Theoretical research on gas seepage in the formations surrounding bedded gas storage salt cavern

When constructing salt cavern gas or petroleum storage in lacustrine sedimentary salt formations rich in mudstone interlayers, the influence of the sealing performance of interlayers and salt-mud interface on the storage tightness should be considered adequately. In order to reveal the gas seepage in deep formations surrounding bedded salt cavern underground storage, a leakage analysis model was established based on the characteristics of a low dip angle and the interbedded structure of bedded rock salt. The gas seepage governing equations for one-dimensional and plane radial flow were derived and solved. A gas seepage simulation experiment was conducted to demonstrate the accuracy and reliability of the theoretical calculation results. The error of the seepage range was approximately 6.70%, which is acceptable. The analysis and calculation results indicate that the motion equation of gas in deep formations satisfies a non-Darcy's law with a threshold pressure gradient and slippage effect. The sufficient condition for the gas flow to stop is that the pressure gradient is equal to the threshold pressure gradient.The relationship between the leakage range and operating time is a positive power function, that is, the leakage range gradually increases with time and eventually stabilizes. As the seepage range increases, the seepage pressure decreases sharply during the early stage, and then decreases gradually until the flow stops.Combining the research results with engineering applications, three quantitative evaluation indexes named the maximum admissible leakage range, leakage volume and leakage rate are proposed for the tightness evaluation of gas storage salt cavern during their operating stage. These indexes can be used directly in actual engineering applications and can be compared with the key design parameters stipulated in the relevant specifications. This work is expected to provide theoretical and technical support for the gas loss and tightness evaluation of gas storage salt caverns.

Evaluation of intermittent-distributed-generation hosting capability of a distribution system with integrated energy-storage systems

The penetration rate of distributed generation is gradually increasing in the distribution system concerned.This is creating new problems and challenges in the planning and operation of the system.The intermittency and variability of power outputs from numerous distributed renewable generators could significantly jeopardize the secure operation of the distribution system.Therefore,it is necessary to assess the hosting capability for intermittent distributed generation by a distribution system considering operational constraints.This is the subject of this study.An assessment model considering the uncertainty of generation outputs from distributed generators is presented for this purpose.It involves different types of regulation or control functions using on-load tap-changers(OLTCs),reactive power compensation devices,energy storage systems,and the reactive power support of the distributed generators employed.A robust optimization model is then attained It is solved by Bertsimas robust counterpart through GUROBI solver.Finally,the feasibility and efficiency of the proposed method are demonstrated by a modified IEEE 33-bus distribution system.In addition,the effects of the aforementioned regulation or control functions on the enhancement of the hosting capability for intermittent distributed generation are examined.

Total Ionization Dose Effects on Charge Storage Capability of Al2O3/HfO2/Al2O3-Based Charge Trapping Memory Cell

Because of the discrete charge storage mechanism, charge trapping memory（CTM） technique is a good candidate for aerospace and military missions. The total ionization dose（TID） effects on CTM cells with Al2O3/HfO2/Al2O3（AHA） high-k gate stack structure under in-situ 10 keV x-rays are studied. The C-V characteristics at different radiation doses demonstrate that charge stored in the device continues to be leaked away during the irradiation,thereby inducing the shift of flat band voltage（V（fb））. The dc memory window shows insignificant changes, suggesting the existence of good P/E ability. Furthermore, the physical mechanisms of TID induced radiation damages in AHA-based CTM are analyzed.

Global Freshwater Storage Capability across Time Scales in the GRACE Satellite Era

Freshwater is recharged mainly by rainfall and stored inland for a period of time,which is directly affected by its storage capability.The storage capability of river basins has different spatiotemporal features that are important for the predictability of freshwater resources.However,the estimation of freshwater storage capability(FSC)remains a challenge due to the lack of observations and quantification indices.Here,we use a metric that characterizes hydrological“inertia”after rainfalls to analyze FSC over the 194 largest global major river basins based on satellite observations from the Gravity Recovery and Climate Experiment(GRACE)and simulations from the Community Land Model version 5(CLM5).During 2003–16,the global land was observed to retain 28%of precipitation after one month based on GRACE observations,and the simulation depicts that the retained proportions decrease from 42%after one day to 26%after one month,with smaller FSC partly attributed to wetter conditions and higher vegetation densities.The root zone contributes about 40%to the global land FSC on daily to monthly time scales.As the time scale increases,the contribution from the surface soil decreases from 26%to 14%,while the contribution from the deep soil increases from 4%to 10%.Snow contributes over 20%of land FSC,especially over high latitudes.With six decades of CLM5 long-term simulations,it is revealed that the change of FSC in most basins is related to internal climate variability.The FSC of river basins which displays the proportion of precipitation retained on land is worthy of further attention regarding the predictability of water resources.

Low-temperature performance and high-rate discharge capability of AB_5-type non-stoichiometric hydrogen storage alloy

Low-temperature performance and high-rate discharge capability of AB5-type non-stoichiometric hydrogen storage are studied. X-ray diffraction(XRD),pressure-composition-temperature(PCT) curves and electrochemical impedance spectroscopy(EIS) are applied to characterize the electrochemical properties of ABx(x=4.8,4.9,5.0,5.1,5.2) alloys. The results show that the non-stoichiometric alloys exhibit better electrochemical properties compared with that of the AB5 alloy.

Revisiting the sodium-ion storage capability of hard carbon in carbonate-based electrolytes via a sodium-metal-free protocol

Common evaluation methodology of sodium(Na)-containing two-electrode or three-electrode configurations overlooks the interference from highly reactive Na metal,leading to the underestimation or inconsistent performance of low-potential hard carbon(HC)electrodes.Herein,the trap of Na metal was systematically investigated with or without applied current,uncovering its inadequacy as the reference or counter electrode in different configurations.A Na-metal-free three-electrode protocol is proposed for evaluating the actual Na^(+)-storage capability of the typical low-potential HC electrode.By avoiding Na crosstalk and precisely controlling the working electrode's potential,the actual electrochemical performance of HC in the carbonate esterbased electrolyte can be recognized with high capacity of 222 mAh g^(-1)at 2 C and 113 mAh g^(-1)at 5 C,correcting the misunderstanding of the inferior performance of HC in coin-type half cells(68%and 50%undervaluation at 2 C and 5 C,respectively).The advanced protocol is expected to reduce misunderstandings or underestimation due to evaluation methods and to guide the development of high-performance battery materials.

Hydrogen storage capabilities of the most stable isomers of Na_nB_m(m+n=6) clusters

The most stable isomers of NanBm （m ＋ n = 6） clusters and their hydrogen storage properties are investigated by means of density functional theory with a 6-311＋G（d） basis set. To study the hydrogen storage properties, all of the stable structures of NanBmHx （m ＋ n =6） clusters have been optimized. It shows that boron atoms of NanBm are separated from the other boron atoms, and form satellite BHx （x = 3, 4） clusters around the centre, which attach to the system by a bridging bond of a hydrogen atom or an Na atom. Compared with the hydrogen storage capabilities, the Na3B3 has the highest hydrogen storage capacity among NanBm clusters. The binding energies, interaction energies of hydrogen atom with NanBm clusters and second difference in energy of Na3B3Hx clusters have been calculated. The results show that the stability of the NanBmHx clusters present an odd-even oscillatory effect, as the number of H atoms increases.

Ultrafine polycrystalline titania nanofibers for superior sodium storage

Sodium ion batteries have a huge potential for large-scale energy storage for the low cost and abundance of sodium resources. In this work, a novel structure of ultrafine polycrystalline TiO2 nanofibers is prepared on nickel foam/carbon cloth by a simple vapor deposition method. The as-prepared TiO2 nanofibers show excellent performance when used as anodes for sodium-ion batteries. Specifically, the TiO2 nanofibers@nickel foam electrode delivers a high reversible capacity of 263.2 m Ahg^-1 at 0.2 C and maintains a considerable capacity of 144.2 m Ahg^-1 at 10 C. The TiO2 nanofibers@carbon cloth electrode also shows excellent high-rate capability, sustaining a capacity of 148 m Ahg^-1 after 20 0 0 cycles at 10 C. It is believed that the novel nanofibrous structure increases the contact area with the electrolyte and greatly shortens the sodium ion diffusion distance, and meanwhile, the polycrystalline nature of nanofibers exposes more intercalation sites for sodium storage. Furthermore, the density functional theory calculations exhibit strong ionic interactions between the exposed TiO2(101) facets and sodium ions, leading to a preferable sodiation/desodiation process. The unique structural features endow the TiO2 nanofibers electrodes great advantages in rapid sodium storage with an outstanding high-rate capability.

计及灾后恢复全过程储能应急响应能力的配电网韧性规划

储能因响应快、灵活性高的特点,已成为可再生能源发展必不可少的支撑技术,不仅具有削峰填谷、改善电能质量的作用,在灾后恢复过程中的应急响应能力同样不可忽视。提出了一种计及灾后恢复全过程储能应急响应能力的配电网韧性规划方法,构建了同时考虑网架增强和储能配置策略的配电网韧性增强双层规划模型,系统地刻画了极端灾害发生后配电网网架重构、设备抢修及复电等灾后恢复全过程的源-网-荷-储互动模式场景。最后,通过IEEE33节点系统的算例分析表明,所提方法能更充分地挖掘储能的应急响应潜力,有效提高增强性规划决策的精准度,获得更佳的投资回报。

抽蓄电站全库盆防渗水库渗流缺陷影响分析

针对抽蓄电站全库盆防渗水库土工膜缺陷导致水库渗流量产生变化的安全问题,结合陕西省某抽蓄电站水库库底土工膜防渗工程,采用单因素影响分析和多因素影响分析方法进行抽蓄电站全库盆防渗水库渗流缺陷影响分析。结果表明,水头大小、缺陷大小、缺陷个数均正向影响抽蓄水库渗流量,而缺陷位置与抽蓄水库渗流量的相关性不明显。其中缺陷大小是影响抽蓄水库渗流量的主要因素,其次为水头大小,再次为缺陷个数。

汪清抽水蓄能电站输水发电系统渗控效果数值模拟研究

抽水蓄能电站输水发电系统埋深较大,受排水廊道、隧洞充水、复杂地质条件、天然地下水等多种因素影响,常形成复杂渗流场。依托汪清抽水蓄能电站工程,基于FEFLOW建立包含输水隧洞、地下厂房、排水廊道、围岩、断层的三维渗流稳态模型,分析了沿输水发电系统纵剖面的渗流场分布特征,并对各部位的渗流量进行预测。根据模拟结果对初始方案进行优化,修改方案取消了不必要的中平段排水廊道,并抬升下平段排水廊道使其以自流方式排出渗水,厂房区排水廊道和洞室群渗流量合计8048.16 m^(3)/d,为地下厂房排水泵选型提供了较大富裕度。修改方案取得较好的防渗排水效果,对类似工程的渗控措施优化具有指导意义。

基于熔盐储热的燃煤机组调峰可行性分析

随着新能源发电装机量增加导致电网调峰压力增大,火电机组要承担更多调峰任务,但目前火电机组的灵活性和调峰能力都较差。针对某亚临界300 MW燃煤机组,进行熔盐储能改造,提出了6种储热策略和2种放热策略,分析了3种工况下储-放热过程对机组调峰能力及热力性能的影响,并用净现值法进行了技术经济分析。结果表明:抽再热蒸汽储热可行性高,调峰深度能到58.9%,但会增加煤耗;放热时,加热给水产生蒸汽做功的发电增量最大,能到额定发电量的11.3%,但对熔盐的温度水平要求高;高温熔盐代替低压加热器预热给水可行性高,但发电增量低;储-放热全过程中,循环电效率最高可达0.987;进行了储热改造经济性分析,计算得动态投资回收期为11.65年,净现值为4911.8万元,改造方案可行。

计及扰动不确定性的储能系统容量鲁棒优化配置

针对高比例可再生能源接入下扰动不确定性增加和有功功率控制资源不足的问题,提出一种计及扰动不确定性的储能系统(ESS)容量鲁棒优化配置方法。首先,基于扩展系统频率响应模型,提取ESS运行功率与系统频率动态间的耦合关系,由多面体扰动不确定集构造暂态频率偏移安全约束。其次,综合考虑频率稳定控制能力和扰动不确定性,以投资成本最小和运行收益最大为目标,建立ESS容量鲁棒优化模型。然后,利用线性加权法和鲁棒对等变换将模型转化为确定性三层规划的形式,并基于列与约束生成方法、强对偶理论和Big-M法求解。最后,通过算例分析验证了所提方法的有效性。

某抽水蓄能电站地下厂房渗流特性及渗控效果研究

地下厂房洞室群是抽水蓄能电站发电的主要部位,厂区渗流场的分布对其结构稳定性至关重要.某抽水蓄能电站深埋于地下,其上下水库水位差超过600 m,在高水库水位和山体高地下水位的作用下,地下厂房周围将产生很高的渗透压力.为研究该地下厂房设计渗控措施下的渗控效果,建立了符合工程区实际地形、地质和输水发电系统的三维有限元模型,基于地质勘测钻孔水位数据,首先对计算模型进行了参数率定及边界验证,然后探讨了地下厂房正常运行和排水系统失效时厂区的渗流特性.计算结果表明:建立的三维模型可用于工程区渗流场分析;厂区设计渗控措施的渗控效果良好,多层排水廊道与排水孔幕结合对于降低渗流自由面效果显著,可以有效缓解厂区渗透压力;排水系统逐渐失效会引起厂区渗流量的增加和不同程度地抬高地下水入渗高程,失效面积过大时,厂房有较大发生渗透破坏的风险.

考虑闭坑后抽水蓄能的露天矿边坡稳定性分析

由于经济、环境及相关政策影响,我国废弃矿井数量与日俱增,将关停的废弃露天矿重新设计改造成抽水蓄能电站可以提高储能能力、调节地区电网负荷、提高电力系统的稳定性和可靠性,并推动废弃矿区生态修复和资源型城市转型。以抚顺市西露天矿作为研究对象,通过对我国废弃矿井及新能源分布现状的阐释,结合辽宁省电网调峰现状,论证西露天矿抽水蓄能电站建设的必要性;根据西露天矿相关工程背景及地质勘探结果,对西露天矿抽水蓄能电站上下水库选址设计和输水系统工程布置进行研究;抽水蓄能电站的建设会改变废弃矿坑的水位,从而影响矿坑的边坡稳定性。构建西露天矿下水库剖面模型并将其导入Geo-studio软件中,采用极限平衡法结合稳态渗流场分析−395 m、−350 m、−250 m水位下考虑水力效应的矿坑边坡稳定性。研究结果表明:抚顺市西露天矿抽水蓄能电站建设在技术上可行,在经济上合理,可以很好地满足辽宁省电网调峰调频需求,缓解电网运行压力大等问题;拟定西露天矿抽水蓄能电站装机容量为1200 MW,满发小时数为5 h,矿坑东侧区域为下水库,南花园湖为上水库,且上下水库的调节库容大致相等。输水线路布置在西露天矿坑南侧的花岗片麻岩内部;西露天矿坑边坡潜在的滑移风险可能发生在特定水位下的几个区域。为保证抽水蓄能电站投入使用后的库岸边坡稳定性,还需要采取进一步的防渗加固工作。

抽水蓄能电站地下厂房防渗排水方案数值模拟研究

抽水蓄能电站地下厂房埋深较大,受排水廊道、隧洞充水、复杂地质条件、天然地下水等多种因素影响,常形成复杂渗流场。基于FEFLOW软件建立包含输水隧洞、地下厂房、排水廊道、围岩、断层的三维渗流稳态模型,根据模拟结果对初始防渗排水方案进行了优化,取消不必要的中平段排水廊道,并抬升下平段排水廊道,使其以自流方式排出渗水。厂房区排水廊道和洞室群渗流量合计8048.16 m^(3)/d,为地下厂房排水泵选型提供较大富余度。

地下水对CAES地下储气库气密性和围岩稳定性影响

压缩空气储能(CAES)储气库密封和稳定是保证电站安全稳定运行的基础,储气库受力影响因素众多,且特性复杂,长期运行过程中气密性和稳定性的精准预测和评估一直是热点和难点。以考虑渗漏和传热过程的压缩空气热力学模型为非稳态边界、以热流固耦合理论为核心建立了储气库多物理场耦合下气密性和稳定性联合分析模型,探讨了洞周围岩中的地下水对储气库气密性和稳定性的影响。研究成果表明:(1)地下水的存在可使储气库每个循环气体损失量降低78%;(2)衬砌结构主要受拉应力作用,顶部和底部出现了应力集中现象,需进行加密配筋;(3)岩体中存在地下水有助于强化储气库内的气体密封效果。

Free-standingβ-Ta_(2)O_(5)/SWCNTs composite film for high-rate Li-ion storage

The rapid development of portable and wearable electronic devices is responding to the urgent demand for high-efficiency flexible energy storage devices.Flexible supercapacitors,showing long cycle life,high power density,and good safety,are considered ideal candidates.Nevertheless,the relatively low energy density restricts their practical applications.With a large dielectric constant of 18-46,Ta_(2)O_(5)-based materials typically exhibit excellent electron-binding ability,which is critical for enhancing the energy density of supercapacitors.In this work,the free-standingβ-Ta_(2)O_(5)/single-walled carbon nanotubes(SWCNTs)composite film was prepared,with a highβ-Ta_(2)O_(5)loading of over 70%.By anchoringβ-Ta_(2)O_(5)nanoparticles onto the surface of SWCNTs,the system’s flexibility and conductivity were significantly enhanced,which also facilitated the intercalation electrodynamics of metal cations.As a result,the flexibleβ-Ta_(2)O_(5)/SWCNTs film exhibits excellent Li-ion storage performance,with a high volumetric specific capacitance of 392.3 F cm^(-3)at the scan rate of 10 mV s^(-1)and 198.9 F cm^(-3)at 500 mV s^(-1).In addition,the asymmetric device,assembled by theβ-Ta_(2)O_(5)/SWCNTs and activated carbon films,shows a high energy density of 45.5 Wh kg^(-1)at the power density of 10.8 kW kg^(-1).This technique opens up a new avenue for improving the energy density and rate performance of flexible supercapacitors.

分散式风储系统频率和电压调节能力评估关键技术

分散式风电点多面广接入中高压配电网成为趋势,导致弱端电网的频率和电压支撑能力不足,分散式风储系统频率和电压调节能力评估有助于调度管理和及时发现避免潜在的稳定性问题,但复杂性和多变性使评估体系构建变得相当复杂。为此,从分散式风储系统频率和电压调节能力的影响因素分析、综合评估指标、综合评估方法三方面入手,分析现有技术方法,点明关键技术挑战。重点阐述包括:多时间尺度的高精度风电出力预测技术,不同条件下风储系统配置方案的调节能力差异等影响因素;在多模态因素耦合下分散式风储系统调频-调压容量裕度和贡献度指标计算方法提升;不确定性条件下评估方法的鲁棒性提升。最后针对技术难题,给出了分散式风储系统频率和电压调节能力评估新思路,以期为我国风电发展提供一些借鉴。

纳米硅的砂磨宏量制备及其碳纤维复合负极的储锂性能研究

硅碳负极材料因具有较高的储锂容量等优势在锂离子电池领域备受关注,但仍面临电导欠佳、体积膨胀及界面兼容性差等问题。本研究从太阳能电池微米硅废料的纳米化处理出发,通过优化砂磨实验参数实现宏量制备颗粒粒径约为300 nm硅纳米颗粒。进一步地,通过静电纺丝法制备铜纳米颗粒修饰的硅碳复合材料,所制硅碳复合材料中的硅与铜纳米颗粒内嵌或附着在纳米纤维上。综合研究其电化学储锂性能发现,该复合材料以碳纳米纤维作为基体,辅以铜纳米颗粒的修饰,可构建出高导电网格并进一步提升复合材料的电导能力,有效克服硅材料的剧烈体积膨胀以及导电性差的缺点,进而表现显著增强的电化学储锂综合性能。特别是,结构优化后的硅碳复合负极材料在1.0 A/g的较高电流密度下循环550次后仍可保持765.9 mAh/g的高可逆容量。因此,本研究为宏量制备硅纳米材料及其硅碳纤维复合负极提供了良好的参考。