超临界氢存储技术的研究进展

氢能的利用是当今世界发展必然趋势,使用超临界氢存储技术可对氢能进行储存。介绍了超临界氢,并详细分析了超临界储氢、气态压缩储氢和低温液态储氢的优缺点。然后,对超临界储氢技术进行了详细论述,介绍了超临界吸附储氢和低温压力容器储存超临界氢两种技术的研究进展。最后,根据超临界氢存储技术的研究现状,提出了一些对超临界氢存储技术的发展及应用具有一定指导意义的建议。     

燃料电池车车载储氢系统的技术发展与应用现状

综述了燃料电池车车载储氢系统技术，包括高压氢、液氢、金属氢化物、低温吸附、纳米碳管高压吸附以及液体有机氢化物等的研究进展及其车载应用现状。参照燃料电池车对车载储氢系统单位重量储氢密度与体积储氢密度的目标要求，对目前已应用和处于研发阶段的一些储氢技术的性能指标和存在问题进行了分析讨论。同时对目前该领域的若干新的研究报道，如超高压轻质复合容器、混合储氢容器、b.c．c．储氢合金、超级活性碳和“浆液”双相储氢等，也作了简要介绍。     

储氢技术的新进展

全面地介绍了各种储氢方式的性能,特点及当前的研究方向。     

金属氢化物复合式高压储氢器的研究

为提高高压储氢容器的体积储氢密度,采用具有高体积储氢密度的储氢合金与轻质高压容器复合组成高压金属氢化物复合式储氢器.为获得高压氢源,研究了Mm-Ml-Ni-Al(Mm为富铈混合稀土,Ml为富镧混合稀土)的储氢特性,并试制了化学热压缩器.采用研制的高压氢源,对具有高吸放氢平台压力的Ce-Ni系合金的高压储氢特性进行了研究.实验结果表明:以Ml或Ca部分取代Mm以及Al对Ni的部分置换后合金活化性能和吸放氢压力滞后明显改善,(Mm-Ml)0.8Ca0.2(Ni-Al)多元合金具有较好的储氢性能,适合于作为化学热压缩合金.CeNi5基多元合金在40MPa氢压条件下,合金具有较好的活化性能和吸放氢动力学性能,合金最大储氢容量分别达到1.6wt%.将优化的储氢合金与自制的轻质高压储氢容器复合组成的金属氢化物复合式高压储氢器,当储氢合金的填充量达到0.2(体积分数)时,其体积储氢密度提高50%.     

车载氢能源技术的分析与展望

伴随着化石燃料的枯竭和日益严重的环境问题,氢作为一种高效、清洁的可再生能源备受重视。分析目前储氢的各种技术,对车载氢能源开发的可行性进行预测并对其未来做出展望。     

有机液态氢化物可逆储放氢技术的研究现状与展望

以甲基环己烷－甲苯－氢（MTH系统）与环己烷－苯－氢（CBH系统）为例介绍了有机物可逆储放氢技术的特点与研究现状。研究表明，该技术作为大规模、长期性的氢能储存和运输手段，作为随车脱氢为汽车提供氢燃料或为氢燃料电池提供氢源，以及用于化学热泵等在技术上都是可行的，但问题的关键是如何提高过程的释氢效率，特别是低温下的释氢效率，开发低温高效脱氢催化剂和采用膜催化反应分离技术是提高释氢过程效率的可行方法。水电解－有机氢载体电化学加氢－氢载体膜催化脱氢技术路线有望改善系统储氢效能，实现氢的高能量密度储存。     

金属氢化物储氢器吸氢过程的数值分析

基于金属氢化物吸氢基本特性,建立圆柱形金属氢化物储氢器吸氢过程的-维数学物理模型.采用有限差分法对金属氢化物床体的传热传质进行计算.分别研究金属氢化物床体各处温度和氢含量在吸氢过程中的变化以及氢气压力、对流传热系数和金属氢化物床体径向厚度对金属氢化物吸氢过程的影响.计算结果表明:初始阶段金属氢化物床均匀吸氢,但随着氢化过程的进行,其中心区域的吸氢速率逐渐低于边缘区域;增加吸氢压力、提高对流传热系数均可促进储氢器的吸氢;金属氢化物床的径向厚度对吸氢速率影响很大,金属氢化物床越薄,氢化反应的速度越快.     

氢经济

目前世界能源经济的基础是化石燃料，作为不可再生能源，对其过度开采，不仅造成了资源的枯竭，而且其利用过程中伴生的污染物及温室气体的排放严重破坏了自然生态环境，有损于社会的可持续发展。氢是世界上最简单、储量最丰富、分布最广的元素。它可以从水、化石燃     

高压钢质无缝氢气瓶的研制

随着我国国民经济的快速发展和能源的广泛利用,常规能源将被大量消耗,同时伴随着程度不同的环境污染。开发对环境污染极小甚至没有污染的、能够替代现有常规能源的未来清洁能源是当务之急。高压氢气是比较理想的清洁能源。储运高压氢气的设备——高压钢质无缝氢气瓶是研发的重点。为了降低高压气体的储运成本,提高高压气体的运载效率,高压氢气的储运压力正在不断提高,一般为35MPa～45MPa。     

液化空气集团参与欧洲氢能源创新项目

欧盟委员会于2008年10月8日批准了6760万欧元的专款,用于支持氢能源创新项目（H2E）。该项目由液化空气集团负责协调,其研究将集中在氢和氢燃料电池领域。在今天地球面临环境和能源双重挑战的背景下,如何获取可持续动力,以减少温室气体排放和城市污染,降低对油基燃料的依赖．就成为了一个战略问题。短期来看,氢能是能够解决上述问题的方案之一。     

On-board and Off-board performance of hydrogen storage options for light-duty vehicles

Leading physical and materials-based hydrogen storage options are evaluated for their potential to meet the vehicular targets for gravimetric and volumetric capacity, cost, efficiency, durability and operability, fuel purity, and environmental health and safety. Our analyses show that hydrogen stored as a compressed gas at 350–700 bar in Type III or Type IV tanks cannot meet the near-term volumetric target of 28 g/L. The problems of dormancy and hydrogen loss with conventional liquid H₂ storage can be mitigated by deploying pressure-bearing insulated tanks. Alane (AlH₃) is an attractive hydrogen carrier if it can be prepared and used as a slurry with >50% solids loading and an appropriate volume-exchange tank is developed. Regenerating AlH₃ is a major problem, however, since it is metastable and it cannot be directly formed by reacting the spent Al with H₂. We have evaluated two sorption-based hydrogen storage systems, one using AX-21, a high surface-area superactivated carbon, and the other using MOF-177, a metal-organic framework material. Releasing hydrogen by hydrolysis of sodium borohydride presents difficult chemical, thermal and water management issues, and regenerating NaBH₄ by converting B–O bonds is energy intensive. We have evaluated the option of using organic liquid carriers, such as n-ethylcarbazole, which can be dehydrogenated thermolytically on-board a vehicle and rehydrogenated efficiently in a central plant by established methods and processes. While ammonia borane has a high hydrogen content, a solvent that keeps it in a liquid state needs to be found, and developing an AB regeneration scheme that is practical, economical and efficient remains a major challenge.     

Enhancement of heat transfer in hydrogen storage tank with hydrogen absorbing alloy (optimum fin layout)

Optimization of the fin layout in a metal hydride (MH) bed has been sought to enhance poor heat transmission in a hydrogen storage tank, and to obtain a maximum hydrogen absorption rate with a smaller volume of fins. Two different fin configurations, radial and circular fins, in a vertical cylindrical reactor vessel were tested with a La‐Ni‐based AB5 type hydrogen storage alloy. A two‐dimensional transient heat conduction analysis, coupled with predicted temperature and concentration of absorbed hydrogen in the bed for the exothermic hydride reaction, was used to evaluate enhancement of the hydrogen absorption time. The estimated temperature and concentration agreed within 6 K and 8.5%, respectively, with our experimental results. The effect of thickness and the spacing and shape of fins on the hydrogen absorption time were analytically evaluated, so that the optimum range of the each fin layout was obtained by the trade off between absorption time and reduction in the MH volume due to the volume occupied by fins. The hydrogen absorption time for the recommended layout of circular fins was reduced to approximately one‐third of that without fins. © 2008 Wiley Periodicals, Inc. Heat Trans Asian Res, 37(3): 165–183, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20195     

Modeling of adsorbent based hydrogen storage systems

A numerical model was developed for the evaluation of adsorbent based hydrogen storage systems. The model utilizes commercial software and simultaneously solves the conservation equations for heat, mass and momentum together with the equations for the adsorbent thermodynamics. Conservation equations were derived for a general adsorbent bed-storage vessel configuration and the adsorbent thermodynamics were a modified form of the Dubinin–Astakhov model. The solver was the Comsol^™ Multiphysics software. Real gas thermodynamic properties for hydrogen were used in the calculations. Model predictions were compared to data for charging an activated carbon based system. Applications of the model were made for charging of MOF-5^™ and MaxSorb^™ based systems that employ flow-through cooling as a means for controlling the adsorbent temperature during charging. In addition, the model was used to evaluate the contribution of pressure work to the total energy released during charging. It was found that flow-through cooling has the potential to be an effective means for heat removal and that the contribution of pressure work can be significant, depending on the type of adsorbent and the charging procedure.     

Thermodynamic simulation of hydrogen based thermochemical energy storage system

The increasing energy demand needs the attention for energy conservation as well as requires the utilisation of renewable sources. In this perspective, hydrogen provides an eco-friendly and regenerative solution toward this matter of concern. Thermochemical energy storage system working on gas-solid interaction is a useful technology for energy storage during the availability of renewable energy sources. It provides the same during unavailability of energy sources. This work presents a performance analysis of metal hydride based thermal energy storage system (MH-TES), which can transform the waste heat into useful high-grade heat output. This system opens new doors to look at renewable energy through better waste heat recovery systems. Experimentally measured PCIs of chosen metal hydride pairs, i.e. LaNi_4.6Al_0.4/La_0.9Ce_0.1Ni₅ (A-1/A-3; pair 1) and LaNi_4.7Al_0.3/La_0.9Ce_0.1Ni₅ (A-2/A-3; pair 2) are employed to estimate the thermodynamic performance of MH-TES at operating temperatures of 298 K, 373 K, 403 K and 423 K as atmospheric temperature (T_atm), waste heat input temperature (T_m), storage temperature (T_s) and upgraded/enhanced heat output temperature (T_h) respectively. It is observed that the system with alloy pair A-1/A-3 shows higher energy storage density of 121.83 kJ/kg with a higher COP of 0.48 as compared to A-2/A-3 pair. This is due to the favourable thermodynamic properties, and the pressure differential between coupled MH beds, which results in higher transferrable hydrogen. Besides, the effect of operating temperatures on COP is studied, which can help to select an optimum temperature range for a particular application.     

Effect of adding different percentages of HfCl4 on the hydrogen storage properties of MgH2

Magnesium hydride (MgH₂) is the best candidate material to store hydrogen in the solid-state form owing to its advantages such as good reversibility, high hydrogen storage capacity (7.6 wt%), low raw material cost and abundance in the earth. Nevertheless, slow desorption/absorption kinetics and high thermodynamic stability are two issues that have constrained the commercialization of MgH₂ as a solid-state hydrogen storage material. So, to boost the desorption/absorption kinetics and to alter the thermodynamics of MgH₂, hafnium tetrachloride (HfCl₄) was used as a catalyst in this study. Different percentages of HfCl₄ (5, 10, 15 and 20 wt%) were added to MgH₂ and their catalytic influences on the hydrogen storage properties of MgH₂ were investigated. Results showed that the 15 wt% HfCl₄-doped MgH₂ sample was the best composite to enhance the hydrogen storage performance of MgH₂. The onset decomposition temperature of the 15 wt% HfCl₄-doped MgH₂ composite was decreased by ~75 °C compared to as-milled MgH₂. Meanwhile, the desorption/absorption kinetic measurements showed an improvement compared to the undoped MgH₂. From the Kissinger analysis, the apparent dehydrogenation activation energy was 167.0 kJ/mol for undoped MgH₂ and 102.0 kJ/mol for 15 wt% HfCl₄-doped MgH₂. This shows that the HfCl₄ addition reduced the activation energy of the hydrogen decomposition of MgH₂. The desorption enthalpy change calculated by the van't Hoff equation showed that the addition of HfCl₄ to MgH₂ did not affect the thermodynamic properties. Scanning electron microscopy showed that the size of the MgH₂ particles decreased and there was less agglomeration after the addition of HfCl₄. It is believed that the decrease in the particle size and in-situ generated MgCl₂ and Hf-containing species had synergistic catalytic effects on enhancing the hydrogen storage properties of the HfCl₄-doped MgH₂ composite.     

Experimental investigation and theoretical modeling of dehydriding process in high-pressure metal hydride hydrogen storage systems

This study explores the endothermic dehydriding (desorption) reaction that takes place in a high-pressure metal hydride (HPMH) hydrogen storage system when hydrogen gas is released to the fuel cell. The reaction is sustained by circulating warm fluid through a heat exchanger embedded in the HPMH powder. A systematic approach to modeling the dehydriding process is presented, which is validated against experimental data using two drastically different heat exchangers, one using a modular tube-fin design and the other a simpler coiled-tube design. Experiments were performed inside a 101.6-mm (4-in) diameter pressure vessel to investigate the influences of hydrogen release rate, heat exchanger fluid flow rate and fluid temperature on the dehydriding process for the HPMH Ti_1.1CrMn. It is shown the dehydriding reaction rate can be accelerated by increasing the fluid temperature and/or the rate of pressure drop. HPMH particles located in warmer locations close to heat exchanger surfaces both began and finished dehydriding earlier than particles farther away. 2-D and 3-D models were created in Fluent to assess the dehydriding performances of the modular tube-fin heat exchanger and coiled-tube heat exchanger, respectively. The models are shown to be quite accurate at predicting the spatial and temporal variations of metal hydride temperature during the dehydriding reaction.     

Assessment of feasible strategies for seasonal underground hydrogen storage in a saline aquifer

Renewable energies fluctuate, resulting in temporary mismatches between demand and supply. The conversion of surplus energy to hydrogen and its storage in geological formations is one option to counteract this energy imbalance. This study evaluates the feasibility of seasonal storage of hydrogen produced from wind power in Castilla-León region (northern Spain). A 3D multiphase numerical model is used to test different extraction well configurations during three annual injection-production cycles in a saline aquifer. Results demonstrate that underground hydrogen storage in saline aquifers can be operated with reasonable recovery ratios. A maximum hydrogen recovery ratio of 78%, which represents a global energy efficiency of 30%, has been estimated. Hydrogen upconing emerges as the major risk on saline aquifer storage without using other cushion gases. However, shallow extraction wells can minimize its effects. Steeply dipping geological structures are key for an efficient hydrogen storage.     

A numerical investigation of hydrogen desorption phenomena in ZrCo based hydrogen storage beds

In this paper, a three-dimensional (3D) hydrogen desorption model is applied to the thin double layered annulus ZrCo based hydrogen storage bed to precisely study the hydrogen desorption reaction and resultant heat and mass transport phenomena inside the bed. The 3D hydrogen desorption simulations are carried out and calculated results are compared with the experimental data measured by Kang et al. [1]. The present model reasonably captures the bed temperature evolution behavior and the hydrogen discharging time for 90% desorption. In addition, the thin double layered annulus metal hydride bed (MHB) design is numerically evaluated by comparing with a simple cylindrical MHB. More uniform distributions in the bed temperature and H/M atomic ratio and resultant superior hydrogen desorption performance are achieved with the thin double layered annulus bed owing to its high external surface to volume ratio and thus more efficient heating. This numerical study indicates that efficient design of the metal hydride bed is key to achieve rapid hydrogen discharging performance and the present 3D hydrogen desorption model is a useful tool for the optimization of bed design and operating conditions.     

Syntheses of alkali-metal carbazolides for hydrogen storage

Metalorganic hydrides are a new class of hydrogen storage materials. Replacing the H of N–H or O–H functional groups using metal hydrides have been recently reported, which substantially improved the dehydrogenation properties of heteroaromatic organic hydrides by lowering their enthalpies of dehydrogenation (ΔH_d), enabling dehydrogenation at much lower temperatures. Among the reported metalorganic hydrides, lithium carbazolide and sodium carbazolide appear to be the most attractive hydrogen storage/delivery material owing to its high hydrogen capacity (>6.0 wt%) and ideal ΔH_d. Nevertheless, the interaction of carbazole and corresponding metal hydride to form metallo-carbazolide is a multistep process involving intensive ball milling and high temperature treatment, where the interaction was not investigated in detail. In this paper, both alkali metal hydrides and amides were employed to react with carbazole to synthesize corresponding carbazolides, aiming to broaden and optimize the synthetic method and understand the reaction mechanism. Our experimental results showed that around one equivalent of H₂ or NH₃ could be released from the reactions of carbazole and corresponding hydrides or amides, respectively. Instrumental spectroscopic analyses proved that metallo-carbazolides were successfully synthesized from all precursors. It is found that the alkali metal amides (i.e., LiNH₂ and NaNH₂) with stronger Lewis basicities as metal precursors could synthesize the metallo-carbazolides under milder conditions. Furthermore, quasi in situ nuclear magnetic resonance results revealed that alkali metal could replace H (H–N) gradually, donating more electrons to carbazole ring. Additionally, the solubilized alkali cation may unselectively interact with π-electron of aromatic systems of both carbazole molecules and carbazolide anions via electrostatic cation-π interactions.     

A comparative analysis of the cryo-compression and cryo-adsorption hydrogen storage methods

While conventional low-pressure LH₂ dewars have existed for decades, advanced methods of cryogenic hydrogen storage have recently been developed. These advanced methods are cryo-compression and cryo-adsorption hydrogen storage, which operate best in the temperature range 30–100 K. We present a comparative analysis of both approaches for cryogenic hydrogen storage, examining how pressure and/or sorbent materials are used to effectively increase onboard H₂ density and dormancy. We start by reviewing some basic aspects of LH₂ properties and conventional means of storing it. From there we describe the cryo-compression and cryo-adsorption hydrogen storage methods, and then explore the relationship between them, clarifying the materials science and physics of the two approaches in trying to solve the same hydrogen storage task (∼5–8 kg H₂, typical of light duty vehicles). Assuming that the balance of plant and the available volume for the storage system in the vehicle are identical for both approaches, the comparison focuses on how the respective storage capacities, vessel weight and dormancy vary as a function of temperature, pressure and type of cryo-adsorption material (especially, powder MOF-5 and MIL-101). By performing a comparative analysis, we clarify the science of each approach individually, identify the regimes where the attributes of each can be maximized, elucidate the properties of these systems during refueling, and probe the possible benefits of a combined “hybrid” system with both cryo-adsorption and cryo-compression phenomena operating at the same time. In addition the relationships found between onboard H₂ capacity, pressure vessel and/or sorbent mass and dormancy as a function of rated pressure, type of sorbent material and fueling conditions are useful as general designing guidelines in future engineering efforts using these two hydrogen storage approaches.