Development of topology-optimized structural cavities macro-encapsulating chloride salt by gel-casting for high-temperature thermal energy storage

Abstract

The thermal energy storage (TES) technology based on high-temperature molten salt is playing an increasingly important role in advanced solar energy utilization and waste heat recovery. However, the high corrosivity and low thermal conductivity of molten salt have limited the efficient application of TES systems. This work reports a facile and novel sacrificial paraffin template method, aiming to create Al2O3 ceramic macrocapsules with topology-optimized structural cavities by paraffin blocks with a reverse-designed structure for macro-encapsulating molten salt. The objective function of the maximum thermal conductivity of the design domain is calculated by a topology-optimized method to optimize the layout of high conductive ceramics. Among them, the optimized macrocapsules with a volume ratio of 25 % ceramic (S25) have a 62.8 % reduction in charging time and a 101.5 % increase in charging rate. Furthermore, after being filled with eutectic chloride salt, S25 could present a satisfactory heat storage density of 272.58 J∙g−1 and 748.3 J∙cm−3 at the temperature range of 550–750 °C. The macrocapsules also show good thermal cycling stability without degradation of thermophysical properties after hundred cycles. These improved results demonstrate the potential application of the macrocapsule in high-temperature TES systems.