Research On Energy Storage Performance Of High Temperature Phase Change Heat Storage Unit For Solar Thermal Power System

With the development of economic society, the supply and demand of energy has gradually become the world common concern problems. As a kind of renewable clean energy, solar energy gets more and more attention of the society with it’s broad existence and tremendous reserve. But it has some defects, such as discontinuity, low energy density and so on, which restricted the application of solar energy. Therefore, the efficient and reliable heat storage device is needed, in order to improve the energy utilization of solar energy. The main content of this study is to design more efficient and reasonable high temperature heat storage system for the solar thermal power generation system.Regenerative technology can effectively weaken the difference of the time, intensity and location between the energy supply and demand, which plays an important role in solar energy utilization. The phase change heat storage technology is widely used with the advantages of the high heat storage density, the stable temperature and easy control of the phase process and so on. Therefore, in this thesis, a high temperature phase change thermal storage devices is designed, which uses phase change thermal storage technology and is applied in the solar thermal power generation system, and also the thermal performance of this device was studied using the FLUENT software. First, aluminum silicon alloy was chosen as the high temperature phase change material from the common ones. Then, the physical and mathematical model of the high temperature phase change thermal storage was established using GAMBIT and FLUENT software, and the numerical simulation was preceded. The changes of the PCM temperature and liquid rate with time in the regenerative process were fully realized, and the relationship between its performance and the initial conditions of fluid, the structure size of heat storage and PCM physical property was obtained. In the initial conditions of hot air 923 K and 10m/s, according to study results of the influence of the changes of the regenerator size and PCM physical parameters on the heat storage performance, the conventional design of phase change thermal storage was optimized and the numerical calculation was carried out. Two different types of high temperature phase change thermal storage were designed, which includes variable diameter arrangement of regenerator and PCM cascading, and the simulations were proceeded using FLUENT software in this two kinds. Through the contrast and analysis, these two types are able to reduce the total time of heat storage differently, drop the influence of heat storage caused by the dead zone in the melting at the end, and improve the overall performance of regenerative heat, which has good practical applications.In this thesis, the simulation study and optimal design of the high temperature phase change thermal storage in the solar energy heat power generation system were made, which provides reference for the application of the phase change thermal storage device in solar thermal power generation systems and the further optimization of the heat storage device.