Conceptual design of novel He-SCO2 Brayton cycles for ultra-high-temperature concentrating solar power

• Published in: Energy conversion and management 2022-05, Vol.260, p.115618, Article 115618
• Main Authors: Li, Qing, E, Erqi, Qiu, Yu, Wang, Jikang, Zhang, Yuanting
• Format: Article
• Language: English
• Subjects: Combined cycle; Concentrating solar power; Conceptual design; Criteria; Design; Design parameters; Efficiency; Energy storage; He-SCO2 Brayton cycles; Heat transfer; High temperature; Multi-objective optimization; Multiple objective analysis; Optimization; Solar energy; Solar power; Temperature; Temperature gradients; Temperature requirements; Thermal energy; Thermodynamic efficiency; Thermodynamic models; Ultra-high-temperature; Ultrahigh temperature
• ISSN: 0196-8904; 1879-2227
• DOI: 10.1016/j.enconman.2022.115618

[Display omitted] •Four new He-SCO2 Brayton cycles are designed for ultra-high-temperature solar power.•Thermal efficiency & fluid temperature difference cannot be maximized concurrently.•The four He-SCO2 cycles are optimized successfully by multi-objective optimizations.•The He-SCO2 cycles can be flexibly selected under different requirements.•Efficiency of 60.5% and temperature difference of 906 °C are obtained concurrently. In this study, to improve the power cycle performance of the ultra-high-temperature (1300 °C) concentrating solar power, four novel He-SCO2 combined Brayton cycles are conceptually designed. After the design, firstly, parameter analysis of the cycles is conducted by developing a thermodynamic model. It is found that two key performance criteria, including the thermal efficiency of the cycle and the temperature difference of the heat transfer fluid, are affected by many parameters, where the temperature difference represents the capability to couple with the thermal energy storage. Moreover, it is found that the two criteria cannot be maximized concurrently by an identical group of operating parameters. Then, multi-objective optimizations are employed to optimize the cycles, where the thermal efficiency and the temperature difference are regarded as the objective functions. The results suggest that the He-SCO2 cycles can achieve better performance than a typical He cycle. Moreover, comparisons of the Pareto optimal fronts of the four He-SCO2 cycles show that the combined cycle with more components can achieve superior performance than those with fewer components. The cycle 4 can yield the highest optimized thermal efficiency of 64.72%, and the cycle 3 can yield the highest temperature difference of 1014.7 °C. Moreover, it is found different cycles can be recommended under different requirements. If the thermal efficiency is required to be as high as possible, the cycles 3 and 4 should be suggested. If the temperature difference is required to be as large as possible, the cycle 1 that needs the fewest components should be recommended. Comparisons among the optimal solutions of the four He-SCO2 cycles show that the cycles 3 and 4 should be recommended when the thermal efficiency and temperature difference are required to be balanced. The optimal cycles 3 and 4 can provide quite high thermal efficiencies of 60.49% and 60.74%, respectively. And their corresponding temperature differences reach 906.1 °C and 899.7 °C, respectively. The abov