Full scale thermal testing of latent heat storage in wallboard

Full scale thermal storage tests were conducted in a room lined with PCM wallboard having latent heat storage capacity. The results were compared with those obtained from tests conducted in a similar room lined with ordinary wallboard. The research showed that PCM wallboard can function efficiently as a thermal storage medium which can be applied to peak load shifting, improved use of waste and solar heat as well as more efficient operation of heating and cooling equipment.     

Energy,exergy, and sensitivity analyses of underwater compressed air energy storage in an island energy system

An underwater compressed air energy storage (UWCAES) system is integrated into an island energy system. Both energy and exergy analyses are conducted to scrutinize the performance of the UWCAES system. The analyses reveal that a round‐trip efficiency of 58.9% can be achieved. However, these two analyses identify different directions for further improvement. The heat exchangers, expanders, compressors, electric motors, and generators account for the most exergy destruction. A sensitivity analysis is also conducted to investigate the importance of different input parameters on the round‐trip exergy efficiency of the UWCAES system. The results of both local and global analyses show that the round‐trip exergy efficiency is most sensitive to the isentropic efficiency of the expanders and compressors, and the efficiencies of the electric motors and generators. The impacts of the heat exchangers, the self‐discharge rate of the air accumulator, the inner diameter of the pneumatic pipelines, and the insulation thickness of the hot‐oil tank on the round‐trip exergy efficiency are shown to be highly nonlinear.     

Analysis of uncertainties in gas uptake measurements using the gravimetric method

A full analysis of the uncertainties in the calculation of the amount of gas absorbed or desorbed by a sample using the gravimetric technique has been made. The gravimetric technique provides a near direct measurement of the uptake of gas by continuously measuring the weight of the sample plus absorbed gas and is frequently used to characterise the uptake of hydrogen in potential hydrogen storage materials. These calculations provide the capability to determine the uncertainty in the final gas uptake measurement given knowledge of the measurement uncertainties. Uptake of hydrogen gas on activated carbon has been modelled to allow individual constants such as the buoyancy volumes as well as measurement uncertainties to be changed while determining the effect on the uptake uncertainty. The measurement uncertainties critical to minimising the overall uptake uncertainty have been identified and a comparison with another popular gas uptake method, the Sieverts technique, has been made.     

d-glucose and its analogue,d-glucosamine,as potential hydrogen storage materials: A quantum mechanical study

Cellulose and chitosan monomers have been studied as potential hydrogen storage materials with good gravimetric density and strong binding strength for the adsorption of hydrogen molecules. DFT calculations have been employed to examine the various available positions on the biomolecules for efficient hydrogen adsorption. FMO and NBO analysis revealed the strength of non-bonded interactions between adsorbent (cellulose, chitosan) and adsorbate (H₂ molecules). MEP analysis helped understand the charge separation upon H₂ adsorption at the available sites. The strong interaction is attributed to the presence of polar hydroxyl groups on the carbon backbone, which interacts with hydrogen through dipole-induced dipole interactions between the hydroxyl oxygen and H₂ molecules. Topological analysis for real space functions like electron density, ELF, LOL, NCI, and electrostatic potential was used to establish the nature of interactions. These findings can significantly impact the design of new hydrogen storage materials based on naturally available biopolymers with high hydrogen storage capacity at ambient temperature.     

Thermodynamic analysis of a novel compressed carbon dioxide energy storage system with low-temperature thermal storage

Research projects on new electrical energy storage (EES) systems are underway because of the role of EES in balancing the electric grid and smoothing out the instability of renewable energy. In this paper, a novel compressed carbon dioxide energy storage with low-temperature thermal storage was proposed. Liquid CO₂ storage was employed to increase the storage density of the system and avoid its dependence on geological formations. Low-temperature thermal energy storage technology was utilized to recycle the heat of compression and reduce the challenges to system components. The system configuration was introduced in detail. Four evaluation criteria, the round trip efficiency (RTE), exergy efficiency (η_Ex), thermal efficiency (η_TE), and energy density (ρ_E) were defined to show the system performance. Parametric analysis was carried out to examine the effects of some key parameters on system performance and the genetic algorithm was adopted for system optimization. The calculated results show that, for the novel EES under the basic working condition, its RTE is 41.4%, η_TE is 59.7%, η_Ex is 45.4%, and ρ_E is 15 kWh m⁻³. The value of ρ_E increases with the increasing pump outlet pressure for a fixed value of pressure ratio, and the changes of RTE, η_TE, and the total exergy destruction of the system (E_D,total) with pump outlet pressure are complicated for different values of pressure ratio. When both pressure ratio and pump outlet pressure are high, the values of RTE and ρ_E can be maximized whereas the value of E_D,total can be minimized. Besides, no matter how pump outlet pressure and pressure ratio change, the exergy destruction of the system mainly come from compressors and regenerators, which accounts for about 50% of the total exergy destruction.     

An exergy analysis of a traditional compressed air energy storage system

压缩空气储能技术是具有较大发展前景的大规模储能技术之一,具有广阔的发展前景。使用Aspen Plus软件以传统压缩空气储能系统为例进行流程模拟,运用分析方法对模拟结果进行热力性能分析。分析结果表明,燃烧室的损失是系统各设备损失中最大的。同时还对压缩空气储能系统各个组成部件的运行效率与储能系统的损失之间的关系进行了敏感性分析,分析结果表明,对系统效率影响最大的参数为燃烧室效率,最小的参数为膨胀透平绝热效率。     

The patents analysis on supercapacitor energy storage

本文以超级电容器储能技术国际专利为研究对象,运用专利文献计量学方法,使用TDA和Innography专利检索与分析平台,对德温特专利数据库（DII）中收录的超级电容器储能技术相关专利的时序分布、来源国家和地区、技术主题、重点申请人等方面进行了分析,对超级电容器储能技术的国际发展现状、态势进行了梳理。     

Synthesis by reactive ball milling and cycling properties of MgH2–TiH2 nanocomposites: Kinetics and isotopic effects

MgH₂, MgH₂–TiH₂ nanocomposites and their deuterated analogues have been obtained by reactive ball milling and their kinetic and cycling hydrogenation properties have been analysed by isotope measurements and high-pressure differential scanning calorimetry (HP-DSC). Kinetics of material synthesis depends on both Ti-content and the isotopic nature of the gas. For pure Mg, the synthesis is controlled by isotope diffusion in Mg and therefore MgH₂ forms faster than MgD₂. For the MgH₂–TiH₂ nanocomposites, the synthesis is controlled by the efficiency of milling. Kinetics of reversible hydrogen/deuterium sorption in nanocomposites have been studied at 548 K. The rate limiting step is isotope diffusion for absorption and Mg/MgH₂ interface displacement for desorption. HP-DSC measurements demonstrate that the TiH₂ phase acts as a gateway for hydrogen sorption even in presence of MgO and provides abundant nucleation sites for Mg and MgH₂ phases. The 0.7MgH₂–0.3TiH₂ nanocomposite exhibits steady hydrogen storage capacity after 100 cycles of absorption–desorption.     

并网型飞轮储能系统金属转子结构优化设计

太阳能和风力发电具有间歇性,经常需要储能系统来平衡其对电网的影响。飞轮储能系统具有响应速度快和功率密度高等优势,可用来解决上述大规模可再生发电系统并网问题。储能密度是衡量飞轮储能系统性能的一项重要指标。该文提出一种在不改变储能总量、转速和转子直径的前提下,仅通过改变金属转子结构来降低转子质量,进而提高系统储能密度的方法。首先应用上述方法把等厚度金属转子设计成厚度沿转子半径而变化的变厚度结构,然后使用有限元分析软件ANSYS Workbench中的Response Surface Optimization模块对得到的转子结构进行优化。仿真结果表明:结构优化后的转子与原转子相比,质量降低16.88%,系统储能密度提高20.40%。     

Assessment of residential battery storage systems and operation strategies considering battery aging

With the increasing popularity of combining residential photovoltaic systems with battery storages, research, industry, and customers look for ways to determine if such an investment is economically profitable. Simulation programs may serve to predict the profitability and lifetime of the system. In this paper, we use techno-economic analysis with a specific account of battery degradation to determine profitability and lifetime of a residential photovoltaic (PV) battery system under different energy management and tariff regimes. This work presents two case studies: the first being a techno-economic comparison for a residential PV-battery system in New South Wales, Australia and Germany, and the second analyzing the profitability and degradation impact of three different operation strategies for a battery storage in Australia. The results reveal that site-specific conditions (i.e., geographical and energy-economic constraints) may have a significant impact on the ideal system configuration and ultimately the anticipated battery lifetime. Furthermore, statistical analysis of different storage operation strategies applied to various prosumer load and generation profiles reveals the effects of storage dispatch strategies on battery aging.     

Study on key parameters design and economic evaluation of the electric heating and solid sensible heat thermal storage device

电制热固体储热系统对可再生能源消纳、能源清洁化利用具有重要意义。电制热固体储热装置的关键参数设计以及经济性分析是提高经济效益的重要手段。因此,本文提出了电制热固体储热装置投资运行费用计算方法。通过对比不同供暖方式所需费用分析了电制热固体储热装置的经济性。同时研究了谷电利用系数对电制热固体储热装置经济性的影响。最后,采用案例分析验证本文所提经济性评估方法的合理性与正确性。本文的研究内容为用户对电制热固体储热装置的选择提供参考。     

Bibliometrical analysis of hydrogen storage

On the basis of literature research and expert consultation on hydrogen storage, this paper is the first to use the bibliometric method to conduct data mining and visualization analysis for the development of international hydrogen storage research. A total of 22612 publications on hydrogen storage published from 1900 to 2019 were obtained. The number of citations and research authors per year is also counted. Some indicators are used in this paper to evaluate countries, research institutions, researchers, journals and so on, such as IF, H-index, TC and CPA. We also use VOS viewer to visualize keywords. Results show that the literature on hydrogen storage has been recently increasing, particularly from 2009 to 2018. The study on hydrogen storage has entered a stable and high-frequency period, with a total of 16348 papers, which account for 72.3% of the total research papers on hydrogen storage. During this period, the number of authors who studied hydrogen storage exceeded 3000 and reached 3265 in 2008. The average number of citations per year was 2672.41. China's total volume of publications reached 7239, with 12 research institutions ranking among the top 20, and 9 researchers ranking among the top 10 in this field. China plays an important role in international research on hydrogen storage. However, the US accounts for the highest h-index (220), the highest TC (233734) and the highest CPA (59.86), which shows that the United States has the strongest influence on the research of hydrogen storage. In terms of the number of articles, the INTERNATIONAL JOURNAL OF HYDROGEN ENERGY ranked first with 3413 articles, followed by the JOURNAL OF ALLOYS AND COMPOUNDS with a total of 2131 articles. Notably, the average number of citations of the articles in the FORUM OF THE AMERICAN CHEMICAL SOCIETY and the ANGEWANDTE CHEMIE-INTERNATIONAL EDITION exceeded 150 times, that is, 165.2 and 157.14 with impact factors of 14.695 and 12.257, respectively. International hydrogen storage disciplines, such as chemistry (71.38%), materials science (38.81%), and energy science (22.10%), are distributed or related interdisciplinary research areas. The research hotspots of hydrogen storage are chemical and adsorption hydrogen storages, such as hydrogen fuel cells, metal hydride, metal–organic framework, and carbon nanotube. By contrast, research on high-pressure gaseous and liquid hydrogen storages is relatively few. Researchers are suggested to give more attention to high-pressure gaseous and liquid hydrogen storages and consider the entire process of hydrogen energy utilization. Moreover, they are suggested to propose the optimal hydrogen storage mode by combining various hydrogen storage methods. Researchers must not only increase the number of their published papers but also enhance the quality. Cooperation between countries and research institutions should be further strengthened, and exchange between different disciplines is also needed to promote the interdisciplinary development of hydrogen storage and transportation.     

Evaluation of the mechanical performance of a composite multi-cell tank for cryogenic storage: Part I - Tank pressure window based on progressive failure analysis

Understanding of the thermal and mechanical behaviour of conformal tanks when utilized in cryogenic fuel storage is considered crucial in the hypersonic aircraft sector. This behaviour is strongly dependent on the way the tank itself is designed. This study focuses on the effect of design on the performance of an innovative Type IV multi-spherical composite-overwrapped pressure vessel at both ambient and cryogenic conditions. A method to evaluate the required number of reinforcement rings at the intersections and thus avoid damage in those regions under pressurization is outlined. A thermo-mechanical FE-based model coupled with a progressive failure analysis (PFA) algorithm enables to evaluate the pressure window of the multi-sphere at ambient conditions. Additionally, a transient analysis -included in this study-is used to determine the different heat transfer mechanisms, temperature and strain evolution at the tank wall throughout cryogenic operation (chill-down, pressure cycling and purging). The temperature dependency of the tank wall materials is obtained by coupon testing and fitting functions and is hereby incorporated in the analysis. The most important outcome here is the absence of damage in the composite overwrap at cryogenic environments; this may be considered as a positive indication about the suitability of the Type IV multi-spherical COPVs for cryogenic storage.     

Highly dispersed metal nanoparticles on TiO2 acted as nano redox reactor and its synergistic catalysis on the hydrogen storage properties of magnesium hydride

In this paper, we have synthesized highly dispersed Co metal nanoparticles with the particle size about 5–10 nm on TiO₂ (25–50 nm) for the first time through an extremely facile solvothermal method. It is supposed that the synthesized Co/TiO₂ composite can combine the catalytic advantage of both Co and TiO₂, exhibiting the superior catalytic effect on the hydrogen de/absorption properties of MgH₂. The experimental data confirmed the above supposition and demonstrated that Co/TiO₂ additive highly enhances the hydrogen de/absorption kinetics of MgH₂ as compared to separate Co or TiO₂ additive. Specifically, the MgH₂Co/TiO₂ composite begins to desorb hydrogen at about 190 °C with a low apparent activation energy of 77 kJ/mol. Besides, the MgH₂Co/TiO₂ composite has a desorption peak temperature of 235.2 °C, which is 53.2, 94.2 and 132.2 °C lower than that of MgH₂TiO₂ (288.4 °C), MgH₂Co (329.4 °C) and ball-milled MgH₂ (367.4 °C). Moreover, MgH₂Co/TiO₂ composite also exhibits low temperature rehydrogenation properties, which can absorb 6.07, 5.56 and 4.24 wt% H₂ within 10 min at the temperature of 165, 130 and 100 °C, respectively. It is supposed that such excellent hydrogen desorption properties and low desorption energy barrier of MgH₂Co/TiO₂ composite are mainly ascribed to the novel synergistic catalytic effects of Co and TiO₂. Herein, we propose a novel catalytic mechanism and think that Co/TiO₂ acts as “nano redox reactor”, which can facilitate the dissociation and recombination process of hydrogen, thus reducing the reaction energy barrier and enhancing the de/rehydrogenation of MgH₂.     

Analysis of the uncertainties in gas uptake measurements using the Sieverts method

An analysis of the uncertainties in the calculation of the amount of gas absorbed or desorbed by a sample has been made for the manometric or Sieverts technique, commonly used for the determination of hydrogen uptake on potential hydrogen storage materials. The analytical derivations provide a means to calculate the uncertainty in each step of a hydrogen absorption isotherm. In addition, a Sieverts system is modelled to allow a detailed investigation of the effect of volumes and other parameters as well as the relative impact of the different measurement uncertainties. Reliable uncertainty estimates are especially important for authoritative measurements of gas uptake by carbons and other nanostructured materials used for hydrogen storage.     

Effect of stratification on energy and exergy capacities in thermal storage systems

The increase in exergy storage capacity that is attained in thermal storages through stratification is assessed. A design‐oriented temperature‐distribution model for vertically stratified thermal storages that facilitates the evaluation of storage energy and exergy contents is utilized. The paper is directed towards demonstrating the thermodynamic benefits achieved through stratification, and increasing the utilization of exergy‐based performance measures for stratified thermal storages. A wide range of realistic storage‐fluid temperature profiles is considered, and for each the relative increase in exergy content of the stratified storage compared to the same storage when it is fully mixed is evaluated. The results indicate that, for all temperature profiles considered, the exergy storage capacity of a thermal storage increases when it is stratified, and increases as the degree of stratification, as represented through greater and sharper spatial temperature variations, increases. Furthermore, the percentage increase in exergy capacity is greatest for storages at temperatures near to the environment temperature, and decreases as the mean storage temperature diverges from the environment temperature (to either higher or lower temperatures). It is concluded that (i) the use of stratification in thermal storage designs should be considered as it increases the exergy storage capacity of a thermal storage and (ii) exergy analysis should be applied in the analysis and comparison of stratified thermal storage systems. Copyright © 2004 John Wiley & Sons, Ltd.     

Two-dimensional thermal analysis of liquid hydrogen tank insulation

Liquid hydrogen (LH₂) storage has the advantage of high volumetric energy density, while boil-off losses constitute a major disadvantage. To minimize the losses, complicated insulation techniques are necessary. In general, Multi Layer Insulation (MLI) and a Vapor-Cooled Shield (VCS) are used together in LH₂ tanks. In the design of an LH₂ tank with VCS, the main goal is to find the optimum location for the VCS in order to minimize heat leakage. In this study, a 2D thermal model is developed by considering the temperature dependencies of the thermal conductivity and heat capacity of hydrogen gas. The developed model is used to analyze the effects of model considerations on heat leakage predictions. Furthermore, heat leakage in insulation of LH₂ tanks with single and double VCS is analyzed for an automobile application, and the optimum locations of the VCS for minimization of heat leakage are determined for both cases.     

带压缩空气储能的冷热电联产系统的

对一种带压缩空气储能的冷热电联产系统进行了热力学(火用)分析,得到了各主要部件和整个系统的(火用)损失及(火用)效率的变化规律.分析结果表明空气透平绝热效率的提高对系统(火用)效率的贡献大于压缩机效率同样提高的功效;在其它参数确定时,存在最佳压比,可使系统的(火用)效率在该条件下达极值;高温换热器是新型冷热电联产系统中产生(火用)损失的主要部件,而循环水量的大小是影响高温换热器(火用)效率的主要因素.     

Finite element-based simulation of a metal hydride-based hydrogen storage tank

In this paper, a novel 3D flexible tool for simulation of metal hydrides-based (LaNi₅) hydrogen storage tanks is presented. The model is Finite Element-Based and considers coupled heat and mass transfer resistance through a non-uniform pressure and temperature metal hydride reactor. The governing equations were implemented and solved using the COMSOL Multiphysics simulation environment. A cylindrical reactor with different cooling system designs was simulated. The shortest reactor fill time (15 min) was obtained for a cooling design configuration consisting of twelve inner cooling tubes and an external cooling jacket. Additional simulations demonstrated that an increase of the hydride thermal conductivity can further improve the reactor dynamic performance, provided that the absorbent bed is sufficiently permeable to hydrogen.     

冰蓄冷系统设计及经济性分析

结合某办公楼冰蓄冷系统的设计实例，演示了蓄冷设计的全过程，并通过与常规空调系统的经济性分析得出冰蓄冷空调切实可行，具有推广意义。