Study on the control strategy of a geothermal organic Rankine cycle system

doi:10.11949/0438-1157.20230878

Abstract

Abstract:

The organic Rankine cycle (ORC) has important applications in the field of low and medium-temperature heat utilization. The control strategy exploration is a necessary process for the commercialization of this technology. In this paper, an ORC unit is designed based on the hot-dry-rock geothermal parameters through thermodynamic calculation and equipment selection. Then, the dynamic models of this unit and equipment were developed. The effect of four strategies on the performance of the ORC unit was investigated: constant superheat operation, constant evaporating pressure operation, constant load operation, and variable load operation. The results show that adjusting the flow rate of the working fluid pump can satisfy the dynamic control of the ORC system and achieve efficient and stable operation of the system. The constant superheat operation not only ensures the safe operation of the system when the heat source temperature fluctuates but also shows the best output performance. The constant evaporation pressure operation, constant load operation, and variable load operation can be applied in their required stable pressure, stable load, and variable load scenarios, but they all have a great influence on the superheat level, which limits their scope of application. Therefore, different operation modes should be combined in the control strategy according to the specific operating scenarios in practical applications.

Key words: geothermal heat source, organic Rankine cycle, dynamic simulation, control strategy, system output work

摘要：

有机朗肯循环在中低温热能利用领域有着重要的应用。对其控制策略的研究是该技术走向实用化的必须过程。基于干热岩地热井口条件，通过热力学计算和设备选型设计了对应的ORC机组，并对该机组进行建模和动态仿真，研究了四种策略对ORC机组性能的影响规律及控制性能：恒定过热度运行，恒定蒸发压力运行，恒定负荷运行以及变负荷运行。结果表明：通过工质泵流量进行调节可以满足ORC系统的动态控制，实现系统的高效和稳定运行。恒定过热度运行不仅能在热源温度波动时保证系统的安全运行，同时也表现出最佳的输出性能。恒定蒸发压力运行、恒定负荷运行和变负荷运行可以在其需要的稳压、稳负荷和变负荷场景中应用，但它们都对过热度有极大的影响，这限制了它们的适用范围。因此在实际应用中应根据具体的工作场景在控制策略中组合不同的运行模式。

关键词: 地热源, 有机朗肯循环, 动态仿真, 控制策略, 系统输出功

CLC Number:

TK 123

Peiwei YAN, Manzheng ZHANG, Meng XIAO, Zheng MIAO. Study on the control strategy of a geothermal organic Rankine cycle system[J]. CIESC Journal, 2023, 74(12): 4810-4819.

闫沛伟, 张曼铮, 肖猛, 苗政. 地热能有机朗肯循环系统控制策略研究[J]. 化工学报, 2023, 74(12): 4810-4819.

Figures/Tables 11

Fig.1 Principle and T-s diagram of the ORC system

Table 1 Cycle performance parameters of working fluid

工质	蒸发压力/MPa	净输出功/kW	热效率/%	蒸发器换热量/kW	冷凝器换热量/kW	泵功/kW
R600a	2.48	984.03	10.42	9442.38	8458.35	121.04
R600	1.53	911.54	9.65	9442.38	8530.84	61.34
R245fa	1.28	919.54	9.74	9442.38	8522.84	45.12
R123	0.65	842.95	8.93	9442.38	8599.43	22.03
R601a	0.66	879.76	9.32	9442.38	8562.62	25.05
R601	0.51	865.16	9.16	9442.38	8577.23	18.59
R141b	0.50	794.01	8.41	9442.38	8648.37	14.93

Table 2 ORC system main state point parameters

状态点	位置	温度/ ℃	压力/ kPa	焓/ （kJ/kg）	熵/ （kJ/(kg·K)）	流量/ （t/h）
1	膨胀机入口	100.47	1280	474.53	1.791	158
2	膨胀机出口	59.65	287	452.57	1.81	158
3	冷凝器露点	44.2	287	436.7	1.76	158
6	泵出口	44.2	1280	259.33	1.20	158
7	预热段出口	100.47	1280	340.53	1.43	158
9	热源入口	160	1000	675.7	1.94	100
10	热源出口	80	1000	335.8	1.08	100
11	冷却水入口	25	500	105.3	0.367	734
12	冷却水出口	35	500	147.1	0.504	734

Fig.2 Schematic diagram of the moving boundary model

Table 3 The heat transfer coefficient of each phase region

换热器相区	传热系数
蒸发器单相区^[27]	$α = 0.023 R e 0.8 P r L 0.4 k d i$
蒸发器两相区^[28]	$α t p = E h L + S h n p$ $α L = 0.023 R e L 0.8 P r L 0.4 k L d i$ $α n p = 55 P r 0.12 (- 0.4343 l n P r) - 0.55 M 0.5 q 0.67$
热源侧^[29]	$α o = 0.23 λ d e d e u o ρ μ 0.6 P r 13 μ μ w 0.14$
冷凝器单相区^[27]	$α = 0.36 k d i R e 0.55 P r 13$
冷凝器两相区^[30]	$α 0 = 0.725 λ L 3 ρ L ρ L - ρ V g γ μ L T s - T w d 1 / 4$
冷源侧^[29]	$α = 0.332 k d i R e 0.5 P r 13$

Table 3 The heat transfer coefficient of each phase region

换热器相区	传热系数
蒸发器单相区^[27]	$α = 0.023 R e 0.8 P r L 0.4 k d i$
蒸发器两相区^[28]	$α t p = E h L + S h n p$ $α L = 0.023 R e L 0.8 P r L 0.4 k L d i$ $α n p = 55 P r 0.12 (- 0.4343 l n P r) - 0.55 M 0.5 q 0.67$
热源侧^[29]	$α o = 0.23 λ d e d e u o ρ μ 0.6 P r 13 μ μ w 0.14$
冷凝器单相区^[27]	$α = 0.36 k d i R e 0.55 P r 13$
冷凝器两相区^[30]	$α 0 = 0.725 λ L 3 ρ L ρ L - ρ V g γ μ L T s - T w d 1 / 4$
冷源侧^[29]	$α = 0.332 k d i R e 0.5 P r 13$

Table 4 Design parameters of the expander

参数	数值
进汽压力/kPa	1280
进汽温度/℃	100.47
进汽流量/(t/h)	158
排汽压力/kPa	287
排汽温度/℃	59.65
排汽流量/(t/h)	158
额定功率/kW	919.54
转速/(r/min)	3000

Fig.3 Transient model of the ORC system

Fig.4 Dynamic response of main system parameters under constant superheat operation

Fig.5 Dynamic response of main system parameters under constant evaporating pressure operation

Fig.6 Dynamic response of main system parameters under constant load operation

Fig.7 Dynamic response of main system parameters under variable load operation

References 31

1	Yan D, Yang F B, Yang F F, et al. Identifying the key system parameters of the organic Rankine cycle using the principal component analysis based on an experimental database[J]. Energy Conversion and Management, 2021, 240: 114252.
2	Yu X L, Li Z, Lu Y J, et al. Investigation of an innovative cascade cycle combining a trilateral cycle and an organic Rankine cycle (TLC-ORC) for industry or transport application[J]. Energies, 2018, 11(11): 3032.
3	Braimakis K, Karellas S. Exergetic optimization of double stage organic Rankine cycle (ORC)[J]. Energy, 2018, 149: 296-313.
4	Tchanche B F, Papadakis G, Lambrinos G, et al. Fluid selection for a low-temperature solar organic Rankine cycle[J]. Applied Thermal Engineering, 2009, 29(11/12): 2468-2476.
5	Hu S Z, Li J, Yang F B, et al. Multi-objective optimization of organic Rankine cycle using hydrofluorolefins (HFOs) based on different target preferences[J]. Energy, 2020, 203: 117848.
6	Świerzewski M, Kalina J. Optimisation of biomass-fired cogeneration plants using ORC technology[J]. Renewable Energy, 2020, 159: 195-214.
7	Vera D, Baccioli A, Jurado F, et al. Modeling and optimization of an ocean thermal energy conversion system for remote islands electrification[J]. Renewable Energy, 2020, 162: 1399-1414.
8	Frate G F, Baccioli A, Lucchesi E, et al. ORC optimal design through clusterization for waste heat recovery in anaerobic digestion plants[J]. Applied Sciences, 2021, 11(6): 2762.
9	Liu P, Shu G Q, Tian H. How to approach optimal practical organic Rankine cycle (OP-ORC) by configuration modification for diesel engine waste heat recovery[J]. Energy, 2019, 174: 543-552.
10	吴双应, 易甜甜, 肖兰. 基于多目标函数的亚临界有机朗肯循环的参数优化和性能分析[J]. 化工学报, 2014, 65(10): 4078-4085.
	Wu S Y, Yi T T, Xiao L. Parametric optimization and performance analysis of subcritical organic Rankine cycle based on multi-objective function[J]. CIESC Journal, 2014, 65(10): 4078-4085.
11	Ping X, Yang F B, Zhang H G, et al. Introducing machine learning and hybrid algorithm for prediction and optimization of multistage centrifugal pump in an ORC system[J]. Energy, 2021, 222: 120007.
12	Chen G B, An Q S, Wang Y Z, et al. Performance prediction and working fluids selection for organic Rankine cycle under reduced temperature[J]. Applied Thermal Engineering, 2019, 153: 95-103.
13	Pei G, Li J, Li Y Z, et al. Construction and dynamic test of a small-scale organic Rankine cycle[J]. Energy, 2011, 36(5): 3215-3223.
14	张红光, 杨宇鑫, 孟凡骁, 等. 有机朗肯循环系统中工质泵的运行性能[J]. 化工学报, 2017, 68(9): 3573-3579.
	Zhang H G, Yang Y X, Meng F X, et al. Running performance of working fluid pump for organic Rankine cycle system[J]. CIESC Journal, 2017, 68(9): 3573-3579.
15	Bekiloğlu H E, Bedir H, Anlaş G. Multi-objective optimization of ORC parameters and selection of working fluid using preliminary radial inflow turbine design[J]. Energy Conversion and Management, 2019, 183: 833-847.
16	李鹏, 韩中合, 贾晓强, 等. 动态透平效率对有机朗肯循环系统性能的影响[J]. 化工学报, 2019, 70(4): 1532-1541.
	Li P, Han Z H, Jia X Q, et al. Influence of dynamic turbine efficiency on performance of organic Rankine cycle system[J]. CIESC Journal, 2019, 70(4): 1532-1541.
17	王羽鹏, 梁俊伟, 罗向龙, 等. 基于神经网络的有机朗肯循环过程及循环性能计算方法[J]. 化工学报, 2019, 70(9): 3256-3266.
	Wang Y P, Liang J W, Luo X L, et al. Novel prediction method of process and system performance for organic Rankine cycle based on neural network[J]. CIESC Journal, 2019, 70(9): 3256-3266.
18	Dal Magro F, Jimenez-Arreola M, Romagnoli A. Improving energy recovery efficiency by retrofitting a PCM-based technology to an ORC system operating under thermal power fluctuations[J]. Applied Energy, 2017, 208: 972-985.
19	Xie H, Yang C. Dynamic behavior of Rankine cycle system for waste heat recovery of heavy duty diesel engines under driving cycle[J]. Applied Energy, 2013, 112: 130-141.
20	Da Lio L, Manente G, Lazzaretto A. A mean-line model to predict the design efficiency of radial inflow turbines in organic Rankine cycle (ORC) systems[J]. Applied Energy, 2017, 205: 187-209.
21	Shi Y, Lin R Z, Wu X L, et al. Dual-mode fast DMC algorithm for the control of ORC based waste heat recovery system[J]. Energy, 2022, 244: 122664.
22	Zhang W, Wang E H, Meng F X, et al. Closed-loop PI control of an organic Rankine cycle for engine exhaust heat recovery[J]. Energies, 2020, 13(15): 3817.
23	Wang X, Wang R, Jin M, et al. Control of superheat of organic Rankine cycle under transient heat source based on deep reinforcement learning[J]. Applied Energy, 2020, 278: 115637.
24	Usman M, Imran M, Lee D H, et al. Experimental investigation of off-grid organic Rankine cycle control system adapting sliding pressure strategy under proportional integral with feed-forward and compensator[J]. Applied Thermal Engineering, 2017, 110: 1153-1163.
25	Quoilin S, Aumann R, Grill A, et al. Dynamic modeling and optimal control strategy of waste heat recovery organic Rankine cycles[J]. Applied Energy, 2011, 88(6): 2183-2190.
26	Wei D H, Lu X S, Lu Z, et al. Performance analysis and optimization of organic Rankine cycle (ORC) for waste heat recovery[J]. Energy Conversion and Management, 2007, 48(4): 1113-1119.
27	Bergman T L. Analysis of heat transfer enhancement in minichannel heat sinks with turbulent flow using H₂O-Al₂O₃ nanofluids[J]. Journal of Electronic Packaging, 2009, 131(2): 1.
28	Gungor K E, Winterton R H S. A general correlation for flow boiling in tubes and annuli[J]. International Journal of Heat and Mass Transfer, 1986, 29(3): 351-358.
29	Kern D Q. Process Heat Transfer[M]. New York: McGraw-Hill, 1950.
30	Hewitt G F, Shires G L, Bott T R. Process Heat Transfer[M]. Boca Raton: CRC Press, 1994.
31	Lemort V, Quoilin S, Cuevas C, et al. Testing and modeling a scroll expander integrated into an organic Rankine cycle[J]. Applied Thermal Engineering, 2009, 29(14/15): 3094-3102.

[1]	Siyu ZHANG, Yonggao YIN, Pengqi JIA, Wei YE. Study on seasonal thermal energy storage characteristics of double U-shaped buried pipe group [J]. CIESC Journal, 2023, 74(S1): 295-301.
[2]	Jiahao SONG, Wen WANG. Study on coupling operation characteristics of Stirling engine and high temperature heat pipe [J]. CIESC Journal, 2023, 74(S1): 287-294.
[3]	Xin YANG, Wen WANG, Kai XU, Fanhua MA. Simulation analysis of temperature characteristics of the high-pressure hydrogen refueling process [J]. CIESC Journal, 2023, 74(S1): 280-286.
[4]	Manzheng ZHANG, Meng XIAO, Peiwei YAN, Zheng MIAO, Jinliang XU, Xianbing JI. Working fluid screening and thermodynamic optimization of hazardous waste incineration coupled organic Rankine cycle system [J]. CIESC Journal, 2023, 74(8): 3502-3512.
[5]	Yurong DANG, Chunlan MO, Kerui SHI, Yingcong FANG, Ziyang ZHANG, Zuoshun LI. Comprehensive evaluation model combined with genetic algorithm for the study on the performance of ORC system with zeotropic mixture [J]. CIESC Journal, 2023, 74(5): 1884-1895.
[6]	Zihao QI, Wenqi ZHONG, Xi CHEN, Guanwen ZHOU, Xiaoliang ZHAO, Meijing XIN, Yi CHEN, Yongchang ZHU. Research on dynamic characteristics of cement raw meal decomposition process based on hybrid modeling [J]. CIESC Journal, 2022, 73(5): 2039-2051.
[7]	Cheng ZHANG, Lizhi PAN, Yuan LI. Fault detection and diagnosis method based on weighted statistical feature KICA [J]. CIESC Journal, 2022, 73(2): 827-837.
[8]	JIANG Jiatong, HU Bin, WANG Ruzhu, LIU Hua, ZHANG Zhiping, LI Hongbo. Dynamic simulation of horizontal condenser of R1233zd(E) high temperature heat pump [J]. CIESC Journal, 2021, 72(S1): 98-105.
[9]	WANG Jiaxing, ZHAO Jiarui, LI Site, FU Yuan, LIU Fengjie, WEI Chang. Influence of different discharge valve flow characteristics on ejection process [J]. CIESC Journal, 2021, 72(S1): 318-325.
[10]	Zihang LI, Zhanbo WANG, Zheng MIAO, Xianbing JI. Working fluid selection and thermo-economic analysis of sub-critical organic Rankine cycle [J]. CIESC Journal, 2021, 72(9): 4487-4495.
[11]	CAO Jian, FENG Xin, JI Xiaoyan, LU Xiaohua. Study on the theoretical limit performance of multi-pressure evaporation ORC based on zeotropic mixture [J]. CIESC Journal, 2021, 72(7): 3780-3787.
[12]	SUN Haoran, LYU Zhongyuan, WU Chengyun, HU Haitao. Dynamic simulation model of enhanced vapor injection refrigeration system for aircraft [J]. CIESC Journal, 2021, 72(5): 2484-2492.
[13]	JIANG Jinbo, TENG Liming, MENG Xiangkai, LI Jiyun, PENG Xudong. Dynamic characteristics of supercritical CO₂ dry gas seal based on multi variables perturbation [J]. CIESC Journal, 2021, 72(4): 2190-2202.
[14]	RONG-YANG Yiming, WU Qiaoxian, ZHOU Xia, FANG Song, WANG Kai, QIU Limin, ZHI Xiaoqin. Research on optimization of self-utilization performance of air compression waste heat in air separation system [J]. CIESC Journal, 2021, 72(3): 1654-1666.
[15]	Kun LUO, Xiaodong MAO, Liping PANG. Cockpit thermal control performance of new helicopter heat pump air conditioning system [J]. CIESC Journal, 2020, 71(S1): 187-193.