Risk assessment for liquid hydrogen fueling stations

In recent years, consumers calling for the protection of the environment on a regional and global scale are demanding the use of vehicles that do not emit harmful exhaust. It is anticipated that one response to this demand is the widespread use of fuel cell vehicles (FCVs). In order to achieve this, it is necessary to provide hydrogen fueling stations where FCVs can refuel.     

Consequence analysis and safety verification of hydrogen fueling stations using CFD simulation

Now that environmental awareness is enhanced on a global basis, great hopes are placed on the expanded use of hydrogen stations and fuel-cell vehicles (FCVs) that economize hydrogen energy. Hydrogen stations must be safe and secure because they store large quantities of hydrogen under higher pressure than the hydrogen actually consumed by FCVs. Thus, multiple safety measures are taken to ensure that hydrogen does not leak from the stations. Furthermore, in the unlikely event of leakage, the damage needs to be kept on an allowable level. For this reason, it is necessary to understand the behavior of hydrogen gas leaking from the stations.     

Identification of public acceptance factors with risk perception scales on hydrogen fueling stations in Japan

This is the first work to describe the characteristics of public acceptance of hydrogen stations (H2 station) in Japan using risk perception scales. We conducted an online survey asking respondents to rate their acceptance of having an H2 station constructed in the gas station nearest their home. Sixty-six percent of respondents indicated a high rate of acceptance, with males tending to be more accepting than females, irrespective of age. We found the following to be explanatory factors for acceptance: gender, degree, vehicle use, knowledge about hydrogen, risk perception of H2 station, and inherent risk acceptance and avoidance. Binominal regression analysis was used to construct an acceptance model, and the risk perception factor “Dread” was dominant among the effective independent variables. This suggests that alleviating inherent dread or fear by providing precise risk information will lead to better acceptance. Our study contributes to improved risk communication on H2 station construction.     

Numerical study on fast filling of 70 MPa type III cylinder for hydrogen vehicle

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 − ? 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.     

Evaluation of Tafel-Volmer kinetic parameters for the hydrogen oxidation reaction on Pt(1 1 0) electrodes

Modelling of PEM fuel cells has long been an active research area to improve understanding of cell and stack operation, facilitate design improvements and support simulation studies. The prediction of activation polarization in most PEM models has concentrated on the cathode losses since anode losses are commonly much smaller and tend to be ignored. Further development of the anode activation polarization term is being undertaken to broaden the application and usefulness of PEM models in general.Published work on the kinetics of the hydrogen oxidation reaction (HOR) using Pt(h k l) electrodes in dilute H₂SO₄ has been recently reassessed and published. Correlations for diffusion-free exchange current densities were developed and empirical predictive equations for the anode activation polarization were proposed for the experimental conditions of the previously published work: Pt(1 0 0), Pt(1 1 0) and Pt(1 1 1) electrodes, pH₂ of 1 atm, and temperatures of 1, 30 and 60 °C. It was concluded that the HOR on Pt(1 1 0) electrodes followed a Tafel-Volmer reaction sequence.The aim of the present paper is to generalize these Tafel-Volmer correlations, apply them to published data for Pt(1 1 0) electrodes and further develop the modelling of anode activation polarization over the range of operating conditions found in PEMFC operation.     

Screening of electrocatalysts for direct ammonia fuel cell: Ammonia oxidation on PtMe (Me: Ir,Rh, Pd,Ru) and preferentially oriented Pt(1 0 0) nanoparticles

Ammonia has attracted attention as a possible fuel for direct fuel cells since it is easy to handle and to transport as liquid or as concentrated aqueous solution. However, on noble metal electrodes ammonia oxidation is a sluggish reaction and the electrocatalyst needs to be improved for developing efficient ammonia fuel cells. In this work, ammonia electrooxidation reaction on 3–4-nm bimetallic PtMe (Ir, Rh, Pd, Ru) and on preferentially oriented Pt(1 0 0) nanoparticles is reported. PtMe nanoparticles have been prepared by using water-in-oil microemulsions to obtain a narrow size distribution whereas preferentially oriented Pt nanoparticles have been prepared through colloidal routes. Among all the bimetallic samples tested, only Pt₇₅Ir₂₅ and Pt₇₅Rh₂₅ nanoparticles show, at the low potential range, an enhancement of the oxidation density current with respect to the behaviour found for pure platinum nanoparticles prepared by the same method. In addition, two Pt(1 0 0) preferentially oriented nanoparticles of different particle size (4 and 9 nm) have been also studied. These oriented nanoparticles show higher current densities than polycrystalline Pt nanoparticles due to the sensitivity of ammonia oxidation toward the presence of surface sites with square symmetry. The reactivity of the different 4-nm nanoparticles parallels well with that expected from bulk PtMe alloys and Pt single crystal electrodes.     

High pressure cryo-storage of hydrogen by adsorption at 77 K and up to 50 MPa

In this paper, we focused on hydrogen adsorption on large surface area solids, combining optimal extreme conditions i.e. very high pressure and low temperature for gas storage process purpose. Therefore, a new volumetric device is elaborated to obtain excess adsorption isotherms at 77 K up to 500 bar. Two activated carbons with different micro-porosities are analysed in the view of hydrogen storage investigation. Also, the results are compared to zeolite adsorption properties. Based on these results, the total mass and volumetric storage capacity are calculated using the bulk density relationship. Thereby, we obtained high storage in situ capacities equal to 5.2 wt% and 54.5 kgH₂/m³. Further, we also considered practical application aspects related to hydrogen storage process in highly porous packed materials.     

Electrochemical behavior of Li3−xM′xV2−yM″y(PO4)3 (M′ = K, M″ = Sc, Mg + Ti)/C composite cathode material for lithium-ion batteries

Composites of monoclinic Li_3−xM′_xV_2−yM″_2y(PO₄)₃ (M′ = K, M″ = Sc, Mg + Ti) with carbon were synthesized by solid-state reaction using oxalic acid or 6% H₂/Ar gas mixture as reducing agents at sintering temperature of 850 °C. The samples were characterized by X-ray diffraction (XRD), voltammetry and electrochemical galvanostatic cycling. The capacity of Li₃V₂(PO₄)₃ synthesized using hydrogen as the reducing agent was 127 mA h g⁻¹ and decreased to 120 mA h g⁻¹ after 20 charge-discharge cycles. The substitution of lithium and vanadium for other ions did not result in the improvement of the electrochemical characteristics of the samples.     

UV-A (315-400 nm) irradiance from measurements at 380 nm for solar water treatment and disinfection: Comparison between model and measurements in Buenos Aires, Argentina and Almería, Spain

A linear correlation between UV-A and 380 nm was developed by means of the TUV 4.1 radiative transfer model. The prediction error of the correlation was evaluated with data from Buenos Aires, Argentina, 2001, and from 2006, Almería, Spain. Percent random mean square error (RMSE%) was calculated for intervals of 10° of solar zenith angles, ranging 4.75% at 20° to 37.70% at 90° in clear days and 22.16% at 20° to 26.17% at 90° for cloudy days in Buenos Aires Argentina, and 1.27% at 20° to 11.27% at 90° for clear days in Almeria, Spain. Clouded days were not assessed with the data from Spain. In Argentina, the UV-A radiometer is located in a rural area and the 380 nm radiometer is located in an urban area 6 km away. Hence the real error of the proposed model is closer to that found in Spain were both measurements were performed at the same site. The objective of the work is to achieve a simple and precise method to assess UV-A availability for environmental applications of solar energy, particularly for solar water treatment, at any desired latitude.     

CFD analysis of fast filling scenarios for 70 MPa hydrogen type IV tanks

High injection pressure is combined with high refueling rate for vehicles storing pressurized gaseous hydrogen onboard. As a drawback, high temperatures are developed inside the tank, which can jeopardize the structural integrity of the storage system. Computational Fluid Dynamics (CFD) codes already proved to be a valuable tool for predicting the temperature distribution within the tank during fast refueling. Results of hydrogen fast filling CFD simulations for a type IV tank, filled to 70 MPa at different working conditions are presented as follow up of the CFD model validation performed against experimental data. Alternative rates of pressure rise, adiabatic and cold filling are investigated to evaluate the effect on maximum hydrogen temperatures inside the tank. Results confirmed that the developed CFD model could be a suitable tool for investigating fast filling scenarios when experimental data are not yet available or of difficult realization.     

Hydrogen refuelling stations in the Netherlands: An intercomparison of quantitative risk assessments used for permitting

As of 2003, 15 hydrogen refuelling stations (HRSs) have been deployed in the Netherlands. To become established, the HRS has to go through a permitting procedure. An important document of the permitting dossier is the quantitative risk assessment (QRA) as it assesses the risks of the HRS associated to people and buildings in the vicinity of the HRS. In the Netherlands, a generic prescribed approach exists on how to perform a QRA, however specific guidelines for HRSs do not exist. An intercomparison among the QRAs of permitted HRSs has revealed significant inconsistencies on various aspects of the QRA: namely the inclusion of HRS sub-systems and components, the HRS sub-system and component considerations as predefined components, the application of failure scenarios, the determination of failure frequencies, the application of input parameters, the consideration of preventive and mitigation measures as well as information provided regarding the HRS surroundings and the societal risk. It is therefore recommended to develop specific QRA guidelines for HRSs.     

Structural and electrochemical characterization of xLi[Li1/3Mn2/3]O2·(1 − x)Li[Ni1/3Mn1/3Co1/3]O2 (0 ≤ x ≤ 0.9) as cathode materials for lithium ion batteries

A series of cathode materials with molecular notation of xLi[Li_1/3Mn_2/3]O₂·(1 − x)Li[Ni_1/3Mn_1/3Co_1/3]O₂ (0 ≤ x ≤ 0.9) were synthesized by combination of co-precipitation and solid state calcination method. The prepared materials were characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) techniques, and their electrochemical performances were investigated. The results showed that sample 0.6Li[Li_1/3Mn_2/3]O₂·0.4Li[Ni_1/3Mn_1/3Co_1/3]O₂ (x = 0.6) delivers the highest capacity and shows good capacity-retention, which delivers a capacity ∼250 mAh g⁻¹ between 2.0 and 4.8 V at 18 mA g⁻¹.     

Ba0.5Sr0.5Co0.8Fe0.2O3 − δ + LaCoO3 composite cathode for Sm0.2Ce0.8O1.9-electrolyte based intermediate-temperature solid-oxide fuel cells

A novel Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3 − δ + LaCoO₃ (BSCF + LC) composite oxide was investigated for the potential application as a cathode for intermediate-temperature solid-oxide fuel cells based on a Sm_0.2Ce_0.8O_1.9 (SDC) electrolyte. The LC oxide was added to BSCF cathode in order to improve its electrical conductivity. X-ray diffraction examination demonstrated that the solid-state reaction between LC and BSCF phases occurred at temperatures above 950 °C and formed the final product with the composition: La_0.316Ba_0.342Sr_0.342Co_0.863Fe_0.137O_3 − δ at 1100 °C. The inter-diffusion between BSCF and LC was identified by the environmental scanning electron microscopy and energy dispersive X-ray examination. The electrical conductivity of the BSCF + LC composite oxide increased with increasing calcination temperature, and reached a maximum value of ∼300 S cm⁻¹ at a calcination temperature of 1050 °C, while the electrical conductivity of the pure BSCF was only ∼40 S cm⁻¹. The improved conductivity resulted in attractive cathode performance. An area-specific resistance as low as 0.21 Ω cm² was achieved at 600 °C for the BSCF (70 vol.%) + LC (30 vol.%) composite cathode calcined at 950 °C for 5 h. Peak power densities as high as ∼700 mW cm⁻² at 650 °C and ∼525 mW cm⁻² at 600 °C were reached for the thin-film fuel cells with the optimized cathode composition and calcination temperatures.     

Improved electrochemical properties of BiOF-coated 5 V spinel Li[Ni0.5Mn1.5]O4 for rechargeable lithium batteries

The electrochemical properties of BiOF-coated 5 V spinel Li[Ni_0.5Mn_1.5]O₄ were investigated at elevated temperatures (55 °C). As observed by scanning and transmission electron microscopy, BiOF nanolayers with ∼10 nm thickness were coated on the surface of Li[Ni_0.5Mn_1.5]O₄. The BiOF coating layer protected the surface of the active materials from HF generated by the decomposition of LiPF₆ in the electrolyte during electrochemical cycling. The dissolution of transition metal elements was also suppressed upon cycling. Therefore, the capacity retention of the BiOF-coated Li[Ni_0.5Mn_1.5]O₄ was obviously improved compared to the pristine Li[Ni_0.5Mn_1.5]O₄ at 55 °C.     

Investigation of fuel lean reburning process in a 1.5 MW boiler

This paper examines a detailed study of fuel lean reburning process applied to a 1.5 MW gas-fired boiler. Experimental and numerical studies were carried out to investigate the effect of the fuel lean reburning process on the NO_X reduction and CO emission. Natural gas (CH₄) was used as the reburn as well as the main fuel. The amount of the reburn fuel, injection location and thermal load of boiler were considered as experimental parameters. The flue gas data revealed that the fuel lean reburning process led to NO_X reduction up to 43%, while CO emission was limited to less than 30 ppm for the 100% thermal load condition. The commercial computational fluid dynamics code FLUENT 6.3, which included turbulence, chemical reaction, radiation and NO modeling, was used to predict the fluid flow and heat transfer characteristics under various operational conditions in the boiler. Subsequently, predicted results were validated with available measured data such as gas temperature distributions and local mean NO_X concentrations. The detailed numerical results showed that the recirculation flow developed inside the boiler was found to play an important role in improving the effectiveness of fuel lean reburning process.     

Chromium doping as a new approach to improve the cycling performance at high temperature of 5 V LiNi0.5Mn1.5O4-based positive electrode

LiCr_2YNi_0.5−YMn_1.5−YO₄ (0 < Y ≤ 0.2) spinels have been synthesized by a sucrose-aided combustion method. Two sets of Cr-doped samples have been obtained by heating the “as-prepared” samples at 700 and 900 °C for 1 h. X-ray diffraction and thermogravimetric data show that pure and single phase spinels with similar lattice parameter have been synthesized. The homogeneity and the sub-micrometric particle size of the spinels have been shown by SEM and TEM. The main effect of the temperature is to increase the particle size from ≈50 to ≈500 nm, on heating from 700 to 900 °C. The study of the influence of Cr-dopant content and thermal treatment on the electrochemical properties at 25 °C and at 55 °C has been carried out by galvanostatic cycling in Li-cells. The discharge capacity (≈130 mAh g⁻¹) does not noticeably change with the synthesis conditions; but the cycling performances are strongly modified. Key factors that control the cycling performances have been determined. The most highlighted result is that spinels heated at 900 °C with Y ≤ 0.1 have very high capacity retention at 55 °C (>96% after 40 cycles, cyclability >99.9% by cycle) indicating that metal doping is a new approach to prepare 5 V LiNi_0.5Mn_1.5O₅-based cathodes with excellent cycling performances at high temperature.     

LiCr0.2Ni0.4Mn1.4O4 spinels exhibiting huge rate capability at 25 and 55 °C: Analysis of the effect of the particle size

The comparison of the rate capability of LiCr_0.2Ni_0.4Mn_1.4O₄ spinels synthesized by the sucrose aided combustion method at 900, 950 and 1000 °C is presented. XRD and TEM studies show that the spinel cubic structure remains unchanged on heating but the particle size is notably modified. Indeed, it increases from 695 nm at 900 °C to 1465 nm at 1000 °C. The electrochemical properties have been evaluated by galvanostatic cycling at 25 and 55 °C between 1 C and 60 C discharge rates. At both temperatures, all samples exhibit high working voltage (∼4.7 V), elevated capacity (∼140 mAh g⁻¹) and high cyclability (capacity retention ∼99% after 50 cycles even at 55 °C). The samples also have huge rate capability. They retain more than 70% of their maximum capacity at the very fast rate of 60 C. The effect of the particle size on the rate capability at 25 and at 55 °C has been investigated. It was demonstrated that LiCr_0.2Ni_0.4Mn_1.4O₄ annealed at 900 °C, with the lowest particle size, has the best electrochemical performances. In fact, among the LiNi_0.5Mn_1.5O₄-based cathodes, SAC900 exhibits the highest rate capability ever published. This spinel, able to deliver 31,000 W kg⁻¹ at 25 °C and 27,500 W kg⁻¹ at 55 °C is a really promising cathode for high-power Li-ion battery.