China, People’s Republic
Effects of Oxidants on Hydrogen Spontaneous Ignition: Experiments and Modelling
Sep 2017
Publication
Experiments were performed on the influence of oxidants (air pure oxygen O2 and pure nitrous oxide N2O at atmospheric pressure) in the straight expansion tube after the burst disk on the hydrogen spontaneous ignition. The lowest pressure at which the spontaneous ignition is observed has been researched for a 4 mm diameter tube with a length of 10 cm for the two oxidant gases. The ignition phenomenon is observed with a high speed camera and the external overpressures are measured. Numerical simulations have also been conducted with the high resolution CFD approach detailed chemistry formerly developed by Wen and co-workers. Comparison is made between the predictions and the experimental data.
Numerical Study on Combustion and Emission Characteristics of a PFI Gasoline Engine with Hydrogen Direct-Injection
Mar 2019
Publication
In this paper the effects of hydrogen blending radio and EGR rate on combustion and emission characteristics of a PFI gasoline engine with hydrogen direct-injection have been investigated by numerical modelling methods using a new generation of CFD simulation software CONVERGE. Results showed that compared with original engine hydrogen direct-injection PFI gasoline engine had a better performance on combustion characteristics but it also had a disadvantage of increasing NOx emissions. With the increase of hydrogen blending radio combustion duration shortened and CA50 advanced and was closer to TDC. And CO and THC emissions decreased however NOx emission increased. The variations of the combustion and emission characteristics followed by the increase of the EGR rate were exactly the opposite to the change of hydrogen blending radio. Considering both the combustion and emission characteristics using moderate EGR rate (15%~20%) under high hydrogen blending radio (15%~20%) condition can realize the simultaneous improvement of combustion and emission performance.
Estimation of Final Hydrogen Temperature From Refueling Parameters
Oct 2015
Publication
Compressed hydrogen storage is currently widely used in fuel cell vehicles due to its simplicity in tank structure and refuelling process. For safety reason the final gas temperature in the hydrogen tank during vehicle refuelling must be maintained under a certain limit e.g. 85 °C. Many experiments have been performed to find the relations between the final gas temperature in the hydrogen tank and refueling conditions. The analytical solution of the hydrogen temperature in the tank can be obtained from the simplified thermodynamic model of a compressed hydrogen storage tank and it serves as function formula to fit experimental temperatures. From the analytical solution the final hydrogen temperature can be expressed as a weighted average form of initial temperature inflow temperature and ambient temperature inspired by the rule of mixtures. The weighted factors are related to other refuelling parameters such as initial mass initial pressure refuelling time refuelling mass rate average pressure ramp rate (APRR) final mass final pressure etc. The function formula coming from the analytical solution of the thermodynamic model is more meaningful physically and more efficient mathematically in fitting experimental temperatures. The simple uniform formula inspired by the concept of the rule of mixture and its weighted factors obtained from the analytical solution of lumped parameter thermodynamics model is representatively used to fit the experimental and simulated results in publication. Estimation of final hydrogen temperature from refuelling parameters based on the rule of mixtures is simple and practical for controlling the maximum temperature and for ensuring hydrogen safety during fast filling process.
Effect of Plastic Deformation at Room Temperature on Hydrogen Diffusion of Hot-rolled S30408
Sep 2017
Publication
The influence of plastic deformation on hydrogen diffusion is of critical significance for hydrogen embrittlement (HE) studies. In this work thermal desorption spectroscope (TDS) slow strain rate test (SSRT) feritscope transmission electron microscope (TEM) and TDS model are used to establish the relationship between plastic deformation and hydrogen diffusion aiming at unambiguously elucidating the effect of pre-existing traps on hydrogen diffusion of hot-rolled S30408. An effective way is developed to deduce hydrogen apparent diffusivity in this paper. Results indicate apparent diffusivities decrease firstly and then increase with increasing plastic strain at room temperature. Hydrogen diffusion changing with plastic deformation is a complicated process involving multiple factors. It is suggested to be divided into two processes controlled by dislocations and strain-induced martensite respectively and the transformation strain is about 20% demonstrated by experiments.
New China National Standard on Safety of Hydrogen Systems- Keys for Understanding and Use
Sep 2011
Publication
Development of regulations codes and standards on hydrogen safety is a primary ingredient in overcoming barriers to widespread use of hydrogen energy. Key points of the new China National Standard Essential safety requirements for hydrogen systems metal hydrogen compatibility and risk control of flammability and explosion are discussed. Features of the new standard such as safety requirements for slush hydrogen systems and solid state hydrogen storage systems and introductions for hydrogen production by renewable energy are analyzed in this paper.
Multi-objective Optimal Configurations of a Membrane Reactor for Steam Methane Reforming
Nov 2021
Publication
The combination of traditional reactor and permeable membrane is beneficial to increase the production rate of the target product. How to design a high efficiency and energy saving membrane reactor is one of the key problems to be solved urgently. This paper utilizes finite-time thermodynamics and nonlinear programming to solve the optimal configurations of the membrane reactor of steam methane reforming (MR-SMR) for two optimization objectives that is heat exchange rate minimization and power consumption minimization. The exterior wall temperature and fixed hydrogen production rate are regarded as the control variable and constraint respectively. The results indicate that the hydrogen production rate and heat exchange rate in MR-SMR are increased by 108.58% and 58.42% respectively while the power consumption is reduced by 33.44% compared with those in the traditional reactor under the same condition. Compared with the results in reference reactor (MR-SMR obtained with initial values) the heat exchange rate is reduced by 1.40% by optimizing the exterior wall temperature and the power consumption is reduced by 5.10% by optimizing the exterior wall temperature and molar flow rate of sweep gas. The optimal distributions of exterior wall temperatures in the optimal reactors of minimum heat exchange rate and power consumption have a theoretical guiding significance for the thermal design of the membrane reactors.
IPHE Regulations Codes and Standards Working Group-type IV COPV Round Robin Testing
Oct 2015
Publication
This manuscript presents the results of a multi-lateral international activity intended to understand how to execute a cycle stress test as specified in a chosen standard (GTR SAE ISO EIHP …). The purpose of this work was to establish a harmonized test method protocol to ensure that the same results would be achieved regardless of the testing facility. It was found that accurate temperature measurement of the working fluid is necessary to ensure the test conditions remain within the tolerances specified. Continuous operation is possible with adequate cooling of the working fluid but this becomes more demanding if the cycle frequency increases. Recommendations for future test system design and operation are presented.
Experimental Study on Hydrogen/Air Premixed Flame Propagation in Closed Rectangular Channels
Sep 2019
Publication
An experimental study of hydrogen/air premixed flame propagation in a closed rectangular channel with the inhibitions (N2 or CO2) was conducted to investigate the inhibiting effect of N2 and CO2 on the flame properties during its propagation. Both Schlieren system and the pressure sensor were used to capture the evolution of flame shape and pressure changes in the channel. It was found that both N2 and CO2 have considerable inhibiting effect on hydrogen/air premixed flames. Compared with N2 CO2 has more prominent inhibition which has been interpreted from thermal and kinetic standpoints. In all the flames the classic tulip shape was observed. With different inhibitor concentration the flame demonstrated three types of deformation after the classic tulip inversion. A simple theoretical analysis has also been conducted to indicate that the pressure wave generated upon the first flame-wall contact can affect the flame deformation depending on its meeting moment with the flame front. Most importantly the meeting moment is always behind the start of tulip inversion which suggests the non-dominant role of pressure wave on this featured phenomenon.
Hydrogen Concentration Distribution in 2.25Cr-1Mo-0.25V Steel under the Electrochemical Hydrogen Charging and Its Influence on the Mechanical Properties
May 2020
Publication
The deterioration of the mechanical properties of metal induced by hydrogen absorption threatens the safety of the equipment serviced in hydrogen environments. In this study the hydrogen concentration distribution in 2.25Cr-1Mo-0.25V steel after hydrogen charging was analyzed following the hydrogen permeation and diffusion model. The diffusible hydrogen content in the 1-mm-thick specimen and its influence on the mechanical properties of the material were investigated by glycerol gas collecting test static hydrogen charging tensile test scanning electron microscopy (SEM) test and microhardness test. The results indicate that the content of diffusible hydrogen tends to be the saturation state when the hydrogen charging time reaches 48 h. The simulation results suggest that the hydrogen concentration distribution can be effectively simulated by ABAQUS and the method can be used to analyze the hydrogen concentration in the material with complex structures or containing multiple microstructures. The influence of hydrogen on the mechanical properties is that the elongation of this material is reduced and the diffusible hydrogen will cause a decrease in the fracture toughness of the material and thus hydrogen embrittlement (HE) will occur. Moreover the Young’s modulus E and microhardness are increased due to hydrogen absorption and the variation value is related to the hydrogen concentration introduced into the specimen.
Effect of the Position and the Area of the Vent on the Hydrogen Dispersion in a Naturally Ventilated Cubiod Space with One Vent on the Side Wall
Dec 2021
Publication
The design of ventilation system has implications for the safety of life and property and the development of regulations and standards in the space with the hydrogen storage equipment. The impact of both the position and the area of a single vent on the dispersion of hydrogen in a cuboid space (with dimensions L x W x H ¼ 2.90 0.74 1.22 m) is investigated with Computational Fluid Dynamics (CFD) in this study. Nine positions of the vent were compared for the leakage taking place at the floor to understand the gas dispersion. It was shown a cloud of 1% mole fraction has been formed near the ceiling of the space in less than 40 s for different positions of the vent which can activate hydrogen sensors. The models show that the hydrogen is removed more effectively when the vent is closer to the leakage position in the horizontal direction. The study demonstrates that the vent height of 1.00 m is safer for the particular scenario considered. The area of the vent has little effect on the hydrogen concentration for all vent positions when the area of the vent is less than 0.045 m2 and the height of the vent is less than 0.61 m.
Hydrogen Effects on X80 Pipeline Steel Under High-pressure Natural Gas & Hydrogen Mixtures
Oct 2015
Publication
Blending hydrogen into existing natural gas pipelines has been proposed as a means of increasing the output of renewable energy systems such as large wind farms. X80 pipeline steel is commonly used for transporting natural gas and such steel is subjected to concurrent hydrogen invasion with mechanical loading while being exposed to hydrogen containing environments directly resulting in hydrogen embrittlement (HE). In accordance with American Society for Testing and Materials (ASTM) standards the mechanical properties of X80 pipeline steel have been tested in natural gas/hydrogen mixtures with 0 5.0 10.0 20.0 and 50.0vol% hydrogen at the pressure of 12 MPa. Results indicate that X80 pipeline steel is susceptible to hydrogen-induced embrittlement in natural gas/hydrogen mixtures and the HE susceptibility increases with the hydrogen partial pressure. Additionally the HE susceptibility depends on the textured microstructure caused by hot rolling especially for the notch specimen. The design calculation by the measured fatigue data reveals that the fatigue life of the X80 steel pipeline is dramatically degraded by the added hydrogen.
Mn-based Borohydride Synthesized by Ball-milling KBH4 and MnCl2 for Hydrogen Storage
Dec 2013
Publication
In this work a mixed-cation borohydride (K2Mn(BH4)4) with P21/n structure was successfully synthesized by mechanochemical milling of the 2KBH4–MnCl2 sample under argon. The structural and thermal decomposition properties of the borohydride compounds were investigated using XRD Raman spectroscopy FTIR TGA-MS and DSC. Apart from K2Mn(BH4)4 the KMnCl3 and unreacted KBH4 compounds were present in the milled 2KBH4–MnCl2. The two mass loss regions were observed for the milled sample: one was from 100 to 160 °C with a 1.6 ± 0.1 wt% loss (a release of majority hydrogen and trace diborane) which was associated with the decomposition of K2Mn(BH4)4 to form KBH4 boron and finely dispersed manganese; the other was from 165 to 260 °C with a 1.9 ± 0.1 wt% loss (only hydrogen release) which was due to the reaction of KBH4 with KMnCl3 to give KCl boron finely dispersed manganese. Simultaneously the formed KCl could dissolve in KBH4 to yield a K(BH4)xCl1−x solid solution and also react with KMnCl3 to form a new compound K4MnCl6.
Numerical Solution for Thermodynamic Model of Charge-discharge Cycle in Compressed Hydrogen Tank
Mar 2019
Publication
The safety and convenience of hydrogen storage are significant for fuel cell vehicles. Based on mass conservation equation and energy conservation equation two thermodynamic models (single zone model and dual zone model) have been established to study the hydrogen gas temperature and tank wall temperature for compressed hydrogen storage tank. With two models analytical solution and Euler solution for single zone (gas zone) charge-discharge cycle have been compared Matlab/Simulink solution and Euler solution for dual zone (gas zone wall zone) charge-discharge cycle have been compared. Three charge-discharge cycle cases (Case 1 constant inflow temperature; Case 2 variable inflow temperature; Case 3 constant inflow temperature variable outflow temperature) and two compressed hydrogen tanks (Type III 25L Type IV 99L) charge-discharge cycle are studied by Euler method. Results show Euler method can well predict hydrogen temperature and tank wall temperature.
Formation and Dissociation Behaviour Studies of Hydrogen Hydrate in the Presence of Tetrahydrofuran by using High Pressure DSC
Mar 2019
Publication
Significant challenges still remain in the development of suitable materials for storing hydrogen for practical applications. Clathrate hydrates as a special inclusion compounds could be tailored by changing the storage pressure and temperature to adapt ambient conditions. In this work the hydrates were adopted to encage hydrogen in tetrahydrofuran (THF) aqueous solution with concentration of 3.0 mol%. The formation and dissociation behaviours were investigated by a high pressure micro-differential scanning calorimeter at the operating pressure of 18 MPa 25 MPa and 34 MPa. Experimental results show that the memory water only affects the hydrate formation behaviour instead of the hydrate dissociation behaviour. The dissociation temperature of the THF-H2 hydrate increases with the increase of the operating pressure and its dissociation equilibrium data can be obtained. The dissociation temperatures of the THF-H2 hydrate are 9.26 ℃ 10.94 ℃ and 12.67 ℃ at the operating pressure of 18 MPa 25 MPa and 34 MPa respectively. It is fundamental for performing the kinetics and microscopic experiments.
Potential Hydrogen Market: Value-Added Services Increase Economic Efficiency for Hydrogen Energy Suppliers
Apr 2022
Publication
Hydrogen energy is a clean zero-carbon long-term storage flexible and efficient secondary energy. Accelerating the development of the hydrogen energy industry is a strategic choice to cope with global climate change achieve the goal of carbon neutrality and realize high-quality economic and social development. This study aimed to analyze the economic impact of introducing valueadded services to the hydrogen energy market on hydrogen energy suppliers. Considering the network effect of value-added services this study used a two-stage game model to quantitatively analyze the revenue of hydrogen energy suppliers under different scenarios and provided the optimal decision. The results revealed that (1) the revenue of a hydrogen energy supplier increases only if the intrinsic value of value-added services exceeds a certain threshold; (2) the revenue of hydrogen energy suppliers is influenced by a combination of four key factors: the intrinsic value of value-added services network effects user scale and the sales strategies of rivals; (3) the model developed in this paper can provide optimal decisions for hydrogen energy suppliers to improve their economic efficiency and bring more economic investment to hydrogen energy market in the future.
Study of Fire Risk and Accidents Emergency Disposal Technology System of Hydrogen Fuel Vehicles
Sep 2017
Publication
As the energy crisis and environment pollution growing severely the hydrogen fuel motor vehicle has got more and more attention many automobile companies and research institutions invest significant R&D resources to research and develop the hydrogen fuel vehicles. With the development of the hydrogen fuel cell vehicles and hydrogen fuel motor vehicles the hydrogen had more to more extensive application. According to the categories of the hydrogen fuel vehicles the characteristics of hydrogen fuel vehicle fire risk and accidents are analyzed in this paper. As for hydrogen fuel cell vehicles the function of its key components such as the fuel cell the high-pressure storage tank is presented firstly. Then based on the low density fast diffusion and flammable of hydrogen the probable scenarios of accident such as fuel leak jet flame are analyzed and the fire risk of the key components and the whole vehicle is evaluated. Finally the development trend of the emergency warning system of hydrogen fuel cell vehicles is analyzed and some recommendations are proposed referring to the detection pre-warning and control technologies used in the industrial sites. Aiming at the hydrogen car structure characteristics and the fire accident modes and accidents evolution rules the emergency disposal technology system for hydrogen fuel motor vehicles is put forward.
Effect of Ternary Transition Metal Sulfide FeNi2S4 on Hydrogen Storage Performance of MgH2
Jan 2022
Publication
Hydrogen storage is a key link in hydrogen economy where solid-state hydrogen storage is considered as the most promising approach because it can meet the requirement of high density and safety. Thereinto magnesium-based materials (MgH2) are currently deemed as an attractive candidate due to the potentially high hydrogen storage density (7.6 wt%) however the stable thermodynamics and slow kinetics limit the practical application. In this study we design a ternary transition metal sulfide FeNi2S4 with a hollow balloon structure as a catalyst of MgH2 to address the above issues by constructing a MgH2/Mg2NiH4−MgS/Fe system. Notably the dehydrogenation/hydrogenation of MgH2 has been significantly improved due to the synergistic catalysis of active species of Mg2Ni/Mg2NiH4 MgS and Fe originated from the MgH2-FeNi2S4 composite. The hydrogen absorption capacity of the MgH2-FeNi2S4 composite reaches to 4.02 wt% at 373 K for 1 h a sharp contrast to the milled-MgH2 (0.67 wt%). In terms of dehydrogenation process the initial dehydrogenation temperature of the composite is 80 K lower than that of the milled-MgH2 and the dehydrogenation activation energy decreases by 95.7 kJ mol–1 compared with the milled-MgH2 (161.2 kJ mol–1). This method provides a new strategy for improving the dehydrogenation/hydrogenation performance of the MgH2 material.
Numerical Study on Fast Filling of 70 MPA Hydrogen Vehicle Cylinder
Sep 2011
Publication
There will be significant temperature rise within hydrogen vehicle cylinder during the fast filling process. The temperature rise should be controlled under the temperature limit (85 °C) of the structure material (set by ISO/TS 15869) because it may lead to the failure of the structure. In this paper a 2-dimensional axisymmetric computational fluid dynamics (CFD) model for fast filling of 70 MPa hydrogen vehicle cylinder is presented. The numerical simulations are based on the modified standard k − ɛ turbulence model. In addition both the equation of state for hydrogen gas and the thermodynamic properties are calculated by National Institute of Standards and Technology (NIST) database: REFPROP 7.0. The thermodynamic responses of fast filling with different pressure-rise patterns and filling times within type III cylinder have been analyzed in detail.
Numerical Simulation of Homogenous/Inhomogeneous Hydrogen-air Explosion in a Rectangular Channel
Sep 2019
Publication
Hydrogen is one of the promising energy sources in the future because it has the advantages of clean combustion products high efficiency and renewable energy. However hydrogen has the characteristics of low ignition energy wide flammable range (4% -75%) and fast burning flame speed which can cause explosion hazards. Typically the accidental release of hydrogen into confined or semi confined enclosures can often lead to a flammable hydrogen-air mixture with concentration gradients and possible flame acceleration and deflagration-to-detonation transition (DDT). The present study aims to test the capability of our in-house density-based solver ExplosionEngFoam for flame acceleration (FA) and deflagration-to-detonation transition (DDT) in homogenous/inhomogeneous hydrogen-air mixtures. The solver is based on the open source computational fluid dynamics (CFD) platform OpenFOAM and uses the modified Weller et al.’s combustion model taking into account LD and RT instabilities turbulence and non-unity Lewis number etc. Numerical simulations were conducted for both homogeneous and inhomogeneous mixtures in a long enclosed channel with 5.4 m in length and 0.06 m in height. The predictions demonstrate good quantitative agreement with the experimental measurements in flame tip position speed and pressure profiles by Boeck et al. The flow characteristics such as flame fine structure wave evolution etc. were also discussed.
Experimental Validation of Hydrogen Fuel−Cell and Battery−Based Hybrid Drive without DC−−DC for Light Scooter under Two Typical Driving Cycles
Dec 2021
Publication
Faced with key obstacles such as the short driving range long charging time and limited volume allowance of battery−−powered electric light scooters in Asian cities the aim of this study is to present a passive fuel cell/battery hybrid system without DC−−DC to ensure a compact volume and low cost. A novel topology structure of the passive fuel cell/battery power system for the electric light scooter is proposed and the passive power system runs only on hydrogen. The power performance and efficiency of the passive power system are evaluated by a self−developed test bench before installation into the scooters. The results of this study reveal that the characteristics of stable power output quick response and the average efficiency are as high as 88% during the Shanghainese urban driving cycle and 89.5% during the Chinese standard driving cycle. The results pre‐ sent the possibility that this passive fuel cell/battery hybrid powertrain system without DC−DC is practical for commercial scooters.
A Dual Zone Thermodynamic Model for Refueling Hydrogen Vehicles
Sep 2017
Publication
With the simple structure and quick refuelling process the compressed hydrogen storage system is currently widely used. However thermal effects during charging-discharging cycle may induce temperature change in storage tank which has significant impact on the performance of hydrogen storage and the safety of hydrogen storage tank. To address this issue we once propose a single zone lumped parameter model to obtain the analytical solution of hydrogen temperature and use the analytical solution to estimate the hydrogen temperature but the effect of the tank wall is ignored. For better description of the heat transfer characteristics of the tank wall a dual zone (hydrogen gas and tank wall) lumped parameter model will be considered for widely representation of the reference (experimental or simulated) data. Now we extend the single zone model to the dual zone model which uses two different temperatures for gas zone and wall zone. The dual zone model contains two coupled differential equations. To solve them and obtain the solution we use the method of decoupling the coupled differential equations and coupling the solutions of the decoupled differential equations. The steps of the method include: (1) Decoupling of coupled differential equations; (2) Solving decoupled differential equations; (3) Coupling of solutions of differential equations; (4) Solving coupled algebraic equations. Herein three cases are taken into consideration: constant inflow/outflow temperature variable inflow/outflow temperature and constant inflow temperature and variable outflow temperature. The corresponding approximate analytical solutions of hydrogen temperature and wall temperature can be obtained. The hydrogen pressure can be calculated from the hydrogen temperature and the hydrogen mass using the equation of state for ideal gas. Besides the two coupled differential equations can also be solved numerically and the simulated solution can also be obtained. This study will help to set up a formula based approach of refuelling protocol for gaseous hydrogen vehicles.
Numerical Simulation of Deflagration-to-detonation Transition in Hydrogen-air Mixtures with Concentration Gradients
Oct 2015
Publication
Flame acceleration in inhomogeneous combustible gas mixture has largely been overlooked despite being relevant to many accidental scenarios. The present study aims to validate our newly developed density-based solver ExplosionFoam for flame acceleration and deflagration-to-detonation transition. The solver is based on the open source computational fluid dynamics (CFD) platform OpenFOAM®. For combustion it uses the hydrogen-air single-step chemistry and the corresponding transport coefficients developed by the authors. Numerical simulations have been conducted for the experimental set up of Ettner et al. [1] which involves flame acceleration and DDT in both homogeneous hydrogen-air mixture as well as an inhomogeneous mixture with concentration gradients in an obstucted channel. The predictions demonstrate good quantitative agreement with the experimental measurements in flame tip position speed and pressure profiles. Qualitatively the numerical simulations reproduce well the flame acceleration and DDT phenomena observed in the experiment. The results have shown that in the computed cases DDT is induced by the interaction of the precursor inert shock wave with the wall close to high hydrogen concentration rather than with the obstacle. Some vortex pairs appear ahead of the flame due to the interaction between the obstacles and the gas flow caused by combustion-induced expansion but they soon disappear after the flame passes through them. Hydrogen cannot be completely consumed especially in the fuel rich region. This is of additional safety concern as the unburned hydrogen can potentially re-ignite once more fresh air is available in an accidental scenario causing subsequent explosions. The results demonstrate the potential of the newly developed density based solver for modelling flame acceleration and DDT in both homogeneous/inhomogeneous hydrogen-air mixture. Further validation needs to be carried out for other mixtures and large-scale cases.
Dependence of Hydrogen Embrittlement on Hydrogen in the Surface Layer in Type 304 Stainless Steel
Sep 2013
Publication
Hydrogen embrittlement (HE) together with the hydrogen transport behaviour in hydrogen-charged type 304 stainless steel was investigated by combined tension and outgassing experiments. The hydrogen release rate and HE of hydrogen-charged 304 specimens increase with the hydrogen pressure for hydrogen-charging (or hydrogen content) and almost no HE is observed below the hydrogen content of 8.5 mass ppm. Baking at 433 K for 48 h can eliminate HE of the hydrogen-charged 304 specimen while removing the surface layer will restore HE which indicates that hydrogen in the surface layer plays the primary role in HE. Scanning electron microscopy (SEM) and scanning tunnel microscopy (STM) observations show that particles attributed to the strain-induced α′ martensite formation break away from the matrix and the small holes form during deformation on the specimen surface. With increasing strain the connection among small holes along {111} slip planes of austenite will cause crack initiation on the surface and then the hydrogen induced crack propagates from the surface to interior.
Validated Equivalent Source Model for an Under-expanded Hydrogen Jet
Oct 2015
Publication
As hydrogen fuel cell vehicles become more widely adopted by consumers the demand for refuelling stations increases. Most vehicles require high-pressure (either 350 or 700 bar) hydrogen and therefore the refuelling infrastructure must support these pressures. Fast running reduced order physical models of releases from high-pressure sources are needed so that quantitative risk assessment can guide the safety certification of these stations. A release from a high pressure source is choked at the release point forming the complex shock structures of an under-expanded jet before achieving a characteristic Gaussian pro le for velocity density mass fraction etc. downstream. Rather than using significant computational resources to resolve the shock structure an equivalent source model can be used to quickly and accurately describe the ow in terms of velocity diameter and thermodynamic state after the shock structure. In this work we present correlations for the equivalent boundary conditions of a subsonic jet as a high-pressure jet downstream of the shock structure. Schlieren images of under-expanded jets are used to show that the geometrical structure of under-expanded jets scale with the square root of the static to ambient pressure ratio. Correlations for an equivalent source model are given and these parameters are also found to scale with square root of the pressure ratio. We present our model as well as planar laser Rayleigh scattering validation data for static pressures up to 60 bar.
Self-ignition and Flame Propagation of Pressurized Hydrogen Released Through Tubes
Sep 2019
Publication
The spontaneous ignition of hydrogen released from the high pressure tank into the downstream pipes with different lengths varied from 0.3m to 2.2m has been investigated experimentally. In this study the development of shock wave was recorded by pressure sensors and photoelectric sensors were used to confirm the presence of a flame in the pipe. In addition the development of jet flame was recorded by high-speed camera and IR camera. The results show that the minimal release pressure in different tube when self-ignition of hydrogen occurred could decrease first and then increase with the increase of the aspect of pipe. And the minimum release pressure of hydrogen self-ignition was 3.87MPa. When the flame of self-ignition hydrogen spouted out of the tube Mach disk was observed. The method of CFD was adopted. The development of shock wave at the tube exit was reproduced and structures as barrel shock the reflected shock and the Mach disk are presented. Because of these special structures the flame at the nozzle is briefly extinguished and re-ignited. At the same time the complete development process of the jet flame was recorded including the formation and separation of the spherical flame. The flame structure exhibits three typical levels before the hemispherical flame separation.
Forecasting the Hydrogen Demand in China: A System Dynamics Approach
Jan 2022
Publication
Many countries including China have implemented supporting policies to promote the commercialized application of green hydrogen and hydrogen fuel cells. In this study a system dynamics (SD) model is proposed to study the evolution of hydrogen demand in China from the petroleum refining industry the synthetic ammonia industry and the vehicle market. In the model the impact from the macro-environment hydrogen fuel supply and construction of hydrogen facilities is considered to combine in incentives for supporting policies. To further formulate the competitive relationship in the vehicle market the Lotka–Volterra (LV) approach is adopted. The model is verified using published data from 2003 to 2017. The model is also used to forecast China’s hydrogen demand up to the year of 2030 under three different scenarios. Finally some forward-looking guidance is provided to policy makers according to the forecasting results.
Estimation of Filling Time for Compressed Hydrogen Refueling
Mar 2019
Publication
In order to facilitate the application of hydrogen energy and ensure its safety the compressed hydrogen storage tank on board needs to be full of hydrogen gas within 3 minutes. Therefore to meet this requirement the effects of refueling parameters on the filling time need to be investigated urgently. For the purpose of solving this issue a novel analytical solution of filling time is obtained from a lumped parameter model in this paper. According to the equation of state for real gas and dimensionless numbers Nu and Re the function relationships between the filling time and the refueling parameters are presented. These parameters include initial temperature initial pressure inflow temperature final temperature and final pressure. These equations are used to fit the reference data the results of fitting show good agreement. Then the values of fitting parameters are further utilized so as to verify the validity of these formulas. We believe this study can contribute to control the hydrogen filling time and ensure the safety during fast filling process.
Comparisons of Hazard Distances and Accident Durations Between Hydrogen Vehicles and CNG Vehicles
Sep 2017
Publication
For the emerging hydrogen-powered vehicles the safety concern is one of the most important barriers for their further development and commercialization. The safety of commercial natural gas vehicles has been well accepted and the total number of natural gas vehicles operating worldwide was approximately 23 million by November 2016. Hydrogen vehicles would be more acceptable for the general public if their safety is comparable to that of commercialized CNG vehicles. A comparison study is conducted to reveal the differences of hazard distances and accident durations between hydrogen vehicles and CNG vehicles during a representative accident in an open environment. The tank blowdown time for hydrogen and CNG are calculated separately to compare the accident durations. CFD simulations for real world situations are performed to study the hazard distances from impinging jet fires under vehicle. Results show that the release duration for CNG vehicle is over two times longer than that for hydrogen vehicle indicating that CNG vehicle jet fire accident is more timeconsuming and firefighters have to wait a longer time before they can safely approach the vehicle. For both hydrogen vehicle and CNG vehicle the longest hazard distance near the ground occur about 1 to 4 seconds after the initiation of the thermally-activated pressure relief devices. Afterwards the flames will shrink and the hazard distances will decrease. For firefighters with bunker gear they must stand 6 m and 14 m away from the hydrogen vehicle and CNG vehicle respectively. For general public a perimeter of 12 m and 29 m should be set around the accident scene for hydrogen vehicle and CNG vehicle respectively.
Comparison of Numerical and Algebraic Models of Low and High Pressure Hydrogen Jet Flows with Ideal and Real Gas Models
Sep 2013
Publication
Hydrogen transportation systems require very high pressure hydrogen storage containers to enable sufficient vehicle range for practical use. Current proposed designs have pressures up to 70 MPa with leakage due to damage or deterioration at such high pressures a great safety concern. Accurate models are needed to predict the flammability envelopes around such leaks which rapidly vary with time. This paper compares CFD predictions of jet flows for low pressure jets with predictions using the integral turbulent buoyant jet model. The results show that the CFD model predicts less entrainment and that the turbulent Schmidt number should be smaller with 0.55 giving better results. Then CFD predictions for very high pressure flows are compared with analytical models for choked flows that generate underexpanded jets into the ambient to evaluate the effects of the model assumptions and the effects of real exit geometries. Real gas effects are shown to accelerate the blowdown process and that real flow effects in the CFD model slow the flow rate and increase the exit temperature.
Aldehyde Replacement Advances Efficient Hydrogen Production in Electrolyser
Mar 2022
Publication
The high energy consumption and production of undesired oxygen greatly restrict the wide adoption of water electrolysis for hydrogen production. In a paper recently published in Nature Catalysis Wang and coworkers rationally introduce aldehydes for oxidation at anode to replace oxygen evolution reaction which can produce hydrogen and value-added products at low potential realizing efficient bipolar hydrogen production with high-purity. Moreover these aldehydes are biomass-derived and contribute to sustainable hydrogen production
Energy Management Strategy of Hydrogen Fuel Cell/Battery/Ultracapacitor Hybrid Tractor Based on Efficiency Optimization
Dec 2022
Publication
With the application of new energy technology hybrid agricultural machinery has been developed. This article designs a hybrid tractor energy management method to solve the problem of high energy consumption caused by significant load fluctuation of the tractor in field operation. This article first analyzes the characteristics of the hydrogen fuel cell power battery and ultracapacitor and designs a hybrid energy system for the tractor. Second the energy management strategy (EMS) of multi-layer decoupling control based on the Haar wavelet and logic rule is designed to realize the multi-layer decoupling of high-frequency low-frequency and steady-state signals of load demand power. Then the EMS redistributes the decoupled power signals to each energy source. Finally a hardware-in-loop simulation experiment was carried out through the model. The results show that compared with single-layer control strategies such as fuzzy control and power-following control the multi-layer control strategy can allocate the demand power more reasonably and the efficiency of the hydrogen fuel cell is the highest. The average efficiency of the hydrogen fuel cell was increased by 2.87% and 1.2% respectively. Furthermore the equivalent hydrogen consumption of the tractor was reduced by 17.06% and 5.41% respectively within the experimental cycle. It is shown that the multi-layer control strategy considering power fluctuation can improve the vehicle economy based on meeting the power demanded by the whole vehicle load.
Inhibition of Confined Hydrogen Explosion by Inert Gases
Sep 2019
Publication
"This paper is aimed at revealing the inhibiting effects of He Ar N2 and CO2 on confined hydrogen explosion. The flame characteristics under thermo diffusive instability and hydrodynamic instability are analyzed using Lewis number and ratio of density ratio to flame thickness. The inhibiting effects of inert gas on confined hydrogen explosion are evaluated using maximum explosion pressure and maximum pressure rise rate. The inhibiting mechanism is obtained by revealing thermal diffusivity maximum mole fraction and net reaction rate of active radicals. The results demonstrated that the strongest destabilization effect of hydrodynamic instability and thermodiffusive instability occurs when the inert gas is Ar and CO2 respectively. Taking maximum explosion pressure and maximum rate of pressure rise as an indicator the effects of confined hydrogen explosion inhibition from strong to weak are CO2 N2 Ar and He. Laminar burning velocity thermal diffusivity maximum mole fraction and net reaction rate of active radicals continues to decrease in the order of He Ar N2 and CO2. The elementary reactions of generating and consuming active radicals at the highest net reaction rate are mainly consisted of R1 (H+O2=OH+O) R2 (H2+O=OH+H) R3 (H2+OH=H2O+H) and R10 (HO2+H=2OH).
Recent Advances on the Thermal Destabilization of Mg-based Hydrogen Storage Materials
Jan 2021
Publication
Magnesium hydride and its compounds have a high hydrogen storage capacity and are inexpensive and thus have been considered as one of the most promising hydrogen storage materials for on-board applications. Nevertheless Mg/MgH2 systems suffer from great drawbacks in terms of kinetics and thermodynamics for hydrogen uptake/release. Over the past decades although significant progress has been achieved with respect to hydrogen sorption kinetics in Mg/MgH2 systems their high thermal stability remains the main drawback which hinders their practical applications. Accordingly herein we present a brief summary of the synthetic routes and a comprehensive overview of the advantages and disadvantages of the promising strategies to effectively tune the thermodynamics of Mg-based materials such as alloying nanostructuring metastable phase formation changing reaction pathway and nano Mg-based composites. Among them nanostructuring and metastable phase formation which have the superiority of changing the thermodynamics without affecting the hydrogen capacity have attracted increasing interest in this field. To further optimize the hydrogen storage performance we specially emphasize novel nanostructured materials which have the advantage of combining alloy engineering nanostructuring and the synergistic effect to change the thermodynamics of Mg/MgH2 to some extent. Furthermore the remaining challenges and the directions of further research on MgH2 including the fundamental mechanism of the Mg–H bond instability advanced synthetic routes stabilizing nanostructures and predicting novel composite materials are proposed.
The Dependence of Fatigue Crack Growth on Hydrogen in Warm-rolled 316 Austenitic Stainless Steel
Sep 2019
Publication
The fatigue crack growth rate of warm-rolled AISI 316 austenitic stainless steel was investigated by controlling rolling strain and temperature in argon and hydrogen gas atmospheres. The fatigue crack growth rates of warm-rolled 316 specimens tested in hydrogen decreased with increasing rolling temperature especially 400 °C. By controlling the deformation temperature and strain the influences of microstructure (including dislocation structure deformation twins and α′ martensite) and its evolution on hydrogen-induced degradation of mechanical properties were separately discussed. Deformation twins deceased and dislocations became more uniform with the increase in rolling temperature inhibiting the formation of dynamic α′ martensite during the crack propagation. In the cold-rolled 316 specimens deformation twins accelerated hydrogen-induced crack growth due to the α′ martensitic transformation at the crack tip. In the warm-rolled specimens the formation of α′ martensite around the crack tip was completely inhibited which greatly reduced the fatigue crack growth rate in hydrogen atmosphere.
Hydrolysis-Based Hydrogen Generation Investigation of Aluminium System Adding Low-Melting Metals
Mar 2021
Publication
In this age of human civilization there is a need for more efficient cleaner and renewable energy as opposed to that provided by nonrenewable sources such as coal and oil. In this sense hydrogen energy has been proven to be a better choice. In this paper a portable graphite crucible metal smelting furnace was used to prepare ten multi-element aluminum alloy ingots with different components. The microstructure and phase composition of the ingots and reaction products were analyzed by X-ray diffraction (XRD) scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The reaction was carried out in a constant temperature water bath furnace at 60°C and the hydrogen production performance of the multi-element aluminum alloys in different proportions was compared by the drainage gas collection method. The experimental results show that the as-cast microstructure of Al–Ga–In–Sn aluminum alloy is composed of a solid solution of Al and part of Ga and a second phase of In3Sn. After the hydrolysis reaction the products were dried at 150°C and then analyzed by XRD. The products were mainly composed of AlOOH and In3Sn. Alloys with different compositions react at the same hydrolysis temperature and the hydrogen production performance is related to the ratio of low-melting-point metal elements. By comparing two different ratios of Ga–In–Sn (GIS) the hydrogen production capacity and production rate when the ratio is 6:3:1 are generally higher than those when the ratio is 7:2:1. The second phase content affects the hydrogen production performance.
Hydrogen Trapping Behavior in Vanadium Microalloyed TRIP-Assisted Annealed Martensitic Steel
Jun 2019
Publication
Transformation induced plasticity (TRIP)-assisted annealed martensitic (TAM) steel combines higher tensile strength and elogangtion and has been increasingly used but appears to bemore prone to hydrogen embrittlement (HE). In this paper the hydrogen trapping behavior and HE of TRIP-assisted annealed martensitic steels with different vanadium additions had been investigated by means of hydrogen charging and slow strain rate tensile tests (SSRT) microstructral observartion and thermal desorption mass spectroscope (TDS). Hydrogen charging test results indicates that apparent hydrogen diffusive index Da is 1.94 × 10−7/cm2·s−1 for 0.21 wt.% vanadium steel while the value is 8.05 × 10−7/cm2·s−1 for V-free steel. SSRT results show that the hydrogen induced ductility loss ID is 76.2% for 0.21 wt.%V steel compared with 86.5% for V-free steel. The trapping mechanism of the steel containing different V contents is analyzed by means of TDS and Transmission electron microscope (TEM) observations. It is found out that the steel containing 0.21 wt.%V can create much more traps for hydrogen trapping compared with lower V steel which is due to vanadium carbide (VC) precipitates acting as traps capturing hydrogen atoms.The relationship between hydrogen diffusion and hydrogentrapping mechanism is discussed in details.
Investigating the Hydrogen Storage Capacity of Surfactant Modified Graphene
Mar 2019
Publication
As the depletion of traditional fossil fuels and environmental pollution become a serious problem of human society researchers are actively finding renewable green energy sources. Considered as a clean efficient and renewable alternative Hydrogen energy is considered the most promising energy source. However the safe and efficient storage of hydrogen has become the major problem that hinders its application. To solve this gap this paper proposes to utilize surfactant modified graphene for hydrogen storage. With Hummers method and ultrasonic stripping method this study prepared graphene from graphene oxide with NaBH4. Surfactant sodium dodecylbenzene sulfonate (SDBS) was used as a dispersant during the reduction process to produce the dispersion-stabilized graphene suspensions. The characteristics of the graphene suspensions then were examined by XRD SEM TEM FT-IR Raman XPS TG and N2 adsorption-desorption tests. The hydrogen adsorption properties of the samples were investigated with Langmuir and Freundlich fitting. The results show that the adsorption behavior is consistent with the Freundlich adsorption model and the process is a physical adsorption.
Two-Stage Energy Management Strategies of Sustainable Wind-PV-Hydrogen-Storage Microgrid Based on Receding Horizon Optimization
Apr 2022
Publication
Hydrogen and renewable electricity-based microgrid is considered to be a promising way to reduce carbon emissions promote the consumption of renewable energies and improve the sustainability of the energy system. In view of the fact that the existing day-ahead optimal operation model ignores the uncertainties and fluctuations of renewable energies and loads a two-stage energy management model is proposed for the sustainable wind-PV-hydrogen-storage microgrid based on receding horizon optimization to eliminate the adverse effects of their uncertainties and fluctuations. In the first stage the day-ahead optimization is performed based on the predicted outpower of WT and PV the predicted demands of power and hydrogen loads. In the second stage the intra-day optimization is performed based on the actual data to trace the day-ahead operation schemes. Since the intra-day optimization can update the operation scheme based on the latest data of renewable energies and loads the proposed two-stage management model is effective in eliminating the uncertain factors and maintaining the stability of the whole system. Simulations show that the proposed two-stage energy management model is robust and effective in coordinating the operation of the wind-PV-hydrogen-storage microgrid and eliminating the uncertainties and fluctuations of WT PV and loads. In addition the battery storage can reduce the operation cost alleviate the fluctuations of the exchanged power with the power grid and improve the performance of the energy management model.
Combustion Features of CH4/NH3/H2 Ternary Blends
Mar 2022
Publication
The use of so-called “green” hydrogen for decarbonisation of the energy and propulsion sectors has attracted considerable attention over the last couple of decades. Although advancements are achieved hydrogen still presents some constraints when used directly in power systems such as gas turbines. Therefore another vector such as ammonia can serve as a chemical to transport and distribute green hydrogen whilst its use in gas turbines can limit combustion reactivity compared to hydrogen for better operability. However pure ammonia on its own shows slow complex reaction kinetics which requires its doping by more reactive molecules thus ensuring greater flame stability. It is expected that in forthcoming years ammonia will replace natural gas (with ~ 90% methane in volume) in power and heat production units thus making the co-firing of ammonia/methane a clear path towards replacement of CH4 as fossil fuel. Hydrogen can be obtained from the precracking of ammonia thus denoting a clear path towards decarbonisation by the use of ammonia/hydrogen blends. Therefore ammonia/methane/hydrogen might be co-fired at some stage in current combustion units hence requiring a more intrinsic analysis of the stability emissions and flame features that these ternary blends produce. In return this will ensure that transition from natural gas to renewable energy generated e-fuels such as so-called “green” hydrogen and ammonia is accomplished with minor detrimentals towards equipment and processes. For this reason this work presents the analysis of combustion properties of ammonia/methane/hydrogen blends at different concentrations. A generic tangential swirl burner was employed at constant power and various equivalence ratios. Emissions OH*/NH*/NH2*/CH* chemiluminescence operability maps and spectral signatures were obtained and are discussed. The extinction behaviour has also been investigated for strained laminar premixed flames. Overall the change from fossils to e-fuels is led by the shift in reactivity of radicals such as OH CH CN and NH2 with an increase of emissions under low and high ammonia content. Simultaneously hydrogen addition improves operability when injected up to 30% (vol) an amount at which the hydrogen starts governing the reactivity of the blends. Extinction strain rates confirm phenomena found in the experiments with high ammonia blends showing large discrepancies between values at different hydrogen contents. Finally a 20/55/25% (vol) methane/ammonia/hydrogen blend seems to be the most promising at high equivalence ratios (1.2) with no apparent flashback low emissions and moderate formation of NH2/OH radicals for good operability.
Study on Critical Technologies and Development Routes of Coal-based Hydrogen Energy
Jul 2019
Publication
Hydrogen is considered a secondary source of energy commonly referred to as an energy carrier. It has the highest energy content when compared to other common fuels by weight having great potential for further development. Hydrogen can be produced from various domestic resources but based on the fossil resource conditions in China coal-based hydrogen energy is considered to be the most valuable because it is not only an effective way to develop clean energy but also a proactive exploration of the clean usage of traditional coal resources. In this article the sorption-enhanced water–gas shift technology in the coal-to-hydrogen section and the hydrogen-storage and transport technology with liquid aromatics are introduced and basic mechanisms technical advantages latest progress and future R&D focuses of hydrogen-production and storage processes are listed and discussed. As a conclusion after considering the development frame and the business characteristics of CHN Energy Group a conceptual architecture for developing coal-based hydrogen energy and the corresponding supply chain is proposed.
Paths to Low-cost Hydrogen Energy at a Scale for Transportation Applications in the USA and China via Liquid-hydrogen Distribution Networks
Dec 2019
Publication
The cost of delivered H2 using the liquid-distribution pathway will approach $4.3–8.0/kg in the USA and 26–52 RMB/kg in China by around 2030 assuming large-scale adoption. Historically hydrogen as an industrial gas and a chemical feedstock has enjoyed a long and successful history. However it has been slow to take off as an energy carrier for transportation despite its benefits in energy diversity security and environmental stewardship. A key reason for this lack of progress is that the cost is currently too high to displace petroleum-based fuels. This paper reviews the prospects for hydrogen as an energy carrier for transportation clarifies the current drivers for cost in the USA and China and shows the potential for a liquid-hydrogen supply chain to reduce the costs of delivered H2. Technical and economic trade-offs between individual steps in the supply chain (viz. production transportation refuelling) are examined and used to show that liquid-H2 (LH2) distribution approaches offer a path to reducing the delivery cost of H2 to the point at which it could be competitive with gasoline and diesel fuel.
Optimal Scheduling of Electricity-Hydrogen Coupling Virtual Power Plant Considering Hydrogen Load Response
Mar 2024
Publication
With the rapid development of hydrogen production by water electrolysis the coupling between the electricity-hydrogen system has become closer providing an effective way to consume surplus new energy generation. As a form of centralized management of distributed energy resources virtual power plants can aggregate the integrated energy production and consumption segments in a certain region and participate in electricity market transactions as a single entity to enhance overall revenue. Based on this this paper proposes an optimal scheduling model of an electricity-hydrogen coupling virtual power plant (EHC-VPP) considering hydrogen load response relying on hydrogen to ammonia as a flexibly adjustable load-side resource in the EHC-VPP to enable the VPP to participate in the day-ahead energy market to maximize benefits. In addition this paper also considers the impact of the carbon emission penalty to practice the green development concept of energy saving and emission reduction. To validate the economy of the proposed optimization scheduling method in this paper the optimization scheduling results under three different operation scenarios are compared and analyzed. The results show that considering the hydrogen load response and fully exploiting the flexibility resources of the EHC-VPP can further reduce the system operating cost and improve the overall operating efficiency.
Optimized Operation Plan for Hydrogen Refueling Station with On-Site Electrolytic Production
Dec 2022
Publication
The cost reduction of hydrogen refueling stations (HRSs) is very important for the popularization of hydrogen vehicles. This paper proposes an optimized operation algorithm based on hydrogen energy demand estimation for on-site hydrogen refueling stations. Firstly the user’s hydrogen demand was estimated based on the simulation of their hydrogenation behavior. Secondly mixed integer linear programming method was used to optimize the operation of the hydrogen refueling station to minimize the unit hydrogen energy cost by using the peak–valley difference of the electricity price. We then used three typical scenario cases to evaluate the optimized operation method. The results show that the optimized operation method proposed in this paper can effectively reduce the rated configuration of electrolyzer and storage tank for HRS and can significantly reduce the unit hydrogen energy cost considering the construction cost compared with the traditional method. Therefore the optimization operation method of a local hydrogen production and hydrogen refueling station proposed in this paper can reduce the cost of a hydrogen refueling station and accelerate the popularization of hydrogen energy vehicles. Finally the scope of application of the proposed optimization method and the influence of the variation of the electricity price curve and the unit cost of the electrolyzer are discussed.
Technical and Economic Analysis of One-Stop Charging Stations for Battery and Fuel Cell EV with Renewable Energy Sources
Jun 2020
Publication
Currently most of the vehicles make use of fossil fuels for operations resulting in one of the largest sources of carbon dioxide emissions. The need to cut our dependency on these fossil fuels has led to an increased use of renewable energy sources (RESs) for mobility purposes. A technical and economic analysis of a one-stop charging station for battery electric vehicles (BEV) and fuel cell electric vehicles (FCEV) is investigated in this paper. The hybrid optimization model for electric renewables (HOMER) software and the heavy-duty refueling station analysis model (HDRSAM) are used to conduct the case study for a one-stop charging station at Technical University of Denmark (DTU)-Risø campus. Using HOMER a total of 42 charging station scenarios are analyzed by considering two systems (a grid-connected system and an off-grid connected system). For each system three different charging station designs (design A-hydrogen load; design B-an electrical load and design C-an integrated system consisting of both hydrogen and electrical load) are set up for analysis. Furthermore seven potential wind turbines with different capacity are selected from HOMER database for each system. Using HDRSAM a total 18 scenarios are analyzed with variation in hydrogen delivery option production volume hydrogen dispensing option and hydrogen dispensing option. The optimal solution from HOMER for a lifespan of twenty-five years is integrated into design C with the grid-connected system whose cost was $986065. For HDRSAM the optimal solution design consists of tube trailer as hydrogen delivery with cascade dispensing option at 350 bar together with high production volume and the cost of the system was $452148. The results from the two simulation tools are integrated and the overall cost of the one-stop charging station is achieved which was $2833465. The analysis demonstrated that the one-stop charging station with a grid connection is able to fulfil the charging demand cost-effectively and environmentally friendly for an integrated energy system with RESs in the investigated locations.
The Effect of Vacancy Concentration on Hydrogen Diffusion in Alpha-Fe by Molecular Dynamic
Sep 2017
Publication
Diffusion coefficient is in significant dependence on vacancy concentration due to that migration of vacancy is the dominant mechanism of atom transport or diffusion in processes such as void formation dislocation movement and solid phase transformation. This study aims to investigate the effect of vacancy concentration on hydrogen diffusion in alpha-Fe by molecular dynamics simulations especially at low temperatures and with loading. Comparisons of the diffusion coefficients between alpha-Fe with a perfect structure and different-concentration vacancies as well as comparisons between experimental and theoretical results had been made to characterize and summarize the effect of vacancy on hydrogen diffusion coefficient.
Multistage Risk Analysis and Safety Study of a Hydrogen Energy Station
Sep 2017
Publication
China has plenty of renewable energy like wind power and solar energy especially in the northwest part of the country. Due to the volatile and intermittent characters of the green powers high penetration level of renewable resources could arise grid stabilization problem. Therefore electricity storage is considered as a solution and hydrogen energy storage is proposed. Instead of storing the electricity directly it converts electricity into hydrogen and the energy in hydrogen will be released as needed from gas to electricity and heat. The transformed green power can be fed to the power grid and heat supply network. State Grid Corporation of China carried out its first hydrogen demonstration project. In the demonstration project an alkaline electrolyzer and a PEM hydrogen fuel cell stack are decided as the hydrogen producer and consumer respectively. Hydrogen safety issue is always of significant importance to secure the property. In order to develop a dedicated safety analysis method for hydrogen energy storage system in power industry the risk analysis for the power-to-gas-topower&heat facility was made. The hazard and operability (HAZOP) study and the failure mode and effects analysis (FMEA) are performed sequentially to the installation to identify the most problematic parts of the system in view of hydrogen safety and possible failure modes and consequences. At the third step the typical hydrogen leak accident scenarios are simulated by using computational fluid dynamics (CFD) computer code. The resulted pressure loads of the possibly ignited hydrogen-air mixture in the facility container are estimated conservatively. Important safeguards and mitigation measures are proposed based on the three-stage risk and safety studies.
Numerical Simulation of Hydrogen Release From High-Pressure Storage Vessel
Sep 2009
Publication
In this paper the deflagration region and characteristics of the hydrogen flow which was generated by high-pressure hydrogen discharge from storage vessels were studied. A 3-D analytic model is established based on the species transfer model and the SST k −ω turbulence model. The established model is applied to the research of the flow characteristics of the hydrogen under-expanded jet under different filling pressures of 30 MPa 35 MPa and 40 MPa respectively. The evolution process of hydrogen combustible cloud is analyzed under the filling pressure of 30 MPa. It is revealed that a supersonic jet is formed after the high-pressure hydrogen discharge outlet In the vicinity of the Mach disk the hydrogen jet velocity and temperature reach the maximum values and the variation of filling pressure has little effect on the peak values of the hydrogen jet flow velocity and temperature during the considered pressure range. In the rear of the Mach disk the variation rates of the hydrogen flow velocity and temperature are in inversely proportional to the hydrogen filling pressure. At the preliminary stage the discharged hydrogen is apple-shaped which expands along the radial and then the axial growth rate of the hydrogen cloud increases with the passage of time.
The Effect of Polyurethane Sponge Blockage Ratio on Premixed Hydrogen-air Flame Propagation in a Horizontal Tube
Oct 2015
Publication
The effects of sponge blockage ratio on flame structure evolution and flame acceleration were experimentally investigated in an obstructed cross-section tube filled with stoichiometric hydrogen-air mixture. Experimental results show that the mechanisms responsible for flame acceleration can be in terms of the positive feedback of the unburned gas field generated ahead of the flame the area change of the gap between the sponge and the tube and the interaction between the flame and the shear layer appearing at the sponge left top corner. Especially the last one dominates the flame acceleration and causes its speed to be sonic. Then both the second and third contribute to the violent flame acceleration. In addition the unburned gas pockets can be found in both upstream and downstream regions of the sponge. With increasing blockage ratio the unburned gas pockets disappear easier and the flame acceleration is more pronounced. Moreover the sponge tilts more evidently and resultantly the maximum tilt angle increases.
Study on the Harm Effect of Liquid Hydrogen Release by Consequence Modeling
Sep 2011
Publication
In this paper the accidental release of hydrogen from cryogenic liquid storage tank and the subsequent consequences are studied including hydrogen cold cloud fire ball jet fire flash fire and vapor cloud explosion. The cold effect thermal effects and explosion overpressures from the above consequences are evaluated using IGC and TNO harm criteria. Results show that for instantaneous releases of liquid hydrogen the sequence of harm effect distances is that vapor cloud explosion>flash fire>cold cloud> fireball. For continuous releases of liquid hydrogen the sequence of harm effect distances is that vapor cloud explosion>jet fire>flash fire>cold cloud. The vapor cloud explosion is the leading consequence of both instantaneous and continuous releases and may be used for the determination of safety distances of a liquid hydrogen tank. Besides the harm effect distances of liquid hydrogen tank are compared with those of compressed hydrogen storages with equivalent mass. Results show that the liquid hydrogen storage may be safer than 70MPa gaseous storage in case of leak scenario but may be more dangerous than 70MPa storage in case of catastrophic rupture. It is difficult to tell which storage is safer from a consequence perspective. Further investigation need to be made from a standpoint of risk which combined both consequences and the likelihood of scenarios.
In Situ Irradiated X-Ray Photoelectron Spectroscopy on Ag-WS2 Heterostructure For Hydrogen Production Enhancement
Oct 2020
Publication
The hot electron transition of noble materials to catalysis accelerated by localized surface plasmon resonances (LSPRs) was detected by in situ irradiated X-ray photoelectron spectroscopy (ISI-XPS) in this article. This paper synthesized an Ag Nanowire (AgNW) @ WS2 core-shell structure with an ultra-thin shell of WS2(3 ∼ 7 nm) and characterized its photocatalytic properties. The AgNW@WS2 core-shell structure exhibited different surface-enhanced Raman spectroscopy (SERS) effects by changing shell thickness indicating that the effect of AgNW could be controlled by WS2 shell. Furthermore the hydrogen production of AgNW@WS2 could reach to 356% of that of pure WS2. The hot electrons arising from the LSPRs effect broke through the Schottky barrier between WS2 and AgNW and transferred to the WS2 shell whose photocatalytic effect was thus enhanced. In addition when the LSPRs effect was intensified by reducing the shell thickness the hot electron transition of noble materials to catalysis was accelerated.
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