Analysis of multilayered carbon fiber winding of cryo-compressed hydrogen storage vessel

In order to meet the hydrogen storage requirements of fuel cell vehicles, and improve the storage density of hydrogen, a cryo-compressed hydrogen storage method was proposed. The performance of cryo-compressed hydrogen storage vessel was analyzed in this paper. Based on the classical laminate theory and heat transfer solution, the stress and displacement of carbon fiber were precisely calculated to guarantee the cryo-compressed vessel severing in the cryogenic condition. Subsequently, the Tsai-Wu failure criterion was used to judge the failure of carbon fiber reinforced plastics layers. The stacking sequence, winding angle, comparison of the vessel's performance at room temperature and low temperature were conducted. The numerical results showed that the properties of storage vessel decreased at cryogenic condition, and the thickness of carbon fiber at cryogenic temperature at least increased by 47.06% than that at the room temperature. Mainly influence of low temperature on the cryo-compressed vessel were concentrated on the hoop stress of helical winding and the axial stress of hoop winding. For the vessel design, it is achievable to increase these two parts by using higher strength resin materials.     

Analysis of multi-layered thick-walled filament-wound hydrogen storage vessels

In this paper a three-dimensional elasticity analysis on multi-layered thick-walled filament-wound hydrogen storage vessels is outlined. An exact solution to stresses of the metal liner and each anisotropic layer is presented, based on Lekhnitskii's theory and the generalized plane strain assumption. The governing equation for determining the radial displacement of the hydrogen vessel is derived and the stresses in the cylindrical coordinates are then obtained. The matrix equation that determines the integration coefficients of the governing equation is formulated by considering the boundary and interface conditions. The normal and in-plane shear stresses and the twisting rate of the vessel are calculated for various thicknesses of the aluminum liner; the results are then compared to those presented by Xia et al. It is shown that the addition of the liner significantly reduces the stress magnitude of the hydrogen vessel; this stress magnitude decreases as the liner thickness increases. The results also revealed that the twisting effect is reduced by increasing the liner thickness. The ratio of hoop-to-axial stress is no longer a constant through the vessel wall and varies within the wall thickness. In addition, various combinations of anisotropic composites and isotropic liner materials are here examined to pinpoint preferable material combinations that lead to a lower equivalent stress level of the liner and higher strength reserve of the composite laminate.     

Fatigue life prediction and verification of high-pressure hydrogen storage vessel

A fatigue life prediction method is developed for the high-pressure hydrogen storage vessel based on theoretical research and experimental verification. Firstly, the finite element model of vessel was built considering wound angle of head, thickness and number of the composite layer, then simulation was performed. The optimum range of autofrettage pressure was obtained by FEA with consideration of the DOT-CFFC and CGH2R standards. The influence of autofrettage pressure, metal liner thickness, and fiber thickness on vessel fatigue life was discussed under internal pressure cyclic load. Finally, the experimental verification was carried out. It was found that fatigue failure first occurred in middle cylinder. The experiment results agree well with theory analysis. Their average error is 6.33%.     

Simulation and burst validation of 70 MPa type IV hydrogen storage vessel with dome reinforcement

The dome reinforcement (DR) technology was studied to reduce the amount of carbon fiber of the type IV hydrogen storage vessel in this paper. Firstly, the influence of the angle and thickness of the dome reinforcement part on the stress distribution of the dome section is studied by finite element analysis. Secondly, the weight reduction of carbon fiber composite layer is studied based on the dome reinforcement model. The strain-based Hashin progressive damage model is used to predict the burst pressure and burst mode with user-defined material subroutine (UMAT) of ABAQUS. Finally, the dome reinforcement technology is further verified in comparison with non-dome reinforcement by burst tests. The results show that the progressive damage model can effectively represent matrix cracking and fiber fracture, and the predicted burst pressure and mode is consistent with the test results. The fiber stress near the equator of the dome section affects the burst mode, and the smaller the angle of dome reinforcement parts, the better the reinforcing effect, and the dome reinforcement technology can help to improve the fiber damage state at the dome, transfer the maximum stress to the cylinder section of the vessel, and ensure the burst mode to be a safe mode. Also, it can help to reduce the consumption of carbon fiber by up to 5.5% in composite material.     

Review on optimization design,failure analysis and non-destructive testing of composite hydrogen storage vessel

Composite hydrogen storage vessels have been increasingly applied to hydrogen fuel cell vehicles. This review focuses on optimization design, failure analysis and nondestructive testing for enhancing the safety of composites hydrogen storage vessels in service. The optimization designs of the composite vessel components help to improve the durability and strength of composite vessels subjected to burst pressure and fatigue loads. In complex service environments, composite vessels may suffer from various failure forms (burst failure, fatigue failure and impact failure) which involve different damage processes and influence factors. More importantly, this review discusses the applications of acoustic emission, digital image correlation, optical fiber in studying the residual performance (burst pressure and fatigue life) and damage modes of the composite vessel. It is expected that the combination of nondestructive testing techniques plays an increasingly important role in developing the composite vessel for structural health monitoring.     

Numerical simulation of hydrogen filling process in novel high-pressure microtube storage device

Novel high-pressure microtube hydrogen storage device has higher hydrogen storage density and safety than conventional hydrogen tanks. A one-dimensional numerical model for hydrogen filling process in microtubes is established, with reasonable calculation methods and accurate physical properties adopted. Based on the analysis of flow parameters variations, three stages of the filling process are summarized. At the beginning of the filling process, the maximum temperature appears at the inlet, but the average temperature does not rise significantly during the whole process. The effects of microtube length, filling pressure and environmental temperature are investigated and discussed. The results show that excessively long microtubes greatly increase the filling time and higher filling pressure reduces the filling time and improves the filling efficiency. The microtube hydrogen storage device achieves higher hydrogen storage density and filling efficiency in lower temperature mediums. It reveals that high filling pressure, low temperature encapsulation and reasonable microtube size design are the future development directions of microtube hydrogen storage for better application.     

Economic potential of complex hydrides compared to conventional hydrogen storage systems

Novel developments of materials for solid hydrogen storage show promising prospects. Complex hydrides exhibit great technical potential to store hydrogen in an efficient and safe way. Nevertheless, so far an evaluation of economic competitiveness is still lacking. In this work, an assessment about the economic feasibility of implementing complex hydrides as hydrogen storage materials is presented. The cost structure of hydrogen storage systems based on NaAlH₄ and LiBH₄/MgH₂ is discussed and compared with the conventional high pressure (700 bar) and liquid storage systems. The vessel construction for the complex hydride systems is much simpler than for the alternative conventional methods because of the milder pressure and temperature conditions during the storage process. According to the economical analysis, this represents the main cost advantage of the complex hydride systems.     

Effect of inside diameter on design fatigue life of stationary hydrogen storage vessel based on fracture mechanics

Design fatigue life of stationary hydrogen storage vessel constructed of the practical materials of low alloy steels was analyzed based on fracture mechanics in hydrogen and air of 45, 85 and 105 MPa using cylindrical model with inside diameter (Di) of 150, 250 and 350 mm. Design fatigue life of five typical model materials was also analyzed to discuss the effect of Di on the design fatigue life by hydrogen-induced crack growth of the vessel. K_IC of all the practical materials qualified the leak before burst. Design fatigue life generally increased slightly with increasing Di in air, while design fatigue life by K_IH was much shorter than that in air. Hydrogen influence on design fatigue life increased with increasing Di due to that K_I at initial crack increased with increasing Di. The design fatigue life data of the model materials under the conditions of Di, pressure, ultimate tensile strength, K_IH, fatigue crack growth rate and regulations in both hydrogen and air were proposed quantitatively for materials selection and development for stationary hydrogen storage vessel.     

Performances comparison of adsorption hydrogen storage tanks at a wide temperature and pressure zone

Large-scale application of hydrogen requires safe, reliable and efficient storage technologies. Among the existing hydrogen storage technologies, cryo-compressed hydrogen (CcH₂) storage has the advantages of high hydrogen storage density, low energy consumption and no ortho-para hydrogen conversion. But it still needs higher hydrogen storage pressure when reaching higher hydrogen storage density. In order to reduce hydrogen storage pressure and improve storage density, solid adsorption technology is introduced in CcH₂. Activated carbon and metal-organic framework materials (MOFs) are employed as adsorbents in this paper. The gravimetric/volumetric hydrogen storage capacities of different adsorption tanks are studied and compared with the hydrogen storage conditions of 1–55 MPa at 77–298 K. The results show that the hydrogen storage density of CcH₂ combined with adsorption is higher than that of pure adsorption hydrogen storage, and the storage pressure is lower than that of pure CcH₂ under the same hydrogen storage capacity. And the combination of two hydrogen storage technologies can achieve a high hydrogen storage capacity equivalent to that of liquid hydrogen at a lower pressure.     

Magnesium and iron loaded hollow glass microspheres (HGMs) for hydrogen storage

The development of a safe and efficient method for hydrogen storage is essential for the use of hydrogen with fuel cells for vehicular applications. Hollow glass microspheres (HGMs) have characteristics suitable for hydrogen storage and are expected to be a potential hydrogen carrier to be used for energy release applications. The HGMs with 10–100 μm diameters, 100–1000 Å pore width and 3–8 μm wall thicknesses are expected to be useful for hydrogen storage. In our research we have prepared HGMs from amber glass powder of particle size 63–75 μm using flame spheroidisation method. The HGMs samples with magnesium and iron loading were also prepared to improve the heat transfer property and thereby increase the hydrogen storage capacity of the product. The feed glass powder was impregnated with calculated amount of magnesium nitrate hexahydrate salt solution to get 0.2–3.0 wt% Mg loading on HGMs. Required amount of ferrous chloride tetrahydrate solution was mixed thoroughly with the glass feed powder to prepare 0.2–2 wt% Fe loaded HGMs. Characterizations of all the HGMs samples were done using FEG-SEM, ESEM and FTIR techniques. Adsorption of hydrogen on all the Fe and Mg loaded HGMs at 10 bar pressure was conducted at room temperature and at 200 °C, for 5 h. The hydrogen adsorption capacity of Fe loaded sample was about 0.56 and 0.21 weight percent for Fe loading 0.5 and 2.0 weight percentage respectively. The magnesium loaded samples showed an increase of hydrogen adsorption from 1.23 to 2.0 weight percentage when the magnesium loading percentage was increased from 0 to 2.0. When the magnesium loading on HGMs was increased beyond 2%, formation of nano-crystals of MgO and Mg was seen on the HGMs leading to pore closure and thereby reduction in hydrogen storage capacity.     

Temperature effect in cavitation risk assessments of polymers for hydrogen systems

Hydrogen storage at high pressure is currently attained by the use of different materials, such as elastomers in sealing joints, thermoplastics and thermosetting polymers in high-pressure containers, and metallic tube connections. Hydrogen containers type IV use a thermoplastic polymer for hydrogen tightness and composite materials for mechanical resistance, usually made with thermosetting resins and carbon or glass fibre. International standards impose a wide range of operative temperatures for such containers, from −40 °C to 85 °C.Once saturated with hydrogen at high pressure, a fast depressurisation process can create stress in the polymeric materials, causing its degradation by the formation of cavities. In a previous work, we were able to make a generalization of cavitation risk by the use of non-dimensional parameters, based on a simplified mechanical failure model. We observed that for the model, material's hydrogen diffusivity and yield strength are of upmost importance. In present work, we analyse the effect of temperature on these two properties, as they have an inverse evolution with temperature. Results confirm the pertinence of considering temperature in the whole application range of technology under analyse.     

Stress measurement of MlNi4.5Cr0·45Mn0.05 alloy during hydrogen absorption-desorption process in a cylindrical reactor

Hydrogen stored in a solid state form of metal hydrides offers a safe and efficient storage technique for hydrogen application. In a closed metal hydride tank, stresses may occur on the tank wall due to hydride expansion during hydrogen absorption process. In the present investigation, a novel testing system for stress evolution of MlNi_4.5Cr_0.45Mn_0.05 alloy in a closed cylindrical reactor during hydrogen absorption-desorption process was built. The results show that considerable swelling stress is developed on the inner reactor wall during activation process though a high free space of 45% is presented. Increasing hydrogen charging pressure and alloy loading fraction increase the as-generated swelling stress. The metal hydride particle expansion caused by hydrogen absorption is the intrinsic factor for swelling stress evolution. The presence of particle agglomerate in a closed tank in which its expansion is constrained is responsible for the observed swelling stress accumulation.     

Storage of cryo-compressed hydrogen in flexible glass capillaries

We present the results of the theoretical calculations and the corresponding experiments with compressed hydrogen storage in flexible glass capillaries both at room and liquid nitrogen temperatures. It was demonstrated that the strength of produced quartz capillaries can be high enough to withstand the internal hydrogen pressure up to 233 MPa and capillary vessels can have relatively high volumetric and gravimetric capacity.     

Structural analysis of metal hydride-based hybrid hydrogen storage systems

Hybrid hydrogen storage systems, which see the adoption of metal hydride materials charged at high pressure, can be a viable method to reach good gravimetric and volumetric capacities under selected conditions, since hydrogen is stored both as element bound to the hydride and as high pressure gas. A general structural model, which can simulate high pressure hybrid storage tanks, has been developed, with the aim of describing the performance of the system under various operating conditions. A baseline case has been simulated, comparing tanks composed of SS316 and IM6 graphite fiber reinforced epoxy composite that contain metal hydride materials that can store weight fractions of bound hydrogen ranging from 2% to 8%. Sensitivity analyses were performed for the baseline studies with the aim of determining the operating conditions that maximize gravimetric and volumetric capacities. Results show that high pressure systems are optimal (in terms of gravimetric and volumetric capacity) for tank materials having low density and a high allowable stress, while a low operating pressure is preferable for high density tank materials, especially when coupled with metal hydrides capable of storing a high weight fraction of bound hydrogen.     

Hydrogen gas filling into an actual tank at high pressure and optimization of its thermal characteristics

Gas with high pressure is widely used at present as fuel storage mode for different hydrogen vehicles. Different types of materials are used for constructing these hydrogen pressure vessels. An aluminum lined vessel and typically carbon fiber reinforced plastic (CFRP) materials are commercially used in hydrogen vessels. An aluminum lined vessel is easy to construct and posses high thermal conductivity compared to other commercially available vessels. However, compared to CFRP lined vessel, it has low strength capacity and safety factors. Therefore, nowadays, CFRP lined vessels are becoming more popular in hydrogen vehicles. Moreover, CFRP lined vessel has an advantage of light weight. CFRP, although, has many desirable properties in reducing the weight and in increasing the strength, it is also necessary to keep the material temperature below 85 °C for maintaining stringent safety requirements. While filling process occurs, the temperature can be exceeded due to the compression works of the gas flow. Therefore, it is very important to optimize the hydrogen filling system to avoid the crossing of the critical limit of the temperature rise. Computer-aided simulation has been conducted to characterize the hydrogen filling to optimize the technique. Three types of hydrogen vessels with different volumes have been analyzed for optimizing the charging characteristics of hydrogen to test vessels. Gas temperatures are measured inside representative vessels in the supply reservoirs (H2 storages) and at the inlet to the test tank during filling.     

Numerical investigation on temperature-rise of on-bus gaseous hydrogen storage cylinder with different thickness of liner and wrapping material

Gaseous hydrogen stored in high-pressure cylinder is a proper solution for the application of hydrogen fuel cell buses (HFCB). As far as the on-bus hydrogen storage system (OBHSS) is concerned, the filling of hydrogen gas needs to be finished in an acceptable time, which unavoidably brings the increase of temperature of hydrogen gas in OBHSS. And excessive temperature of hydrogen gas is unfavorable to mechanical properties of wrapping material and even the service life of the storage cylinder, so it is urgent to work out effective strategies on the temperature-rise in the storage cylinder. It is noticed that the studies on the relationship between the temperature-rise and the geometrical parameters of on-bus gaseous hydrogen storage cylinder (OBGHSC), e.g. thickness of liner and fiber/epoxy composite laminate, are still not deep enough. Motivated by this fact, this research is therefore devoted to studying the relationship between the temperature-rises of both hydrogen gas and solid materials in OBGHSC and the geometrical parameters of wrapping material and liner of OBGHSC, and to developing several temperature-rise correlations. To do so, a 2-dimensional (2D) axisymmetric computational fluid dynamics (CFD) model is applied for the simulation of fast filling process and holding process of 70 MPa OBGHSC. The simulation results show that the temperature distribution during the filling is different for different type III storage cylinders, while the highest temperature is always in the head dome junction region for type IV storage cylinders. For the carbon fiber/epoxy composite laminate (CFEC), the temperature varying tendencies are not the same for different type III storage cylinders, while the temperature in type IV storage cylinder decreases with the increase of thickness of CFEC. At last, based on the obtained numerical data, the correlations for highest value of mass-averaged temperature-rise of hydrogen gas and the correlations for maximum temperature-rise of CFEC that account for the effects of dimensionless parameters are proposed. The correlations reveal the relationship between the temperature-rise and the structure of hydrogen storage cylinder and can be used to direct the fast filling process for OBHSS in this research.     

潜艇燃料电池AIP氢燃料活性炭低温吸附储存

设计利用潜艇液氧冷量的燃料电池(FC)-AIP活性炭低温吸附储氢系统,在模拟潜艇航行中晃动和振动的平台上,测试氢在活性炭上的吸附等温线和储氢系统在为质子交换膜燃料电池(PEMFC)供气时的特性。结果表明,吸附等温线受平台晃振的影响小;温度为113K、压力为6MPa时,比表面积为1450m2.g-1的SAC-02活性炭储氢系统的质量储氢密度可超过当前艇用储氢合金的质量储氢密度;在2kW PEMFC电堆典型工况所需的氢气量(质量流率21.44L.min-1)下,通过充气过程的液氧预冷和放气过程的循环介质加热,可使储罐中心和壁面在整个过程中的最大温差小于5℃。活性炭低温吸附储氢系统的质量密度和储放氢特性能满足艇用FC-AIP系统的要求。     

Vehicular storage of hydrogen in insulated pressure vessels

This paper describes an alternative technology for storing hydrogen fuel onboard vehicles. Insulated pressure vessels are cryogenic capable vessels that can accept cryogenic liquid hydrogen, cryogenic compressed gas or compressed hydrogen gas at ambient temperature. Insulated pressure vessels offer advantages over conventional storage approaches. Insulated pressure vessels are more compact and require less carbon fiber than compressed hydrogen vessels. They have lower evaporative losses than liquid hydrogen tanks, and are lighter than metal hydrides.

The paper outlines the advantages of insulated pressure vessels and describes the experimental and analytical work conducted to verify that insulated pressure vessels can be safely used for vehicular hydrogen storage. Insulated pressure vessels have successfully completed a series of certification tests. A series of tests have been selected as a starting point toward developing a certification procedure. An insulated pressure vessel has been installed in a hydrogen fueled truck and tested over a six month period.