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The present paper offers a thorough examination of the safety measures enforced at hydrogen filling stations, emphasizing their crucial significance in the wider endeavor to advocate for hydrogen as a sustainable and reliable substitute for conventional fuels. The analysis reveals a wide range of crucial safety aspects in hydrogen refueling stations, including regulated hydrogen dispensing, leak detection, accurate hydrogen flow measurement, emergency shutdown systems, fire-suppression mechanisms, hydrogen distribution and pressure management, and appropriate hydrogen storage and cooling for secure refueling operations. The paper therefore explores several aspects, including the sophisticated architecture of hydrogen dispensers, reliable leak-detection systems, emergency shut-off mechanisms, and the implementation of fire-suppression tactics. Furthermore, it emphasizes that the safety and effectiveness of hydrogen filling stations are closely connected to the accuracy in the creation and upkeep of hydrogen dispensers. It highlights the need for materials and systems that can endure severe circumstances of elevated pressure and temperature while maintaining safety. The use of sophisticated leak-detection technology is crucial for rapidly detecting and reducing possible threats, therefore improving the overall safety of these facilities. Moreover, the research elucidates the complexities of emergency shut-off systems and fire-suppression tactics. These components are crucial not just for promptly managing hazards, but also for maintaining the station's structural soundness in unanticipated circumstances. In addition, the study provides observations about recent technical progress in the industry. These advances effectively tackle current safety obstacles and provide the foundation for future breakthroughs in hydrogen fueling infrastructure. The integration of cutting-edge technology and materials, together with the development of upgraded safety measures, suggests a positive trajectory towards improved efficiency, dependability, and safety in hydrogen refueling stations. [ABSTRACT FROM AUTHOR]

Liquid hydrogen is a promising energy carrier in the global hydrogen value chain with the advantages of high volumetric energy density/purity, low operating pressure, and high flexibility in delivery. Safe and high-efficiency storage and transportation are essential in the large-scale utilization of liquid hydrogen. Aiming at the two indicators of the hold time and normal evaporation rate (NER) required in standards, this paper focuses on the thermal behaviors of fluid during the no-vented storage of liquid hydrogen and thermal insulations applied for the liquid hydrogen tanks, respectively. After presenting an overview of experimental/theoretical investigations on thermal behaviors, as well as typical forms/testing methods of performance of thermal insulations for liquid hydrogen tanks, seven perspectives are proposed on the key challenges and recommendations for future work. This work can benefit the design and improvement of high-performance LH2 tanks. [ABSTRACT FROM AUTHOR]

Hydrogen represents a promising renewable fuel, and its broad application can lead to drastic reductions in greenhouse gas emissions. Keeping hydrogen in liquid form helps achieve high energy density, but also requires cryogenic conditions for storage as hydrogen evaporates at temperatures of about 20 K, which can lead to a large pressure build-up in the tank. This paper addresses the unsteady thermal modeling of cryogenic tanks with liquid hydrogen. Considering the liquid and vapor phases in the tank as two nodes with averaged properties, a lumped-element method of low computational cost is developed and used for simulating two regimes: self-pressurization (also known as autogenous pressurization, or pressure build-up in the closed tank due to external heat leaks) and constant-pressure venting (when some hydrogen is let out of the tank to maintain pressure at a fixed level). The model compares favorably (within several percent for pressure) to experimental observations for autogenous pressurization in a NASA liquid hydrogen tank. The two processes of interest in this study are numerically investigated in tanks of similar shapes but different sizes ranging from about 2 to 1200 m3. Pressure and temperature growth rates are characterized in closed tanks, where the interfacial mass transfer manifests initial condensation followed by more pronounced evaporation. In tanks where pressure is kept fixed by venting some hydrogen from the vapor domain of the tank, the initial venting rate significantly exceeds evaporation rate, but after a settling period, magnitudes of both rates approach each other and continue evolving at a slower pace. The largest tank demonstrates a six-times-lower pressure rise than the smallest tank over a 100 h period. The relative boil-off losses in continuously vented tanks are found to be approximately proportional to the inverse of the tank diameter, thus generally following simple Galilean scaling with a few percent deviation due to scale effects. The model developed in this work is flexible for analyzing a variety of processes in liquid hydrogen storage systems, raising efficiencies, which is critically important for a future economy based on renewable energy. [ABSTRACT FROM AUTHOR]

The geological storage of hydrogen is a seasonal energy storage solution, and the storage capacity of saline aquifers is most appropriately defined by quantifying the amount of hydrogen that can be injected and reproduced over a relevant time period. Cushion gas, stored in the reservoir to support the production of the working gas, is a CAPEX, which should be reduced to decrease implementation cost for gas storage. The cushion gas to working gas ratio provides a sufficiently accurate reflection of the storage efficiency, with higher ratios equating to larger initial investments. This paper investigates how technical measures, such as well configurations and adjustments to the operational size and schedule, can reduce this ratio, and the outcomes can inform optimisation strategies for hydrogen storage operations. Using a simplified open saline aquifer reservoir model, hydrogen storage is simulated with a single injection and production well. The results show that the injection process is more sensitive to technical measures than the production process; a shorter perforation and a smaller well diameter increases the required cushion gas for the injection process but has little impact on the production. If the storage operation capacity is expanded, and the working gas volume increased, the required cushion gas to working gas ratio increases for injection, reducing the efficiency of the injection process. When the reservoir pressure has more time to equilibrate, less cushion gas is required. It is shown that cushion gas plays an important role in storage operations and that the tested optimisation strategies impart only minor effects on the production process, however, there is significant need for careful optimisation of the injection process. It is suggested that the recoverable part of the cushion gas could be seen as a strategic gas reserve, which can be produced during an energy crisis. In this scenario, the recoverable cushion gas could be owned by the state, and the upfront costs for gas storage to the operator would be reduced, making the implementation of more gas storage and the onset of hydrogen storage more attractive to investors. [ABSTRACT FROM AUTHOR]

In this paper we report the effect of three different preparation methods on the first hydrogenation of the vanadium-rich BCC alloy Ti16V60Cr24: one-time cold rolling, 5 min ball milling and addition of 4 wt.% of Zr. All samples were synthesized by arc melting. Without Zr addition the alloy was single phase, but when 4 wt.% Zr was added, a secondary zirconium-rich phase was present. However, X-ray diffraction patterns only showed a single-body-centred cubic phase before hydrogenation for all samples. The crystal structure of the fully hydrogenated samples was body-centred tetragonal. The highest hydrogen capacity (3.8 wt.%) was measured for the Zr-doped alloy. The ball-milled alloy also exhibited a high storage capacity and fast kinetics. However, the maximum hydrogen storage capacity slightly decreased after cold rolling. It was found that air exposure increases incubation time for the first hydrogenation. The incubation time was shortened by cold rolling which, however, reduced the hydrogen storage capacity. The Pressure-Composition isotherms of Ti16V60Cr24 + 4 wt.% Zr at 297, 303 and 323 K were determined. The determined enthalpy and entropy of hydrides formation were −41 ± 5 kJ/mol and −134 ± 14 J/mol/K, respectively. [ABSTRACT FROM AUTHOR]

Humanity is confronted with one of the most significant challenges in its history. The excessive use of fossil fuel energy sources is causing extreme climate change, which threatens our way of life and poses huge social and technological problems. It is imperative to look for alternate energy sources that can replace environmentally destructive fossil fuels. In this scenario, hydrogen is seen as a potential energy vector capable of enabling the better and synergic exploitation of renewable energy sources. A brief review of the use of hydrogen as a tool for decarbonizing our society is given in this work. Special emphasis is placed on the possibility of storing hydrogen in solid-state form (in hydride species), on the potential fields of application of solid-state hydrogen storage, and on the technological challenges solid-state hydrogen storage faces. A potential approach to reduce the carbon footprint of hydrogen storage materials is presented in the concluding section of this paper. [ABSTRACT FROM AUTHOR]

The use of hydrogen storage tanks at 100% of nominal working pressure (NWP) is expected only after refuelling. Driving between refuellings is characterised by the state of charge SoC <100%. There is experimental evidence that Type IV tanks tested in a fire at initial pressures below 1/3 NWP, leaked without rupture. This paper aims at understanding this phenomenon. The numerical research has demonstrated that the heat transfer from fire through the composite overwrap at storage pressures below NWP/3 is sufficient to melt the polymer liner. This melting initiates hydrogen microleaks through the composite before it loses the load-bearing ability. The fire-resistance rating (FRR) is defined as the time to rupture in a fire of a tank without or with blocked thermally activated pressure relief device. The dependence of a FRR on the SoC is demonstrated for the tanks with defined material properties and volumes in the range of 36–244 L. A composite wall thickness variation is shown to cause a safety issue by reducing the tank's FRR and is suggested to be addressed by tank manufacturers and OEMs. The effect of a tank's burst pressure ratio on the FRR is investigated. Thermal parameters of the composite wall, i.e., decomposition heat and temperatures, are shown in simulations of a tank failure in a fire to play an important role in its FRR. [ABSTRACT FROM AUTHOR]

As part of the ongoing transition from fossil fuels to renewable energies, advances are particularly expected in terms of safe and cost-effective solutions. Publicising instances of such advances and emphasising global safety considerations constitute the rationale for this communication. Knowing that high-strength steels can prove economically relevant in the foreseeable future for transporting hydrogen in pipelines by limiting the pipe wall thickness required to withstand high pressure, one advance relates to a bench designed to assess the safe transport or renewable-energy-related buffer storage of hydrogen gas. That bench has been implemented at the technology readiness level TRL 6 to test initially intact, damaged, or pre-notched 500 mm-long pipe sections with nominal diameters ranging from 300 to 900 mm in order to appropriately validate or question the use of reputedly satisfactory predictive models in terms of hydrogen embrittlement and potential corollary failure. The other advance discussed herein relates to the reactivation of a previously fruitful applied research into safe mass solid-state hydrogen storage by magnesium hydride through a new public–private partnership. This latest development comes at a time when markets have started driving the hydrogen economy, bearing in mind that phase-change materials make it possible to level out heat transfers during the absorption/melting and solidification/desorption cycles and to attain an overall energy efficiency of up to 80% for MgH2-based compacts doped with expanded natural graphite. [ABSTRACT FROM AUTHOR]

Hydrogen (H2) storage is one of the most problematic issues regarding the widespread use of hydrogen, and solid-state hydrogen storage materials are promising in this regard. Hydrogen storage by sodium borohydride (NaBH4) takes attention with its advantages and idiosyncratic properties. In this study, potentials and challenges of sodium borohydride are evaluated considering storage conditions, safety, hydrogen purity, storage capacity, efficiency, cost, and the maturity. Moreover, marine use of NaBH4 is demonstrated, and the pros and cons of the NaBH4 hydrogen storage method are stated. According to evaluations, whereas advantages can be sorted as fuel availability, fuel recyclability, mild storage conditions, exothermicity of reaction, pressure flexibility, and H2 purity, challenges can be sorted as high costs, catalyst deactivation, regeneration, and practical/technical implementation issues. The great potential of NaBH4 marine use (against road/aerial vehicles) is water availability, no need to carry all the required water for the entire journey, and reduced system weight/volume by this way. [ABSTRACT FROM AUTHOR]

This study aims to numerically assess the impact of wettability and relative permeability hysteresis on hydrogen losses during underground hydrogen storage (UHS) and explore strategies to minimize them by using an appropriate cushion gas. The research utilizes the Carlson model to calculate the saturation of trapped gas and the Killough model to account for water hysteresis. By incorporating the Land coefficient based on laboratory-measured data for a hydrogen/brine system, our findings demonstrate a significant influence of gas hysteresis on the hydrogen recovery factor when H2 is used as a cushion gas. The base model, which neglects the hysteresis effect, indicates a recovery factor of 78% by the fourth cycle, which can be improved. In contrast, the modified model, which considers hysteresis and results in a trapped gas saturation of approximately 17%, shows a hydrogen recovery factor of 45% by the fourth cycle. Additionally, gas hysteresis has a notable impact on water production, with an observed 12.5% increase in volume in the model that incorporates gas hysteresis. Furthermore, optimization of the recovery process was conducted by evaluating different cushion gases such as CO2, N2, and CH4, with the latter proving to be the optimal choice. These findings enhance the accuracy of estimating the H2 recovery factor, which is crucial for assessing the feasibility of storage projects. [ABSTRACT FROM AUTHOR]

Hydrogen storage in general is an indispensable prerequisite for the introduction of a hydrogen energy-based infrastructure. In this respect, high-pressure metal hydride (MH) tank systems appear to be one of the most promising hydrogen storage techniques for automotive applications using proton exchange membrane (PEM) fuel cells. These systems bear the potential of achieving a beneficial compromise concerning the comparably large volumetric storage density, wide working temperature range, comparably low liberation of heat, and increased safety. The debatable term "unstable metal hydride" is used in the literature in reference to metal hydrides with high dissociation pressure at a comparably low temperature. Such compounds may help to improve the merits of high-pressure MH tank systems. Consequently, in the last few years, some materials for possible on-board applications in such tank systems have been developed. This review summarizes the state-of-the-art developments of these metal hydrides, mainly including intermetallic compounds and complex hydrides, and offers some guidelines for future developments. Since typical laboratory hydrogen uptake measurements are limited to 200 bar, a possible threshold for defining unstable hydrides could be a value of their equilibrium pressure of peq > 200 bar for T < 100 °C. However, these values would mark a technological future target and most current materials, and those reported in this review, do not fulfill these requirements and need to be seen as current stages of development toward the intended target. For each of the aforementioned categories in this review, special care is taken to not only cover the pioneering and classic research but also to portray the current status and latest advances. For intermetallic compounds, key aspects focus on the influence of partial substitution on the absorption/desorption plateau pressure, hydrogen storage capacity and hysteresis properties. For complex hydrides, the preparation procedures, thermodynamics and theoretical calculation are presented. In addition, challenges, perspectives, and development tendencies in this field are also discussed. [ABSTRACT FROM AUTHOR]

This article analyzes the processes of compressing hydrogen in the gaseous state, an aspect considered important due to its contribution to the greater diffusion of hydrogen in both the civil and industrial sectors. This article begins by providing a concise overview and comparison of diverse hydrogen-storage methodologies, laying the groundwork with an in-depth analysis of hydrogen's thermophysical properties. It scrutinizes plausible configurations for hydrogen compression, aiming to strike a delicate balance between energy consumption, derived from the fuel itself, and the requisite number of compression stages. Notably, to render hydrogen storage competitive in terms of volume, pressures of at least 350 bar are deemed essential, albeit at an energy cost amounting to approximately 10% of the fuel's calorific value. Multi-stage compression emerges as a crucial strategy, not solely for energy efficiency, but also to curtail temperature rises, with an upper limit set at 200 °C. This nuanced approach is underlined by the exploration of compression levels commonly cited in the literature, particularly 350 bar and 700 bar. The study advocates for a three-stage compression system as a pragmatic compromise, capable of achieving high-pressure solutions while keeping compression work below 10 MJ/kg, a threshold indicative of sustainable energy utilization. [ABSTRACT FROM AUTHOR]

Long-duration energy storage is the key challenge facing renewable energy transition in the future of well over 50% and up to 75% of primary energy supply with intermittent solar and wind electricity, while up to 25% would come from biomass, which requires traditional type storage. To this end, chemical energy storage at grid scale in the form of fuel appears to be the ideal option for wind and solar power. Renewable hydrogen is a much-considered fuel along with ammonia. However, these fuels are not only difficult to transport over long distances, but they would also require totally new and prohibitively expensive infrastructure. On the other hand, the existing natural gas pipeline infrastructure in developed economies can not only transmit a mixture of methane with up to 20% hydrogen without modification, but it also has more than adequate long-duration storage capacity. This is confirmed by analyzing the energy economies of the USA and Germany, both possessing well-developed natural gas transmission and storage systems. It is envisioned that renewable methane will be produced via well-established biological and/or chemical processes reacting green hydrogen with carbon dioxide, the latter to be separated ideally from biogas generated via the biological conversion of biomass to biomethane. At the point of utilization of the methane to generate power and a variety of chemicals, the released carbon dioxide would be also sequestered. An essentially net zero carbon energy system would be then become operational. The current conversion efficiency of power to hydrogen/methane to power on the order of 40% would limit the penetration of wind and solar power. Conversion efficiencies of over 75% can be attained with the on-going commercialization of solid oxide electrolysis and fuel cells for up to 75% penetration of intermittent renewable power. The proposed hydrogen/methane system would then be widely adopted because it is practical, affordable, and sustainable. [ABSTRACT FROM AUTHOR]

The effect of the partial substitution of Cr with Fe on the thermodynamic parameters of vanadium-rich Ti16V60Cr24-xFex alloys (x = 0, 4, 8, 12, 16, 20, 24) was investigated. For each composition, a pressure–concentration isotherm (PCI) was registered at 298, 308, and 323 K. The PCI curves revealed a reduction in plateau pressure and a decrease in desorbed hydrogen capacity with an increasing amount of Fe. For all alloys, about 50% or less of the initial hydrogen capacity was desorbed for all chosen temperatures. Entropy (ΔS) and enthalpy (ΔH) values were deducted from corresponding Van't Hoff plots of the PCI curves: the entropy values ranged from −150 to −57 J/K·mol H2, while the enthalpy values ranged from −44 to −21 kJ/mol H2. They both decreased with an increasing amount of Fe. Plotting ΔS as function of ΔH showed a linear variation that seems to indicate an enthalpy–entropy compensation. Moreover, a quality factor analysis demonstrated that the present relationship between entropy and enthalpy is not of a statistical origin at the 99% confidence level. [ABSTRACT FROM AUTHOR]

The reversible hydrogenation/dehydrogenation of aromatic molecules, known as liquid organic hydrogen carriers, is considered as an attractive option for the safe storage and release of elemental hydrogen. The recently reported efficient synthetic routes to obtain methoxy-biphenyls in high yield make them promising candidates for hydrogen storage. In this work, a series of methoxy-substituted biphenyls and their structural parent compounds were studied. The absolute vapour pressures were measured using the transpiration method and the enthalpies of vaporisation/sublimation were determined. We applied a step-by-step procedure including structure–property correlations and quantum chemical calculations to evaluate the quality of thermochemical data on the enthalpies of phase transitions and enthalpies of formation of the studied methoxy compounds. The data sets on thermodynamic properties were evaluated and recommended for calculations in chemical engineering. A thermodynamic analysis of chemical reactions based on methoxy-biphenyls in the context of hydrogen storage was carried out and the energetics of these reactions were compared with the energetics of reactions of common LOHCs. The influence of the position of the methoxy groups in the rings on the enthalpies of the reactions relevant for hydrogen storage was discussed. [ABSTRACT FROM AUTHOR]

Hydrogen storage is a key enabling technology for the extensive use of hydrogen as energy carrier. This is particularly true in the widespread introduction of hydrogen in car transportation. Indeed, one of the greatest technological barriers for such development is an efficient and safe storage method. So, in this tutorial review the existing hydrogen storage technologies are described with a special emphasis on hydrogen storage in hydrogen cars: the current and the ongoing solutions. A particular focus is given on solid storage and some of the recent advances on plasma hydrogen ion implantation, which should allow not only the preparation of metal hydrides, but also the imagination of a new refluing circuit. From hydrogen discovery to its use as an energy vector in cars, this review wants to be as exhaustive as possible, introducing the basics of hydrogen storage, and discussing the experimental practicalities of car hydrogen fuel. It wants to serve as a guide for anyone wanting to undertake such a technology and to equip the reader with an advanced knowledge on hydrogen storage and hydrogen storage in hydrogen cars to stimulate further researches and yet more innovative applications for this highly interesting field. [ABSTRACT FROM AUTHOR]

For the few past decades, study of new hydrogen storage materials has been captivating scientists worldwide. Magnesium hydride, MgH2, is considered one of the most promising materials due to its low cost, high hydrogen capacity, reversibility and the abundance of Mg. However, it requires further research to improve its hydrogen storage performance as it has some drawbacks such as poor dehydrogenation kinetic, high operational temperature, which limit its practical application. In this study, we introduce an overview of recent progress in improving the hydrogen storage performance of MgH2 by the addition of titanium-based additives, which are one of the important groups of additives. The role of Ti-based additive hydrides, oxides, halides, carbides and carbonitrides are overviewed. In addition, the existing challenges and future perspectives of Mg-based hydrides are also discussed. [ABSTRACT FROM AUTHOR]

The realization of a carbon-neutral civilization, which has been set as a goal for the coming decades, goes directly hand-in-hand with the need for an energy system based on renewable energies (REs). Due to the strong weather-related, daily, and seasonal fluctuations in supply of REs, suitable energy storage devices must be included for such energy systems. For this purpose, an energy system model featuring hybrid energy storage consisting of a hydrogen unit (for long-term storage) and a lithium-ion storage device (for short-term storage) was developed. With a proper design, such a system can ensure a year-round energy supply by using electricity generated by photovoltaics (PVs). In the energy system that was investigated, hydrogen ( H 2 ) was produced by using an electrolyser (ELY) with a PV surplus during the summer months and then stored in an H 2 tank. During the winter, due to the lack of PV power, the H 2 is converted back into electricity and heat by a fuel cell (FC). While the components of such a system are expensive, a resource- and cost-efficient layout is important. For this purpose, a Matlab/Simulink model that enabled an energy balance analysis and a component lifetime forecast was developed. With this model, the results of extensive parameter studies allowed an optimized system layout to be created for specific applications. The parameter studies covered different focal points. Several ELY and FC layouts, different load characteristics, different system scales, different weather conditions, and different load levels—especially in winter with variations in heating demand—were investigated. [ABSTRACT FROM AUTHOR]

In this paper we report the effect of three different preparation methods on the first hydrogenation of the vanadium-rich BCC alloy Ti16V60Cr24: one-time cold rolling, 5 min ball milling and addition of 4 wt.% of Zr. All samples were synthesized by arc melting. Without Zr addition the alloy was single phase, but when 4 wt.% Zr was added, a secondary zirconium-rich phase was present. However, X-ray diffraction patterns only showed a single-body-centred cubic phase before hydrogenation for all samples. The crystal structure of the fully hydrogenated samples was body-centred tetragonal. The highest hydrogen capacity (3.8 wt.%) was measured for the Zr-doped alloy. The ball-milled alloy also exhibited a high storage capacity and fast kinetics. However, the maximum hydrogen storage capacity slightly decreased after cold rolling. It was found that air exposure increases incubation time for the first hydrogenation. The incubation time was shortened by cold rolling which, however, reduced the hydrogen storage capacity. The Pressure-Composition isotherms of Ti16V60Cr24 + 4 wt.% Zr at 297, 303 and 323 K were determined. The determined enthalpy and entropy of hydrides formation were −41 ± 5 kJ/mol and −134 ± 14 J/mol/K, respectively.

This study presents a methodology of a quantitative risk assessment for the scenario of an onboard hydrogen storage tank rupture and tunnel fire incident. The application of the methodology is demonstrated on a road tunnel. The consequence analysis is carried out for the rupture of a 70 MPa, 62.4-litre hydrogen storage tank in a fire, that has a thermally activated pressure relief device (TPRD) failed or blocked during an incident. Scenarios with two states of charge (SoC) of the tank, i.e., SoC = 99% and SoC = 59%, are investigated. The risks in terms of fatalities per vehicle per year and the cost per incident are assessed. It is found that for the reduction in the risk with the hydrogen-powered vehicle in a road tunnel fire incident to the acceptable level of 10−5 fatality/vehicle/year, the fire-resistance rating (FRR) of the hydrogen storage tank should exceed 84 min. The FRR increase to this level reduces the societal risk to an acceptable level. The increase in the FRR to 91 min reduces the risk in terms of the cost of the incident to GBP 300, following the threshold cost of minor injury published by the UK Health and Safety Executive. The Frequency–Number (F–N) of the fatalities curve is developed to demonstrate the effect of mitigation measures on the risk reduction to socially acceptable levels. The performed sensitivity study confirms that with the broad range of input parameters, including the fire brigade response time, the risk of rupture of standard hydrogen tank-TPRD systems inside the road tunnel is unacceptable. One of the solutions enabling an inherently safer use of hydrogen-powered vehicles in tunnels is the implementation of breakthrough safety technology—the explosion free in a fire self-venting (TPRD-less) tanks. [ABSTRACT FROM AUTHOR]

Humanity is confronted with one of the most significant challenges in its history. The excessive use of fossil fuel energy sources is causing extreme climate change, which threatens our way of life and poses huge social and technological problems. It is imperative to look for alternate energy sources that can replace environmentally destructive fossil fuels. In this scenario, hydrogen is seen as a potential energy vector capable of enabling the better and synergic exploitation of renewable energy sources. A brief review of the use of hydrogen as a tool for decarbonizing our society is given in this work. Special emphasis is placed on the possibility of storing hydrogen in solid-state form (in hydride species), on the potential fields of application of solid-state hydrogen storage, and on the technological challenges solid-state hydrogen storage faces. A potential approach to reduce the carbon footprint of hydrogen storage materials is presented in the concluding section of this paper.

A theoretical model was selected among three potentially applicable models and then used to analyze the absorption isotherms of the hydrogen storage alloys LaNi5 and LaNi4.75Pb0.25 at three different temperatures (T = 303 K, 313 K, 323 K). The theoretical expressions of the model were based on the statistical physics formalism and simplifying hypotheses. The model selected was the one with the highest correlation with the experimental data. The model had six adjustable parameters: the number of hydrogen atoms per site n α , n β , the receptor site densities N α , N β and the energy parameters P α , P β . The fitted parameters obtained for the Pb-doped and nondoped alloys were compared and discussed in relationship to the absorption isotherms. Finally, the fitted parameters or the model were further applied to calculate thermodynamic functions, such as entropy, Gibbs free energy and internal energy, which govern the absorption mechanism. [ABSTRACT FROM AUTHOR]

Hydrogen jet fires from a thermally activated pressure relief device (TPRD) on onboard storage are considered for a vehicle in a naturally ventilated covered car park. Computational Fluid Dynamics was used to predict behaviour of ignited releases from a 70 MPa tank into a naturally ventilated covered car park. Releases through TPRD diameters 3.34, 2 and 0.5 mm were studied to understand effect on hazard distances from the vehicle. A vertical release, and downward releases at 0°, 30° and 45° for TPRD diameters 2 and 0.5 mm were considered, accounting for tank blowdown. direction of a downward release was found to significantly contribute to decrease of temperature in a hot cloud under the ceiling. Whilst the ceiling is reached by a jet exceeding 300 °C for a release through a TPRD of 2 mm for inclinations of either 0°, 30° or 45°, an ignited release through a TPRD of 0.5 mm and angle of 45° did not produce a cloud with a temperature above 300 °C at the ceiling during blowdown. The research findings, specifically regarding the extent of the cloud of hot gasses, have implications for the design of mechanical ventilation systems. [ABSTRACT FROM AUTHOR]

The hydrogen economy relies on effective and environmentally friendly processes for energy conversion and storage. To this end, hydrogen is progressively holding the role of preferred energy vector. Within this frame, electrochemical science and technology is actively contributing in developing advanced fuel cells and water electrolyzers to be integrated in (i) energy parks to decouple production and consumption; (ii) exploit renewable sources; (iii) favour the progressive reduction of fossil fuels and reduce the greenhouse effect via decarbonization. The exploitation of the relevant processes and devices call for the sound control over the environmental impact from production to end-of-life steps. Here, life-cycle analyses were performed and discussed focusing on both acid and alkaline fuel cells, i.e., proton exchange membrane fuel cells (PEMFC) and anionexchange membrane fuel cells (AEMFC), and assessing their contribution to key environmental impact categories such as, for example, global warming and ozone layer depletion. Within these premises, the study points to the benefits of replacing platinum by low load Pd/CeO2 bifunctional electrocatalyst on electrochemical hydrogen production and usage. [ABSTRACT FROM AUTHOR]