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In this paper, a new molten salt/ceramic composite phase change thermal storage material was prepared by sol-gel method and powder compacting method. The surface of molten salt particles was encapsulated with SiO2 or TiO2 by sol-gel method, then the molten salt particles were combined with MgO to prepare composite phase change thermal storage materials. By this method, the density of the composite increased by 8.74%, the thermal conductivity increased by 16.27%, after high-temperature heat. The decline of the heat loss rate was only 2.67%. [ABSTRACT FROM AUTHOR]

In recent years, heat storage technology has attracted wide attention in the fields of renewable energy storage for its relatively high melting point, high heat storage capacity and economy, Na2CO3 and eutectic salt mixtures containing Na2CO3 are promising candidates in the field of solar energy storage. In this paper, a molecular dynamics (MD) simulation of Na2CO3 was conducted with the Born–Mayer potential function. The simulated solid–liquid phase change temperature is 1200 K, and the error is 5.4%. The heat capacity at constant pressure (Cp) is higher in liquid than in solid, the average Cp of solid is 1.45 J/g and that of liquid is 1.79 J/g, and the minimum error is 2.8%. The simulation results revealed the change rules of density and thermal expansion coefficient of Na2CO3 in the process of heating up, and these changes were analyzed by radial distribution functions (RDF) and angular distribution functions (ADF). Moreover, the RDF and ADF results show that the atomic spacing of Na2CO3 increases, the coordination number decreases, and the angle distribution between atoms becomes wider as the temperature rises. Finally, this paper examined the microscopic changes of ions during the phase transition of Na2CO3 from solid to liquid. It is concluded that the angle change of CO 3 2 − in the liquid state is more sharply. This study improves the understanding of the thermodynamic properties and local structure of Na2CO3 and provides theoretical support for Na2CO3 heat storage materials. [ABSTRACT FROM AUTHOR]

• A novel shape-stabilized composite PCMs of Na 2 CO 3 -K 2 CO 3 /MgO/glass was fabricated. • The problem of dusting of shape-stabilized PCMs in humid environment was solved. • Thermal storage property of shape-stabilized PCMs in humid environment was assessed. • Mechanical property of shape-stabilized PCMs in humid environment was assessed. The novel shape-stabilized phase change composite of Na 2 CO 3 -K 2 CO 3 /MgO/glass was fabricated by using glass as a binding material to prevent from dusting. In the composite, molten salt as heat storage medium, hard-burning MgO and glass provide structural strength, the composite phase change materials (PCMs) body has a good moisture-proof performance, there is no cracking and dusting phenomenon, the composite PCMs body still has a practical compressive strength under 80% relative humidity condition for 72 h and the heat energy storage performance of this material before and after hygroscopicity test is about 58 J/g and 36 J/g, respectively. [ABSTRACT FROM AUTHOR]