Research On Performance Model Modeling And Operating Characteristics Of Solar Thermal Power Tower Plant

Compared with three types of solar thermal power generation systems including trough,dish and linear Fresnel,solar thermal power tower plant is a concentrating solar plant(CSP)system with mature technology,high concentration ratio,and high comprehensive power generation efficiency,which is easy to realize large-scale commercial power generation.The concentration system uses a plurality of heliostats to concentrate the solar radiation energy to a receiver which generates a hightemperature heat transfer fluid.Then the heat transfer fluid(HTF)turns water into hightemperature and high-pressure steam,which drives the turbine to generate electricity.The output power of solar thermal power tower plant is susceptible to the fluctuations of solar radiation energy.Therefore,establishing a performance model of solar thermal power tower plant and analyzing the operating characteristics are instructive to the optimization of design and operation of solar thermal power tower plant.This research focus on the performance model modeling and operation characteristics analysis of solar thermal power tower plant.The main research achievements are as following.(1)Based on the circular staggered arrangement method,the arrangement of the heliostat field is generated.According to the ray tracing method,a heliostat field subsystem model is established to calculate the efficiency of concentrator field.The temperature of the heat transfer fluid at the outlet of the receiver is obtained through the receiver subsystem model,which is based on the heat transfer mechanism of the cylindrical receiver.According to the working mode of the double-tank molten salt thermal energy storage system,the model of the thermal energy storage system is established.And the power block system model of the two-stage extraction heat recovery cycle is established to calculate the output power of this plant.(2)By means of modular modeling,the overall performance model of the solar thermal power tower plant is established by combining with the subsystem model.And a 50 MW solar thermal power tower plant is used as the simulation object,the simulation results are compared with the simulation results of the SAM software developed by the NREL,which verifies the accuracy of this model.(3)Based on the performance model of solar thermal power tower plant,the influence of irradiation conditions,focusing strategies and mirror reflectance on the operation characteristics of the unit are analyzed for the heliostat concentrating system;the influence of the type of the heat transfer fluid,the temperature of the heat transfer fluid at the inlet and outlet of the receiver and the flow pattern of the heat transfer fluid on the operation characteristics of the unit are analyzed for the receiver system;the influence of the energy storage period of the thermal energy storage system on the operation characteristics of the unit is analyzed for the thermal energy storage system;and the influence of back pressure of the turbine on the operation characteristics of the unit is analyzed for power block system.According to the analysis of the influence of these key parameters on the operating characteristics of the unit,corresponding optimization measures are proposed in the design and operation of the solar thermal power tower plant.