Study on performance of a packed bed latent heat thermal energy storage unit integrated with solar water heating system

In thermal systems such as solar thermal and waste heat recovery systems, the available energy supply does not usually coincide in time with the process demand. Hence some form of thermal energy storage (TES) is necessary for the most effective utilization of the energy source. This study deals with the experimental evaluation of thermal performance of a packed bed latent heat TES unit integrated with solar flat plate collector. The TES unit contains paraffin as phase change material (PCM) filled in spherical capsules, which are packed in an insulated cylindrical storage tank. The water used as heat transfer fluid (HTF) to transfer heat from the solar collector to the storage tank also acts as sensible heat storage material. Charging experiments were carried out at varying inlet fluid temperatures to examine the effects of porosity and HTF flow rate on the storage unit performance. The performance parameters such as instantaneous heat stored, cumulative heat stored, charging rate and system efficiency are studied. Discharging experiments were carried out by both continuous and batchwise processes to recover the stored heat, and the results are presented.

Research on Operation of Electrothermal Integrated Energy System Including Heat Pump and Thermal Storage Units Based on Capacity Planning

In view of the Three North areas existing wind power absorption and environment pollution problems,the previous scholars have improved the wind abandon problem by adding electrothermal coupling equipment or optimizing power grid operation.In this paper,an electrothermal integrated energy system including heat pump and thermal storage units was proposed.The scheduling model was based on the load data and the output characteristics of power units,each power unit capacity was programmed without constraints,and the proposed scheduling model was compared with the traditional combined heat and power scheduling model.Results showed that the investment and pollutant discharge of the system was reduced respectively.Wind power was fully absorbed.Compared with the traditional thermal power unit,the proportion of the output was significantly decreased by the proposed model.The proposed system could provide a new prospect for wind power absorption and environment protection.

Effect of Radial Porosity Oscillation on the Thermal Performance of Packed Bed Latent Heat Storage

Owing to its high heat storage capacity and fast heat transfer rate,packed bed latent heat storage(LHS)is considered as a promising method to store thermal energy.In a packed bed,the wall effect can impact the packing arrangement of phase change material(PCM)capsules,inducing radial porosity oscillation.In this study,an actual-arrangement-based three-dimensional packed bed LHS model was built to consider the radial porosity oscillation.Its fluid flow and heat transfer were analyzed.With different cylindrical sub-surfaces intercepted along the radial direction in the packed bed,the corresponding relationships between the arrangement of capsules and porosity oscillation were identified.The oscillating distribution of radial porosity led to a non-uniform distribution of heat transfer fluid(HTF)velocity.As a result,radial temperature distributions and liquid fraction distributions of PCMs were further affected.The effects of different dimensionless parameters(e.g.,tube-to-capsule diameter ratio,Reynolds number,and Stefan number)on the radial characteristics of HTF and PCMs were discussed.The results showed that different diameter ratios correspond to different radial porosity distributions.Further,with an increase in diameter ratio,HTF velocity varies significantly in the near wall region while the non-uniformity of HTF velocity in the center region will decrease.The Reynolds and Stefan numbers slightly impact the relative velocity distribution of the HTF-while higher Reynolds numbers can lead to a proportional improvement of velocity,an increase in Stefan number can promote heat storage of the packed bed LHS system.

Effect of Periodic Variation of Sol-air Temperature on the Performance of Integrated Solar Collector Storage System

Parametric study is carried out in the present article to investigate the unsteady performance of solar energy gain and heat retention of two different integrated-collector-storage systems. The systems are the conventional rectangular-shaped storage tank and the modified tank shaped as rectangular cuboid with one semi -circular top. The two systems have the same absorber surface area and volume for water. The heat and fluid flow is assumed to be unsteady, two-dimensional, laminar and incompressible. The performances of the two systems are evaluated based on the maximum temperature in the system during daytime heating period and nighttime cooling period. For comprehensive study, 24 hours simulations for 3 cases with different wall boundary condition impose on the absorber plate are investigated. The simulation results show that the modified system has better heat retain than the conventional system. Periodic variations of both systems are investigated, and it is found that both systems show consistent results on different days. The modified system is able to store most of the thermal energy in the semi-circular top region with higher temperature than that of the conventional system.

State of the Art Treatment of Non-Ferrous Castings 3-in-l Heat Treatment Systems Combine Foundry Processes

The interior of a high-pressure die-casting is of an unsatisfactory quality. Engine blocks made with this die casting process show lower specific engine performance. Pressure die-casting can hardly be heat treated for obvious reasons. PSM (Precision Sand Molds) process uses sand and organic binder to generate a mold and even allows the manufacturing of complex diesel engine blocks in aluminum alloys. Combined technologies are available for semi-permanent mold castings with cores and castings made in Precision Sand Molds with organic binders. Castings are placed into the special heat treatment furnace immediately after pouring without the operations in stand alone machinery. This patented Sand Lion 3- in-1 technology processes hot castings and carries out three (3) foundry processes simultaneously in one (1) automated machine: 1) De-coring and sand removal; 2) Thermal sand reclamation; 3) Solution heat treatment of castings. The combination of several main casting processes is reflected in significant reductions of energy consumption, of production costs, and improving the quality of the castings. Audits in foundries using the 3-in-l process showed an average reduction in production costs of more than 30%.

储液式CCS耦合P2G的综合能源系统低碳经济调度

为应对电转气P2G(power-to-gas)和碳捕集系统CCS(carbon capture system)在可再生能源出力不足时耦合失效的问题,考虑对常规CCS引入CO_(2)储液罐以加强P2G和CCS的耦合。首先,构建储液式CCS和P2G的耦合模型,利用储液罐将CCS捕集的CO_(2)时移至可再生能源富足时段,供P2G再利用;其次,构建储液式CCS与P2G耦合的电热气综合能源系统日前优化调度模型;最后,以北方某工业园区为例进行仿真。结果证明所提模型可以充分利用CCS捕集的CO_(2),从而获得更好的经济和环境效益。

集成蓄热装置的火电机组调峰特性分析

【目的】随着新能源的大规模发展,新能源出力不确定性和波动性问题展现出来,而为了弥补新能源出力缺点,火电机组承担起了调峰作用。为了提升火电机组的调峰能力,对其调峰特性进行了研究。【方法】首先,以某350 MW供热机组作为分析对象,应用仿真软件搭建热力系统模型,并验证该模型的精确性。其次,以蓄热系统为辅助系统,研究机组在满足供热需求情况下的机组调峰能力,并分析蓄热等储能单元对机组调峰能力的影响。最后,采用启发式粒子群算法对蓄热水罐运行策略进行优化,得到随热负荷变化的储热罐最优运行模式。【结果】通过蓄热水罐与火电机组耦合的方法有效提升了机组的调峰和供热能力,并提出可以根据实际热负荷数据确定最大化收益的运行模式。【结论】该方法对机组的运行策略具有指导意义。

隧道热害环境下电力机车蓄冷式冷却塔散热性能研究

针对西部某铁路所处的高原隧道热害环境,提出一种电力机车蓄冷式冷却塔结构及其运行方案,通过对蓄冷及释冷过程进行仿真,分析换热器的冷却性能并对其结构进行优化。研究结果表明:当换热器蓄冷运行时,相对于壳体两侧无翅片结构,采用壳体空气侧加翅片和壳体双侧加翅片,相变蓄冷时间从113 min分别缩短至80 min和47 min;当换热器释冷运行时,乙二醇水溶液经相变蓄冷换热器冷却,传热管道添加间距为8 mm的翅片,有效冷却时间(冷却介质出口温度低于55℃)从无翅片结构的1.5 min延长至16 min,超过设计要求的14 min,有效解决了机车冷却塔的散热难题。

氢储能系统容量双层鲁棒随机优化配置方法

氢能作为一种清洁无污染、能量密度大的二次能源,是大规模消纳新能源的理想储能载体,耦合氢储能系统和可再生能源的电热氢综合能源系统为消纳新能源提供新的思路和方案。围绕电热氢综合能源系统中如何以经济合理的方式投入氢储能设备展开研究,解决氢储能设备容量的合理配置问题以及考虑源荷不确定性对电热氢综合能源系统运行的影响,提出了一种考虑季节性存储和源荷不确定性的电热氢综合能源系统中氢储能容量优化配置方法。首先针对风电功率预测误差较大,电热气负荷预测精度较高的特点,分别采用不确定集和抽样场景描述源和荷两侧的不确定性。然后建立了考虑源荷不确定性和季节性存储的氢储能容量配置双层鲁棒随机优化模型,其上层问题以年化投资成本和运行成本的总成本最小化为目标确定氢储能系统装置容量,下层问题采用两阶段鲁棒随机优化模型模拟电热氢综合能源系统典型日在风电出力最恶劣场景下的最优运行方案。由于该模型难以直接求解,提出基于粒子群优化算法和列与约束生成算法对该类复杂模型进行求解。最后,通过对某个电热氢综合能源系统算例进行分析,算例分析结果验证了所提方法的有效性,获得的氢储能系统容量优化配置方案能够促进风电消纳和提高系统运行的经济性。

一种三维集成的Ku波段高功率T/R模块

基于硅基微电子机械系统(MEMS)三维(3D)异构集成工艺,设计并制作了用于相控阵天线系统的三维堆叠式Ku波段四通道高功率收发(T/R)模块。该模块由两层硅基封装堆叠而成,层间采用球栅阵列(BGA)植球堆叠,实现模块小型化;采用高低阻抗匹配建模,保证低损耗输出,采用导热垫加微流道散热板达到了良好的散热效果,实现模块高功率输出;对模块的微波垂直互连结构和散热进行建模和仿真。测试结果表明,在14~18 GHz内发射通道饱和输出功率大于40 dBm,接收通道增益大于21 dB,噪声系数小于3.5 dB,模块尺寸仅为14.0 mm×14.0 mm×3.3 mm。该模块在兼顾高集成度的同时性能指标得到了进一步提升。

Optimal operation of electricity, natural gas and heat systems considering integrated demand responses and diversified storage devices

In recent years, the increasing penetration level of renewable generation and combined heat and power(CHP) technology in power systems is leading to significant changes in energy production and consumption patterns. As a result, the integrated planning and optimal operation of a multi-carrier energy(MCE) system have aroused widespread concern for reasonable utilization of multiple energy resources and efficient accommodation of renewable energy sources. In this context, an integrated demand response(IDR) scheme is designed to coordinate the operation of power to gas(P2 G) devices, heat pumps,diversified storage devices and flexible loads within an extended modeling framework of energy hubs. Subsequently, the optimal dispatch of interconnected electricity,natural gas and heat systems is implemented considering the interactions among multiple energy carriers by utilizing the bi-level optimization method. Finally, the proposed method is demonstrated with a 4-bus multi-energy systemand a larger test case comprised of a revised IEEE 118-bus power system and a 20-bus Belgian natural gas system.

考虑变掺氧富氧燃烧与利用LNG冷能的LAES的综合能源系统低碳经济调度

为促进风电消纳,减少火电机组的碳排放,解决综合能源系统(Integrated Energy System,IES)低碳经济运行问题,文中引入变掺氧富氧燃烧技术对燃气机组进行改造,并结合利用液化天然气(Liquefied Natural Gas,LNG)冷能的液化空气储能(Liquid Air Energy Storage,LAES),提出了一种电热气冷IES低碳经济优化策略。首先,构建含变掺氧富氧燃烧燃气机组、利用LNG冷能的LAES、电转气(Power To Gas,P2G)设备、中央空调和溴化锂制冷机的IES架构,并建立各设备的数学模型;其次,引入阶梯式碳交易机制,建立了以系统运行成本最小为目标的电热气冷IES低碳经济调度模型;最后,采用MATLAB调用GUROBI求解器对多个场景进行求解,验证了文中提出的低碳经济优化调度策略可以提高系统的风电消纳、有效降低系统运行成本,实现碳减排。

Parametric analysis of a packed bed thermal storage device with phase change material capsules in a solar heating system application

The goal of this study is to investigate the effect of key design parameters on the thermal performance of the packed bed heat storage device by numerical calculation.A one-dimensional,non-equilibrium packed bed latent heat storage mathematical model was established and the applicability of the model was verified.The results demonstrate that the inlet temperature of the heat transfer fluid(HTF)had the greatest influence on each index.When the inlet temperature increased from 333 K to 363 K,exergy destruction increased threefold,effective heat storage time decreased by 67%,effective heat storage increased by 38%,and exergy efficiency decreased by 11%.The decrease of the capsule diameter had a positive effect on each evaluation index.According to the sensitivity analysis,the order of importance of each parameter within their variation range was HTF inlet temperature,HTF flow rate,PCM capsule size and PCM initial temperature.

基于风电场景概率的电热混合储能优化配置

为有效提高风电入网的经济性和可行性,文中提出一种考虑风电典型场景概率的电热混合储能优化配置方案。首先通过场景分析,利用K-means聚类法将大量风机历史出力数据简化为6个典型出力场景,确定各场景发生的概率,其中聚类数目由肘部曲线法和Dunn指数法综合确定;其次提出电热混合储能系统控制策略,建立适用于多场景的风储联合系统模型;最后,以经济性成本最低与弃风量最小为目标,建立包含电、热负荷综合响应的容量配置优化模型,并将场景概率以权值的形式加入到目标函数中,采用粒子群算法求解模型。通过仿真分析和与其他储能配置场景对比,发现所提配置策略能够提高风电利用率约16.12%,同时减少系统综合成本约43.76%,验证了所提策略的合理性和有效性。

家用空气源热泵蓄热式热管散热器的自然对流传热特性

提出带蓄热材料的热管式自然对流散热末端新型式,在热管式末端的换热管上外加套管,管间填充蓄热材料。管内蒸气通过凝结换热,将热量传递给蓄热材料后再传递给外套管,外套管与室内空气进行自然对流传热和辐射传热,构造出新型家用空气源热泵系统。建立了带固体蓄热材料的热管式散热末端的传热模型,研究热泵系统启停过程,蓄热材料种类、厚度对温度分布随时间变化的影响;分析热泵系统的制热量、压缩机功率等宏观性能系数的变化规律。结果表明:固体蓄热材料中镁砖效果较好;热泵运行时间和蓄热材料外表面温度受蓄热体厚度影响,且存在一个临界厚度;当选取12 mm厚的镁砖蓄热材料时,带蓄热末端的家用空气源热泵运行12 min,供热时间26 min,表面温度变化在35~50℃。

亚临界循环流化床机组近零深度调峰蓄释热计算及实践

随着可再生能源的快速发展,对火电机组深度调峰提出了更高的要求。以亚临界循环流化床锅炉(CFB)焖炉压火方式参与近零深度调峰为基础,建立一套近零深度调峰蓄释热量的计算方法,为后续多次进行近零深度调峰提供指导。基于对亚临界CFB机组在近零深度调峰过程中锅炉各有蓄热能力部分的具体分析,提出了一套针对CFB近零深度调峰过程中蓄释热量的计算方法,并将此方法应用于山西省某300 MW亚临界CFB机组的近零深度调峰运行实践。应用计算方法得出,锅炉视在蓄热总量为415.5 GJ,其中浇注层、金属壁、床料载体、汽水、烟气视在蓄热量分别为205.6、140.4、32.7、11.1、36.8 GJ。汽轮机做有效功的总热耗量为65.2 GJ,锅炉本体散热为6.1 GJ,数据展示了各蓄热部分随近零深度调峰过程的下降趋势。该计算方法实现了对亚临界循环流化床蓄释热量的量化计算,为后续预测指导近零深度调峰时长,研究锅炉的严密性和传热特性,以及为获得更多蓄热量提升蓄热效率和改善锅炉性能提供了数据支持。

太阳能供暖用蓄热-散热复合型睡床热特性研究

为了研究太阳能在蓄热和建筑供暖方面的应用,设计了一种新型的集蓄热与散热于一体的复合型睡床,其特征是在床下设置蓄热水箱并在水箱上表面与床板之间设置可启闭的水平空气层。对复合型睡床进行动态热特性和影响因素研究。结果显示:(1)基本条件下(水箱尺寸长为2 m、宽为1.2 m、高为0.3 m,水箱表面温度35℃,床板与水箱之间的水平空气层厚度为20 mm),睡床总散热量为289.8 W,其中水箱上表面散热占比47.6%,侧面散热占比52.4%。床板上表面温度为21.1℃;(2)睡床总散热量随着水平空气层厚度的增加而增加,床板上表面温度随着水平空气层厚度的增加而降低,水平空气层厚度由20 mm升至50 mm时,总散热量增加了36.0%,床板上表面温度降低了2.1℃;(3)睡床总散热量与床板上表面温度均随着水箱表面发射率的增加而增加,水箱表面发射率由0.3升至0.9时,总散热量增加了30.5%,床板上表面温度提高了0.8℃。

350 MW热电联产循环流化床机组负荷响应特性

近年来热电联产机组在燃煤机组中的比重增加,而火力发电渐渐承担调峰重任,灵活性需求增强,提高热电联产机组的变负荷能力对于深度调峰具有重大意义。热电联产循环流化床(CFB)机组可利用锅炉汽水侧和热网蓄热提高机组快速变负荷能力,因此提出一种超临界热电联产CFB机组汽水侧蓄热和热网蓄热的定量计算方法。以某350 MW热电联产CFB机组为例,分析该机组汽水侧工质流程和热网抽汽及循环水分析,结合机组设计参数与历史运行数据,计算不同负荷(35%~90%)工况下锅炉汽水侧蓄热系数C_(sw)和热网蓄热系数C_(h),进一步分析机组负荷响应特性及蓄热利用可持续时间。结果表明:随着机组负荷增大,汽水侧蓄热系数C_(sw)增大,且在机组高负荷阶段汽水工质蓄热C_(sw)变化较大,而热网蓄热系数C_(h)几乎不变;机组蓄热利用可持续时间与机组负荷成正比,与机组变负荷速率成反比;热网蓄热利用可持续时间大于汽水侧蓄热,且热网蓄热能力几乎不随机组负荷变化而变化;在4%/min变负荷速率下,热网蓄热利用可持续时间约285 s,而汽水侧蓄热利用可持续时间161.5~249.7 s。表明在机组参与深度调峰期间,热网蓄热可提供更稳定的变负荷能力。以上计算结果为超临界热电联产CFB机组深度调峰及快速变负荷运行提供理论指导。

液态空气储能耦合综合能源系统热电联储联供优化配置研究

液态空气储能(LAES)在多能耦合的综合能源系统中极具应用前景,合理的储能容量配置更有利于综合能源系统低碳经济运行,但目前研究未充分考虑LAES热电联储联供强相关的特性和优势。因此,本文提出了一种LAES耦合综合能源系统的热电联储联供优化配置方法,针对综合能源系统的基本架构,构建了各组成单元的热电联储/供调度约束模型,并以设备初始投资成本、设备运维成本、购能成本、弃风弃光成本等为目标函数,考虑了系统能量平衡约束、设备容量约束、设备出力约束、外网交互功率约束以及储能约束,建立了相应的优化配置模型,并基于混合整数线性规划方法进行模型求解。以某实际园区为例,设置了5种场景进行优化结果对比分析,结果表明:考虑LAES热电联储联供特性的综合能源系统能实时有效地满足系统用能需求,同时能实现更好的经济效益和环境效益,相较于传统分供系统,系统总经济成本下降37.1%,实现碳减排71.50%,并在消纳可再生能源和减少弃光弃风方面更具潜力。本研究可为LAES耦合系统热电联储联供优化模型的有效性提供理论依据,有助于推动LAES在综合能源系统中的商业化应用。

基于AA-CAES电站和综合需求响应的供暖期弃风消纳策略

“双碳”目标背景下,为解决热电联产机组“以热定电”模式导致的大规模弃风问题,本文提出基于先进绝热压缩空气储能电站(advanced adiabatic compressed air energy storage,AA-CAES)和综合需求响应的综合能源系统(integrated energy system,IES)供暖期弃风消纳策略。首先,在“源-储”两侧建立热电联产机组与AA-CAES电站耦合运行模型,分析耦合运行实现热电解耦机理;其次,在“荷”侧引入价格型和替代型需求响应机制来探寻负荷侧优化系统调度潜力;然后,在IES中引入碳捕集系统和阶梯型碳交易机制来约束碳排放,并在碳排放量最少、综合成本最低为目标构建IES运行基础上,引入模糊机会规划约束模型来分析风、光不确定性对系统调度影响;最后,利用西北某地区实际数据进行算例验证。结果表明:热电机组与AA-CAES电站耦合运行相较于未耦合运行可提高风电消纳率84.55%、降低总成本11.42%、减少碳排放20.28%;综合需求响应机制的引入可进一步提高风电消纳率35.00%、降低总成本20.93%、减少碳排放24.43%;风光不确定性的上升会提高与外部电网的交互成本。