Understanding attitudes of hydrogen fuel-cell vehicle adopters in Japan

As of January 2021, Japan had the world's largest hydrogen station network with merely 4600 hydrogen fuel-cell vehicles (HFCVs) on roads, as compared to the 9000 HFCVs in the US, with only one-third of the hydrogen refueling stations in Japan. To understand behavioral differences among Japanese adopters, we administered a survey, in cooperation with public and private sector stakeholders, involving 89 private HFCV adopters in the Aichi Prefectural region, which hosts the largest number of HFCVs and refueling stations in Japan. Results suggest that HFCV adopters have a higher socioeconomic status than non-adopters, are mostly male in their 50s and above, and have a higher interest in new vehicle fuel technology. HFCV adopters who leased and bought vehicles were similar in terms of socioeconomic status, with differences in attitudes toward governmental incentives. The lack of refueling stations and station business hours restrict HFCV adopters from continuing with this fuel technology.     

Simulation of high-pressure liquid hydrogen releases

Sandia National Laboratories is working with stakeholders to develop scientific data for use by standards development organizations to create hydrogen codes and standards for the safe use of liquid hydrogen. Knowledge of the concentration field and flammability envelope for high-pressure hydrogen leaks is an issue of importance for the safe use of liquid hydrogen. Sandia National Laboratories is engaged in an experimental and analytical program to characterize and predict the behavior of liquid hydrogen releases. This paper presents a model for computing hydrogen dilution distances for cold hydrogen releases. Model validation is presented for leaks of room temperature and 80 K high-pressure hydrogen gas. The model accounts for a series of transitions that occurs from a stagnate location in the tank to a point in the leak jet where the concentration of hydrogen in air at the jet centerline has dropped to 4% by volume. The leaking hydrogen is assumed to be a simple compressible substance with thermodynamic equilibrium between hydrogen vapor, hydrogen liquid and air. For the multi-phase portions of the jet near the leak location the REFPROP equation of state models developed by NIST are used to account for the thermodynamics. Further downstream, the jet develops into an atmospheric gas jet where the thermodynamics are described as a mixture of ideal gases (hydrogen–air mixture). Simulations are presented for dilution distances in under-expanded high-pressure leaks from the saturated vapor and saturated liquid portions of a liquid hydrogen storage tank at 10.34 barg (150 PSIG).     

Releases from hydrogen fuel-cell vehicles in tunnels

An important issue concerning the safe use of hydrogen-powered fuel-cell vehicles is the possibility of accidents inside tunnels resulting in the release of hydrogen. To investigate the potential consequences, a combined experimental and modeling study has been performed to characterize releases from a hydrogen fuel-cell vehicle inside a tunnel. In the scenario studied, all three of the fuel-cell vehicle’s onboard hydrogen tanks were simultaneously released through three thermal pressure relief devices (TPRDs) toward the road surface. Computation fluid dynamics (CFD) simulations were used to model the release of hydrogen from the fuel-cell vehicle and to study the behavior of the ignitable hydrogen cloud inside the tunnel. Deflagration overpressure simulations of the hydrogen cloud within the tunnel were also performed for different ignition delay times and ignition locations. To provide model validation data for these simulations, experiments were performed in a scaled tunnel test facility at the SRI Corral Hollow Experiment Site (CHES). The scaled tunnel tests were designed to resemble the full-scale tunnel simulations using Froude scaling. The scale factor, based on the square route of the ratio of the SRI tunnel area to the full-scale tunnel area was 1/2.53. The same computational models used in the full-scale tunnel simulations were applied to these scaled tunnel tests to validate the modeling approach.     

An insight into potential early adopters of hydrogen fuel-cell vehicles in Japan

With the inauguration of the world's largest green hydrogen facility, the Government of Japan is steadily advancing towards its goal of transforming into a hydrogen-based society, but the lack of interest in adopting hydrogen fuel cell vehicles (HFCVs) among consumers is noticeable. This study examines the socioeconomic profiles of 500 potential car buyers with and without interest in HFCVs. The results show that the potential early adopters of HFCVs exhibit similar trends of sex, employment status, number of people in the households, weekly distance traveled, and frequency of using expressways that influence their decision. They have a significant variance in income, previous battery electric vehicle (BEV) experiences, and knowledge of HFCVs. The results suggest that knowledge of HFCVs and related technologies, and previous experience in driving BEVs encourage respondents to purchase HFCVs. The study suggests that the greater awareness of HFCV can assist policymakers in the successful market adoption.     

A study of barrier walls for mitigation of unintended releases of hydrogen

Hydrogen jet flames resulting from ignition of unintended releases can be extensive in length and pose significant radiation and impingement hazards. Depending on the leak diameter and source pressure, the resulting consequence distances can be unacceptably large. One possible mitigation strategy to reduce exposure to jet flames is to incorporate barriers around hydrogen storage and delivery equipment. An experimental and modeling program has been performed at Sandia National Laboratories to better characterize the effectiveness of barrier walls to reduce hazards. This paper describes the experimental and modeling program and presents results obtained for various barrier configurations. The experimental measurements include flame deflection using standard and infrared video and high-speed movies (500 fps) to study initial flame propagation from the ignition source. Measurements of the ignition overpressure, wall deflection, radiative heat flux, and wall and gas temperature were also made at strategic locations. The modeling effort includes three-dimensional calculations of jet flame deflection by the barriers, computations of the thermal radiation field around barriers, predicted overpressure from ignition, and the computation of the concentration field from deflected unignited hydrogen releases. The various barrier designs are evaluated in terms of their mitigation effectiveness for the associated hazards present. The results show that barrier walls are effective at deflecting jet flames in a desired direction and can help attenuate the effects of ignition overpressure and flame radiative heat flux.     

Overview of the DOE hydrogen safety,codes and standards program,part 3: Advances in research and development to enhance the scientific basis for hydrogen regulations,codes and standards

Hydrogen fuels are being deployed around the world as an alternative to traditional petrol and battery technologies. As with all fuels, regulations, codes and standards are a necessary component of the safe deployment of hydrogen technologies. There has been a focused effort in the international hydrogen community to develop codes and standards based on strong scientific principles to accommodate the relatively rapid deployment of hydrogen-energy systems. The need for science-based codes and standards has revealed the need to advance our scientific understanding of hydrogen in engineering environments. This brief review describes research and development activities with emphasis on scientific advances that have aided the advancement of hydrogen regulations, codes and standards for hydrogen technologies in four key areas: (1) the physics of high-pressure hydrogen releases (called hydrogen behavior); (2) quantitative risk assessment; (3) hydrogen compatibility of materials; and (4) hydrogen fuel quality.     

Well-to-wheel analysis of hydrogen fuel-cell electric vehicle in Korea

This study provides methodologies, data collection and results of well-to-wheel greenhouse gas analysis of various H₂ production pathways for fuel-cell electric vehicle (FCEV) in Korea; naphtha cracking, steam methane reforming, electrolysis and coke oven gas purification. The well-to-wheel (WTW) greenhouse gas emissions of FCEV are calculated as 32,571 to 249,332 g-CO₂ eq./GJ or 50.7 to 388.0 g-CO₂ eq./km depending on the H₂ production pathway. The landfill gas (on-site) pathway has the lowest GHG emissions because the carbon credit owing to use landfill gas. The electrolysis with Korean grid mix (on-site) pathway has the highest GHG emissions due to its high emission factor of the power generation process. Furthermore, the results are compared with other powertrain vehicles in Korea such as internal combustion engine vehicle (ICEV), hybrid electric vehicle (HEV) and electric vehicle (EV). The averaged WTW result of FCEV is 35% of ICEV, is 47% of HEV, and is 63% of EV.     

Hydrogen dispersion phenomenon in nominally closed spaces

The hydrogen dispersion phenomenon in an enclosure depends on the ratio of the gas buoyancy-induced momentum and diffusive motions. Random diffusive motions of individual gas particles become dominative when the release momentum is low, and a uniform hydrogen concentration appears in the enclosure instead of the gas cumulation below the ceiling. The expected hydrogen behavior could be projected by the Froude number, which value ~1 predicts a decline of buoyancy. This paper justifies this hypothesis by demonstrating full-scale experimental results of hydrogen dispersion within a confined space under six different release variations. During the experiments, hydrogen was released into the test room of 60 m³ volume in two methods: through a nozzle and through 21 points evenly distributed on the emission box cover (multi-point release). Each release method was tested with three volume flow rates (3.2 × 10⁻³ m³/s, 1.6 × 10⁻³ m³/s, 3.3 × 10⁻⁴ m³/s). The tests confirm the decrease of hydrogen buoyancy and its stratification tendencies when the Mach, Reynolds, and Froud number values decrease. Because the hydrogen dispersion phenomenon would impact fire and explosive hazards, the presented experimental results could help fire protection systems be in an enclosure designed, allowing their effectiveness optimization.     

Well-to-wheels analysis of hydrogen based fuel-cell vehicle pathways in Shanghai

Due to high energy efficiency and zero emissions, some believe fuel cell vehicles (FCVs) could revolutionize the automobile industry by replacing internal combustion engine technology, and first boom in China. However, hydrogen infrastructure is one of the major barriers. Because different H₂ pathways have very different energy and emissions effects, the well-to-wheels (WTW) analyses are necessary for adequately evaluating fuel/vehicle systems. The pathways used to supply H₂ for FCVs must be carefully examined by their WTW energy use, greenhouse gases (GHGs) emissions, total criteria pollutions emissions, and urban criteria pollutions emissions.     

Evaluation of barrier walls for mitigation of unintended releases of hydrogen

Hydrogen jet flames resulting from ignition of unintended releases can be extensive in length and pose significant radiation and impingement hazards. Depending on the leak diameter and source pressure, the resulting consequence distances can be unacceptably large. One possible mitigation strategy to reduce exposure to jet flames is to incorporate barriers around hydrogen storage and delivery equipment. While reducing the extent of unacceptable consequences, the walls may introduce other hazards if not properly configured. An experimental and modeling program has been performed at Sandia National Laboratories to better characterize the effectiveness of barrier walls to reduce hazards. This paper describes the experimental and modeling program and presents results obtained for various barrier configurations. The experimental measurements include flame deflection using standard and infrared video and high-speed movies (500 fps) to study initial flame propagation from the ignition source. Measurements of the ignition overpressure, wall deflection, radiative heat flux, and wall and gas temperature were also made at strategic locations. The modeling effort includes three-dimensional calculations of jet flame deflection by the barriers, computations of the thermal radiation field around barriers, predicted overpressure from ignition, and the computation of the concentration field from deflected unignited hydrogen releases. The various barrier designs are evaluated in terms of their mitigation effectiveness for the associated hazards present. The results show that barrier walls are effective at deflecting jet flames in a desired direction and can help attenuate the effects of ignition overpressure and flame radiative heat flux.     

Modeling and analysis of hydrogen diffusion in an enclosed fuel cell vehicle with obstacles

Hydrogen has been utilized in FCV and leakage can cause safety issues. In this study, the vehicle is simplified as a cuboid enclosure with obstacles. The influence of obstacle locations on the hydrogen diffusion behavior is investigated with the iso-surfaces of 1% and 4% volume fraction of hydrogen. The time of the iso-surface of 4% volume fraction to reach the ceiling and the sidewalls without any obstacles is 1.42 and 1.25 times of that with an obstacle, respectively. Both height and the width of the flammable zone in the enclosure with an obstacle are greater than that without obstacles. The distance between the obstacle and the leakage affects significantly the hydrogen diffusion and the influence of the obstacle on the hydrogen diffusion strengthens with the decrease of the distance. Yet as the distance keeps same, the obstacle position relative to the leakage has no significant effect on hydrogen diffusion, and it makes little effect difference whether the obstacle is located in front of leakage or side of leakage.     

Experimental investigation of hydrogen release and ignition from fuel cell powered forklifts in enclosed spaces

Due to rapid growth in the use of hydrogen powered fuel cell forklifts within warehouse enclosures, Sandia National Laboratories has worked to develop scientific methods that support the creation of new hydrogen safety codes and standards for indoor refueling operations. Based on industry stakeholder input, conducted experiments were devised to assess the utility of modeling approaches used to analyze potential consequences from ignited hydrogen leaks in facilities certified according to existing code language. Release dispersion and combustion characteristics were measured within a scaled test facility located at SRI International's Corral Hollow Test Site. Moreover, the impact of mitigation measures such as active/passive ventilation and pressure relief panels was investigated. Since it is impractical to experimentally evaluate all possible facility configurations and accident scenarios, careful characterization of the experimental boundary conditions has been performed so that collected datasets can be used to validate computational modeling approaches.     

An assessment on the quantification of hydrogen releases through oxygen displacement using oxygen sensors

Gas sensors that respond directly to hydrogen are typically used to detect and quantify unintended hydrogen releases. However, alternative means to quantify or mitigate hydrogen releases are sometimes proposed. One recently explored approach has been to use oxygen sensors. This method is based on the assumption that a hydrogen release will displace oxygen, which can be quantified using oxygen sensors. The use of oxygen sensors to monitor ambient hydrogen concentration has drawbacks, which are explored in the current study. It was shown that this approach may not have adequate accuracy for safety applications and may give misleading results under certain conditions for other applications. Despite its shortcomings, the Global Technical Regulation (GTR) for Hydrogen and Fuel Cell Vehicles has explicitly endorsed this method to verify hydrogen vehicles' fuel system integrity. Experimental evaluations designed to impartially assess the ability of oxygen and hydrogen sensors to reliably measure hydrogen concentration changes are presented. Specific limitations on the use of oxygen sensors for hydrogen measurements are identified and alternative sensor technologies that meet the requirements for several applications, including those of the GTR, are proposed.     

The possibility of an accidental scenario for marine transportation of fuel cell vehicle: Hydrogen releases from TPRD by radiant heat from lower deck

In case fires break out on the lower deck of a car carrier ship or a ferry, the fuel cell vehicles (FCVs) parked on the upper deck may be exposed to radiant heat from the lower deck. Assuming that the thermal pressure relief device (TPRD) of an FCV hydrogen cylinder is activated by the radiant heat without the presence of flames, hydrogen gas will be released by TPRD to form combustible air-fuel mixtures in the vicinity. To investigate the possibility of this accident scenario, the present study investigated the relationship between radiant heat and TPRD activation time and evaluated the possibility of radiant heat causing hydrogen releases by TPRD activation under the condition of deck temperature reaching the spontaneous ignition level of the tires and other automotive parts. It was found: a) the tires as well as polypropylene and other plastic parts underwent spontaneous ignition before TPRD was activated by radiant heat and b) when finally TPRD was activated, the hydrogen releases were rapidly burned by the flames of the tires and plastic parts on fire. Consequently it was concluded that the explosion of air-fuel mixtures assumed in the accident scenario does not occur in the real world.     

Influence of wind turbine power curve and electrolyzer operating temperature on hydrogen production in wind-hydrogen systems

Current simulation tools used to analyze, design and size wind-hydrogen hybrid systems, have several common characteristics: all use manufacturer wind turbine power curve (obtained from UNE 61400-12) and always consider electrolyzer operating in nominal conditions (not taking into account the influence of thermal inertia and operating temperature in hydrogen production). This article analyzes the influence of these parameters. To do this, a mathematical wind turbine model, that represents the manufacturer power curve to the real behaviour of the equipment in a location, and a dynamic electrolyzer model are developed and validated. Additionally, hydrogen production in a wind-hydrogen system operating in “wind-balance” mode (adjusting electricity production and demand at every time step) is analyzed. Considering the input data used, it is demonstrated that current simulation tools present significant errors in calculations. When using the manufacturer wind turbine power curve: the electric energy produced by the wind turbine, and the annual hydrogen production in a wind-hydrogen system are overestimated by 25% and 33.6%, respectively, when they are compared with simulation results using mathematical models that better represent the real behaviour of the equipments. Besides, considering electrolyzer operating temperature constant and equal to nominal, hydrogen production is overestimated by 3%, when compared with the hydrogen production using a dynamic electrolyzer model.     

Risk assessment of Hydrogen fueling stations for 70 MPa FCVs

People are placing their hopes on the future of fuel-cell vehicles (FCVs) to replace today's gasoline-fueled vehicles. To encourage the widespread use of FCVs, however, these vehicles must be able to drive a distance of at least 500 km, mileage comparable to today's gasoline-fueled vehicles. To achieve this distance, automobile manufacturers are focusing their efforts on developing new hydrogen fuel tanks that will raise pressure to 70 MPa from the current 35 MPa. At the same time, hydrogen stations will also have to be able to provide 70 MPa compressed hydrogen gas to service these improved FCVs. Regulations for hydrogen fueling stations where pressure is no higher than 40 MPa were established in 2005 in Japan but it goes without saying that these regulations are inadequate for hydrogen fueling stations of 70 MPa.     

Data requirements for improving the Quantitative Risk Assessment of liquid hydrogen storage systems

Quantitative Risk Assessment (QRA) supports the development of risk-informed safety codes and standards which are employed to enable the safe deployment of hydrogen technologies essential to decarbonize the transportation sector. System reliability data is a necessary input for rigorous QRA. The lack of reliability data for bulk liquid hydrogen (LH₂) storage systems located on site at fueling stations limits the use of QRAs. In turn, this hinders the ability to develop the necessary safety codes and standards that enable worldwide deployment of these stations. Through a QRA-based analysis of a LH₂ storage system, this work focuses on identifying relevant scenario and probability data currently available and ascertaining future data collection requirements regarding risks specific to liquid hydrogen releases. The work developed consists of the analysis of a general bulk LH₂ storage system design located at a hydrogen fueling station. Failure Mode and Effect Analysis (FMEA) and traditional QRA modeling tools such as Event Sequence Diagrams (ESD) and Fault Tree Analysis (FTA) are employed to identify, rank, and model risk scenarios related to the release of LH₂. Based on this analysis, scenario and reliability data needs to add LH₂-related components to QRA are identified with the purpose of improving the future safety and risk assessment of these systems.     

Application and validation of algebraic methods to predict the behaviour of crystalline silicon PV modules in Mediterranean climates

Predicting both PV module and generator performances under natural sunlight is a key issue for designers and installers. Five simple algebraic methods addressed to predict this behaviour in Mediterranean climates have been empirically validated. Firstly, the calibration in STC of all significant electrical parameters of both a monocrystalline and a polycrystalline silicon PV modules was entrusted to an accredited independent laboratory. Then, a 12-month test and measurement campaign carried out on these modules in the city of Jaén (Spain, latitude 38°N, longitude 3°W) has provided the necessary experimental data. Results show that (a) crystalline silicon PV module outdoors performance may be described with sufficient accuracy – for PV engineering purposes – only taking into account incident global irradiance, cell temperature, and using any one of two simple algebraic methods tried in this paper and (b) regardless the used method, poor results may be achieved if the PV specimens under study are not electrically characterised in STC prior to analysing their outdoors performance. Even so, the methods recommended in (a) perform best.     

Overview of the DOE hydrogen safety,codes and standards program part 2: Hydrogen and fuel cells: Emphasizing safety to enable commercialization

Safety is of paramount importance in all facets of the research, development, demonstration and deployment work of the U.S. Department of Energy's (DOE) Fuel Cell Technologies Program. The Safety, Codes and Standards sub-program (SC&S) facilitates deployment and commercialization of fuel cell and hydrogen technologies by developing and disseminating information and knowledge resources for their safe use. A comprehensive safety management program utilizing the Hydrogen Safety Panel to raise safety consciousness at the project level and developing/disseminating a suite of safety knowledge resources is playing an integral role in DOE and SC&S efforts. This paper provides examples of accomplishments achieved while reaching a growing and diverse set of stakeholders involved in research, development and demonstration; design and manufacturing; deployment and operations. The work of the Hydrogen Safety Panel highlights new knowledge and the insights gained through interaction with project teams. Various means of collaboration to enhance the value of the program's safety knowledge tools and training resources are illustrated and the direction of future initiatives to reinforce the commitment to safety is discussed.     

Hydrogen production with integrated CO2 capture in a membrane assisted gas switching reforming reactor: Proof-of-Concept

This paper presents a new membrane reactor concept for ultra-pure hydrogen production with integrated CO₂ capture: the membrane-assisted gas switching reforming (MA-GSR). This concept integrates alternating exothermic and endothermic redox reaction stages in a single fluidized bed consisting of catalytically active oxygen-carrier particles, by switching the feed between air and methane/steam, where the produced hydrogen is selectively removed via Pd-based membranes. This concept results in overall autothermal conditions and allows easier operation at high pressure compared to alternative novel technologies. In this work, the MA-GSR concept is demonstrated at lab scale using four metallic supported membranes (Pd–Ag based) immersed into a fluidized bed consisting of a Ni-based oxygen carrier. The performance of the reactor has been tested under different experimental operating conditions and high methane conversions (>50%) have been obtained, well above the thermodynamic equilibrium conversion of a conventional fluidized bed as a result of the selective H₂ extraction, with (ultra-pure) H₂ recoveries above 20% at relatively low temperatures (<550 °C). These results could be further improved by working at elevated pressures or by integrating more membranes. Even though the concept has been successfully demonstrated, further research is required to develop suitable membranes since post-mortem membrane characterization has revealed defects in the membrane selective layer as a consequence of the frequent exposure to thermal cycles with alternating oxidative and reducing atmospheres.