Search

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]

At present, the steel industry produces a large amount of steel slag during the smelting process, which causes serious pollution to the environment and land. Therefore, new technologies must be used to deal with steel slag. In this study, the steel slag powder refined by the wet grinding technology is used as the matrix material, MgO as material additive, and the clay is used as the binder to prepare a new type of composite heat storage material. The results indicate that the mass ratio of wet grinding steel slag powder, MgO powder and clay is 6:3:1, the composite heat storage material can have a strong compressive strength of 70.9 MPa. The thermal conductivity of the heat storage material is 0.98 W/m⋅K and can reach 1.27 J/g⋅K at 720 ℃, which has good thermal conductivity and long service life. When the heat storage material rises to 900 ℃, the heat storage density can reach 905 J/g, with good heat storage performance and thermal cycle stability. The objective is to develop sustainable and low-cost thermal energy storage material for industry waste heat recovery and in renewable energy applications. At the same time, this valuable market for slag in the energy field provide a new way to directly utilize steel slag with extraordinary economic and environmental benefits. [ABSTRACT FROM AUTHOR]