Analysis Performance Of Supercritical CO₂ Brayton Cycle Coupled With The Waste Heat Utilization Schemes Based On Solar Tower

Supercritical carbon dioxide recompression Brayton cycle(SCRBC)combined with Kalina cycle(KC)and organic Rankine cycle(ORC)has the advantages of compact structure and high energy conversion efficiency and is considered to be an important development direction of combined cycle power generation technology.This paper takes the SCRBC combined cycle system as the research object and conducts the following research.In order to make full use of the cycle waste heat resources and further improve the efficiency of energy conversion,this article has set up a tower-type solar thermal plant(STP).Joint cycle thermal system scheme,i.SCRBC with KC as the bottom cycle of the SCRBC/KC system,ii.SCRBC with ORC as the bottom cycle of the SCRBC/ORC system,iii.SCRBC with KC and ORC in parallel as the bottom cycle of the SCRBC/KC-ORC system,iv.SCRBC with KC and ORC in the twilight as the bottom cycle of the SCRBC/KC/ORC system.Establishing the different circulating cloth formats of power system mathematics models,using computer-aided computing software and combining the Refprop physical parameters software,comprehensive thermodynamic analysis,and exergy analysis of circulating work substance and parameters on system performance.The genetic optimization algorithm is calculated on the thermal efficiency and economic cost of the target systems.The research analysis results show that within the parameter range of the research,in terms of setting parameters,the SCRBC/KC/ORC system has the highest performance,SCRBC/ORC system performance is second,SCRBC/KC-ORC system performance is third,SCRBC/KC system performance is worst.In terms of circulating substance,the R600 is the ORC,and the ammonia aquatic solution with a quality score of 50% is the working substance KC,which can make SCRBC/KC/ORC(R600)highest,followed by SCRBC/KC/ORC(R245fa)system and SCRBC/KC/ORC(R11)system performance.As far as circulating work substance parameters are concerned,the working substance temperature and pressure of the SCRBC turbine,the bottom circulation evaporation temperature,and the bottom circulating work substance expansion ratio of the main compressor will help improve system performance.By optimizing the target parameters of the SCRBC/KC/ORC system,the SCRBC/KC/ORC(R245fa)system performance is greatly improved,so that the SCRBC/KC/ORC(R245fa)system becomes the best system in the optimized target system.The thermal efficiency and exergy efficiency were 47.69%and 70.72%,respectively.On the basis of the above optimization results,through multi-target optimization,the thermal performance and exergy-economic performance of the SCRBC/KC/ORC(R245fa)system are optimized.The optimal thermal efficiency,efficiency,and system exergy economic costs were 47.72%,70.76%,and 6.79 $/GJ,respectively.The optimal layout scheme SCRBC/KC/ORC system that of four different circulation layout forms was found through research analysis and comparison.The genetic optimization algorithm is used to optimize the performance of the target system and calculate the optimal system operating conditions corresponding to the optimal performance of the SCRBC/KC/ORC(R245fa)system,which improves the overall system energy conversion efficiency and optimizes the exergy-economic performance of the system.The research results of this study clarify the direction of SCRBC combined cycle system optimization and provide a certain reference for the application of SCRBC to the thermal utilization of solar thermal parameters..