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The widespread use of hydrogen as an energy carrier for road transport and industrial applications was indicated as a promising solution for reducing pollutant emissions. The high flammability of this substance and its tendency to permeate and embrittle most structural materials make hydrogen handling and storage inherently challenging. Hence, inspection and maintenance activities are essential to guarantee the components' integrity and fitness for service. However, guidelines for inspecting and maintaining hydrogen refueling stations are still under development. The manufacturer is responsible for indicating the optimal inspection procedures for each facility. The lack of a unified regulatory framework and the limited operational experience with these technologies make human errors a potential cause of undesired events. In this context, the study evaluates the probability of human error during the high-pressure storage system inspection procedures in hydrogen refueling stations. The Petro-HRA methodology has been used to quantify the likelihood of unsafe or inappropriate actions. In addition, a Bayesian Network approach is proposed to investigate the conditional dependencies among human errors and performance shaping factors. The critical analysis of the results allowed the authors to provide recommendations regarding safety procedures that operators can adopt to reduce the likelihood of accidents in the hydrogen industry.

Hydrogen is assuming a pivotal role in the energy sector, intending to lead the decarbonization and overcome the fossil fuel use. In evaluating its key applications, the role of hydrogen in mobility stands out. It could transform one of the most polluting sectors, drastically reducing emissions without changing the drivers’ needs. In this perspective, the focus should be placed on hydrogen refueling infrastructures, which are a key factor, along with fuel cell vehicles, for extending the hydrogen chain in the mobility sector. Given this, the study analyzes the hydrogen refueling station performance, investigating the hydrogen flow features, and estimating the evolution of pressure and temperature within the vehicle tank. An ad-hoc model for hydrogen performance analysis is used by customizing its main blocks. In addition, the main safety aspects of the hydrogen refueling stations are evaluated. The behavior of each component of the refueling infrastructure, such as hydrogen storage tanks, compressors, and cooling systems, is examined and introduced in the model, characterizing the whole system. The model is then validated by comparing its performance with experimental data. The results show the pressure, temperature, and mass flow rate between the dispenser and the vehicle tank. These findings could help boost hydrogen use in mobility since crucial aspects are investigated and important information is provided for promising integrated systems, based on the interconnection between infrastructures and vehicles.

The issue of global warming imposes a change of paradigm in the energy sector to mitigate the human impact on the environment. In this perspective, hydrogen can be produced through water electrolysis and used in fuel-cell systems with near-zero pollutant emissions. Nevertheless, the distribution system represents one of the main bottlenecks for a future transition to a hydrogen economy. The possibility of transporting hydrogen through the existing pipeline network is economically attractive. Nevertheless, most pipeline steels are prone to hydrogen-induced damage, and their mechanical properties are degraded by hydrogen gas to an extent that could result in sudden component failures. Hydrogen embrittlement can be responsible for undesired releases with potentially catastrophic consequences. This study evaluates the safety of existing European natural gas pipelines for hydrogen transport through machine learning tools. The material susceptibility to hydrogen embrittlement is predicted under different working conditions in order to prevent loss of material integrity and eventual releases. This study aims at bridging the gap between safety and material science, as it can optimize predictive maintenance of hydrogen pipelines, thus promoting the widespread utilization of hydrogen in the forthcoming years.

Hydrogen has the potential to promote sustainable road transport in the forthcoming years, thus significantly reducing the human impact on the environment. This energy carrier can be produced by renewable energy through water electrolysis and used in fuel cell-powered vehicles (FCVs) with elevated efficiency and no pollutant emissions. The number of FCVs being used around the world is rapidly increasing, reaching 34,804 vehicles and 540 refueling stations by the end of 2020. Nevertheless, hydrogen is highly flammable and can permeate and embrittle most metallic materials, making its containment extremely challenging. A leak in a hydrogen refueling station can rapidly escalate to a major disaster if not promptly detected and addressed. In this perspective, gas sensors play a critical role in detecting leakages and undesired hydrogen releases. When selecting a hydrogen gas detector, it is important to consider the environmental conditions in which it is expected to operate, its performance, reliability, and cost, as well as the optimal positioning within the refueling station. This study analyzes several hydrogen releases from a high-pressure storage tank to optimize sensor positioning, given a certain detection probability. This research contributes towards advancing the modelling of safety barriers in hydrogen refueling stations considering accident scenarios. In this vein, this study aims at expanding the current knowledge of facility operators and stakeholders for related risks, thus enabling the widespread utilization of hydrogen in road transport.

Hydrogen is widely considered a promising energy carrier capable of mitigating human environmental impact. Nevertheless, safety aspects represent one of the major bottlenecks for the widespread utilization of hydrogen technologies. Industrial equipment operating in hydrogen environments is prone to hydrogen-induced damages, which may manifest through a reduction of mechanical properties, fracture toughness, and fatigue performance. They may cause component failures at stress levels significantly below the design level, therefore determining loss of containment. The occurrence of hydrogen embrittlement (HE) relies on the synergy of several factors, such as hydrogen concentration, operating conditions, level of internal and applied stress, microstructure and chemical composition of the material. However, the interlinked dependence of these factors makes a direct and clear evaluation challenging, subsequently creating serious difficulties in planning inspection and maintenance activities. In this study, a comprehensive review of the experimental data of tensile tests carried out in hydrogen was performed and analyzed through an advanced machine learning approach. This study can provide critical insights into the susceptibility to hydrogen embrittlement for several materials operating under different environmental conditions. In particular, the Embrittlement Index was estimated and used as determining parameter to predict the likelihood of component failures. The model demonstrated accurate and reliable predicting capabilities. The outcome of this study can increase the understanding of hydrogen-induced material damages and facilitate decision-making processes in planning the inspection and maintenance of hydrogen technologies.

Hydrogen is considered a promising energy carrier to achieve the ambitious target of a zero-emission society in the forthcoming years. Despite its environmental advantages, hydrogen-induced material damages represent a serious safety concern. Hence, inspection and maintenance activities must be performed to guarantee the equipment's integrity. The risk-based inspection (RBI) is the most beneficial methodology for inspection planning but has never been adopted for components operating in hydrogen environments. The probability of failure of each piece of equipment is quantified through the definition of the damage factor, a parameter that accounts for the damage mechanism likely to occur. Hydrogen embrittlement (HE) is the main active degrading mechanism in equipment exposed to hydrogenated environments; if not appropriately accounted for, it can cause failures at unexpectedly low stress levels. This study aims to bridge a gap in knowledge by proposing a qualitative methodology to assess the degradation of equipment operating in hydrogenated environments and potentially subjected to HE. The environmental severity is estimated based on the operating conditions, while the material’s susceptibility depends on microstructure, strength, and adoption of post-weld heat treatments. This study could set the basis for the application of the RBI methodology to industrial equipment for producing, handling, and storing hydrogen. Hence, it will facilitate the inspection and maintenance of emerging hydrogen technologies.

Hydrogen has not only the potential of tackling climate-related issues by replacing fossil fuels, but it also plays a main role in the energy transition which will have several geopolitical implications. According to the International Renewable Energy Agency (IRENA), relations between countries and communities will be transformed by “a new energy age” changing the concept of power, security, energy independence and prosperity. For these reasons, the interest in hydrogen recently skyrocketed as shown by the hydrogen strategies developed by many countries in the world. This will result in a considerable increase of hydrogen produced, stored, and consumed worldwide in the near future. Safety aspects must always be considered during the whole hydrogen lifecycle. The aim of this study is to pinpoint the consequences of failure for hydrogen technologies and the most common types of techniques developed and validated to assess them. Different types of models including theoretical and numerical ones were adopted to assess these consequences in the past. The advantages and drawbacks of these types of techniques are highlighted in this work. The intent is to provide critical insights to analysts carrying out the risk assessment in order to improve the overall safety of hydrogen technologies.

The adoption of hydrogen has been largely indicated as a feasible solution to support society in achieving its ambitious targets for a low-carbon future. The increased knowledge in liquefaction techniques has encouraged the study of technological solutions based on liquid hydrogen (LH2). Moreover, handling and distribution under cryogenic conditions represent attractive options due to the elevated energy density of LH2. Despite these advantages, the bottleneck for its widespread adoption is represented by safety aspects. Considering that an LH2 tank truck has a probability of suffering a car accident like all other road vehicles, an emergency auto-thermal burner has been designed in this work. This safety system has the purpose to dispose of the content of a tank truck to avoid the loss of containment. The disposal process includes the vaporization and pre-heating of the LH2, the mixing with ambient air, and its combustion. This device is completely self-supporting since the heat required to vaporize the LH2 is entirely provided by the combustion of the fuel itself. Firstly, the equation of energy balance around the burner was numerically solved to estimate the temperature of flue gases. Then, inner and outer heat transfer coefficients were determined for each section of the coiled-tube heat exchanger. Finally, the heat transfer surface was calculated. The spontaneous conversion between two spin isomers of hydrogen was considered. From the perspective of the heating process, the enthalpy of conversion represents an additional energy request. If the decrease of para-hydrogen fraction was neglected, the length of the heat exchanger would be significantly underestimated. Based on the obtained results, it is possible to conclude that the designed device can be transported on-site and started up easily, making it suitable for emergency response.