Optimization And Performance Analysis Of Molten Salt/Solid Composite Heat Storage Materials In Solar CSP Systems

The solar thermal power generation system requires huge heat storage equipment and space,mainly including the light collection system,heat collection system,heat transfer system and heat storage system,in which the performance of the heat storage material will significantly affect the efficiency of the heat storage system.A heat storage material with excellent performance should have excellent heat storage performance and thermal conductivity.At present,the most common heat storage materials in solar thermal power plants are molten salts,of which binary salts and ternary salts are the main ones.Molten salt has an ideal heat storage capacity,but its thermal conductivity is poor,corrosive to the pipeline and will block the pipeline after excessive cooling.Therefore,this paper focuses on the composite materials made of molten salt and solid phase,and prepares the core-shell structure,focusing on the influence of the core-shell structure with ceramic shell on the thermal performance of the heat storage unit.In addition,SiO2 nanoparticles with large specific heat capacity and high thermal conductivity are evenly added to the molten salt to enhance the performance of heat storage and heat release.Experimental results show that using this method can make the heat storage unit have a wider operating temperature range.The analysis shows that the heat storage material of the new structure has better heat storage performance and heat conduction performance,and its heat release process is more stable.At the same time,the space-time distribution of temperature satisfies the correlation of the composite index,and the corresponding natural convection velocity is estimated accordingly,and the dimensionless numbers such as Nusselt number and Bier number of the new heat storage material are calculated.On the basis of this structure,Ansys finite element simulation was used to analyze the temperature changes of the core-shell structure when the new material was placed in the high-temperature concrete base during the heat absorption and release process.Through the simulation calculation of the heat storage module added with high temperature concrete,the temperature distribution in the heat storage block is observed to verify the experimental conclusion.By changing parameters such as the location of the heat storage sphere distribution and the flow rate of the heat transfer medium,the heat storage performance of the heat storage block is further optimized.