| The tower photothermal S-CO2Brayton cycle power generation system can meet the requirements of the development of photothermal power generation to large scale and high parameters because of its non-toxic working medium,wide source and high stability.For tower photothermal S-CO2Brayton cycle power generation system,the system efficiency is determined by the efficiency of mirror field,heat storage and Brayton cycle system.The design of the heat collection system includes the analysis of the DNI annual change and sunshine duration of the plant site;Design the size of the heliostat;The layout of mirror field is simulated.The law of the change of the efficiency and loss of the mirror field and the curve of the efficiency change are obtained.The model of S-CO2Brayton cycle was established,and the parameters of the partial flow ratio,pressure ratio and turbine inlet temperature of tower solar photothermal system with S-CO2re-compression Brayton cycle were studied.It is found that the total heat loss of the heat absorber increases from 6.19MW at 500℃to14.54MW at 800℃and 134.9%when the inlet temperature of the turbine is 500℃.The system cycle efficiency reaches the maximum at 750℃with the increase of turbine inlet temperature;When the ratio of the mass flow through the main compressor to the total circulation flow is about 0.7,the system cycle efficiency reaches the maximum.The genetic algorithm is used to optimize the pressure ratio based on the cycle efficiency.The analysis and comparison of the types of molten salts in the heat storage system shows that chloride has the advantages of low viscosity,high specific heat,high thermal conductivity,high latent heat and good stability compared with other molten salts.It can be mixed to prepare mixed molten salt with low melting point according to different proportion.In this paper,Li Cl-KCl（45%and 55%by mass）is used as the heat absorbing medium.The efficiency of the heat storage system and the variation of the heat storage time with seasons are calculated.The results show that the average annual heat storage time is 11.59h.The whole heat storage system can ensure the power station can be fully generated for 10 hours without light source.The temperature cloud chart of molten salt in the tank changes with time by simulating the calculation of the heat storage tank.It is found that the temperature of molten salt in the tank decreases from 900℃to 858℃in 12 hours,and its average temperature is higher than 800℃,so as to meet the cycle requirements. |
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