The Study And Optimization Of Cascade Integrated Solar Combined Cycle

Nowadays,we confront with a lot of practical problems,such as energy shortage,the greenhouse effect and environmental deterioration.The development of new clean energy has become a hot topic in society.Solar energy because of its characteristics comes into the people’s vision,like almost unlimited reserves,cleanliness and other characteristics,it is recognized as one of the most promising new energy sources.However,solar energy also has the inherent shortcomings such as low energy density,resulting in a high cost and low efficiency of solar-only thermal power generation system.This paper starts from the matching of energy level,and based on Integrated Solar Combined Cycle(ISCC)system,mainly focuses on the optimization of the key processes of the system.The solar thermal-to-power conversion efficiency is improved,the consumption of fossil fuels and the emission of CO2 and other greenhouse gases are reduced.The dual goals of energy saving and emission reduction are achieved.The details are as follows:(1)Due to the time-varying and environmental impact characteristics of solar energy,Integrated Solar Combined Cycle(ISCC)system stay in variable operating conditions for most time,the system performance is reduced.Knowing and mastering the variable operating mode of ISCC system is the key point to improve system performance.Based on the single-pressure ISCC system,this paper studies the operating conditions of ISCC system under different conditions,aiming at optimization of the quantity of water which is sent to solar collector when the solar energy is off-design.The low/mid temperature solar heat is hybrid with water supply evaporation process,so that the performance of the Heat Recovery Steam Generator(HRSG)is improved,and the working fluid flow of the bottom Rankine cycle is increased.The improving of energy level of low/mid temperature solar heat and a high heat-to-power efficient are achieved.The conclusion is expected to provide guidance for variable calculation of ISCC system.(2)Cascade ISCC system is the system that normal combined cycle system hybrid with two solar collectors according to different characteristics of different solar collectors,the evaporators in different pressure level are replaced by Direct Steam Generation system(DSG)solar collector and Evacuated Tube collector which are in different collector temperature.The two-stage ISCC system is constructed.The main purpose is to improve the work ability of the solar energy and reduce the irreversible loss of the dynamic sub-process,to realize the cascade complementary of the conventional fossil fuel and solar energy.The DSG system is coupled with the high pressure steam evaporation process,while the Evacuated Tube collector is used for the low pressure steam generation process.In order to optimize the parameters such as spacing and angle of the collector in the Evacuated Tube collector field,and study the effective solar heat energy and the influence of average heat collection efficiency.The optimization results of the solar collector field are applied to the cascade ISCC system,and the thermal efficiency of the system is simulated and calculated.