Dynamic modeling and response characteristics of a solar-driven fuel cell hybrid system based on supercritical CO2 Brayton cycle

Abstract

This study proposes and evaluates a solar-driven system coupled with a solid oxide fuel cell and the supercritical carbon dioxide cycle, aiming to fully utilize the potential of solar energy while ensuring the safe and stable operation of the energy system. The dynamic mathematical model is established by the lumped parameter method, with a maximum model error of less than 5%. This study analyzes the integrated system based on its harsh off-design conditions, with short-term (in seconds), medium-term (in minutes), and long-term (in hours) dynamic responses. Meanwhile, based on the second law of thermodynamics, a study is conducted on the irreversibility of the operation of heat exchangers. Finally, analyze the mismatch between supply and demand in the time scale caused by solar energy fluctuations. The results show that the system can meet 5 h of hydrogen production work in summer and only 2 and a half hours in winter. The transient entropy generation mainly occurs in the first 5 s, with the highest transient additional entropy generation ratio of 71.7%. The findings of this study provide useful information and a reference for ensuring the safe and flexible operation of renewable power generation systems.