The Kalina cycle (KC) and the organic Rankine cycle (ORC) were used and modeled as the bottom cycles, to economically and efficiently recover the waste heat of the supercritical carbon dioxide Brayton cycle (SCBC). Parametric analysis was conducted and the NSGA-II multi-objective genetic algorithm was performed for these combined systems to optimize the parameters. The optimization results were compared with the SCBC system performance to display the benefits of combined cycles. Parametric analysis results showed that there was an optimal pressure ratio for the thermodynamic performances of both integrated cycle schemes. The thermodynamic performances of the two schemes were improved by raising the turbo expansion ratio of bottom cycles, and the exergoeconomic performances of the systems were promoted by upping the inlet temperature of the bottom cycle turbine. Comparison results showed that the optimized SCBC/KC system’s thermal efficiency and exergy efficiency increased by 9.27% and 8.69% respectively compared with that of the pre-optimized SCBC system, and its exergoeconomic cost increased by 0.92%. The thermal efficiency and exergy efficiency of SCBC/ORC system increased by 10.73% and 10.08% respectively, and the exergoeconomic cost increased by 1.87%. Comparative analysis showed that the SCBC/KC system was more exergy economical, while SCBC/ORC system was more energy efficient.
Ting-fang YU,Ling SONG. Performance analysis and optimization of supercritical CO2 Brayton cycle waste heat recovery system. Journal of ZheJiang University (Engineering Science), 2023, 57(2): 404-414.
Tab.4Exergoeconomic balance equations for each components in SCBC/ORC system
Fig.4Program design flowchart for SCBC/KC and SCBC/ORC systems
循环
设定参数
不同工况
ηtr/%
ηt/%
Δ/%
KC[4]
wk=0.5, p05=681 kPa
θw=100 ℃,pg=1 767 kPa
6.60
6.41
2.88
θw=120 ℃,pg=2 411 kPa
8.87
8.80
0.79
θw=140 ℃,pg=3 161 kPa
10.05
10.64
5.87
ORC[19]
R245fa
θw=119.80 ℃,p010=178.00 kPa
13.68
13.63
0.37
R601
θw=125.50 ℃,p010=82.00 kPa
14.59
14.57
0.14
SCBC[4]
PR=3, p1=7 400 kPa, θ5=550 ℃
—
39.61
39.60
0.03
SCBC/KC[4]
wk=0.5, θw=120 ℃,pg=1 200 kPa, p05=410 kPa
—
41.29
41.26
0.07
Tab.5Model validation of SCBC and SCBC/KC and bottom cycle KC and ORC
循环参数
数值
循环参数
数值
p1/kPa
7400
pr
3
θ1/℃
35
ηT,ηTK
0.9
θ5/℃
550
ηC
0.85
PR
3
ηTO
0.8
ΦER/MW
600
ηH、ηL
0.86
wk
0.45
cQ/($·MW?1·h?1)
7.4
θw/℃
120
CI,p/CI,o[19]
1.26
pg/kPa
1500
—
—
Tab.6Setting parameter values of SCBC/KC and SCBC/ORC combined cycle systems
决策变量
设定边界范围
θ5/℃
500~600
PR
2.2~4.0
θw/℃
100~130
pr
2.2~4.0
Tab.7Scope boundaries of decision variables for multi-objective optimization
Fig.5Variation in thermodynamic performances and outputs of SCBC/KC and SCBC/ORC combined cycle systems with top cycle pressure ratio
Fig.6Variation in exergoeconomic costs of SCBC/KC and SCBC/ORC combined cycle systems with top cycle pressure ratio
Fig.7Variation in thermodynamic performances of SCBC/KC and SCBC/ORC combined cycle systems with turbine expansion ratio
Fig.8Variation in exergoeconomic costs of SCBC/KC and SCBC/ORC combined cycle systems with turbine expansion ratio
Fig.9Optimal Pareto front sets of multi-objective optimization in SCBC/KC and SCBC/ORC combined cycle systems
系统
SCBC/KC
SCBC/ORC
PR
3.34
3.27
θ5/℃
593.93
599.85
θw/℃
128.97
127.76
pr
3.39
3.37
ηt/%
43.27
43.85
ηe/%
64.51
65.33
c /($·GJ?1)
10.82
10.92
Tab.8Multi-objective optimization results for SCBC/KC and SCBC/ORC combined cycle systems
状态点
p/kPa
θ/℃
h/(kJ·kg?1)
s/(kJ·kg?1·K?1)
e/(kJ·kg?1)
qm/(kg·s?1)
1
7400.00
35.00
402.40
1.66
200.84
1931.28
2
24716.00
123.33
454.58
1.68
247.39
1931.28
3
24716.00
286.70
701.68
2.21
344.94
2646.26
4
24716.00
412.52
860.45
2.47
431.27
2646.26
5
24716.00
593.93
1087.18
2.76
575.00
2646.26
6
7400.00
447.25
923.27
2.79
403.85
2646.26
7
7400.00
309.18
764.49
2.54
314.27
2646.26
8
7400.00
149.35
584.16
2.18
236.44
1931.28
9
7400.00
100.82
525.47
2.03
219.65
1931.28
01
1500.00
128.97
1884.81
6.35
398.67
60.31
02
442.48
40.37
1705.02
6.42
200.61
60.31
03
1500.00
128.97
478.31
1.98
81.42
175.50
04
1500.00
53.05
130.70
1.02
4.60
175.50
04v
442.48
53.24
130.70
1.03
3.56
175.50
05
442.48
67.93
533.33
2.42
61.77
235.81
06
442.48
42.37
97.06
1.09
2.56
235.81
07
1500.00
42.86
98.69
1.09
3.88
235.81
08
1500.00
90.52
357.40
1.84
48.65
235.81
Tab.9Thermodynamic state point parameters for SCBC/KC system under optimized operation conditions
状态点
p/kPa
θ/℃
h/(kJ·kg?1)
s/(kJ·kg?1·K?1)
e/(kJ·kg?1)
qm/(kg·s?1)
1
7400.00
35.00
402.40
1.66
200.84
1945.09
2
24198.00
121.73
453.36
1.68
246.29
1945.09
3
24198.00
281.92
696.46
2.21
341.30
2641.42
4
24198.00
417.94
867.76
2.48
434.43
2641.42
5
24198.00
599.85
1094.91
2.77
579.03
2641.42
6
7400.00
455.03
932.38
2.80
409.40
2641.42
7
7400.00
306.16
761.08
2.54
312.52
2641.42
8
7400.00
147.55
582.06
2.17
235.75
1945.09
9
7400.00
84.26
503.44
1.97
214.69
1945.09
09
1500.00
127.76
505.35
1.86
61.21
677.22
010
445.10
94.67
485.51
1.88
37.52
677.22
011
445.10
58.66
278.39
1.26
5.40
677.22
012
1500.00
59.37
279.52
1.26
6.29
677.22
Tab.10Thermodynamic state point parameters for SCBC/ORC system under optimized operation conditions
[1]
GARG P, KUMAR P, SRINIVASAN K Supercritical carbon dioxide Brayton cycle for concentrated solar power[J]. The Journal of Supercritical Fluids, 2013, 76: 54- 60
doi: 10.1016/j.supflu.2013.01.010
[2]
MECHERIA M, MOULLE Y L Supercritical CO2 Brayton cycles for coal-fired power plants [J]. Energy, 2016, 103: 758- 771
doi: 10.1016/j.energy.2016.02.111
[3]
AçıKKALP E Ecologic and sustainable objective thermodynamic evaluation of molten carbonate fuel cell–supercritical CO2 Brayton cycle hybrid system [J]. International Journal of Hydrogen Energy, 2017, 42: 6272- 6280
doi: 10.1016/j.ijhydene.2016.12.110
[4]
LI H, XU M, YAN X, et al Preliminary conceptual exploration about performance improvement on supercritical CO2 power system via integrating with different absorption power generation systems [J]. Energy Conversion and Management, 2018, 173: 219- 232
doi: 10.1016/j.enconman.2018.07.075
[5]
ZHANG F, LIAO G, E J, et al Comparative study on the thermodynamic and economic performance of novel absorption power cycles driven by the waste heat from a supercritical CO2 cycle [J]. Energy Conversion and Management, 2021, 228: 113671
[6]
LI Z, LIU X, SHAO Y, et al Research and development of supercritical carbon dioxide coal-fired power systems[J]. Journal of Thermal Science, 2020, 29 (3): 546- 575
doi: 10.1007/s11630-020-1282-6
[7]
MOHAMMED R H, ALSAGRI A S, WANG X Performance improvement of supercritical carbon dioxide power cycles through its integration with bottoming heat recovery cycles and advanced heat exchanger design: a review[J]. International Journal of Energy Research, 2020, 44: 7108- 7135
doi: 10.1002/er.5319
[8]
曹宇, 王治红, 马宁, 等 超临界二氧化碳布雷顿/有机朗肯循环联合系统的热力学特性[J]. 热能动力工程, 2020, 35 (4): 9- 23 CAO Yu, WANG Zhi-hong, MANG Ning, et al Thermodynamic properties of supercritical CO2 Brayton/organic Rankine cycle combined system [J]. Journal of Engineering for Thermal Energy and Power, 2020, 35 (4): 9- 23
doi: 10.16146/j.cnki.rndlgc.2020.04.002
[9]
BESARATI S M, YOGI G D Analysis of advanced supercritical carbon dioxide power cycles with a bottoming cycle for concentrating solar power applications[J]. Journal of Solar Energy Engineering, 2014, 136: 1- 7
[10]
SONG J, WANG Y, WANG K, et al Combined supercritical CO2 (SCO2) cycle and organic Rankine cycle (ORC) system for hybrid solar and geothermal power generation: thermoeconomic assessment of various configurations [J]. Renewable Energy, 2021, 174: 1020- 1035
doi: 10.1016/j.renene.2021.04.124
[11]
AKBARI A D, MAHMOUDI S M S Thermoeconomic analysis and optimization of the combined supercritical CO2 (carbon dioxide) recompression Brayton/organic Rankine cycle [J]. Energy, 2014, 78: 501- 512
doi: 10.1016/j.energy.2014.10.037
[12]
LI H, WANG M, WANG J, et al Exergoeconomic analysis and optimization of a supercritical CO2 cycle coupled with a Kalina cycle [J]. Journal of Energy Engineering, 2017, 143: 1- 13
[13]
FAN G, DAI Y P Thermo-economic optimization and part-load analysis of the combined supercritical CO2 and Kalina cycle [J]. Energy Conversion and Management, 2021, 245: 114572
[14]
FENG Y, DU Z, SHREKA M, et al Thermodynamic analysis and performance optimization of the supercritical carbon dioxide Brayton cycle combined with the Kalina cycle for waste heat recovery from a marine low-speed diesel engine[J]. Energy Conversion and Management, 2020, 206: 112483
[15]
NEMATI A, NAMI H, RANJBAR F, et al A comparative thermodynamic analysis of ORC and Kalina cycles for waste heat recovery: a case study for CGAM cogeneration system[J]. Case Studies in Thermal Engineering, 2017, 9: 1- 13
doi: 10.1016/j.csite.2016.11.003
[16]
FIASCHI D, MANFRIDA G, ROGAI E, et al Exergoeconomic analysis and comparison between ORC and Kalina cycles to exploit low and medium-high temperature heat from two different geothermal sites[J]. Energy Conversion and Management, 2017, 154: 503- 516
doi: 10.1016/j.enconman.2017.11.034
[17]
WANG Y, TANG Q, WANG M, et al Thermodynamic performance comparison between ORC and Kalina cycles for multi-stream waste heat recovery[J]. Energy Conversion and Management, 2017, 143: 482- 492
doi: 10.1016/j.enconman.2017.04.026
[18]
OZAHI E, ABUSOGLU A, TOZLU A A comparative thermoeconomic analysis and optimization of two different combined cycles by utilizing waste heat source of an MSWPP[J]. Energy Conversion and Management, 2021, 228: 113583
[19]
WANG S, LIU C, ZHANG S, et al Multi-objective optimization and fluid selection of organic Rankine cycle (ORC) system based on economic-environmental-sustainable analysis[J]. Energy Conversion and Management, 2022, 254: 115238