Encapsulation of phase change materials for heat storage

Abstract

Encapsulated paraffin wax was prepared by complex coacervation and spray-drying methods. The influence of parameters on the characteristics and performance of microparticles in terms of encapsulation efficiency, core to coating recovery, energy storage and release capacities has been investigated. The optimum condition for complex coacervation at different core to coating ratios was 10 minutes homogenization time and 6-8 ml cross-linking agent. Then, the optimum core to coating ratio was 1:2 for both methods. DSC results showed that microcapsules prepared either by complex coacervation and spray-drying method have energy storage/release capacity 91-239 J/g. SEM and inner structure analysis gave polymeric matrix surrounding numerous paraffin wax particles. Thermal stability of both samples was also determined with respect to various numbers of thermal cycles. DSC and FTIR results showed that both samples have good thermal reliability in view of latent heat of fusion, melting temperature and specific heat capacity and chemical stability with respect to thermal cycling for thermal energy storage application in long term. Then, thermal performance of air-heated/cooled fluidized bed latent heat storage system was tested and evaluated. It was found that energy charging/discharging time was about 10 and 12 min respectively. Total energy storage and release capacities were found to be 74 and 61 J/g.