Thermodynamic analysis of a coupled energy storage system in a coal-fired power plant

doi:10.19799/j.cnki.2095-4239.2025.0107

Abstract

Abstract:

Energy is a fundamental element of human production and life, serving as the foundation for survival and social development. In future power systems, thermal power plants will primarily serve as auxiliary peak regulation sources, providing greater flexibility to accommodate renewable energy integration. This requires combined heating and power units (CHP) to enhance their operational flexibility and avoid frequent start-stop cycles during peak regulation. In this study, a CHP unit is coupled with a compressed carbon dioxide energy storage system (CCES) and a steam ejector (SE), and three improvement schemes are proposed. The technical potential of the CHP-SE-CCES coupling system (CSC) is investigated through a thermodynamic model, and its operational feasibility is analyzed. The advantages of the different schemes relative to the basic system are evaluated, and the influence of key parameters on the performance of the CCES and the CSC is discussed. The results indicate that the addition of an SE significantly improves the operational flexibility of the coupled system. Underrated thermal load conditions, schemes 2 and 3 can reduce the electric load by 68.56 MW and 50.56 MW, respectively, thus expanding the feasible operating range and enhancing thermoelectric decoupling capability. Increasing the hot water tank temperature improves the system power efficiency from 48.84% to 66.84%, the energy storage density from 1.07 kWh/m³ to 1.47 kWh/m³, and the power change ratio from 55.85% to 57.82%. Considering overall energy consumption, scheme 2 emerges as the optimal approach. The proposed method promotes flexible transformation of CHP units and provides a technical reference for integrating thermoelectric units with CCES technology.

Key words: combined heating and power unit, thermoelectric decoupling, compressed carbon dioxide energy storage, steam ejector, thermodynamic analysis

CLC Number:

TM 621

Xiaopeng WANG, Xiuao ZHANG, Hongxia ZHAO, Qiuyan SUN, Hao ZHANG, Gongming XIN, Chao BAI. Thermodynamic analysis of a coupled energy storage system in a coal-fired power plant[J]. Energy Storage Science and Technology, 2025, 14(9): 3509-3520.

Figures/Tables 17

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工作介质	压力/MPa	温度/K	密度/(kg/m³)	状态
空气	1	303.15	11.52	气态
	1	77.15	887.49	液态
	10	303.15	283.74	超临界
	20	303.15	269.81	超临界

CO₂	1	303.15	18.35	气态
	1	233.15	1117.20	液态
	10	313.15	628.61	超临界
	20	313.15	839.81	超临界

参数/单位	值
额定电负荷/MW	350
额定热负荷/MW	250
主蒸汽压力/MPa	16.67
THA工况主蒸汽温度/K	811.15
THA工况再热蒸汽压力/MPa	3.266
THA工况再热蒸汽温度/K	811.15
THA工况主蒸汽质量流量/(t/h)	1037.41
THA工况背压/kPa	4.9

参数/单位	值
环境压力/kPa	101
环境温度/K	298.15
CO₂质量流量/(kg/s)	1000
压缩机等熵效率/%	85
涡轮等熵效率/%	90
回热器效率/%	85
总压缩比	3
总膨胀比	2.71
冷水罐温度/K	288.15
冷水罐压力/kPa	202
CO₂低压储罐温度/K	310.15
CO₂低压储罐压力/kPa	7500
充/放电时间/h	8

组件	Ėx_F,_k	Ėx_P,_k	Ėx_D,_k
COMP1	W_COMP1	Ėx₂-Ėx₁	Ėx_F,COMP1-Ėx_P,COMP1
COMP2	W_COMP2	Ėx₄-Ėx₃	Ėx_F,COMP2-Ėx_P,COMP2
IC1	Ėx₃-Ėx₂	Ėx_w2-Ėx_w1	Ėx_F,IC1-Ėx_P,IC1
IC2	Ėx₅-Ėx₄	Ėx_w3-Ėx_w1	Ėx_F,IC2-Ėx_P,IC2
TURB1	Ėx₈-Ėx₉	W_TURB1	Ėx_F,TURB1-Ėx_P,TURB1
TURB2	Ėx₁₀-Ėx₁₁	W_TURB2	Ėx_F,TURB2-Ėx_P,TURB2
HE1	Ėx_m1-Ėx_m2	Ėx_w5-Ėx_w4	Ėx_F,HE1-Ėx_P,HE1
HE2	Ėx_w10-Ėx_w11	Ėx₁₁-Ėx₁₀	Ėx_F,HE2-Ėx_P,HE2
RH1	Ėx_w7-Ėx_w8	Ėx₇-Ėx₆	Ėx_F,RH1-Ėx_P,RH1
RH2	Ėx_w7-Ėx_w9	Ėx₉-Ėx₈	Ėx_F,RH2-Ėx_P,RH2

工况	电负荷/MW			汽轮机热耗/(kJ/kWh)
工况	计算值	参考设计值	相对误差/%	计算值	参考设计值	相对误差/%
100% THA	352.7	350	0.78	7771.7	7807.0	-0.45
70% THA	246.5	245	0.61	7905.1	7943.7	-0.49
50% THA	176.1	175	0.63	8298.7	8237.5	0.74
30% THA	105.8	105	0.69	8973.4	8899.4	0.83