Design and economic analysis of molten salt thermal storage system for 600 MW condensing unit

doi:10.3969/j.issn.2097-0706.2026.05.007

Abstract

Abstract:

To achieve deep peak shaving and flexible operation of thermal power units under the "dual carbon" goals and to enhance the grid adaptability of high-capacity pure condensing units， a coupled design and economic analysis of a molten salt heat storage system for a 600 MW condensing unit is conducted. The aim is to propose a technical retrofit scheme that balances peak-shaving capability and thermal economy. A thermodynamic system simulation model of the unit was established based on the EBSILON software， and its accuracy was verified. Two steam extraction and heat storage schemes were proposed. Scheme 1 extracted reheated steam， and scheme 2 extracted main steam. Under rated operating conditions， and based on a heat storage load of 90 MW， a coupled heat storage and release system model was established. A comparative analysis was carried out across five dimensions： peak-shaving capacity， overall plant heat efficiency， absolute electrical efficiency， system cycle efficiency， and engineering applicability. Combined with the peak-valley electricity price policy in Hebei Province， the average daily revenue and static investment payback period of the system were estimated. The simulation results showed that the peak-shaving capacities of scheme 1 and scheme 2 were 38.85 MW and 54.70 MW， respectively， and the system cycle efficiencies were 84.6% and 60.1%， respectively. Under typical peak-valley electricity prices， the average daily net revenues of scheme 1 and scheme 2 were 98 100 yuan and 70 500 yuan， respectively. The static investment payback periods were 2.08 years and 3.53 years， respectively. Scheme 1 demonstrated more excellent performance in terms of system cycle efficiency， absolute electrical efficiency， and economic performance. For the molten salt heat storage retrofit of high-capacity condensing units， the scheme extracting reheated steam ensured significant peak-shaving capability while possessing better thermal economic performance and a shorter investment payback period. With better comprehensive performance， it can be recommended as a technical route for the flexibility retrofit of similar units.

Key words: condensing unit, flexibility retrofit, molten salt heat storage, simulation, economic analysis

CLC Number:

TK01

YUE Baiyang, GENG Shimin, CHENG Siyuan. Design and economic analysis of molten salt thermal storage system for 600 MW condensing unit[J]. Integrated Intelligent Energy, 2026, 48(5): 64-73.

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参数	数值
主蒸汽压力p₀/MPa	16.702 0
主蒸汽温度t₀/℃	531.80
高压缸排汽压力p₂/MPa	3.828 0
高压缸排汽温度t₂/℃	301.72
再热蒸汽进口压力${p}_{\mathrm{r}\mathrm{h}}^{\mathrm{i}\mathrm{n}}$/MPa	3.218 0
再热蒸汽进口温度${t}_{\mathrm{r}\mathrm{h}}^{\mathrm{i}\mathrm{n}}$/℃	300.94
再热蒸汽出口压力${p}_{\mathrm{r}\mathrm{h}}^{\mathrm{o}\mathrm{u}\mathrm{t}}$/MPa	3.218 0
再热蒸汽出口温度${t}_{\mathrm{r}\mathrm{h}}^{\mathrm{o}\mathrm{u}\mathrm{t}}$/℃	531.80
低压缸排汽压力p_c/MPa	0.004 5
低压缸排汽干度x_c	0.905 6
给水泵出口压力${p}_{\mathrm{p}\mathrm{u}}^{\mathrm{o}\mathrm{u}\mathrm{t}}$/MPa	18.784 0
给水泵出口温度${t}_{\mathrm{p}\mathrm{u}}^{\mathrm{o}\mathrm{u}\mathrm{t}}$/℃	171.88
小汽轮机排汽压力p_c,xj/MPa	0.006 0
小汽轮机排汽比焓h_c,xj/（kJ·kg^-1）	2 422.6

项目	三元熔盐(Hitec)	二元熔盐(Solar Salt)
成分	53% KNO₃，7% NaNO₃，40% NaNO₂	60% NaNO₃， 40% KNO₃
密度/(kg·m^-3)	1 983 (150 ℃)	1 899 (300 ℃)
比热容/[kJ·(kg·℃)^-1]	1.55	1.46
热导率/[W·(m·℃)^-1]	0.570	0.520
热稳定性温度/℃	454	600

设备	抽汽换热仿真值/（kJ·kg^-1）	抽汽换热设计值/（kJ·kg^-1）	相对误差/%
H1	253.1	261.5	3.2
H2	390.9	378.4	3.3
H3	573.7	597.3	3.9
H4	755.0	806.8	6.4
H5	912.9	1 002.0	8.9
H6	1 062.5	1 165.5	8.8
H7	1 257.1	1 265.5	0.6
H8	1 336.6	14.0	6.1

参数	仿真值	设计值	相对误差/%
再热器换热量/（kJ·kg^-1）	536.4	527.0	1.7
主蒸汽质量流量/（t·h^-1）	1 784.7	1 818.8	1.8

参数	压力/MPa	温度/℃	比焓/（kJ·kg^-1）
再热蒸汽	3.218	531.8	3 526.35
回水	3.218	205.0	875.55