Integrated Intelligent Energy

Optimized operation method for CHP integrated energy systems driven by power flow and exergy flow

GE Leijiao, LI Jingjing, LI Peng, SU Hang

2023, 45(12): 1-9. doi:10.3969/j.issn.2097-0706.2023.12.001

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To realize the joint optimization of power systems and thermal systems and improve their energy utilization efficiency and economic benefits， an optimized operation method driven by power flow and exergy flow for a combined heat and power integrated energy system（CHP-IES） is proposed. Firstly， the Newton-Raphson method is used to calculate the power flow in polar coordinates. After iteration， important parameters such as electrical quantity and power at each node of the power network， temperature and flow rate at each node of the thermal network are obtained. Then， the exergy flow calculation mechanism of coupling elements such as power network， thermal network and CHP units is explored. Taking the CHP-IES composed of a 4-node electricity system and a 6-node thermal system as the object， the exergy flow distribution and exergy loss at each link are analyzed， and the joint optimization for the power system and thermal system is realized. The example proves that the optimization can keep the local and global exergy balance of the system， and the exergy efficiency of the thermal system is about 97 %.

Research on solar assisted air source heat pump heating systems

ZHANG Siliang, QI Lintong, QU Haowei, ZANG Dehua, ZHOU Wenhan, WANG Lidi

2023, 45(12): 10-19. doi:10.3969/j.issn.2097-0706.2023.12.002

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To achieve the dual carbon target， China has carried out a series of policies，such as "coal to electricity". To control the excessive heating cost resulting from taking air source heat pumps alone for heating in northern China， PV power generation systems are coupled with heat pumps to assist their heating capacity. The simulation model of a solar assisted heat pump （SAHP）heating system is constructed by Matlab and TRNSYS platform in a laboratory of a Shenyang college. With a designed system operation strategy and maximum power point tracking （MPPT） control algorithm， the PV system output under various irradiation， DC bus voltage， voltage and current varying with the charging and discharging of batteries and other parameters of an SAHP heating system are studied. The influences of the indoor and outdoor temperatures， heat pump power consumption on economic and environmental benefits in heating seasons of the system are analyzed. The results show that the total heating capacity of the SAHP system in one heating season is 4 627.66 kW·h，which meets the heating requirement of keeping the indoor temperature above 19.12 ℃. Furthermore， the cost of the SAHP system per heating season is only 56.68% of that of a pure heat pump system. In terms of the environmental benefits， the SAHP system can reduce the CO₂ emission by 974.24 kg and SO₂ emission by 7.89 kg per year， compared with the traditional boiler.

Design of the integrated energy heating（cooling） system for a commercial and residential park and its economy analysis

LIU Yuanyuan, LIU Fangfang, JIA Tianxiang, HAN Zhao, SHANG Yongqiang, JIANG Shu

2023, 45(12): 20-28. doi:10.3969/j.issn.2097-0706.2023.12.003

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In the context of dual carbon， combining renewable energy with integrated energy systems is an important way to expand the current heating capacity and provide clean heating（cooling），so as to meet people's livelihood needs， and achieve building energy conservation and emission reduction simultaneously. Taking the comprehensive energy heating（cooling）project of a commercial and residential park in north China as the research object，this paper carries out project load analysis，regional resource analysis，and cold and heat source optimization analysis，and puts forward two comprehensive energy heating（cooling）schemes with "central heat network + renewable energy" concept. Scheme 1 removes air source heat pumps，adds an energy storage system and uses an electric boiler as heat source in extremely cold periods. The results of the comparative analysis on two installation schemes and operational economy show that the total expense including electricity bill and heat purchase cost in heating season of scheme 1 is 18.6% lower than that of scheme 2. And the installation capacity of refrigeration unit， electricity bill for cooling， and annually operational cost of scheme 1 are 30.8%， 35.4% and 20.8% lower than that of scheme 2， respectively. This analysis provides reference for the design and operation strategy optimization of integrated energy projects of the same type.

Intelligent scheduling and control of a geothermal-gas complementary heating system based on model prediction

ZHONG Wei, BO Qiming, CAI Chenyu, LU Shimeng, LI Manjie

2023, 45(12): 29-35. doi:10.3969/j.issn.2097-0706.2023.12.004

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In recent years， geothermal heating technology has been doing applied to large-scale central heating for cities in northern China. However， due to the uncertainty and volatility of geothermal heating technology， coordinating and optimizing the outputs of the geothermal heat sources and fossil energy sources is the key to the safe， reliable， efficient and low-carbon operation of the whole heating system. In view of complexity of the heating system for Xiong'an New District geothermal-gas complementary heating system， an intelligent scheduling and control method based on model prediction for this heating system is proposed. Prediction on heat load is made based on the multi-layer perceptron （MLP）， and geothermal heating capacity prediction model is established， in order to provide complementary scheduling and control strategy for a geothermal-gas heating system in different heating stages. The trial operation of the system shows that the scheduling and control method can effectively guarantee the stable operation of the complex heating system with a users' heating load fluctuation under 15%. The strategy realizes the efficient complementary operation between geothermal sources and gas-fired boilers， and improves the flexibility and economy of the heating system.

XGBoost-based regulation and prediction method for the heating station's heating system

YONG Hezhong, ZHANG Ning, HUANG Wei, WEI Zheng, WU Yanling, ZHONG Wei

2023, 45(12): 36-42. doi:10.3969/j.issn.2097-0706.2023.12.005

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Accurate prediction and control of heating stations provide solid data support for the heating systems' energy consumption reduction， users' thermal comfort improvement and pollutant emission alleviation. Making full use of a heating station's key data， such as historical operating states，the set openings of valves and the weather characteristics， a heating station control and prediction method based on Extreme Gradient Boost（XGBoost） is proposed to make accurate regulation on secondary heating supply and return water temperature. Preprocessing， feature construction and model training are conducted on the data above，then a heating station temperature response prediction model is generated. Combining the model and temperature delay time of the secondary network， the valve control strategy is thereafter made. The error between the 24 h predicted temperature and the measured temperature is kept within 0.47 ℃， which verifies the accuracy and reliability of the heating station temperature response prediction model. The proposed strategy can guide the temperature control of heating stations.

Performance simulation and analysis on photovoltaic and photothermal integration system in Baiyin area

JI Mingda, GOU Yujun, ZHONG Xiaohui

2023, 45(12): 43-52. doi:10.3969/j.issn.2097-0706.2023.12.006

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An indirect expansion solar heat pump system is a novel and efficient way to comprehensively utilize solar energy resources. To investigate the impact of different operation modes on the performance of an indirect expansion photovoltaic and photothermal（PV/T） integrated heat pump heating system in winter，a simulation model of the system was established on the Matlab/Simulink platform based on energy balance. Taking the environmental data from Baiyin area as the example，the operation status of the integrated heating system under different operating modes was analyzed. The heating performance of solar heat pumps is better than that of air source heat pumps under the same heating power，and the time control mode performs better than temperature control mode. In the time control mode，taking solar radiation as the control objective is conducive to showing the excellent heating performance and energy utilization efficiency of solar heat pumps.

Compressed supercritical carbon dioxide energy storage system coupled with heat pump and thermodynamic analysis

QIAO Long, XIE Ligang, XIONG Chen, SONG Nanxin, PU Wenhao

2023, 45(12): 53-62. doi:10.3969/j.issn.2097-0706.2023.12.007

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To address the challenge of recovering low-grade compression heat in compressed carbon dioxide energy storage systems， a novel supercritical carbon dioxide（S-CO₂） energy storage system coupled with a heat pump is proposed， and its steady-state analysis model is conducted. Considering the heat capacity matching and heat transfer temperature differences of intercoolers and recuperators， the impacts of hot water flow rate， S-CO₂ temperature at the compressor inlet， temperature differences of intercoolers and recuperators， heat pump evaporating and condensing temperatures on the system performance are studied. To further explore the significance of the influences brought by the temperature differences of intercoolers and recuperators， four modes with different weighting factors of the temperature differences are analyzed. Under a constant total heat transfer temperature difference，four modes are classified with an increasing proportion of intercooler cold end temperature difference and consistent variation of heat transfer temperature differences at heat end and cold end. The research results indicate that， keeping the S-CO₂ flow rate at 50 kg/s and the system's round-trip efficiency （RTE） ranging from 78.2% to 79.6%， the optimal water flow rate range is 19.5 kg/s to 23.5 kg/s. The RTE will peak at 79.62% and the coefficient of performance（COP）of the system will reach 5.9 under mode 3 in which the variations of intercooler heat end and cold end temperature differences are consistent and the cold end temperature difference accounts for a smaller proportion. The fluctuation of the RET changing with pressure is merely 2.1%.

Application analysis on a geothermal + multi-energy complementary energy system for an oilfield area

SUN Guanyu, WANG Yongzhen, YAN Yican, WANG Yufei, ZHANG Ping, ZHANG Lanlan

2023, 45(12): 63-70. doi:10.3969/j.issn.2097-0706.2023.12.008

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As a kind of renewable and clean energy， geothermal energy can be widely applied in green and sustainable heating. Based on the thermal and electricity demands of Jidong Oilfield， a geothermal + multi-energy complementary energy system is designed for this area. The dynamic model of the system is constructed by TRSYS software to analyse its daily and annual operating conditions. The simulation results show that the typical daily cumulative power productions of the photovoltaic module in non-heating season and heating season are 1 726.0 kW·h and 1 301.0 kW·h， respectively， and its daily cumulative off-grid power are 4 636.6 kW·h and 5 355.9 kW·h， respectively. On annual scale， the cumulative power output of the photovoltaic module and the off-grid power are 475.8 MW·h and 1 856.7 MW·h. The installation of a water source heat pump rises the annual utilization rate of heat in waste water by 47.7%. The coefficient of performance （COP） can be improved by increasing geothermal water temperature and flow rate on source side， but cannot be improve by increasing flow rate on source side alone while lowering the heat pump outlet temperature. In terms of environmental protection， the photovoltaic module can reduce the CO₂ emissions from this system by 271.3 t per year. As 92.3% energy of the system is generated by clean energy， this system shows excellent environmental performance.

Capacity optimization configuration of wind-solar complementary electricity-alcohol cogeneration system

YANG Zhengjun, LIANG Shixing, XU Gang, LIU Wenyi, WANG Ying, CUI Jianwei

2023, 45(12): 71-78. doi:10.3969/j.issn.2097-0706.2023.12.009

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In order to advance the application of clean energy in multiple fields and achieve the "dual carbon" target， a wind-solar complementary electricity-alcohol cogeneration system has been proposed. A capacity optimal allocation model for the wind-solar system is established subject to pursue the maximum annual revenue of the electricity-alcohol cogeneration system. Taking the historical data from a wind-solar-hydrogen production base in Inner Mongolia as an example，energy analysis and economic analysis are carried out on the proposed cogeneration system by simulation. The new cogeneration system proposed above can utilize the storage capacity of hydrogen energy after taking optimized configuration and collaborative schedule of wind and solar capacity， ensuring continuous and stable running of methanol synthesis equipment at its minimum load rate of 40% or above. The results show that when the photovoltaic capacity is 25.4 MW， and the wind power capacity is 74.6 MW， the system integrating electricity generation system with alcohol generation system can boost the renewable energy accommodation capacity with a 2.9% decrease in renewable energy curtailment rate. Meanwhile， the annual net income of the new system is 17.73 million yuan， 6.6% higher than that of the system without alcohol generation system. The research provides a feasible technical roadmap for the multi-energy complementation system， with decent economic and environmental benefits.

Complementarity analysis of solar energy and gas turbine combined cycle

GENG Zhi, CHEN Keyu, LIU Yuanyuan, ZHANG Bin, WANG Jianli, SHI Tianqing, LI Fang, GU Yujiong

2023, 45(12): 79-86. doi:10.3969/j.issn.2097-0706.2023.12.010

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In the fight against global energy shortage， how to improve the availability of existing energy has become a research hotspot. As a kind of clean energy， solar energy provides a new developing direction for the gas turbine combined cycle （GTCC） system. The power generation system in which solar energy and gas turbines are integrated in the top cycle （Brayton cycle） can realize multi-energy comprehensive utilization.The thermodynamic models for an ISCC system and a GTCC system are established in line with the first law of thermodynamics. Then， the performance parameters of these two systems are comparatively analyzed by Ebsilon simulation software， and the operating characteristics and energy-saving performance of the ISCC system under different direct normal radiation（DNI） and ambient temperature are studied. The research results show the circulating thermal efficiencies of the GTCC system and ISCC system are 39.8% and 44.1% respectively with a 10 kg/s gas inflow rate. On the premise that ISCC system's electric output remains unchanged， the ISCC system can saved 2.638 kg/s natural gas compared with the GTCC system. The coupling of solar energy and traditional GTCC can improve the thermal efficiency， electric output and economy of the whole system.

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