Optimization And Performance Analyses Of Thermal Storage Device Of Solar Thermal Power Plants

Solar energy is the most abundant reserves of clean and renewable energy,but it is often accompanied by intermittent and non stability characteristics in the process of solar energy utilization.In order to ensure the efficient of power system,it is proposed that the energy storage system can be used to store the solar energy in the form of heat energy.Thermal storage technology has become one of the key technologies in the solar thermal power generation industry.Research on heat storage technology,especially in high temperature thermal storage technology,it is of great significance to improve the efficiency of thermal power generation and reduce the cost of investment.At present,the most widely used heat storage system is the dual tank heat storage system with high investment cost.Therefore,it is put forward that the thermalcline storage system can effectively reduce the investment cost of the heat storage system compared with the dual tank heat storage system.The cold and hot working substance stored in the same single tank,and the natural stratification of the working substance is realized by the density difference.Because of the exist of thermalcline,the heat release efficiency of the thermalcline storage system is generally low.In this paper,on the basis of the single tank structure,a shell and tube type phase change heat exchanger is added to the upper part of the single tank to improve the heat release efficiency of the system.Based on enthalpy method,the numerical model of phase change thermal storage unit is established.The influence of structure and inlet parameters on the performance of the thermal storage unit was studied.And the influence of the thermal conductivity and the melting point of the PCM on the heat performance were discussed.And the numerical model of the mixed heat storage tank is established.After comparing the simulation results with the experimental results,the performance of the mixed heat storage tank were studied and optimized.In the same case,the difference of the heat release performance between the mixed tank and the thermalcline tank is studied.The influence of the parameters such as the boundary condition,the structure of the tank and the packed bed on the heat release performance was also explored.The research of this paper has a certain guiding significance to the optimization design of the heat storage tank.