Thermal Performance Simulation of Solar Thermal Power Tower System Based on Supercritical CO2 Brayton-Organic Rankine Cycle

doi:10.12096/j.2096-4528.pgt.260219

Abstract

Abstract:

Objectives The supercritical CO₂(SCO₂) Brayton cycle offers higher power generation efficiency compared with conventional steam Rankine cycles, which has good application prospects in solar power generation (SPT). Therefore, the thermodynamic performance of an SCO₂ Brayton cycle-based SPT system for solar thermal power generation is studied. Methods A recompression SCO₂ Brayton cycle (SCRBC), known for its high thermoelectric conversion efficiency, is employed as the top cycle, while an organic Rankine cycle (ORC) is served as the bottom cycle to recover waste heat from the SCRBC. A simulation model for the SCRBC/ORC-based SPT system (SCRBC/ORC-SPT) is developed using Matlab. Among six initially selected ORC working fluids, R600 is chosen as the bottom cycle working fluid for the SCRBC/ORC-SPT system. From a thermodynamic perspective, the impact of key parameters on the thermodynamic performance of the SCRBC/ORC-SPT system is analyzed. With the goal of maximizing system power generation efficiency, a genetic algorithm is applied for global parameter optimization. Results The system efficiency first increases and then decreases with the increase in the split ratio and turbine inlet pressure, indicating the existence of optimal split ratio and optimal cycle pressure ratio that yield the best thermodynamic performance of the system. Moreover, the optimal split ratio exhibits a monotonically increasing trend with the increase in cycle pressure ratio. Increasing the turbine inlet temperature and lowering the main compressor inlet temperature can effectively enhance the system’s power generation efficiency to some extent. Conclusions The maximum power generation efficiency and exergy efficiency obtained by the optimized SCRBC/ORC-SPT system are 34.19% and 36.80%, respectively, which are effectively improved by 4.31% compared with the SCRBC-SPT system. The findings provide theoretical support for enhancing the power generation efficiency of conventional SCO₂ Brayton cycle-based SPT systems and promoting the application of SCO₂Brayton cycle power generation technology.

Key words: solar power tower (SPT), supercritical CO₂ (SCO₂), Brayton cycle, organic Rankine cycle (ORC), combined cycle, thermal performance simulation, parameter optimization

CLC Number:

TK 123

Bin ZHAO, Xuan GAO, Jiaxiang CHEN, Zhang BAI, Kun WANG. Thermal Performance Simulation of Solar Thermal Power Tower System Based on Supercritical CO₂Brayton-Organic Rankine Cycle[J]. Power Generation Technology, 2026, 47(2): 431-442.

Figures/Tables 15

References 21

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参数	数值	参数	数值
太阳辐照度/(W·m^-2)	800	高温回热器换热效能/%	95
定日镜场面积/m²	1 000	低温回热器换热效能/%	89
定日镜场效率/%	75	透平等熵效率/%	90
表面吸收比	0.95	主压缩机等熵效率/%	89
表面发射率	0.85	再压缩机等熵效率/%	89
吸热器管道外径/m	0.019	透平入口压力/MPa	18~28
吸热器管壁厚度/m	0.001 65	透平入口温度/℃	350~750
对流传热系数/(W·m^-2·K^-1)	10	主压缩机入口压力/MPa	7.4
视角因子	1	主压缩机入口温度/℃	32~46
集热器温差/℃	150	分流比	0.45~0.95
风速/(m·s^-1)	5	循环压比	2.0~4.0
管程数	500	膨胀机等熵效率/%	93
蒸发温度/℃	50~95	工质泵等熵效率/%	88
冷凝温度/℃	25	过热度/℃	2
回热器传热温差/℃	5	蒸发器窄点温差/℃	2

参数	数值	参数	数值
太阳辐照度/(W·m^-2)	800	高温回热器换热效能/%	95
定日镜场面积/m²	1 000	低温回热器换热效能/%	89
定日镜场效率/%	75	透平等熵效率/%	90
表面吸收比	0.95	主压缩机等熵效率/%	89
表面发射率	0.85	再压缩机等熵效率/%	89
吸热器管道外径/m	0.019	透平入口压力/MPa	18~28
吸热器管壁厚度/m	0.001 65	透平入口温度/℃	350~750
对流传热系数/(W·m^-2·K^-1)	10	主压缩机入口压力/MPa	7.4
视角因子	1	主压缩机入口温度/℃	32~46
集热器温差/℃	150	分流比	0.45~0.95
风速/(m·s^-1)	5	循环压比	2.0~4.0
管程数	500	膨胀机等熵效率/%	93
蒸发温度/℃	50~95	工质泵等熵效率/%	88
冷凝温度/℃	25	过热度/℃	2
回热器传热温差/℃	5	蒸发器窄点温差/℃	2

有机工质	临界温度/℃	临界压力/MPa	ODP	GWP	成本/(元/kg)	安全性
R245fa	155.11	3.649	0	859	75	B1
R601a	187.80	3.370	0	20	70	A3
R11	198.05	4.408	1	4 660	24	A1
R123	183.70	3.670	0.012	120	228	B1
R600a	134.95	3.648	0	20	36	A3
R600	151.98	3.796	0	4	34	A3

有机工质	临界温度/℃	临界压力/MPa	ODP	GWP	成本/(元/kg)	安全性
R245fa	155.11	3.649	0	859	75	B1
R601a	187.80	3.370	0	20	70	A3
R11	198.05	4.408	1	4 660	24	A1
R123	183.70	3.670	0.012	120	228	B1
R600a	134.95	3.648	0	20	36	A3
R600	151.98	3.796	0	4	34	A3

参数	文献测量值	本文计算值	误差/%
透平功率^[20]	388.00 MW	394.71 MW	1.73
主压缩机功耗^[20]	56.30 MW	57.65 MW	2.34
再压缩机功耗^[20]	45.89 MW	46.63 MW	1.59
高温回热器功率^[20]	1 452.34 MW	1 465.37 MW	0.90
低温回热器功率^[20]	375.00 MW	375.65 MW	0.17
SCRBC净输出功率^[20]	285.81 MW	290.42 MW	1.59
SCRBC热效率^[20]	47.60%	47.86%	0.54
ORC循环热效率^[21]	14.89%	14.59%	2.01

Thermal Performance Simulation of Solar Thermal Power Tower System Based on Supercritical CO₂Brayton-Organic Rankine Cycle

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循环设计参数		数值
透平入口压力/MPa		19.865
分流比		0.668
循环压比		2.684
底循环热效率/%		14.29
常规塔式光热电站发电效率/%		25.51^[21]
顶循环发电系统	发电效率/%	32.78
顶循环发电系统	㶲效率/%	35.28
SPT联合系统	发电效率/%	34.19
SPT联合系统	㶲效率/%	36.80
发电效率提升量/%		4.31
㶲效率提升量/%		4.31

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