Research of Thermal Energy Storage Technology in the Solar Thermodynamic Power

Recently, although renewable energy has a great development, primary source is still thermal power generation, which uses fossil fuel as the energy source. Supply and demand of fossil fuel are essential for social and economy development. However, development pattern that excessively relies on the natural source is impossible to provide a sustainable development way for us. As a result, we should combine renewable energy with new energy technology as the aim of economy. It means that it is urgent to exploit new energy. Meanwhile, the ratio of energy waste cannot be ignored. How to decrease energy waste is also significant. Construction sector costs a lot of energy, which is mainly used for heating and refrigeration. In the new energy generation technology, thermal energy can be transformed to electricity with combination of BIPV and thermal energy storage technology. Photovoltaic generation has a great progress in the building construction. As a result, the thermal energy storage technology becomes the key link in the production chain. In this paper, feasibility of applying phase-change material (PCM) in the thermal energy storage will be analyzed. And analysis results are provided with a relative mathematical model.

Enhancing Heat Transfer and Energy Storage Performance of Shell-and-Tube Latent Heat Thermal Energy Storage Unit with Unequal-Length Fins

Previous studies in literatures adequately emphasized that inserting fins into phase change material is among the most promising techniques to augment thermal performance of shell-and-tube latent heat thermal energy storage unit.In this study,the novel unequal-length fins are designed from the perspective of synergistic benefits of heat transfer and energy storage performance,and the effects of arrangement,number and total length of unequal-length fins are numerically investigated.Results show that utilization of fins with ascending length,when short and long fins are located in the inlet and outlet of heat transfer fluid respectively,can further promote the heat transfer and energy storage performance compared with equal length fins,and a maximum 6.17%and 0.43%increment of heat transfer performance and stored energy is achieved in full melting time,respectively.The number of unequal-length fins plays a major role in the energy storage,and 18.95%and 0.91%improvement of heat transfer performance and stored energy is realized when equipped with 2 unequal-length fins.A 21.17%improvement of the heat transfer performance is obtained when the total length of unequal-length fins is 18 mm.The present study is helpful to make further efforts to enhance heat transfer and energy storage of shell-and-tube latent heat thermal energy storage unit with unequal-length fins.

基于内管移动的卧式管壳式相变储热器储热性能优化研究

相变储热技术能够实现对固态储放氢过程热量的回收和供给,实现固态储氢罐内的自热平衡,提高储放氢性能。研究针对卧式管壳式相变储热器,提出了一种新型的内管偏心放置绕中心轴线旋转的运动方式,采用Fluent数值模拟软件,基于动网格技术编写了用户自定义函数UDF,重点研究了内管偏心距离与旋转速度对储热性能的影响。结果表明:与传统中心内管静止布置相比,偏心内管的旋转运动能够显著提高储热性能,当偏心距离为9 mm,旋转速度为0.10 r/min时,储热时间达到最小值,储热时间减少了92.16%,时间平均储热速率是内管静止布置的11.51倍;当偏心距离为9 mm,旋转速度由0.30 r/min减少至0.10 r/min时,储热时间减少了13.57%;当旋转速度为0.10 r/min,偏心距离由3 mm增至9 mm时,储热时间减少了70.48%。该研究结果可为卧式管壳式相变储热器在储氢领域的性能优化研究提供新思路。

中深层地热田开发利用技术研究进展

地热能是重要的可再生能源,是我国“十四五”期间重点发展的可再生能源之一。我国地热能直接利用量连续多年保持世界第一,但中深层地热田开发利用技术与国外先进水平尚有差距。当前全球地热初创公司快速增长,地热资源开发力度持续加大,地热能利用场景多样化,地热发电装机容量稳步增长,开发利用技术取得较大进展。具体表现为4个方面:(1)中深层闭式换热系统设计技术逐渐成熟;(2)EGS技术取得历史性突破,应用潜力巨大;(3)多国重视含水层储热在弥补能源供需不平衡上的作用,加快推进含水层储热场址选择、热回收率及风险分析等方面的研究;(4)回灌成为中深层水热型热储开发的通用做法,回灌数值模拟及方案设计、防腐蚀、防结垢、防堵塞等技术进步有效延长了地热田的生命周期。“双碳”背景下,我国应将关键技术研发作为发展新质生产力的主要突破口,快速升级中深层地热田开发利用技术,有效提升地热项目经济性,实现地热利用规模持续增长。

压缩空气储能技术研究现状及发展趋势

[目的]压缩空气储能具有储能容量大、安全性高、寿命长、经济环保、建设周期短等优势,是未来和抽水蓄能相媲美的长时储能技术,成为未来储能重点布局的方向。在此背景下,文章通过对压缩空气储能技术现状进行综述,分析不同压缩空气储能技术的工作原理、面临挑战及解决方案,以期对压缩空气储能技术的发展提供参考。[方法]文章首先对压缩空气储能技术原理进行了介绍;对系统中的压缩机、透平膨胀机和换热器等关键设备进行了阐述,分析了大规模压缩空气储能用的关键设备;并从地面关键工艺技术和地下储气设施两个角度介绍了大规模压缩空气储能系统的常用关键技术、发展现状及工程案例;最后对压缩空气储能技术的未来发展趋势进行了分析。[结果]结果表明:蓄热式压缩空气储能是当前国内的主流技术,且高温储热成为未来压缩空气储能发展方向,也是压缩空气储能提高效率的重要途径。同时,系统关键设备和技术优化、成本降低、应用场景发展等方面尚有一定改进空间。[结论]压缩空气储能作为一种长时储能,对未来构建新型电力系统具有重要的支撑作用。

合金材料在储能技术中的应用与发展

铝硅合金相变材料的密度和热导率高,稳定性强,在储能储热系统中有着极大的研究价值和应用潜力。本文针对铝硅合金材料在储能领域的应用发展进行综述,文章首先回顾了铝硅相变材料国内外研究实例,总结核心物理参数,以此为基础提出相变储热材料与换热技术的研发方向,包括容器材料稳定性、铝硅相变物理性以及相变蓄热器的结构优化,最后总结了铝硅合金的未来应用发展方向。

Solidification in a shell-and-tube thermal energy storage unit filled with longitude fins and metal foam:A numerical study

In this study,an innovative thermal energy storage design method was developed by adding the combination of metal foam and fin to phase change materials(PCMs).A numerical model was built and verified based on the comparison among the present model prediction,experimental measurements,and numerical results in open lit-erature.To highlight the novel design method,four cases including fin-PCM,foam-PCM,fin-foam-PCM,and PCM unit were compared by means of solidification features.The temperature distribution,solidification front propa-gation,and buoyancy-induced convection in the liquid PCM were accounted for.Numerical results demonstrated that metal foam outperformed fin regarding the improvement on solidification phase change.The combination of foam and fin achieved the best performance,leading to a 90.5%reduction in complete energy release time in comparison with the PCM unit.The proposed design method provided reference potentials for advancing energy storage engineering.However,buoyancy-induced convection in the liquid PCM before solidification was harmful to the formation of solidification front and its movement.A maximal 11.5%prolonging time for the complete solidification was found.

Enhanced Phase Change Heat Storage of Layered Backfill Body under Different Boundary Conditions

In view of the high temperature problem faced by mining activities,the coordinated mining of ore deposit and geothermal energy is a solution in line with the concept of green mining.The layered backfill body with finned double-pipe heat exchanger continuously exchanges heat with the surrounding thermal environment,which plays an effective role in gathering geothermal energy.In this paper,the heat storage process of each layered backfill body under different boundary conditions is simulated by Fluent.The results show the heat storage characteristic of layered backfill body can be significantly improved by adding fins to the double-pipe heat exchanger.On the whole,the heat storage effect of bottom layer backfill body(BLBB)is the best.The total heat storage capacity of top layer backfill body(TLBB),middle layer backfill body(MLBB)and BLBB with the finned double-pipe heat exchanger is 666.3 kJ,662.2 kJ,1003.0 kJ;1639.0 kJ,1760.8 kJ,1911.2 kJ and 1731.1 kJ,1953.3 kJ,1962.8 kJ respectively at 1 h,8 h and 24 h.This study explores the law of heat storage of layered backfill body under different boundary conditions and also expands the idea for layered backfill body to efficiently accumulate geothermal energy.

A simultaneous approach for integration of thermal energy storages in industrial processes using multiperiod heat integration

In times of increasing global warming,enormous efforts are required to rapidly reduce greenhouse gas(GHG)emissions.Due to the EU’s target of climate neutrality by 2050 and the even more ambitious goal of becoming climate-neutral in Germany by 2045,it is necessary to systematically increase energy efficiency and decarbonize the industrial heat sector.The methods of heat integration can be used to exploit existing potentials for waste heat utilization and to integrate renewable technologies for heating and cooling.By using a non-stationary,multiperiod approach,additional energy savings can be achieved by integrating a thermal energy storage(TES)that enables heat transportation over time.This paper presents a simultaneous approach for thermal energy storage integration into multiperiod heat integration problems.The approach can be used to minimize energy demand,costs and CO 2 emissions and is demonstrated in two case studies.In case study 1,it is shown that the presented approach is capable of integrating a TES properly into a simple multiperiod heat integration problem with two periods.In case study 2,a simplified example from a cosmetics manufactory is investigated.The total utility demand can be reduced by up to 44.3%due to TES integration and the energetic optimal storage size can be determined as 125 m 3.The savings are strongly dependent on the constellation of heat flows between the periods,on the temperature levels and on the storage size.Significant reductions of energy demand,costs and CO 2 emissions can be achieved with TES being properly integrated into a suitable operating environment.

一种垂直换热管对拱型温室大棚热环境的影响研究

为了调节温室大棚内由于太阳辐射随昼夜变化所带来的能量不平衡问题,提出利用垂直换热管作为换热装置将白天富余的太阳辐射能传输到地下土壤中储存,夜间通过换热管将储存的能量释放在大棚内来提高棚内空气温度,剩余部分能量储存在地下土壤中用于应对阴天天气导致的太阳能供能不足的现象。实验在内蒙古新能源实验示范基地展开,建造两个同尺寸的大棚,分别记为实验组和对照组,无作物。实验结果表明:在9 d的实验期间,通过实验组与对照组比较发现,实验组大棚在夜间棚内不同位置的温度有不同程度提高,棚内空气温度最大提升3.2℃;地表温度最大提升4.4℃;地面以下10 cm处温度最大提升3.3℃,地面以下30 cm处温度最大提升1.2℃,地面以下50 cm处温度最大提升1.0℃。该实验可达到利用换热管将太阳辐射能合理分配应用的预期效果,可强化土壤的白天储能、夜间放能,将富余的太阳辐射能储存在地下土壤中来提升土壤温度,为温室大棚内热环境的调控提供新途径。

中压废热锅炉换热装置节能控制技术及效益研究

中压废热锅炉换热装置受换热面积裕度、换热面积等因素的影响,导致其换热能耗较高,为此以管壳式相变储能换热器为研究对象,提出了其节能控制技术,并探究该技术的应用效果。以管壳式相变储能换热器的蓄放热特性为基础,将管壳式相变储能换热器的储能材料和管材作为约束条件,构建节能控制优化目标函数。利用粒子群算法求解构建的目标函数,实现管壳式相变储能变换器的节能控制。实验结果表明,所提技术应用后可有效降低管壳式相变储能换热器的换热面积裕度、实际换热面积,具有较强的节能控制性能,同时减少了换热器费用,提高了其成本效益。

深部矿井埋管充填体换热器蓄/释热过程中的热干扰问题

矿床开采形成的丰富地下空间为太阳能等可再生能源的大规模存储提供了基本条件。将地埋管换热器置入矿井充填体中构建出具有蓄/释热功能的埋管充填体换热器是实现太阳能等可再生能源跨季节存储的新方法,但是热干扰问题会影响其蓄/释热性能而不容忽视。利用COMSOL仿真软件建立并验证了典型蛇形埋管充填体换热器的三维非稳态传热模型,通过管间热干扰系数(I_(tub))和层间热干扰系数(I_(lay))量化研究了管间距、管径、充填体导热系数和比热容对埋管充填体换热器的单层蛇形管管间和多层蛇形管层间热干扰影响,通过引入相对灵敏度参数讨论分析了管间和层间热干扰对研究参数的敏感度。结果分析表明,I_(tub)随蓄/释热时间呈先下降后上升的变化趋势,整体变化不大(0.92~1.00),说明单层蛇形管管间热干扰影响较小。I_(lay)呈单调显著递减,在蓄/释热阶段末分别低于0.25和0.49,说明多层蛇形埋管层间热干扰随着蓄/释热的进行严重恶化。通过灵敏度分析发现,I_(lay)对研究参数的敏感度明显高于I_(tub)。I_(lay)对充填体比热容、管间距、充填体导热系数和管内径的敏感度依次降低,其中充填体比热容和管间距为正面影响,另外2个为负面影响。I_(tub)在蓄/释热的大部分时间段对管间距最敏感。本研究量化了关键参数对埋管充填体换热器热干扰的影响,为优化蛇形埋管布置及充填材料制备以降低热干扰影响提供了依据。

壳管式相变储能换热器性能强化研究

基于流体动力学软件CFD进行仿真模拟,从传热面积和流场两方面考虑肋片对相变换热器换热过程的影响。分析了3种结构形式(双肋式、三肋式、四肋式)下肋高及肋片排布对换热性能的影响,得出最佳结构形式和规格尺寸参数。结果表明:采用双肋式结构可极大的改善相变储能放热器的储能过程,采用三肋式结构可更快的进入流场扩张期,对称四肋式换热管在竖向和水平方向均有较高的融化速率;在同等传热面积下,双肋式结构具有显著优势。当肋片长度与换热管半径之比为1.5时,缩短了80%的放热时间,同时凝固总量也提升至87%,高出光管的76%。

数据中心用壳管式相变储能换热器的储能特性

针对相变储能换热器储/放能率低的问题,本工作设计了一种壳管式相变储能换热器,以相变温度为25℃的石蜡为储能材料,以水为传热流体,研究传热流体对换热器储能性能的影响。搭建了壳管式相变储能换热器的实验平台,并利用FLUENT软件对其进行三维瞬态建模,通过改变边界工况进行储能数值模拟,并对最优工况进行分析。研究结果表明:数值模拟不同传热流体温度和流速对蓄/放热过程的影响,传热流体温度与相变温度的差值越大,相变单元蓄/放热速率越快,平均储/放能率越大;温差增大5℃,平均储能率最大提高91%,平均放能率最大提高124%,但温差增大造成的不可逆㶲损失也越大;而在凝固过程中,由于相变材料内部自然对流的作用非常小,放热速率远低于蓄热速率,温差同为5℃时平均放能率仅为平均储能率的64%,温度差是主要影响因素。随着传热流体流速的增加,流体侧对流换热的加强会加快换热,加快熔化,但对壳管式换热器的平均储能率和㶲损失影响不大。综合考虑平均储/放能率和㶲损失,本研究中换热器性能最佳的蓄热工况为40℃,放热工况为10℃,流速工况为0.5m/s,研究结果可为储能换热器在数据中心的应用提供一定参考。

地源热泵系统能效提升途径

浅层地热可被用于路面融雪除冰,建筑供热、制冷等。闭环垂直地埋管是浅层地热资源利用最常见形式,其在终端负荷作用下与岩土体进行热量交换。单根地埋管获取地热资源能力有限,多根埋管组合形式(地埋管群)被广泛应用于地源热泵系统。然而,地下温度场受管群与岩土换热性能影响,在设计、运行等不合理条件下可导致岩土体温度场不平衡,进而造成地源热泵系统能效降低,甚至失效。因此,管群设计、运行等方案优化是解决地温场不平衡问题的必要途径。基于国内外相关研究成果,梳理管群优化设计方法、储能和去能方法、辅助热源和冷源方法、运行控制策略。其中,管群优化设计方法主要聚焦管群间距设计、排布方式等;储能和去能方法主要介绍利用太阳能、工业废热等外部热源和冷源对地下岩土体进行加热和降温等的最新研究成果;辅助热源和冷源部分重点介绍太阳能、冷却塔等在地源热泵系统中的应用;运行控制策略主要分析地源热泵系统运行控制方案,包括峰点冷热负荷运行、间歇性运行、分区运行、系统控制策略等方案。总结了管群优化设计方法、运行控制策略等,剖析了各方案的优点与不足,可为管群岩土体温度场不平衡解决方案与地源热泵系统能效提升途径提供参考。

低能耗建筑地源热泵蓄热特征数值仿真

为准确分析不同蓄热模式与工况下的蓄热特征,为低能耗建筑科学合理运用地源热泵系统提供依据,对低能耗建筑地源热泵的蓄热特征完成数值仿真。构建低能耗建筑的空气-地源热泵系统,并引以为例,构建空气换热器、U型地埋管与热泵机组数学模型,实现对该系统蓄热特征的数值仿真。仿真结果表明,在上述系统处于有蓄热工况下时,土壤温度较无蓄热工况时得到明显提升;U型地埋管周边土壤半径越低所获得的蓄热效果越好;U型地埋管深度不变时,蓄热时间越长,其耗电量与整体蓄热量越高,平均蓄热率与蓄热能效比越低;相同蓄热模式下蓄热时间不变时,U型地埋管的深度越高,整体蓄热量、蓄热能效比及平均蓄热率越高,耗电量不变,单位埋深蓄热率则越低;日平均蓄热率最高值与室外日平均温度最高值出现在同一日,且二者的变化趋势相同,不受其蓄热时间与U型地埋管深度所影响。

Experimental research and numerical simulation of the thermal performance of a tube-fin cold energy storage unit using water/modified expanded graphite as the phase change material

In this study,experimental and numerical investigations were conducted on a tube-fin heat-exchanger latent-heat cold energy storage unit.The fin side of the heat exchanger was filled with water as the energy storage medium,and modified expanded graphite(MEG)was employed to improve the thermal characteristics of water.The water contact angle of the expanded graphite decreased from 106.31°to 0°,and the hydrophilicity and the absorption rate of water significantly improved after the modification.Moreover,the experimental analyses of the charge/discharge process showed that the cooling capacity of the system filled with 90 wt.%water/MEG was 80.8%of that of pure water,whereas its cooling time was only 69.7%of that of pure water.The average power increased by 15.9%compared with that of water.The system filled with 90 wt.%water/MEG completed two energy charging and discharging cycles,whereas the system filled with water completed only 1.5 cycles within 15000 s.Furthermore,the effects of the flow rate and inlet temperature of the heat transfer fluid on the charging process were explored.Finally,a numerical model was built and validated to investigate the phase change behavior and the effect of the structure size on the performance of the system.The heat-exchanger fin spacing had no significant effect on the cold energy storage unit,whereas the vertical spacing of the tube pass had the highest effect.It can be concluded that the heat exchanger combined with high-thermal-conductivity water/MEG exhibits better energy storage capacity and working power,showing a wide application prospect in the field of cold energy storage.

Designing Sustainable Thermal Energy System with Electro-Photo Conversion

Thermal energy conversion and also storage system is to advance knowledge and develop practical solutions at the intersection of micro and nano-scale engineering,energy conversion,and sustainability.This research addresses the challenge of enhancing these critical aspects to ensure prolonged system performance and durability in the context of evolving energy technologies.This research analyses the anti-oxidation and filtration behaviours of micro and nano-scale structures in the context of electro-and photo-thermal energy conversion and also storage systems.A micro multiscale hierarchical structure strategy is presented to fabricate multi-scale double-layer porous wick evaporators with the electrospun nanofibers made of gelatin-polyamide 6(GPA6)and Ti_(3)C_(2)T_(x)MXene/silver nanowire with Cellulose Micro/NanoFibers(CMNF)cryogens by using spark plasma sintering(SPS)based high-pressure hydrothermal treatment model.An excellent anti-oxidation effect was offered by coating the film in thermal conditions and the anti-oxidation properties were further examined from 500℃to850℃.The results are analysed using Matlab software to improve the efficiency of energy conversion processes by integrating nanostructures into thermal systems,to increase energy output while minimizing losses.The silver nanowire is with a heat transfer coefficient of 78%,a mass remaining rate of 98.7%,and an energy storage efficiency of 23.8%.This study enhances energy density and duration by integrating nanostructures into thermal systems while minimizing energy losses,and it not only exhibits excellent anti-oxidation properties but also possesses superior filtration capabilities for designing and engineering multifunctional nanomaterials.

冰箱新型节能技术发展现状

调研了冰箱最新节能技术发展现状,包括微通道换热器技术、相变材料蓄能、耦合双循环制冷系统和纳米制冷剂。相关研究的数值模拟或实验测试结果证明,以上新型技术对于冰箱能效有显著提升,具有较好的推广使用潜力。

Numerical simulation of underground seasonal cold energy storage for a 10 MW solar thermal power plant in north-western China using TRNSYS

This paper aims to explore an efficient, cost-effective, and water-saving seasonal cold energy storage technique based on borehole heat exchangers to cool the condenser water in a 10 MW solar thermal power plant. The proposed seasonal cooling mechanism is designed for the areas under typical weather conditions to utilize the low ambient temperature during the winter season and to store cold energy. The main objective of this paper is to utilize the storage unit in the peak summer months to cool the condenser water and to replace the dry cooling system. Using the simulation platform transient system simulation program (TRNSYS), the borehole thermal energy storage (BTES) system model has been developed and the dynamic capacity of the system in the charging and discharging mode of cold energy for one-year operation is studied. The typical meteorological year (TMY) data of Dunhuang, Gansu province, in north-western China, is utilized to determine the lowest ambient temperature and operation time of the system to store cold energy. The proposed seasonal cooling system is capable of enhancing the efficiency of a solar thermal power plant up to 1.54% and 2.74% in comparison with the water-cooled condenser system and air-cooled condenser system respectively. The techno-economic assessment of the proposed technique also supports its integration with the condenser unit in the solar thermal power plant. This technique has also a great potential to save the water in desert areas.