* corresponding author(s) 1 DOI: 10.17185/duepublico/48879 3 rd European supercritical CO2 Conference September 19-20, 2019, Paris, France 2019-sCO2.eu-119 DYNAMIC MODELING AND TRANSIENT ANALYSIS OF A MOLTEN SALT HEATED RECOMPRESSION SUPERCRITICAL CO2 BRAYTON CYCLE Pan ZHOU* EDF R&D China Beijing, China Email: Pan.zhou@edf.fr Jinyi ZHANG EDF R&D China Beijing, China Yann LE MOULLEC EDF R&D China Beijing, China ABSTRACT Supercritical CO2 power generation cycle is a promising power generation technology with a high potential to reach high thermal efficiency and high flexibility. In this work, a recompression cycle with intercooling and preheating is selected for the application of supercritical CO2 cycle in concentrated solar power. Given the design boundary conditions, all the equipment are designed and optimized by in-house code, which gives a preliminary geometry for the equipment. The calculated geometries are then integrated into dynamic modules to simulate the off-design behaviors of equipment. Based on the developed equipment dynamic modules, a dynamic physical model of selected cycle is built in Modelica language implemented in Dymola. Part load transient scenarios are defined with technical constraints, such as minimum main compressor inlet temperature and minimum molten salt outlet temperature. With these key scenarios defined and constraints integrated into the model, sensitivity analyses are carried out to understand system dynamics. Global operation and control strategies for system protection, regulation and performance optimization are proposed and designed within MATLAB&SIMULINK to satisfy the pre-defined performance criteria. Finally, scenario simulations are done with the proposed control strategy and tuned control parameters to justify its feasibility. INTRODUCTION Supercritical CO2 (sCO2) cycle has drawn much attention for power generation industry in recent years. Compared to water steam Rankine cycle, it has advantages of simpler cycle layout, more compact turbo-machineries and high potential to reach higher efficiency. In the meantime, CO2 is inexpensive, dense and less corrosive than water at same high temperature, with an easily reachable critical point at 30.98°C and 73.8 bar. sCO2 power cycles could be applied to various potential heat source including nuclear power, coal-fired power, waste heat recovery and renewable energy sources such as concentrated solar power (CSP) and fuel cells [1]. CSP can provide carbon free and renewable energy to meet the energy demand. With integration of thermal storage system, CSP can decouple the solar-to-thermal and thermal-to-electric conversion regardless of the weather condition. However, the Levelized Cost of Electricity (LCOE) of CSP is still non- competitive (120$/MWh, average by 2020, reported in IRENA). Compared with the water steam Rankine cycle utilized in the existing CSP industry, sCO2 cycles coupled with high temperature solar receivers and thermal storage are considered to be a solution to increase cycle efficiency and system flexibility, then to reduce the LCOE of CSP [2]. Dynamic modelling is a useful and efficient tool to help verify the equipment and to develop or optimize the control strategy of the power cycle. Yan [3] has carried out dynamic analysis and control system design for a nuclear gas turbine power plant, in which utilization of inventory control and by pass control is recommended respectively for keeping cycle efficiency and providing fast load regulation. Moisseytsev et al. [4] has developed a detailed dynamic model for a recompression sCO2 Brayton cycle and has studied the cycle automatic control including inventory control, flow split control and etc. In the thesis of Carstens [5], a dynamic model for a sCO2 recompression cycle of 600 MWth has been developed and part load simulation has been carried out with designed PID controllers. In this work, pre-design of a 10 MWe recompression with intercooling and preheating sCO2 Brayton cycle for CSP using molten salt as heat transfer fluid has been carried out and a dynamic model has been developed in Dymola with Modelica language. This cycle was designed for Shouhang – EDF demonstration project signed in 2018, with the objective of retrofit the Shouhang 10MWe CSP plant with sCO2 Brayton cycle before the end of 2020. Transient analysis, temperature control and part load control have been carried out to analyze the dynamic behavior of the model and to study different control strategy for cycle part load.