Hydrogen

This review sets out to investigate the detrimental impacts of hydrogen gas (H₂) on critical boiler components and provide appropriate state-of-the-art mitigation measures and future research directions to advance its use in industrial boiler operations. Specifically, the study focused on hydrogen embrittlement (HE) and high-temperature hydrogen attack (HTHA) and their effects on boiler components. The study provided a fundamental understanding of the evolution of these damage mechanisms in materials and their potential impact on critical boiler components in different operational contexts. Subsequently, the review highlighted general and specific mitigation measures, hydrogen-compatible materials (such as single-crystal PWA 1480E, Inconel 625, and Hastelloy X), and hydrogen barrier coatings (such as TiAlN) for mitigating potential hydrogen-induced damages in critical boiler components. This study also identified strategic material selection approaches and advanced approaches based on computational modeling (such as phase-field modeling) and data-driven machine learning models that could be leveraged to mitigate potential equipment failures due to HE and HTHA under elevated H₂ conditions. Finally, future research directions were outlined to facilitate future implementation of mitigation measures, material selection studies, and advanced approaches to promote the extensive and sustainable use of H₂ in industrial boiler operations. Full article

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. Full article

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. Full article

The transition to cleaner energy sources, particularly in hard-to-abate industrial sectors, often requires the gradual integration of new technologies. Hydrogen, crucial for decarbonization, is explored as a fuel in blended combustions. Blending or replacing fuels impacts combustion stability and heat transfer rates due to differing densities. An extensive literature review examines blended combustion, focusing on hydrogen/methane mixtures. While industrial burners claim to accommodate up to 20% hydrogen, theoretical support is lacking. A novel thermodynamic analysis methodology is introduced, evaluating methane/hydrogen combustion using the Wobbe index. The findings highlight practical limitations beyond 25% hydrogen volume, necessitating a shift to “totally hydrogen” combustion. Blended combustion can be proposed as a medium-term strategy, acknowledging hydrogen’s limited penetration. Higher percentages require burner and infrastructure redesign. Full article

The maritime industry is a major source of greenhouse gas (GHG) emissions, largely due to ships running on fossil fuels. Transitioning to hydrogen-powered marine transportation in the Mediterranean Sea requires the development of a network of hydrogen refueling stations across the region to ensure a steady supply of green hydrogen. This paper explores the technoeconomic viability of harnessing wave energy from the Mediterranean Sea to produce green hydrogen for hydrogen-powered ships. Four promising island locations—near Sardegna, Galite, Western Crete, and Eastern Crete—were selected based on their favorable wave potential for green hydrogen production. A thorough analysis of the costs associated with wave power facilities and hydrogen production was conducted to accurately model economic viability. The techno-economic results suggest that, with anticipated cost reductions in wave energy converters, the levelized cost of hydrogen could decrease to as low as 3.6 €/kg, 4.3 €/kg, 5.5 €/kg, and 3.9 €/kg for Sardegna, Galite, Western Crete, and Eastern Crete, respectively. Furthermore, the study estimates that, in order for the hydrogen-fueled ships to compete effectively with their oil-fueled counterparts, the levelized cost of hydrogen must drop below 3.5 €/kg. Thus, despite the competitive costs, further measures are necessary to make hydrogen-fueled ships a viable alternative to conventional diesel-fueled ships. Full article

H₂ is considered a practical substitute for fossil fuels, especially for transportation by road and air, created either from fossil fuels or through the process of electrolysis of water. Research questions were included based on numerous research and the analysis of articles. The cost analysis of H₂ processes, techno-economic hurdles in commercialization, and the economic comparison of various H₂-production methods were the basis for the study of papers. The current research examines the different methods of thermochemical, biological, and electrochemical processes utilized in converting biomass into hydrogen. The benefits, constraints, and significant enhancements of every procedure are outlined. The examination assesses the cost of production, the level of technology readiness, and the potential for scalability. Thermochemical techniques, such as gasification and steam reforming, are effective at producing hydrogen. Steam gasification is perfect for moist and dry biomass in the absence of an oxidizing agent. Dark fermentation is more efficient for biological conversion because it requires less energy. Moreover, the electrochemical procedure is viable for biomass. Thermochemical treatment is significantly more advanced than biological or electrochemical treatment when it comes to scaling opportunities based on comparisons of current processes. The results of this research show that biomass–hydrogen processes have the potential for increasing H₂ production, but further enhancements are needed to produce larger quantities for competitiveness. Full article

Sustainable technologies to replace current fossil solutions are essential to meet future CO₂ emission reduction targets. Therefore, this paper compares key performance indicators of a hydrogen- and a methane-flame-fired crucible furnace with computational fluid dynamics simulations at identical firing powers, aiming to fully decarbonize the process. Validated numerical models from the literature were used to compare temperatures, radiation fields, radiation parameters and heat transfer characteristics. As a result, we observed higher combustion temperatures and a 19.0% higher fuel utilization rate in the hydrogen case, indicating more efficient operating modes, which could be related to the increased radiant heat flux and temperature ranges above 1750 K. Furthermore, higher scattering of the heat flux distribution on the crucible surface could be determined indicating more uneven melt bath temperatures. Further research could focus on quantifying the total fuel consumption required for the heating up of the furnace, for which a transient numerical model could be developed. Full article

This paper investigated the opportunities and challenges of integrating ports into hydrogen (H₂) supply chains in the context of Australia and Japan because they are leading countries in the field and are potential leaders in the upcoming large-scale H₂ trade. Qualitative interviews were conducted in the two countries to identify opportunities for H₂ ports, necessary infrastructure and facilities, key factors for operations, and challenges associated with the ports’ development, followed by an online survey investigating the readiness levels of H₂ export and import ports. The findings reveal that there are significant opportunities for both countries’ H₂ ports and their respective regions, which encompass business transition processes and decarbonisation. However, the ports face challenges in areas including infrastructure, training, standards, and social licence, and the sufficiency and readiness levels of port infrastructure and other critical factors are low. Recommendations were proposed to address the challenges and barriers encountered by H₂ ports. To optimise logistics operations within H₂ ports and facilitate effective integration of H₂ applications, this paper developed a user-oriented working process framework to provide guidance to ports seeking to engage in the H₂ economy. Its findings and recommendations contribute to filling the existing knowledge gap pertaining to H₂ ports. Full article

This study proposes a combination system consisting of a biogas dry reforming reactor and a solid oxide fuel cell (SOFC). Since biogas dry reforming is an endothermic reaction, this study adopted a membrane reactor operated due to the non-equilibrium state with H₂ separation from the reaction space. This study aimed to clarify the performance of the Ni/Cr/Ru catalyst using a biogas dry reforming membrane reactor. Additionally, this study also undertook a comparison of the performance of the Ni/Cr/Ru catalyst with that of the Ni/Cr catalyst. The impact of operation temperature, the molar ratio of CH₄:CO₂, the differential pressure between the reaction chamber and the sweep chamber, and the introduction of a sweep gas on the performance of the biogas dry reforming membrane reactor using a Pd/Cu membrane and a Ni/Cr/Ru catalyst was examined. The concentration of H₂ using the Ni/Cr/Ru catalyst was greater than that using the Ni/Cr catalyst by 2871 ppmV for the molar ratio of CH₄:CO₂ = 1.5:1 at the reaction temperature of 600 °C and the differential pressure of 0 MPa without a sweep gas in particular. Under this condition, CH₄ conversion, H₂ yield, and thermal efficiency were 67.4%, 1.77 × 10⁻²%, and 0.241%, respectively. Full article

Poly(vinyl acetate) nanofibers doped with PdS-ZnS nanoparticles (PdS-ZnS/PVAc nanofibers) were fabricated via an electrospinning technique. PdS-ZnS nanoparticles were in situ synthesized by adding (NH₄)₂S solution to poly(vinyl acetate)/zinc acetate/palladium acetate solution. Electrospinning of the formed colloidal solution led to the formation of poly(vinyl acetate) nanofibers containing uniformly distributed PdS-ZnS nanoparticles. The prepared samples were characterized by field emission scanning electron microscopy, X-ray diffraction, transmission electron microscopy and Fourier transform infrared spectroscopy. In photocatalytic activity investigation, the PdS-ZnS/PVAc nanofibers showed remarkably enhanced performance towards water photosplitting under solar irradiation compared to the ZnS/PVAc nanofibers. This enhanced performance is attributed to the synergistic effects of heterostructured PdS-ZnS nanoparticles, which can improve photogenerated charge migration and solar light absorption. Full article

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. Full article

The local binding and migration behavior of the proton defect in cubic yttria-stabilized zirconia (YSZ) is studied by first-principles calculations and muon-spin spectroscopy (μSR) measurements. The calculations are based on density-functional theory (DFT) supplemented with a hybrid-functional approach with the proton defect embedded in quasi-random supercells of 10.3 mol% yttria content, where the yttrium–zirconium substitutional defects are charge compensated by oxygen vacancies. Representative migration pathways for the proton comprising both transfer and bond reorientation modes are analysed and linked to the underlying microstructure of the YSZ lattice. The μSR data show the evolution of the diamagnetic fraction corresponding to the muon-isotope analogue with an activation energy of diffusion equal to 0.17 eV. Comparisons between the calculations and the experiment allow an assessment of the character of the short-range migration of the proton particle in cubic YSZ. Full article

Proton-exchange membrane fuel cells (PEMFCs) are highly regarded as a promising technology for renewable energy generation; however, the environmental burden in their life cycle is a subject of concern. This study aimed to assess the environmental impact of producing a 1 kW PEMFC by a well-detailed cradle-to-gate evaluation, using mid-point and end-point impact assessment methods. The environmental impacts are related to the extraction of raw materials, consumption of energy, and transportation processes. Mid-point analysis shows that raw materials extraction and processing have a significant share in some impacts, including freshwater eutrophication, human carcinogenic toxicity, and terrestrial acidification. On the other hand, the energy consumed in fuel cell production plays a significant role in the impact categories of fossil resource depletion and global warming. The highest impact is attributed to the human health end-point analysis (0.000866 DALY), followed by the damage to ecosystems (1.04 × 10⁻⁶ species/yr) and resources (USD2013 6.16844). Normalization results further strengthen the importance of human health impacts and the necessity to solve problems regarding toxicity. The results of this work can provide directions toward enhancing the environmental sustainability of PEMFC technology and present a case for adopting a holistic approach to sustainability by looking across the life cycle of the technology. Full article

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. Full article

This review explores recent advancements in hydrogen gas (H₂) safety through the lens of artificial intelligence (AI) techniques. As hydrogen gains prominence as a clean energy source, ensuring its safe handling becomes paramount. The paper critically evaluates the implementation of AI methodologies, including artificial neural networks (ANN), machine learning algorithms, computer vision (CV), and data fusion techniques, in enhancing hydrogen safety measures. By examining the integration of wireless sensor networks and AI for real-time monitoring and leveraging CV for interpreting visual indicators related to hydrogen leakage issues, this review highlights the transformative potential of AI in revolutionizing safety frameworks. Moreover, it addresses key challenges such as the scarcity of standardized datasets, the optimization of AI models for diverse environmental conditions, etc., while also identifying opportunities for further research and development. This review foresees faster response times, reduced false alarms, and overall improved safety for hydrogen-related applications. This paper serves as a valuable resource for researchers, engineers, and practitioners seeking to leverage state-of-the-art AI technologies for enhanced hydrogen safety systems. Full article

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. Full article

Onboard hydrogen storage tanks are currently fitted with thermally activated pressure relief devices (TPRDs), enabling hydrogen to blowdown in the event of fire. For release diameters below the critical diameter, the flame from the TPRD may blow-out during a pressure drop. Flame blow-outs pose a safety concern for an indoor or covered environment, e.g., a garage or carpark, where hydrogen can accumulate and deflagrate. This study describes the application of a validated computational fluid dynamics (CFD) model to simulate the dynamic flame behaviour from a TPRD designed to exclude its blow-out. The dynamic behaviour replicates a real scenario. Flame behaviour during tank blowdown through two TPRDs with different nozzle geometries is presented. Simulations confirm flame blow-out for a single-diameter TPRD of 0.5 mm during tank blowdown, while the double-diameter nozzle successfully excludes flame blow-out. The pressure at which the flame blow-out process is initiated during blowdown through a single-diameter nozzle was predicted. Full article

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 p_eq > 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. Full article

Water is a potential green source for the generation of clean elemental hydrogen without contaminants. One of the most convenient methods for hydrogen generation is based on the oxidation of different metals by water. The inspection of the catalytic activity toward hydrogen formation from water performed in this study was carried out using four different metals, namely, zinc, magnesium, iron, and manganese. The process is catalyzed by in situ-generated nickel nanoparticles. The zinc–water system was found to be the most effective and exhibited 94% conversion in 4 h. The solid phase in the latter system was characterized by PXRD and SEM techniques. Several blank tests provided a fundamental understanding of the role of each constituent within the system, and a molecular mechanism for the catalytic cycle was proposed. Full article