Simulation Study On Solar Power Tower System Based On Supercritical CO₂ Brayton Cycle

Supercritical CO₂ Brayton cycle combined with solar tower power technology is considered the next generation of solar thermal technology development,with high efficiency,high power density,simple cycle and so on.In this thesis,supercritical CO₂ Brayton cycle combined with solar tower power system was studied.A solar tower power system based on supercritical CO₂ was first designed in this thesis first.The solar energy resources at the site were evaluated and analyzed in detail.The parameters such as the size and arrangement of the heliostats,the form and the flow pattern of the receiver was carried out,and the design of the power cycle system was analyzed.Then the modeling of tower solar thermal system based on supercritical CO₂ is carried out,including the establishment of the mathematical model of the modules such as the mirror field,the receiver system and the power cycle system.The model results are compared with those of the New Energy Research Laboratory.The results are analyzed and compared to verify the reliability of the system model.Through the simulation of the model,the key parameters of tower solar thermal system based on supercritical CO₂,such as receiver area,convection loss and radiation loss of receiver,receiver efficiency,mirror efficiency and plant efficiency were analyzed in this thesis.With the increase of turbine inlet temperature,the efficiency of Brayton cycle increases,the efficiency of receiver decreases,and the efficiency of the mirror field increases.The efficiency of the whole plant first increases and then decreases,reaching the maximum at about 750 ℃.As the inlet temperature of the turbine increases,the receiver area decreases and the area of the heliostat field decreases.Turbine inlet temperature from 500 ℃ to 800 ℃,receiver area decreased by 21.7%,heliostat area reduced by 22.2%.Finally,the operating parameters of the solar power tower system based on supercritical CO₂ cycle were studied by selecting the operating conditions of the inlet temperature of the turbine at 750℃.The energy supply of the typical day system and the typical solar thermal system Hourly efficiency were studied.The tower solar thermal system based on the supercritical CO₂ cycle has the highest supply ratio of 50%in the summer solstice and the lowest in the solstice with only 27.4%.The average energy supply ratio is about 39.7%.Typical day-by-hour receiver and plant efficiency is the first increase and then decrease.Comparing the average efficiency of four typical daytime plant,the summer solstice day efficiency slightly higher than the equinox and autumnal equinox 0.8 percentage points;the winter solstice The efficiency is lower than the vernal equinox and the autumnal equinox by 5.5 percentage points.The average efficiency of the four typical days is about 20.36%.