Analysis of energy coupling characteristics between cogeneration units and compressed air energy storage integrated systems in thermal power plants

doi:10.19799/j.cnki.2095-4239.2020.0385

Abstract

Abstract:

A new scheme for integrating cogeneration units and compressed air energy storage systems is proposed to improve the regulation flexibility of cogeneration units in thermal power plants and increase the peak load regulation capacity of systems and the proportion of renewable energy into the grid. In the enhanced heating stage, a compressed air energy storage system is used to store electric energy, and the compressed heat is used for heating to improve the heating ratio of the system. In the enhanced power supply stage, the extraction steam of a cogeneration unit is used to heat the inlet air of the expander to increase the power generation ratio of the system. Compared with that of the reference system, the scheme's exergy efficiency can be increased by 4%—31.4%, and the heat to power ratio has been widened. The effects of different component parameters on the thermal efficiency, exergy efficiency, and thermoelectric decoupling performance of the system are compared. On this basis, the basic points of several heating conditions are analyzed. The results show that the airflow rate of the compressed air energy storage system has a great influence on the thermal efficiency of the new integrated system, whereas the inlet air temperature of the expander has a greater impact on the thermoelectric ratio of the new integrated system. With the increase in the main steam flow into the steam turbine, the system's total process efficiency and thermal efficiency increase by 5% and 8%, respectively. The loss analysis shows the loss of boiler components. The largest proportion is about 20%, followed by cold source loss, which is about 10%.

Key words: compressed air energy storage, cogeneration, thermoelectric decoupling, exergy analysis

CLC Number:

TM 611

Xiaolu WANG, Huan GUO, Hualiang ZHANG, Yujie XU, Yingjun LIU, Haisheng CHEN. Analysis of energy coupling characteristics between cogeneration units and compressed air energy storage integrated systems in thermal power plants[J]. Energy Storage Science and Technology, 2021, 10(2): 598-610.

Figures/Tables 22

Fig. 1

Table 1

Calculation formula of entropy production and loss"

部件	熵产
锅炉	$S g = m s 2 - s 1 - s f = m s 2 - s 1 - Q T$
汽轮机	$S g = m s 2 - s 1$
换热器	$S g = m h Δ s h + m c Δ s c$
泵	$S g = m s 2 - s 1$
混合器	$S g = ∑ i m i Δ s i$
压缩机	$S g = m s 2 - s 1$
膨胀机	$S g = m s 2 - s 1$

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Table 6

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参数	数值
汽轮机进口压力/MPa	16.67
回热抽汽级数	3高+3低+1除氧
汽轮机进口温度/℃	538
采暖抽汽压力/MPa	0.4
再热蒸汽进气阀前温度/℃	538
再热蒸汽压力/MPa	3.508
额定抽汽工况主蒸汽流量/t·h^-1	1017920
额定抽汽工况抽汽量/t·h^-1	250

参数	取值
压缩机流量/kg·s^-1	50
压缩机等熵效率	0.84
每级间冷器两端换热温差/K	5
间冷(热)器换热压损/MPa	0.02
冷却水压/MPa	1.2
各级压缩机压比	2.9518
膨胀机流量/kg·s^-1	50
膨胀段入口温度/K	443.15
各级膨胀机膨胀比	2.8043
膨胀机等熵效率	0.88

点	流量/kg·s^-1	温度/K	压力/MPa
1	282.8	811.5	16.67
2	234.1	811.7	3.508
3	22.61	695.1	8.143
4	26.01	592.5	3.898
5	9.589	708.4	1.794
6	14.21	608.1	0.8611
7	69.44	516.5	0.4000
8	5.766	516.5	0.4000
9	6.633	424.7	0.1624
10	6.138	380.8	0.0990
11	50.00	300.2	0.1013
12	48.93	303.2	1.200
13	50.00	300.2	6.924
14	26.38	516.5	0.4000

指标	数值
热效率	56.14%
?效率	59.64%
热电比	0.5912

过程	?效率/%
储能过程	86.03
释能过程	80.31
储-释总过程	73.89