咸水层储能与含水介质渗透性变化的实验研究

针对三维渗流砂箱实验系统,通过储热与储冷实验,结合咸水层储能模型以及胶体稳定性理论探索储能过程中导致含水介质空间结构以及渗透性能变化的主要原因。研究结果表明,储能过程中回灌溶液温度变化造成含水介质空间结构发生空间非均质性改变,最终导致渗透性能在相对短时间内发生变化。在回灌60℃咸水溶液工况下,砂箱相对渗透率下降到73%,流出溶液黏粒质量浓度最高达5.2g/L;回灌5℃咸水溶液工况下,相对渗透率只下降8%,流出液中没有黏粒物质出现。在储热与储冷实验中,引起黏粒物质重新分布的机制不同。     

咸水层储能回灌溶液盐度变化对含水介质渗透性能的影响

基于现场勘测结果,结合实验室现有条件,建立定流量供液一维砂柱渗流系统。通过对砂柱试验系统进行回灌溶液盐度突、渐变试验,结合双电层理论揭示咸水层储能过程中含水介质渗透性能以及空间结构变化的主要原因。研究结果表明,地下咸水层储能过程中,回灌溶液盐度发生变化造成含水介质粘粒产生释放、迁移与聚沉现象,最终导致渗透性能在相对短时间内发生变化。回灌溶液盐度变化幅度与递减梯度越大,粘粒释放量也越大,渗透系数变化幅度增大。在回灌100%去离子水突变试验中,流出溶液粘粒浓度最高达8.6 g/L,相对渗透系数下降53.8%;渐变试验中,流出溶液粘粒浓度最高只有3.7 g/L,相对渗透系数只下降28%。     

回灌溶液温度对咸水层渗透性能的影响

作为清洁环保的供暖和制冷方式,季节性含水层储能与热泵技术相耦合,具有很好的经济效益和环境效益。然而,当咸水储层作为储能介质时,由于回灌溶液盐度和温度的变化会导致咸水层中黏土颗粒的释放、运移和沉积,引起孔隙通道的堵塞,造成储层的渗透性能降低。通过室内一维砂柱实验,在不同回灌水头下采用不同温度的地下原水回灌时,对溶液在含有蒙脱石矿物成分的砂样中的渗透系数变化进行了实验测试,分析了回灌温度对含水层渗透性能的影响。结果显示:随着回灌温度升高,溶液在砂样内的渗透系数减小;回灌溶液温度越高,渗透系数下降程度越大,当回灌水头为0.10 m时,回灌溶液温度由5升高至80℃,渗透系数下降了14.0%;在回灌温度一定的情况下,回灌水头差越大,渗透系数下降的幅度越大,当回灌水头为0.20和0.48 m时,溶液在砂样中的渗透系数分别下降了16.0%和18.2%。通过定量地分析流体在储层内的渗透系数与回灌温度的变化规律,得到了不同回灌水头下,溶液渗透系数与回灌温度间的函数关系。     

地下咸水层水-热-盐耦合模型及其储能利用研究

基于地下水水热运移的基本原理,针对地下咸水层储能系统中地下水密度及粘滞性系数变化显著的特点,建立地下咸水层水-热-盐耦合储能模型。应用校正后的数学模型,对天津滨海某地下咸水层储能系统未来5 a的地下水动力场和温度场的变化进行了预测。结果表明:在地下咸水层水文地质条件不变的情况下,渗透系数随地下咸水层温度和浓度的增减而增减;在夏季储热期,地下水渗透流速随地下温度的上升呈逐渐上升趋势;在冬季储冷期,地下水渗透流速随地下水温度的下降呈逐渐下降趋势,从而影响地下咸水层温度场的变化,在第5年供冷期末,3#抽水井水温上升0.5℃,发生热突破现象。     

地下承压含水层水-热运移特性的模拟研究

依据地下水文地质的相关概念和渗流力学的理论基础,建立了地下含水层热量运移的数学模型.以微山地区一工程为背景,对1抽2灌井群的热量分布规律进行了求解,得出了井群的水流速度场、水头压力场以及温度场分布.经计算分析得出:①在抽灌状态下,水压的变化较温度场快,影响范围也较大.相对应的温度影响半径相对较小,变化速度较慢且不明显;②温度场的影响半径主要集中在井周围约30m范围内,其温度的变化梯度为0.17℃/m.而超出此范围的区域,影响的相应时间较长,幅度不大;③夏季抽灌温差采用:10℃大温差运行,有利于避免或减小热贯通现象,且可减少抽灌水量.     

大规模储能系统控制模式研究

大规模储能系统是解决新能源并网和智能电网建设的有效途径和重要方案。文章首先介绍了储能系统的工作原理和组成,分析研究了储能系统的控制模式,包括波动平抑控制模式、调峰控制模式、调压调频控制模式、跟踪计划出力控制模式和孤岛运行控制模式,最后简要介绍了相关的支撑技术。     

低温储能设备内部流动传热特性的数值研究

低温储能技术可以实现电力需求侧的调节管理,是促进可再生能源利用的新技术。采用计算流体力学(CFD)方法研究了用于实现低温储能的低温斜温层蓄冷罐的内部的流动传热特性。获得了斜温层厚度随时间的连续变化规律,分析了低温斜温层蓄冷罐内部的温度分布。结果表明,供冷时降低流量可有效减小斜温层厚度,且停止排出斜温层时的斜温层厚度越小效果越明显。“首次蓄冷形成斜温层-蓄冷结束时排出斜温层直至斜温层厚度为0.4m-停运一段时间-50%额定流量启动供冷0.5h后以额定流量完成正式供冷”的运行方案能够较为有效地减小供冷结束时的斜温层厚度。研究成果可为低温斜温层蓄冷罐的结构设计和操作运行提供参考指导。     

多层打孔隔热材料热分析计算模型研究

基于能量守恒定律,构建可应用于空间机构热防护的多层打孔隔热材料热性能分析计算模型,该模型考虑相邻两层反射屏间辐射换热、反射屏与间隔物接触导热、间隔物本身导热以及残余气体导热,能够准确预测多层打孔隔热材料内部传热特性。并在此基础上,进行了隔热材料热真空实验研究,以验证所建热分析计算模型的准确度。     

储能系统锂电池电热耦合建模及参数辨识方法研究

针对电化学机理模型存在全阶结构复杂度高、电池温度变化过程无法精确描述的问题,该文提出将简化电化学模型与热力学模型耦合,建立简化电化学-热力学耦合模型,通过智能辨识算法获取模型相关参数。实验表明,该方法建立的模型在宽环境温度范围、常用放电倍率工况下仿真曲线与实际测试曲线的拟合效果较好,能较好地描述电池电压、电流和温度变化。该模型以较低的模型复杂度和较高的模型精度描述电池内部电化学、热力学行为,可支撑电池状态估计和剩余寿命预测研究。     

能量地下蓄存及其传热效能分析

储能技术是实现能源可再生化和高效利用的一种有效途径,提高其综合利用率和实现能源的实时补充。着重论述地下蓄能技术发展状况和面临的研究问题,并通过实验和模拟计算,对蓄能的传热作用进行了分析和探讨,指出蓄能改变地下蓄能体的能位,并表现为蓄能体温度和分布的变化,这种变化随时间而改变。建议进一步开展完善地下蓄能理论研究,推动中国地下蓄能技术的发展。     

Research progress on heat transfer enhancement technology of phase change energy storage

相变储能是通过相变材料吸/放热过程来实现能量储存的技术,它能够解决热量供需时间、空间和强度上的不匹配,并以其高储能密度成为储能领域的研究热点,但由于相变材料的热导率较低,使其应用受到限制。针对相变储能材料熔化/凝固过程中热导率低引起的传热速率慢的问题,从优化储能设备结构、添加剂提高相变材料热导率以及联合强化传热技术三方面综述国内外相变材料储能强化传热技术的最新进展。通过比较各种强化传热方式的优劣,实验和模拟均显示复合强化传热即可解决相变材料热导率低,又增大传热面积,从而提高相变材料的传热性能;多孔金属作为导热添加剂增强导热效果更好;并提出了相变储能强化传热技术未来需要解决的相关技术难题。     

Optimization for operating modes based on simulation of seasonal underground thermal energy storage

A simulation was performed, which concerned the feasibility of seasonal underground thermal energy storage (UTES) in Tianjin, China. The investigated system consisted of 8 boreholes. In summer, residual solar thermal energy was emitted into the soil surrounding the borehole heat exchangers through which the stored energy was extracted in winter with a ground coupled heat pump (GCHP) to provide a proper heating temperature. A simulation study was performed to study the influence of system operation modes on thermal recovery based on the experimental data of a GCHP system, local meteorological conditions and soil properties in Tianjin. The results indicate a thermal recovery ratio of less than 67% and different temperature distributions under three modes. Finally, an operation mode was suggested based on both lower loss and better thermal recovery in the UTES. __________ Translated from Journal of North China Electric Power University, 2007, 34(2): 74–77 [译自: 华北电力大学学报]     

复合相变储能材料的传热性能研究进展

总结近年来国内外相变储能材料的研究状况,包括相变储能材料的制备、传热性能、相变过程数值模拟和应用等,并对复合相变储能材料的传热性能研究方法的前景作了展望。     

Comparative study on adsorbent characteristics for adsorption thermal energy storage system

The adsorption performance of the thermal energy storage (TES) system changes depending on the material properties of the adsorbent itself, but the change of the hardware structure can also substantially change the adsorption characteristics. In this study, a laboratory‐scale adsorption‐based TES system was constructed, and the adsorption performance of three adsorbents was evaluated in the same system to compare the adsorption performance between adsorbents. The adsorption characteristics of silica gel, zeolite 13X, and 4A, which are the most preferred adsorbents in the physical adsorption‐based TES system, were selected for evaluation. Experiments with each adsorbent were performed, including heat recovery to evaluate the heat transfer effect and the amount of heat recoverable in the actual TES system. Experimental results have identified several key characteristics of the adsorption and performance of each adsorbent in the TES system, as well as operating parameters that determine the influence of adsorption performance on the TES system. The actual energy storage density of the adsorbent is affected not only by the enthalpy of adsorption of the material itself but also by other factors. These factors include the difference in thermal conductivity that causes a difference in temperature distribution and the magnitude of mass transfer resistance due to the shape of the adsorbent particle and the actual TES system reactor structure. If the reaction heat generated during the adsorption reaction cannot be effectively released, the adsorption performance is significantly lowered due to the increased temperature of the reactor inside. This phenomenon was commonly observed in adsorbents examined in the present study. The uptake amount, X [g/g], was increased by allowing the inside of the reactor to be maintained at a lower temperature through heat recovery. In case of silica gel, the temperature rise during adsorption reaction is not high due to the difference of isotherm characteristics compared with zeolites, but it is possible to absorb more amount of adsorbate and to recover heat for a longer time. The energy storage density is affected by the temperature increase effect and the uptake amount of adsorbate during the adsorption reaction. The experimental results show that the energy storage density of zeolite 13X is 15% and 28.7% higher than that of silica gel and 4A, respectively, and the temperature rise due to heat generation during adsorption reaction is also high, which is advantageous in adsorption TES system performance.     

Augmentation of solar-assisted humidification-dehumidification water desalination system using heat recovery and thermal energy storage system

In previous investigations, humidification-dehumidification (HDH) solar-assisted desalination systems were designed produce the daily fresh water during sun hours which lead to big sizes and unsteady systems. In the present study, integration of solar-assisted HDH desalination system with heat recovery and thermal energy storage unit is developed to enhance system productivity, reduces auxiliary power consumptions and system size and assure system continuous operation. The mathematical modelling based on energy and mass conservation equations is presented and solved using iterative techniques by C++ and engineering equation solver software. Detailed parametric study of the developed system is conducted for wide ranges of operating conditions and design parameters to study the effects of integrating the HDH system with solar collectors, heat recovery and thermal energy storage units on the system performance. The results revealed that (i) this integration improves system productivity and reduces operating cost, (ii) increasing air to water mass ratio and sea water temperature and decreasing ambient humidity decrease water productivity and gained output ratio (GOR) and increase operating cost parameter (OCP) and (iii) increasing air inlet temperature and sea water flow rates increase GOR and decrease OCP. Comparison with previous systems showed that the proposed system reduces the electric heating power of the system at solar noon by 37% at MR = 0.5 and gives daily fresh water productivity (123.7 kg/h) two times more than previous systems with comparable OCP (0.099 $/kg).     

Simulation of heat transfer in the cool storage unit of a liquid–air energy storage system

An energy storage system that stores energy in the form of liquid air was studied. In this system, the cool storage unit was the most important unit. From the viewpoint of safety and economy, it was most promising to store the cold energy as the sensitive heat of a solid such as pebbles or concrete. A simulator was developed to predict temperature variations of the solid cool storage unit. The simulator calculated unsteady heat transfer between a supercritical gas flow and the solid material. Comparison of calculated and experimental results showed that the temperature variation of the metal cool storage medium was accurate within 11%. The calculated results showed for the concrete cool storage unit that a smaller quantity of medium was required with a smaller pitch of the tube. The minimum quantity of concrete calculated at the smallest pitch was three times that of concrete, which was simply estimated from the heat capacity of concrete and air. The volume required for concrete cool storage was less than 1/100 that of reservoirs for a pumped‐hydro power station having a vertical drop of 500 m. © 2002 Wiley Periodicals, Inc. Heat Trans Asian Res, 31(4): 284–296, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.10035     

An experimental and numerical investigation of heat transfer during technical grade paraffin melting and solidification in a shell-and-tube latent thermal energy storage unit

The latent thermal energy storage system of the shell-and-tube type during charging and discharging has been analysed in this paper. An experimental and numerical investigation of transient forced convective heat transfer between the heat transfer fluid (HTF) with moderate Prandtl numbers and the tube wall, heat conduction through the wall and solid–liquid phase change of the phase change material (PCM), based on the enthalpy formulation, has been presented. A fully implicit two-dimensional control volume Fortran computer code, with algorithm for non-isothermal phase transition, has been developed for the solution of the corresponding mathematical model. The comparison between numerical predictions and experimental data shows good agreement for both paraffin non-isothermal melting and isothermal solidification. In order to provide guidelines for system performance and design optimisation, unsteady temperature distributions of the HTF, tube wall and the PCM have been obtained by a series of numerical calculations for various HTF working conditions and various geometric parameters, and the thermal behaviour of the latent thermal energy storage unit during charging and discharging has been simulated.     

相变蓄冷装置内传热及相变特性研究

建立了三种不同蓄冷球球径堆叠方式的相变蓄冷装置模型,对其进行了数值模拟以研究其内部传热及相变特性。结果表明：随着流速的提高、蓄冷球直径的减小,蓄冷结束后三种方案中装置内蓄冷球的凝固率提升显著;双球径方案与单球径方案装置内蓄冷球凝固率随时间变化的规律在蓄冷过程初段相类似,但两方案中相同球径部分蓄冷球相变结束,双球径方案中发生相变的蓄冷球由大直径转变为小直径时,其凝固率随时间变化的速度逐渐超过单球径方案。该研究可为相变蓄冷装置的实际设计及性能优化提供参考