Particle Size Optimization of Thermochemical Salt Hydrates for High Energy Density Thermal Storage

Thermal energy storage(TES)solutions offer opportunities to reduce energy consumption,greenhouse gas emissions,and cost.Specifically,they can help reduce the peak load and address the intermittency of renewable energy sources by time shifting the load,which are critical toward zero energy buildings.Thermochemical materials(TCMs)as a class of TES undergo a solid-gas reversible chemical reaction with water vapor to store and release energy with high storage capacities(600 kWh m^(-3))and negligible self-discharge that makes them uniquely suited as compact,stand-alone units for daily or seasonal storage.However,TCMs suffer from instabilities at the material(salt particles)and reactor level(packed beds of salt),resulting in poor multi-cycle efficiency and high-levelized cost of storage.In this study,a model is developed to predict the pulverization limit or Rcrit of various salt hydrates during thermal cycling.This is critical as it provides design rules to make mechanically stable TCM composites as well as enables the use of more energy-efficient manufacturing process(solid-state mixing)to make the composites.The model is experimentally validated on multiple TCM salt hydrates with different water content,and effect of Rcrit on hydration and dehydration kinetics is also investigated.

Spatiotemporal phase change materials for thermal energy long-term storage and controllable release

Phase change materials(PCMs)have attracted much attention in the field of solar thermal utilization recently,due to their outstanding thermal energy storage performance.However,PCMs usually release their stored latent heat spontaneously as the temperature below the phase transition temperature,rendering thermal energy storage and release uncontrollable,thus hindering their practical application in time and space.Herein,we developed erythritol/sodium carboxymethylcellulose/tetrasodium ethylenediaminetetraacetate(ERY/CMC/EDTA-4Na)composite PCMs with novel spatiotemporal thermal energy storage properties,defined as spatiotemporal PCMs(STPCMs),which exhibit the capacity of thermal energy long-term storage and controllable release.Our results show that the composite PCMs are unable to lose latent heat due to spontaneous crystallization during cooling,but can controllably release thermal energy through cold crystallization during reheating.The cold-crystallization temperature and enthalpy of composite PCMs can be adjusted by proportional addition of EDTA-4Na to the composite.When the mass fractions of CMC and EDTA-4Na are both 10%,the composite PCMs can exhibit the optical coldcrystallization temperature of 51.7℃ and enthalpy of 178.1 J/g.The supercooled composite PCMs without latent heat release can be maintained at room temperature(10-25℃)for up to more than two months,and subsequently the stored latent heat can be controllably released by means of thermal triggering or heterogeneous nucleation.Our findings provide novel insights into the design and construction of new PCMs with spatiotemporal performance of thermal energy long-term storage and controllable release,and consequently open a new door for the development of advanced solar thermal utilization techniques on the basis of STPCMs.

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.

Efficient Technique for Long-Term <i>in Vitro</i>Storage of Transgenic Aspen Genotypes

In vitro culture of isolated cells from tissues and organs is sometimes used to preserve and reproduce unique genotypes of woody plants. The technique, however, requires regular subculturing which raises storage costs and creates risks for contamination and accumulation of somaclonal variations. We examined the effects of sugar composition of culture medium, the length of photoperiod, light intensity, and ambient temperature on the survival of plant material in vitro. The study was performed on 49 genotypes of Populus tremula (46 transgenic genotypes carrying GFP-, Xeg- and Gus-genes, and 3 control (wild-type) genotypes). It was shown that effective storage of plants was achieved through optimization of the combined effects of all storage parameters under study. Based on the experimental data, we developed a protocol for long-term in vitro storage of desirable genotypes without subculture and with a survival rate of up to 98%. The best results were obtained when the plant material was pre-cultured on a WPM medium containing 15 g/L sucrose, 7.5 g/L sorbitol and 7.5 g/L mannitol, and then stored at +4°C under a 24-hour light day cycle with only 8 hours of light per day and maximum light intensity of 2000 lux. Post-storage recovery was done by culturing on a medium containing 1 mg/L gibberellic acid. The developed method can be used for effective in vitro storage of the studied genotypes for up to 24 months without subculture.

Cost Optimization Strategy for Long-Term Storage of Scientific Workflow

With the rapid development of cloud environment, the capabilities of systems have been promoted with powerful computing and storage. But for the characteristic of “pay-as-you-go” of cloud resources, it is necessary to consider the different data storage cost. Especially for processing of “old data” in longterm storage, an appropriate strategy is needed to reduce users’ cost. Considering the characteristics of price stratification in the current commercial cloud environment, a three-level price stratified storage strategy is proposed based on the CTT-SP algorithm, which stores part of the “old data” on relatively inexpensive secondary and tertiary storage, and ensures that the time delay caused by three-level storage does not exceed the deadline. Compared with other storage methods, the experimental result shows the strategy proposed can guarantee the time delay while reducing the cost of users significantly in longterm storage.

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.

Multi-Time-Scale Resource Allocation Based on Long-Term Contracts and Real-Time Rental Business Models for Shared Energy Storage Systems

The push for renewable energy emphasizes the need for energy storage systems(ESSs)to mitigate the unpre-dictability and variability of these sources,yet challenges such as high investment costs,sporadic utilization,and demand mismatch hinder their broader adoption.In response,shared energy storage systems(SESSs)offer a more cohesive and efficient use of ESS,providing more accessible and cost-effective energy storage solutions to overcome these obstacles.To enhance the profitability of SESSs,this paper designs a multi-time-scale resource allocation strategy based on long-term contracts and real-time rental business models.We initially construct a life cycle cost model for SESS and introduce a method to estimate the degradation costs of multiple battery groups by cycling numbers and depth of discharge within the SESS.Subsequently,we design various long-term contracts from both capacity and energy perspectives,establishing associated models and real-time rental models.Lastly,multi-time-scale resource allocation based on the decomposition of user demand is proposed.Numerical analysis validates that the business model based on long-term contracts excels over models operating solely in the real-time market in economic viability and user satisfaction,effectively reducing battery degradation,and leveraging the aggregation effect for SESS can generate an additional increase of 10.7%in net revenue.

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.

Carbon dioxide reforming of methane over bimetallic catalysts of Pt-Ru/γ-Al_2O_3 for thermochemical energy storage

The reaction of CO2 reforming of CH4 has been investigated with y-A1203-supported platinum and ruthenium bimetallic catalysts, with the specific purpose of thermochemical energy storage. The catalysts were prepared by using the wetness impregnation method. The prepared catalysts were characterized by a series of physico-chemical characterization techniques such as BET surface area, thermo-gravimetric （TG）, transmission electron microscope （TEM） and X-ray photoelectron spectroscopy （XPS）. In addition, the amount of carbon deposits on the surface of the catalysts and the type of the carbonaceous species were discussed by TG. It was found that the bimetallic Pt-Ru/7-A1203 catalysts exhibit both superior catalytic activity and remarkable stability by comparison of monometallic catalysts. During the 500 h stability test, the bimetallic catalyst showed a good performance at 800 ~C in CO2 reforming of CH4, exhibiting an excellent anti-carbon performance with the mass loss of less than 8.5%. The results also indicate that CO2 and CH4 have quite stable conversions of 96.0 % and 94.0 %, respectively. Also, the selectivity of the catalysts is excellent with the products ratio of CO/H2 maintaining at 1.02. Furthermore, it was found in TEM images that the active carbonaceous species were formed during the catalytic reaction, and well-distributed dot-shaped metallic particles with a relatively uniform size of about 3 nm as well as amorphous carbon structures were observed. Combined with BET, TG, TEM tests, it is concluded that the selected bimetallic catalysts can work continuously in a stable state at the high temperature, which has a potential to be utilized for the closed-loop cycle of the solar thermochemical energy storage in future industry applications.

Assessment of Fatigue Strength of An Offshore Floating Production and Storage Unit

The procedure of assessment of structural fatigue strength of an offshore floating production and storage and offloading unit (FPSO) in this paper. The emphasis is placed on the long-term prediction of wave induced loading, the refined finite element model for hot spot stress calculation, the combination of stress components, and fatigue damage assessment based on S-N curve.

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。

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。

面向风光储系统的多时空尺度容量置信度评估方法

随着新能源逐渐成为主体电源并且通过跨省跨区互济,广域新能源系统供电能力刻画对保障电力系统可靠供应具有重要意义。储能可有效平抑新能源波动性,从而有效提升其供电能力,容量置信度是刻画新能源-储能系统供电能力的重要指标。因此,首先提出了面向跨省跨区风光储系统的多时空尺度容量置信度评估指标体系和计算方法,将容量置信度评估周期拓展到短期运行态、中期运行态和规划态等多时间尺度,以更好地支撑关键场景下的电力系统保供电需求;并研究了面向风光场站、省级电网、跨区电网等多空间尺度的容量置信度评估方法,从而支撑广域风光储系统的供电能力刻画。此外,从时间和空间2个维度提出了将运行模拟加速算法用于广域风光储系统容量置信度评估。结合RTS-GMLC跨区算例验证了所提评估方法的有效性,研究结果表明:净负荷高峰关键场景对新能源储能系统的容量置信度影响较大,通过广域源荷互补和储能接入可有效提升新能源系统的容量置信度。

Achieving an ion-homogenizing and corrosion-resisting interface through nitro-coordination chemistry for stable zinc metal anodes

Suppression of uncontrollable dendrite growth and water-induced side reactions of Zn metal anodes is crucial for achieving long-lasting cycling stability and facilitating the practical implementations of aqueous Zn-metal batteries.To address these challenges,we report in this study a functional nitro-cellulose interfacial layer(NCIL)on the surface of Zn anodes enlightened by a nitro-coordination chemistry strategy.The NCIL exhibits strong zincophilicity and superior coordination capability with Zn^(2+)due to the highly electronegative and highly nucleophilic nature of the nitro functional group.This characteristic facilitates a rapid Zn-ion desolvation process and homogeneous Zn plating,effectively preventing H_(2) evolution and dendrite formation.Additionally,the negatively charged surface of NCIL acts as a shield,repelling SO_(4)^(2-)anions and inhibiting corrosive reactions on the Zn surface.Remarkably,reversible and stable Zn plating/stripping is achieved for over 5100 h at a current density of 1 mA cm^(-2),which is nearly 30 times longer than that of bare Zn anodes.Furthermore,the Zn/V_(2)O_(5) full cells with the functional interface layer deliver a high-capacity retention of 80.3%for over 10,000 cycles at 5 A g^(-1).This research offers valuable insights for the rational development of advanced protective interface layers in order to achieve ultra-long-lifeZnmetal batteries.

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.