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Comparison of heat transfer characteristics between air-cooled and liquidcooled energy storage battery modules
YE Xinglian;ZHONG Zhitao;ZHANG Chucheng;SU Yinbiao;Han Zhigang;[Objective] During the operation of lithium-ion energy storage batteries, a large amount of heat is generated,and high temperatures can lead to thermal runaway, affecting battery safety. The thermal management system is a keyfactor affecting the stability and efficiency of lithium-ion energy storage batteries. [Methods] Using numerical simulationmethods, the heat transfer characteristics of parallel air-cooled and liquid-cooled battery modules are quantitativelycompared and discussed, including heat transfer performance, flow resistance performance, overall flow heat transferperformance, and the influence of ambient temperature. [Results] The results show that when considering themaximum temperature and maximum temperature difference of the battery module, there is a threshold for thetemperature difference between the inlet and outlet of the cooling medium in the selection between air-cooled and liquid-cooled methods. The overall temperature uniformity of the liquid-cooled method is better than that of air-cooled, with atemperature difference of only 0.5 ℃ between each cell, while air-cooled shows 6.1 ℃. The heat transfer performance ofthe liquid-cooled method is better than that of air-cooled, while the flow resistance performance of the liquid-cooledmethod is inferior to that of air-cooled. However, overall, the comprehensive flow heat transfer performance of the liquid-cooled method is better than that of air-cooled, and the performance advantage gradually increases with the increase incooling medium flow rate. In the environment temperature range of 0 ℃ to 30 ℃, the liquid-cooled method has astronger ability to adapt to environmental temperature changes than air-cooled, with its heat transfer performance beingless affected by environmental temperature, resulting in a maximum temperature increase of only 1.1 ℃. [Conclusion] Theresearch methods and results described in this paper can provide references for related research, which is conducive to thefurther optimization of energy storage cooling methods.
Research progress of desulfurization technology in circulating fluidized bed boiler
HAN Kaize;LIU Fang;ZHANG Guangxue;[Objective] Circulating fluidized bed(CFB) boilers can achieve desulfurization during combustion by addingcalcium-based desulfurizer to the furnace, and the original emission concentration of SO_2 at the furnace outlet is low.However, in the face of increasingly stringent emission standards for air pollutants in thermal power plants, how tooptimize the furnace desulfurization process and consolidate the advantages of low-cost pollutant emission control ofCFB boilers is a very concerned issue in engineering. It is necessary to carry out a more in-depth understanding of theSO_2 generation and furnace desulfurization characteristics of CFB boilers. [Methods] This paper summarizes theinfluence of various design or operation parameters on the desulfurization efficiency in the furnace by combing therelevant research on the desulfurization in the furnace of CFB boiler in recent years, and puts forward the correspondingcontrol measures for the desulfurization in the furnace. [Results] The research shows that under the given desulfurizerand boiler load, improving the efficiency of the separator and the performance of the material circulation system, usingultra-fine limestone matching with the high-efficiency separator, reasonably designing and regulating the furnacetemperature(800~850 ℃) and oxygen content, determining the appropriate limestone feeding position, andappropriately increasing the calcium-sulfur ratio but not higher than 3.3, can effectively improve the desulfurizationefficiency in the furnace. Even under specific working conditions, it can directly meet the SO_2 ultra-low emissionstandards without relying on the tail flue gas desulfurization system. However, in-furnace desulfurization usually leads toan increase in NO_x emissions. When the calcium-sulfur ratio exceeds 2, the increase in boiler heat loss reduces theboiler efficiency. In addition, the increase in CaO and desulfurization products in fly ash also has a certain impact on thetail dust removal performance. [Conclusion] It is necessary to optimize the desulfurization performance of CFB boiler,and pay attention to the overall operation economy of the boiler..
Controlled preparation and calcium-doping modification of Li[Ni0.8Co0.1Mn0.1]O_2 Cathode material for Lithium-Ion batteries
AN Pengyan;WANG Shuran;DONG Mohan;FU Shizheng;ZHANG Yilong;WANG Jiashun;ZHANG Deliu;LIU Zhaomeng;[Objective]As the core component of battery module, cathode material is the key point of to high energydensity of battery. Among them, the high nickel ternary material has become the first choice for cathode materialsbecause of its low cost and high capacity. However, due to the presence of nickel elements, lithium-nickel mixing occurs and the battery cycle stability is extremely poor. Herein, the preparation and calcium doping modification of terpolymer Li[Ni)(0.8)Co0.1Mn0.1]O_2(NCM811) were studied. [Methods]The precursor of ternary material NCM811 was prepared by coprecipitation method. The optimum synthesis conditions were obtained by analyzing the effects of different standing time on the morphology, structure and electrochemical properties of the particles. Calcium is used as doping element and modify ternary material to improve their capacity and circulation performance. [Results]The study showed that the multiplicity of 10 h of resting showed better performance, but the first discharge capacity is higher at 1 h. The specific discharge capacity and capacity retention rate after 100 cycles for 1 h and 10 h are very close to each other. When the calcium doping is 3%, the opposite effect will appear, leading to the intensification of cationic mixing, and the deterioration of circulation and magnification properties. The result is calcium doped at 2% for the optimal doping amount. The NCM material with a doping capacity of 2% has a discharge specific capacity of 178.25 mA·h/g at 0.1 C, a Coulomb efficiency of 81.55%, a discharge specific capacity of 154.64 mA·h/g and a capacity retention rate of 86.37% after 100 cycles at 1 C. Material synthesised with a resting time of 10 h has better multiplicative properties. [Conclusion]Appropriate amount of calcium doping can reduce the degree of cation mixing and discharging, which significantly improves the discharge specific capacity and capacity retention of ternary materials, and improves the cycling and multiplication performance of ternary materials.and the battery cycle stability is extremely poor.Herein,the preparation and calcium doping modification of terpolymer Li[Ni0.8Co0.1Mn0.1]O_2(NCM811) were studied.[Methods]The precursor of ternary material NCM811 was prepared by coprecipitation method.The optimum synthesis conditions were obtained by analyzing the effects of different standing time on the morphology,structure and electrochemical properties of the particles.Calcium is used as doping element and modify ternary material to improve their capacity and circulation performance.[Results]The study showed that the multiplicity of 10 h of resting showed better performance,but the first discharge capacity is higher at 1 h.The specific discharge capacity and capacity retention rate after 100 cycles for 1 h and 10 h are very close to each other.When the calcium doping is 3%,the opposite effect will appear,leading to the intensification of cationic mixing,and the deterioration of circulation and magnification properties.The result is calcium doped at 2% for the optimal doping amount.The NCM material with a doping capacity of 2% has a discharge specific capacity of 178.25 mA·h/g at 0.1 C,a Coulomb efficiency of 81.55%,a discharge specific capacity of 154.64 mA·h/g and a capacity retention rate of 86.37%after 100 cycles at 1 C.Material synthesised with a resting time of 10 h has better multiplicative properties.[Conclusion]Appropriate amount of calcium doping can reduce the degree of cation mixing and discharging,which significantly improves the discharge specific capacity and capacity retention of ternary materials,and improves the cycling and multiplication performance of ternary materials.
Liquid cooling model design and multi-objective optimization of battery parameters based on liquid metal cooling
YANG Liwei;MA Kailun;ZHOU Xiaoming;[Objective] To address the heat generation issue of lithium batteries under high-rate discharge, a liquidcooling scheme based on liquid metal was designed, aiming to enhance thermal performance and system stabilitythrough multi-objective optimization.[Methods] A single-inlet double-outlet cooling loop using gallium-based liquid metalwas proposed. Numerical simulations via Fluent were conducted to analyze the effects of coolant velocity, channelheight, branch width increment, and inclination angle on thermal performance. Orthogonal experiments and the NSGA-IImulti-objective genetic algorithm were employed for parameter screening and optimization. [Results]The optimalparameters were determined as coolant velocity 0.42 m/s, branch width increment 0.13 mm, inclination angle 87.38°,and channel height 5.76 mm. The optimized system achieved a maximum temperature of 312.66 K, temperaturedifference of 11.66 K, and pressure drop of 0.712 kPa. Compared to the initial design, the maximum temperature andtemperature difference decreased by 0.53% and 8.04%, respectively, with a slight increase in pressure drop.[Conclusion] Liquid metal cooling significantly improves heat dissipation efficiency, with velocity and channel heightbeing dominant factors. The NSGA-II algorithm effectively balances thermal performance and pressure drop, offering apractical solution for high-rate battery thermal management..
Heat transfer characteristics of a new refractory brick thermal storage system coupled with air convection
SONG Yanmei;YANG Yusen;WANG Xinran;DU Cangbao;YANG Xiaofeng;CHEN Weixiong;SUN Lin;State Key Laboratory of Multiphase Flow in Power Engineering (Xi'an Jiaotong University);[Objective] In this paper, a new type of refractory brick solid heat storage system is designed to optimize thepeaking performance of gas-fired combined cycle units, to solve the problem of nighttime industrial steam supply underthe mode of daytime on/nighttime off of the units, and to realize the energy laddering utilization and cogeneration.[Methods] By establishing a numerical simulation model of steam-coupled refractory bricks thermal storage, the phasechange heat transfer are analyzed, convective heat transfer and thermal conductivity characteristics of the preheat,evaporation and superheat sections. Computational fluid dynamics simulation is combined with experimental validationto investigate the trends and differences of thermal diffusion in the heat storage/exothermic process of the heat storagebody. The mesh-independence validation is applied to ensure the accuracy of the simulation. [Results] The heatstorage system unit reaches more than 80% of heat storage and heat release within 4 h. The maximum average heatstorage rate and heat release rate are 15.9 kW/m3 and 22.0 kW/m3, respectively. It can quickly and efficiently store theheat of the steam and release the heat to the steam, and the experimental and simulation results are in good agreementwith the simulation results, which verifies the feasibility of the technology. The heat transfer temperature and pressure inthe energy release stage is significantly higher than that in the energy storage stage, indicating that the system is moreefficient in releasing energy. [Conclusion] The device can efficiently store and release steam heat, enhance the peakshifting capability of gas-fired units, reduce the dependence on gas boilers, and at the same time realize deep peakshifting and stable supply of thermal energy through heat storage, which can effectively solve the impact of low load ofcoal-fired boilers on the operational safety of the units, and it has significant economic benefits and popularization value.
Comprehensive evaluation of energy storage policies based on multi-objectives
SHEN Haotian;ZHANG Hualiang;XU Yujie;SU Xu;MEN Jingjing;WANG Yao;CHEN Haisheng;Nanjing Institute of Future Energy System;[Objective]The energy storage policy system is relatively complex and a scientific and comprehensiveevaluation is an effective means to promote the development of the energy storage industry. [Methods]This paper usesthe entropy weight and Topsis method along with the analytic hierarchy process to conduct comprehensive evaluations ofenergy storage policies under various provinces and reflect the level of promotion of energy storage projects by policies.Firstly, considering the effectiveness of policy implementation and combined with the actual application scenarios of energystorage power plants, a comprehensive evaluation system of seven indicators covering economic, technical andenvironmental indicators has been established. Then, the representative policies from Qinghai, Zhejiang, Inner Mongolia,and Henan provinces are selecting and the results of multi-index scenario analysis based on policy content has beenevaluated with entropy weight and Topsis method. Besides, the Analytic Hierarchy Process is used to comprehensivelyevaluate energy storage policies under thinking of different focuses of multiple objectives. [Results]The results indicatethat the entropy weight and Topsis method has the optimal energy storage policy in Zhejiang Province, reflecting therelative maximization of operational efficiency of energy storage power stations under the policy support of ZhejiangProvince. Under the subjective intentions of considering economic, technical, and environmental goals separately, theenergy storage policies in Zhejiang, Henan, and Zhejiang are the most optimal which reflects the level of support fordifferent goals in the three provinces, [Conclusion] indicating the demand to establish a priority order for subjectiveevaluation of policies.
Research on simulation technology of coupled molten salt heat storage and peak regulation in coal-fired power plant
YIN Qiuyu;LI Debo;FANG Lijun;YU Fengjian;CHAI Yongquan;JIN Fengchu;CHEN Zhaoli;[Objective]To further improve the flexibility of coal-fired power plants, the peak shifting depth is increased.[Methods] In this paper, a 670 MW supercritical primary reheat coal-fired unit is taken as the research object, and athermal system model is established based on Ebsilon 16.4 to simulate the combination of three heat storage schemesand three heat release schemes. The performances of different combination schemes are evaluated by comparing theindexes of peaking depth, heat storage power, efficiency and thermal efficiency. [Results]Under the heat storagecondition, extracting the exhaust steam from the medium-pressure cylinder can significantly reduce the load of the low-pressure cylinder up to 78%.It is necessary to combine with reheat steam to increase the temperature of the molten salt;the electric heating heat storage scheme has the highest heat storage power up to 100.17 MW·h, but the molten saltdosage is larger. In the heat release condition, heating high-pressure feedwater step by step can reduce the amount ofsteam extraction, and the maximum electric load is increased by 7.4%. The analysis of the combined scheme showsthat the scheme of electrically heated heat storage combined with step-by-step heating of feedwater has the optimalperformance, with its whole-process exergy efficiency of 40.71%, thermal efficiency of 42.3%, and peak shifting depthsignificantly better than other schemes. In addition, the working temperature range of molten salt has a significant effecton energy utilization, and the temperature difference control can reduce the energy loss. The electrically heated heatstorage scheme is better than the traditional steam extraction heat storage in terms of energy reuse rate and systemefficiency, and is suitable for scenarios requiring fast response to peak shifting. The strategy of heating the high-pressurefeedwater step by step when releasing the heat can maximize the flexibility of the unit. [Conclusion] The results of thestudy provide a theoretical basis for the design and modification of the coupled molten salt thermal storage system incoal-fired power plants, which is an important reference value for new energy consumption and grid stability improvement.
FBG-based study of in-situ strain and temperature evolution in prismatic cell
HUANG Danru;GE Xiaoyu;ZHANG Yi;PEI Fei;HUANG Qiaosheng;WANG Jianhao;MOU Shenzhou;XU Xing;[Objective] Prismatic cells generate strains and heat during charging and discharging due to changes of theelectrodes' lattice structure and electro-chemical reactions, and such strains and heat have an important impact on keyindicators such as the state of charge, safety performance, and service life of the cells. [Methods] In order to monitorand analyze strain and temperature change more accurately, fiber bragg grating(FBG) technology is used to conduct anin-depth study on prismatic cells composed of lithium iron phosphate(LFP) and graphite, including the optimalapplication of FBG, the monitoring of single-electrode strain changes and correlation analysis with the changes in thecrystalline structure of the electrode material, and the application of FBG to monitor the temperature change of the cellmodule in the energy storage power station. [Results] The results show that using fiber optic strain gauges on the sideof the cell or indirectly monitoring the strain of the front of the cell through a fixture can stably capture the strain changeof the cell during cycling, and the strain during the cycling process is about 500 με on the front, and 50 με on the side.The change of the crystal lattice volume caused by lithium ions insertion and extraction is the fundamental cause of thechange of the cell strain. The cell side area has the most serious heat accumulation compared(3 ℃ higher). Theperformance of the FBG in temperature measurement accuracy is comparable to that of thermocouples but themultiplexing is better, which realizes the use of one optical fiber etched with two FBGs to monitor the temperaturechanges of two batteries. [Conclusion] Therefore, the FBG technology reveals the mechanism of strain andtemperature evolution in the cycling process of prismatic cells, and has a broad application prospect in the field ofbattery monitoring.
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Introduction
Electric Power Technology and Environmental Protection
Bimonthly issued
CN 32-1808/X
ISSN 1674-8069
Governed by:
China Energy Investment Group Co., Ltd.
Sponsored by:
China Energy Group Science and Technology Research Institute Co., Ltd.
Academic support：
State Key Laboratory of Low-carbon Smart Coal-fired PowerGeneration and Ultra-clean Emission
Columns:
Thermal Energy Engineering, Clean Power Generation, New Energy Generation, Integrated Power Generation.
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