developed by the technique of impregnating capric acid (CA) into the hollow core of the cenosphere (Ce) under vacuum followed by sealing it with SiO2. The morphology of the prepared CeCA composite was investigated by FESEM. Mineralogical characterization by XRD suggested that the mineral structure of the CeCA composite has remained unaltered. Phase change temperature and latent heat of CeCA composite were evaluated as 27.60°C and 69.07 J/g for melting and 23.16°C and 71.30 J/g for freezing, respectively. Thermo-Gravimetric Analysis (TGA) of CeCA indicated the enhanced thermal stability of the composite. CeCA composite indicated good chemical compatibility between Ce, CA, and SiO2; hence, the composite is chemically stable, as revealed by FTIR analysis. Accelerated thermal cycling of CeCA composite indicates a relatively modest change in phase change temperature of 0.6°C for melting and 0.1°C for solidification. Further characterization by TGA and FTIR, suggested that the CeCA composite is reliable for the long term. It implies that the CeCA composite has significant potential as a PCM for thermal energy storage application in construction materials and structures.