This review examines the central role of hydrogen, particularly green hydrogen from renewable sources, in the global search for energy solutions that are sustainable and safe by design. Using the hydrogen square, safety measures across the hydrogen value chain—production, storage, transport, and utilisation—are discussed, thereby highlighting the need for a balanced approach to ensure a sustainable and efficient hydrogen economy. The review also underlines the challenges in safety assessments, points to past incidents, and argues for a comprehensive risk assessment that uses empirical modelling, simulation-based computational fluid dynamics (CFDs) for hydrogen dispersion, and quantitative risk assessments. It also highlights the activities carried out by our research group SaRAH (Safety, Risk Analysis, and Hydrogen) relative to a more rigorous risk assessment of hydrogen-related systems through the use of a combined approach of CFD simulations and the appropriate risk assessment tools. Our research activities are currently focused on underground hydrogen storage and hydrogen transport as hythane.

Salt caverns are accepted as an ideal solution for high-pressure hydrogen storage. As well as considering the numerous benefits of the realization of underground hydrogen storage (UHS), such as high energy densities, low leakage rates and big storage volumes, risk analysis of UHS is a required step for assessing the suitability of this technology. In this work, a preliminary quantitative risk assessment (QRA) was performed by starting from the worst-case scenario: rupture at the ground of the riser pipe from the salt cavern to the ground. The influence of hydrogen contamination by bacterial metabolism was studied, considering the composition of the gas contained in the salt caverns as time variable. A bow-tie analysis was used to highlight all the possible causes (basic events) as well as the outcomes (jet fire, unconfined vapor cloud explosion (UVCE), toxic chemical release), and then, consequence and risk analyses were performed. The results showed that a UVCE is the most frequent outcome, but its effect zone decreases with time due to the hydrogen contamination and the higher contents of methane and hydrogen sulfide.

In the context of the near-future hydrogen economy, ammonia is regarded as one of the most promising hydrogen carriers in the short-to-medium term. As part of the broader transition to a new energy paradigm, the well-established and extensive ammonia infrastructure can serve as a platform for green hydrogen transportation, storage, and utilization. This study analyzes various process configurations integrated with different types of fuel cells for ammonia utilization through Aspen Plus simulations. The evaluation focuses on overall energetic efficiency (ranging from 31.20 to 51.50% depending on the adopted configuration), autothermality (42.00 to 100.00%, based on the adopted process configuration), and emissions from external heat sources (0.03-0.07 kg_CO2/kWh). Assessments are conducted parametrically across different fuel cell efficiencies (50.0-65.0%). Results suggest that high-temperature PEMFC and direct ammonia solid oxide fuel cells (SOFCs) offer a balance between overall efficiency (40.2-51.5 and 35.00-52.0%, respectively) and feasibility of achieving autothermal operations under nitrogen dilution (up to 25.0%). Considering technological maturity and operational lifespan, high-temperature PEMFCs and SOFCs emerge as a promising component for such integrated systems.

Energy and environmental issues are of great importance in the present era. The transition to renewable energy sources necessitates technological, political, and behavioral transformations. Hydrogen is a promising solution, and many countries are investing in the hydrogen economy. Global demand for hydrogen is expected to reach 120 million tonnes by 2024. The incorporation of hydrogen for efficient energy transport and storage and its integration into the transport sector are crucial measures. However, to fully develop a hydrogen-based economy, the sustainability and safety of hydrogen in all its applications must be ensured. This work describes and compares different technologies for hydrogen production, storage, and utilization (especially in fuel cell applications), with focus on the research activities under study at SaRAH group of the University of Naples Federico II. More precisely, the focus is on the production of hydrogen from bio-alcohols and its storage in formate solutions produced from renewable sources such as biomass or carbon dioxide. In addition, the use of materials inspired by nature, including biowaste, as feedstock to produce porous electrodes for fuel cell applications is presented. We hope that this review can be useful to stimulate more focused and fruitful research in this area and that it can open new avenues for the development of sustainable hydrogen technologies.

Several phenomena (e.g., initial turbulence level, overdriving, underdriving, etc.) affect the measurement of dust explosion parameters in the 20 L and 1 m³ standard test vessels. Estimating the role of each phenomenon is crucial to understand the discrepancies observed over the years between the data collected using these vessels. In this work, we focus on the role of the pyrotechnic ignitors on the pressure trend and the temperature distribution. We run explosion tests in the 20 L vessel to measure the pressure–time history generated by the explosion of pyrotechnic ignitors. Moreover, we performed CFD simulations to simulate the spatial/temporal evolution of the temperature map from the hot core due to the igniter explosion toward the vessel walls. The explosion of the pyrotechnic ignitors shows a significant increase of pressure in the 20 L vessel, suggesting that flame propagation is occurring inside the vessel. Furthermore, the localized increase of temperature due to the ignitor explosions, diffuse, and then uniformize much more rapidly in the 20 L vessel than in the 1 m³ vessel. The flame propagation generated by the ignitors is very relevant in the 20 L sphere leading to the overdriving phenomenon. This result justifies the fact that for many organic dusts, the deflagration index values measured in the 20 L are much higher than those measured in the 1 m³ vessel. CFD simulations show that the hot core generated by the ignitors dissipate much faster in the 20 L vessel than in the 1 m³ vessel, due to the higher turbulence level of the smaller vessel. Therefore, dusts whose combustion is controlled by particle heating are more prone to sustain combustion in the 1 m³ than in the 20 L vessel.