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 Al 2 O 3 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 (S 25 ) have a 62.8 % reduction in charging time and a 101.5 % increase in charging rate. Furthermore, after being filled with eutectic chloride salt, S 25 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.
Nan Sheng,Yunfei Ge,Yunqi Guo,Chunyu Zhu,Zhonghao Rao
This study reports the successful fabrication of Cu@Al 2 O 3 macro-encapsulated metallic PCMs for high-temperature thermal storage over 1000 °C. Cu powders are employed as raw material which are spherulitized to core balls in millimeter-size, and subsequently the core balls are cladded with Al 2 O 3 ceramic shells. After the low-temperature pre-sintering and subsequent high-temperature sintering treatment, the Cu@Al 2 O 3 macrocapsules which contain gaps between the shells and cores are successfully prepared. The core balls are consisted of Cu powders which are not densified but are porous, offering buffer spaces to accommodate the thermal volume expansion during high-temperature sintering and melting of Cu. As a comparison, Cu@Al 2 O 3 macrocapsules prepared by directly coating the commercial solid Cu balls are leaky. Thermal analysis indicates that the metallic core PCM has a melting temperature of 1063 °C and a latent heat of around 210 J/g. The macrocapsules are also highly durable as confirmed by the melting-solidification cycling test. These results demonstrate that the Cu@Al 2 O 3 macrocapsules are applicable as high-temperature heat storage media, which can find useable applications in advanced high-temperature thermal energy storage systems .
Developing high-performance materials for integrated thermal energy storage and oxygen production is critical for advancing sustainable energy systems. Aluminum as heat storage phase change materials has a high latent heat storage density, but suffering from the leakage problems. The SrFeO 3− δ (SFO) oxygen carrier exhibits exceptional redox activity for air separation with a high reduction enthalpy of 96 kJ/mol. In this study, we report a multifunctional composite macrocapsules composed of SFO shell and metallic aluminum core, engineered to synergistically combine thermochemical, latent, and sensible heat storage with air separation capabilities. The composite macrocapsule has a high heat storage capacity of 435.9 J/g at a temperature duration of 873 K to 1073 K and an oxygen storage capacity of 1.69 wt%. After conducting 50th thermal cycles in air for the composite macrocapsules, the samples remain unbroken and the oxygen absorption/release and heat storage capacities remain stable. The synergy between the thermochemical properties of SFO and the phase change heat storage of aluminum enables dual functionality, i.e., efficient high-temperature heat storage and on-demand air separation for chemical looping applications. This work provides a scalable paradigm for multifunctional energy materials, bridging the gap between thermal management and carbon neutral technologies.
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