Publications

The need to reduce the carbon footprint of conventional energy sources has made green hydrogen a promising solution for the energy transition. The most environmentally friendly way to produce hydrogen is through water-based production using renewable energy. However the availability of fresh water is limited so switching to wastewater instead of fresh water is the key solution to this problem. In response to this issue the present review reports the main findings of the research studies dealing with the feasibility of hydrogen production from wastewater using various technologies including biological electrochemical and advanced oxidation routes. These methods have been studied in a large number of experiments with the aim of investigating and improving the potential of each method. On the other hand the maturity of solar energy technologies has led researchers to focus on the possibility of harnessing this source and combining it with wastewater treatment techniques for the production of green hydrogen. Therefore the present review pays special attention to solar driven hydrogen production from wastewater by highlighting the potential of several technologies for simultaneous water treatment and green hydrogen production from wastewater. Recent results limitations challenges possible improvements and techno-economic assessments reported by several authors as well as future directions of research and industrial implementation in this field are reported.

With the rising potential of underground hydrogen storage (UHS) in depleted oil and gas reservoirs or deep saline aquifers questions remain regarding changes to geological units due to interaction with injected hydrogen. Of particular importance is the integrity of potential caprocks/seals with respect to UHS. The results of this study show significant dissolution of calcite fossil fragments in claystone caprock proxies that were treated with a combination of hydrogen and 10 wt% NaCl brine. This is the first time it has been experimentally observed in claystones. The purpose of this short communication is to document the initial results that indicate the potential alteration of caprocks with injected hydrogen and to further highlight the need for hydrogen-specific studies of caprocks in areas proposed for UHS.

Hydrogen (H2) offers a green medium for storing the excess from renewables production instead of dumping it thus being crucial to decarbonisation efforts. Hydrogen also offers a storage medium for the grid’s cheap electricity to be used during grid peak demand or grid power cutoffs. Funded by the Scottish Government’s Emerging Energy Technologies this paper presents the design and performance analysis of a hydrogen uninterruptible power supply (H2GEN) for Cygnas Solutions Ltd. which is intended to enable continuity of supply in the residential sector while eradicating the need for environmentally and health risky lead–acid batteries and diesel generator backup. This paper presents the design optimal sizing and analysis of two H2Gen architectures one powered by the grid alone and the other powered by both the grid and a renewable (PV) source. By developing a model of each architecture in the HOMER space and using residential location weather data the home yearly load–demand profile and the grid yearly power outages profile in the developed models the optimal sizing of each H2Gen design was realised by minimising the costs while ensuring the H2Gen meets the home power demand during grid outages To enable HOMER to optimise its selection the sizes technical specifications and costs of all the market-available H2GEN components were added in the HOMER search space. Moreover the developed models were also used in assessing the sensitivity of the simulation outputs to several changes in the modelled system design and settings. Using a residential home with frequent power outages in New Delhi India as a case study it was found that the optimal sizing of H2Gen Architecture 1 is comprised of a 2 kW electrolyser a 0.2 kg type-I tank and a 2 kW water-cooled fuel cell directly connected to the AC bus offering an operational lifetime of 14.3 years. It was also found that the optimal sizing of Architecture 2 is comprised of a 1 kV PV utilised with the same 2 kW electrolyser 0.2 kg type-I tank and 2 kW water-cooled fuel cell connected to the AC bus. While the second design was found to have a higher capital cost due to the added PV it offered a more cost-effective and environmentally friendly architecture which contributes to the ongoing energy transition. This paper further investigated the capacity expansion of each H2GEN architecture to meet higher load demands or increased grid power outages. From the analysis of the simulation results it has been concluded that the most feasible and cost-effective H2GEN system expansion for meeting increased power demands or increased grid outages can be realised by using the developed models for optimally sizing the expanded H2Gen on a case-by-case basis because the increase in these profiles is highly time-dependent (for example an increased load demand or increased grid outage in the morning can be met by the PV while in the evening it must be met by the H2GEN). Finally this paper investigated the impact of other environmental variables such as the temperature and relative humidity on the H2GEN’s performance and provided further insights into increasing the overall system efficiency and cost benefit through utilising the H2GEN’s exhaust heat in the home space for heating/cooling and selling the electrolyser exhaust’s O2 as a commodity.

In the current context of increasing demand for clean transportation hydrogen usage in internal combustion engines (ICEs) represents a viable solution to abate all engine-out criteria pollutants and almost zeroing CO2 tailpipe emissions. Indeed the wider flammability limits thanks to the higher flame propagation speed and the lower minimum ignition energy compared with conventional fuels extend the stable combustion regime to leaner mixtures thus allowing high thermal efficiency keeping under control the NOX emissions. To fully exploit the potential of hydrogen as a fuel and to avoid undesired abnormal combustion processes a deep characterization of the combustion process is needed. With this aim a 6-cylinder 12.9-L heavy-duty engine was converted from a port-fuel injected compressed natural gas to a direct injected hydrogen spark ignition one. A wide experimental campaign was carried out consisting of several sweeps of relative air-fuel ratios spark advances and injection timings at different engine speeds and loads aiming to define a preliminary engine map. The effect of each calibration parameter at different engine load and speed has been analyzed through the combination of relevant combustion parameters as well as NOX emissions. The results have demonstrated the critical influence of the mixture inhomogeneity when the injection is retarded through the top dead center firing as indicated by the increase in NOX emissions and combustion variability. The analysis of the combustion timing has indicated the dependence of the optimal MFB50 on the relative air-fuel ratio. Lastly the analysis of 200 consecutive cycles for each operating condition has allowed the evaluation of the influence of the main calibration parameters on the cyclic variability thus providing further insights about the lean limit of hydrogen in ICE.

Water electrolysis using a proton exchange membrane (PEM) holds substantial promise to produce green hydrogen with zero carbon discharge. Although various techniques are available to produce hydrogen gas the water electrolysis process tends to be more cost-effective with greater advantages for energy storage devices. However one of the challenges associated with PEM water electrolysis is the accumulation of gas bubbles which can impair cell performance and result in lower hydrogen output. Achieving an in-depth knowledge of bubble dynamics during electrolysis is essential for optimal cell performance. This review paper discusses bubble behaviors measuring techniques and other aspects of bubble dynamics in PEM water electrolysis. It also examines bubble behavior under different operating conditions as well as the system geometry. The current review paper will further improve the understanding of bubble dynamics in PEM water electrolysis facilitating more competent inexpensive and feasible green hydrogen production.

The chances of a global hydrogen economy becoming a reality have increased significantly since the COVID pandemic and the war in Ukraine and for net zero carbon emissions. However intercontinental hydrogen transport is still a major issue. This study suggests transporting hydrogen as a gas at atmospheric pressure in balloons using the natural flow of wind to carry the balloon to its destination. We investigate the average wind speeds atmospheric pressure and temperature at different altitudes for this purpose. The ideal altitudes to transport hydrogen with balloons are 10 km or lower and hydrogen pressures in the balloon vary from 0.25 to 1 bar. Transporting hydrogen from North America to Europe at a maximum 4 km altitude would take around 4.8 days on average. Hydrogen balloon transportation cost is estimated at 0.08 USD/kg of hydrogen which is around 12 times smaller than the cost of transporting liquified hydrogen from the USA to Europe. Due to its reduced energy consumption and capital cost in some locations hydrogen balloon transportation might be a viable option for shipping hydrogen compared to liquefied hydrogen and other transport technologies.

To reduce carbon dioxide emissions from the steel industry efforts are made to introduce a steelmaking route based on hydrogen reduction of iron ore instead of the commonly used cokebased reduction in a blast furnace. Changing fundamental pieces of steelworks affects the functions of most every system unit involved and thus warrants the question of how such a transition could optimally take place over time and no rigorous attempts have until now been made to tackle this problem mathematically. This article presents a steel plant optimization model written as a mixed-integer non-linear programming problem where aging blast furnaces and basic oxygen furnaces could potentially be replaced with shaft furnaces and electric arc furnaces minimizing costs or emissions over a long-term time horizon to identify possible transition pathways. Example cases show how various parameters affect optimal investment pathways stressing the necessity of appropriate planning tools for analyzing diverse cases.

This work undertakes a techno‑economic comparative analysis of the design of photo‑ voltaic panel/wind turbine/electrolyzer‑H2 tank–fuel cell/electrolyzer‑H2 tank (configuration 1) and photovoltaic panel/wind turbine/battery/electrolyzer‑H2 tank (configuration 2) to supply electricity to a simulated house and a hydrogen‑powered vehicle on Jeju Island. The aim is to find a system that will make optimum use of the excess energy produced by renewable energies to power the hydrogen vehicle while guaranteeing the reliability and cost‑effectiveness of the entire system. In addition to evaluating the Loss of Power Supply Probability (LPSP) and the Levelized Cost of Energy (LCOE) the search for achieving that objective leads to the evaluation of two new performance indicators: Loss of Hydrogen Supply Probability (LHSP) and Levelized Cost of Hydrogen (LCOH). After anal‑ ysis for 0 < LPSP < 1 and 0 < LHSP < 1 used as the constraints in a multi‑objective genetic algorithm configuration 1 turns out to be the most efficient loads feeder with an LCOE of 0.3322 USD/kWh an LPSP of 0% concerning the simulated house load an LCOH of 11.5671 USD/kg for a 5 kg hydrogen storage and an LHSP of 0.0043% regarding the hydrogen vehicle load.

As the most attractive energy carrier hydrogen production through electro-chemical water splitting (EWS) is promising for resolving the serious environ-mental problems derived from the rapid consumption of fossil fuels globally. Theproton exchange membrane water electrolyzer (PEMWE) is one of the mostpromising EWS technologies and has achieved great advancements. To offer atimely reference for the progress of the PEMWE system the latest advancementsand developments of PEMWE technology are systematically reviewed. The keycomponents including the electrocatalysts PEM and porous transport layer(PTL) as well as bipolar plate (BPP) are first introduced and discussed followedby the membrane electrode assembly and cell design. The highlights are put onthe design of the electrocatalyst and the relationship of each component on theperformance of the PEMWE. Moreover the current challenges and future per-spectives for the development of PEMWE are also discussed. There is a hope thatthis review can provide a timely reference for future directions in PEMWEchallenges and perspectives.

Hydrogen energy has been proposed as a reliable and sustainable source of energy which could play an integral part in demand for foreseeable environmentally friendly energy. Biomass fossil fuels waste products and clean energy sources like solar and wind power can all be employed for producing hydrogen. This comprehensive review paper provides a thorough overview of various hydrogen storage technologies available today along with the benefits and drawbacks of each technology in context with storage capacity efficiency safety and cost. Since safety concerns are among the major barriers to the broad application of H2 as a fuel source special attention has been paid to the safety implications of various H2 storage techniques. In addition this paper highlights the key challenges and opportunities facing the development and commercialization of hydrogen storage technologies including the need for improved materials enhanced system integration increased awareness and acceptance. Finally recommendations for future research and development with a particular focus on advancing these technologies towards commercial viability.

Carbon capture utilization and storage (CCUS) technology plays a pivotal role in China’s “Carbon Peak” and “Carbon Neutrality” goals. This approach offers low-carbon zero-carbon and even negative-carbon solutions. This paper employs bibliometric analysis using the Web of Science to comprehensively review global CCUS progress and discuss future development prospects in China. The findings underscore it as a prominent research focus attracting scholars from both domestic and international arenas. China notably leads the global landscape in terms of research paper output with the Chinese Academy of Sciences holding a prominent position in total published papers. The research predominantly centers on refining geological storage techniques and optimizing oil and gas recovery rates. Among the CCUS pathways enhanced oil recovery technology stands out due to its relative maturity and commercial applicability particularly within the conventional oil and gas reservoirs. The application potential of enhanced gas recovery technology especially in the Sichuan and Ordos Basins in China necessitates robust research and demonstration efforts. Within China’s current energy landscape “Blue Hydrogen” emerges as the primary solution for hydrogen production in conjunction with CCUS technology. The underground coal gasification approach holds significant promise as a hydrogen production avenue albeit with inherent ecological and environmental challenges tied to geological storage that require meticulous consideration. The establishment of effective risk identification and evaluation methodologies for geological storage is imperative. The trajectory ahead involves a strategic convergence of policy technology and market dynamics to enhance China’s CCUS policy framework legislative framework standardization initiatives and pioneering technological advancements. These collective efforts converge to outline an exclusive development pathway in China. This study assumes a pivotal role in accelerating CCUS technology research and deployment enhancing oil and gas recovery efficiency and ultimately realizing the overarching goals of a “Dual Carbon” future.

Zero-carbon-dioxide-emitting hydrogen-powered aircraft have in recent decades come back on the stage as promising protagonists in the fght against global warming. The main cause for the reduced performance of liquid hydrogen aircraft lays in the fuel storage which demands the use of voluminous and heavy tanks. Literature on the topic shows that the optimal fuel storage solution depends on the aircraft range category but most studies disagree on which solution is optimal for each category. The objective of this research was to identify and compare possible solutions to the integration of the hydrogen fuel containment system on regional short/medium- and large passenger aircraft and to understand why and how the optimal tank integration strategy depends on the aircraft category. This objective was pursued by creating a design and analysis framework for CS-25 aircraft capable of appreciating the efects that diferent combinations of tank structure fuselage diameter tank layout shape venting pressure and pressure control generate at aircraft level. Despite that no large diferences among categories were found the following main observations were made: (1) using an integral tank structure was found to be increasingly more benefcial with increasing aircraft range/size. (2) The use of a forward tank in combination with the aft one appeared to be always benefcial in terms of energy consumption. (3) The increase in fuselage diameter is detrimental especially when an extra aisle is not required and a double-deck cabin is not feasible. (4) Direct venting has when done efciently a small positive efect. (5) The optimal venting pressure varies with the aircraft confguration performance and mission. The impact on performance from sizing the tank for missions longer than the harmonic one was also quantifed.

This paper aims at the development and validation of a computational fluid dynamic (CFD) model for simulations of the refuelling process through the entire equipment of the hydrogen refuelling station (HRS). The absence of such models hinders the design of inherently safer refuelling protocols for an arbitrary combination of HRS equipment hydrogen storage parameters and environmental conditions. The CFD model is validated against the complete process of refuelling lasting 195s in Test No.1 performed by the National Renewable Energy Laboratory (NREL). The test equipment includes high-pressure tanks of HRS pressure control valve (PCV) valves pipes breakaway hose and nozzle all the way up to three onboard tanks. The model accurately reproduced hydrogen temperature and pressure through the entire line of HRS equipment. A standout feature of the CFD model distinguishing it from simplified models is the capability to predict temperature non-uniformity in onboard tanks a crucial factor with significant safety implications.

Green hydrogen holds potential for decarbonizing the energy sector but high production costs are a major barrier. This study provides a comprehensive techno-economic-financial-environmental analysis of PV-based grid-connected hydrogen production plants targeting hard-to-abate industries having constant hydrogen demand across all Italy. Using real hourly data the Multi Energy System Simulator (MESS) an in-house developed rule-based tool was employed and integrated with Genetic Algorithm for optimal plant sizing. The aim is to minimize the Levelized Cost of Hydrogen (LCOH) while complying with regulatory frameworks for green hydrogen incentives access. Key findings show that hydrogen storage is more advantageous than battery storage for supply-side flexibility and the optimal PV-to-electrolyzer size ratio ranges from 1.8 in Southern Italy to 2.1 in Northern Italy with hydrogen tank designed for daily storage. Considering photovoltaic electrolyzer and battery aging models grid dependence increases by 60 % when comparing the first and worst year of operation and leads to a 7 % increase in LCOH. Transitioning from the strictest (hourly) to the least stringent (annual) temporal correlation increases certified green hydrogen by 22 % while LCOH decreases by only 3 % suggesting that the environmental benefits of stringent temporal requirements outweigh their moderate economic drawbacks. These findings underscore the need for additional national-level incentives to allow the deployment of this technology and achieving cost parity with grey hydrogen.

The scientific and industrial communities worldwide have recently achieved impressive technical advances in developing innovative electrocatalysts and electrolysers for water and seawater splitting. The viability of water electrolysis for commercial applications however remains elusive and the key barriers are durability cost performance materials manufacturing and system simplicity especially with regard to running on practical water sources like seawater. This paper therefore primarily aims to provide a concise overview of the most recent disruptive water-splitting technologies and materials that could reshape the future of green hydrogen production. Starting from water electrolysis fundamentals the recent advances in developing durable and efficient electrocatalysts for modern types of electrolysers such as decoupled electrolysers seawater electrolysers and unconventional hybrid electrolysers have been represented and precisely annotated in this report. Outlining the most recent advances in water and seawater splitting the paper can help as a quick guide in identifying the gap in knowledge for modern water electrolysers while pointing out recent solutions for cost-effective and efficient hydrogen production to meet zero-carbon targets in the short to near term.

In order to realize carbon mitigation and the efficient utilization of waste biogas the biogas-to-methanol process is an important method. The syngas produced by the conventional biogas reforming technology is rich in CO2 and CO whereas it is poor in hydrogen. Therefore additional H2 is introduced into the system to adjusted the syngas ratio promoting the efficient conversion of the biogas. However the use of traditional H2 production technologies generally results in considerable carbon emissions. Given these points low-carbon H2 production technologies namely methane pyrolysis technology and chemical looping reforming technology are integrated with the biogas-to-methanol process to enhance carbon conversion carbon reduction and cost-saving potentials. Comprehensive technical and economic comparisons of the integrated processes are conducted. The process coupled with chemical looping reforming technology has a higher carbon conversion efficiency (73.52%) and energy efficiency (70.41%) and lower unit carbon emissions (0.73 t CO2/t methanol). Additionally the process coupled with methane pyrolysis technology has higher product revenue whereas that including chemical looping reforming technology has a lower net production cost (571.33 USD/t methanol). In summary the novel chemical looping reforming technology provides a cleaner and more sustainable pathway with which to promote the efficient conversion of biogas into methanol.

This study presents sector-coupled PyPSA-Earth: a novel global open-source energy system optimization model that incorporates major demand sectors and energy carriers in high spatial and temporal resolution to enable energy transition studies worldwide. The model includes a workflow that automatically downloads and processes the necessary demand supply and transmission data to co-optimize investment and operation of energy systems of countries or regions of Earth. The workflow provides the user with tools to forecast future demand scenarios and allows for custom user-defined data in several aspects. Sector-coupled PyPSA-Earth introduces novelty by offering users a comprehensive methodology to generate readily available sector-coupled data and model of any region worldwide starting from raw and open data sources. The model provides flexibility in terms of spatial and temporal detail allowing the user to tailor it to their specific needs. The capabilities of the model are demonstrated through two showcases for Egypt and Brazil. The Egypt case quantifies the relevant role of PV exceeding 35 GW and electrolysis in Suez and Damietta regions for meeting 16% of the EU hydrogen demand. Complementarily the Brazil case confirms the model’s ability in handling hydrogen planning infrastructure including repurposing of existing gas networks which results in 146 M€ lower costs than building new pipelines. The results prove the suitability of sector-coupled PyPSA-Earth to meet the needs of policymakers developers and scholars in advancing the energy transition. The authors invite the interested individuals and institutions to collaborate in the future developments of the model within PyPSA meets Earth initiative.

The yield of photovoltaic hydrogen production systems is influenced by a number of factors including weather conditions the cleanliness of photovoltaic modules and operational efficiency. Temporal variations in weather conditions have been shown to significantly impact the output of photovoltaic systems thereby influencing hydrogen production. To address the inaccuracies in hydrogen production capacity predictions due to weather-related temporal variations in different regions this study develops a method for predicting photovoltaic hydrogen production capacity using the long short-term memory (LSTM) neural network model. The proposed method integrates meteorological parameters including temperature wind speed precipitation and humidity into a neural network model to estimate the daily solar radiation intensity. This approach is then integrated with a photovoltaic hydrogen production prediction model to estimate the region’s hydrogen production capacity. To validate the accuracy and feasibility of this method meteorological data from Lanzhou China from 2013 to 2022 were used to train the model and test its performance. The results show that the predicted hydrogen production agrees well with the actual values with a low mean absolute percentage error (MAPE) and a high coefficient of determination (R2 ). The predicted hydrogen production in winter has a MAPE of 0.55% and an R2 of 0.985 while the predicted hydrogen production in summer has a slightly higher MAPE of 0.61% and a lower R2 of 0.968 due to higher irradiance levels and weather fluctuations. The present model captures long-term dependencies in the time series data significantly improving prediction accuracy compared to conventional methods. This approach offers a cost-effective and practical solution for predicting photovoltaic hydrogen production demonstrating significant potential for the optimization of the operation of photovoltaic hydrogen production systems in diverse environments.

With growing concerns about carbon emissions and the need for decarbonization hydrogen is a promising hy pothesis for the replacement of fossil fuels. Blending hydrogen with natural gas and using existing natural gas transmission networks is a strategy that could reduce carbon emissions. However a significant challenge with using hydrogen in transmission networks is its potential to cause embrittlement compromising the structural integrity of pipelines. This paper provides an overview of the complexities involved in blending and injecting hydrogen into natural gas transmission pipelines and discusses methods to enhance system performance and mitigate these challenges by reviewing studies focused on these topics. The paper highlights the multidisciplinary nature of hydrogen injection into natural gas pipelines and discusses ongoing research efforts to address this issue. The study shows significant progress in the technological development of injection strategies mixing solutions sensors and materials. Still challenges remain regarding experimental work sensors capable of operating in high-pressure transmission pipelines and material solutions such as coatings that can inhibit embrittlement and be applied in-situ in operating pipelines. Although numerous numerical studies exist experimental research on mixing and injection systems remains limited. While real-time measurement tech nology is advancing more innovation is needed for high-pressure environments. New coatings and linings have been developed to mitigate embrittlement but their application in operating pipelines requires further investigation.

Nowadays integrating renewable energy sources (RESs) poses significant challenges due to the deterioration of performance indices especially in cold-climate unbalanced microgrids. Beyond network unbalance harsh conditions with low irradiance weak wind speeds and low temperatures necessitate hydrogen storage systems (HSSs) to address seasonal mismatches between RES generation and demand. This paper proposes a two-stage multi-timescale planning framework that integrates RESs plug-in electric vehicles (PEVs) battery energy storage systems (BESSs) seasonal HSSs and a dynamic demand response (DDR) program. In the short term BESSs are coordinated under slow and fast charging/discharging modes for responding to daily load shifting and peak shaving or sudden demand fluctuations. Smart converters with active/reactive power control are equipped with RES and BESS for local voltage regulation. Furthermore the proposed DDR program which combines load reduction and valley filling strategies enables consumer flexibility based on real-time market signals across seasonal variations. Seasonal HSSs are designed to store excess hydrogen produced from RESs for long-term use across different seasons. The proposed strategy is validated in two stages. The first stage guarantees multitimescale coordination of BESSs seasonal HSSs and the DDR. In turn the second stage optimally plans RESs BESSs and HSSs in a unified manner to reduce voltage unbalance and line congestion while maximizing microgrid RES hosting capacity. Simulation results for six interconnected microgrids demonstrate a 12.5% reduction in voltage unbalance 21% alleviation of line congestion and a 108% increase in hosting capacity highlighting the effectiveness of the proposed planning approach for unbalanced RES-rich microgrids.

To reveal the influence mechanisms of seasonal climatic factors (wind speed wind direction temperature) and leakage direction on hydrogen dispersion and explosion behavior from single-source leaks at typical risk locations (hydrogen storage tanks compressors dispensers) in hydrogen refueling stations (HRSs) this work established a full-scale 1:1 three-dimensional numerical model using the FLACS v22.2 software based on the actual layout of an HRS in Xichang Sichuan Province. Through systematic simulations of 72 leakage scenarios (3 equipment types × 4 seasons × 6 leakage directions) the coupled effects of climatic conditions equipment layout and leakage direction on hydrogen dispersion patterns and explosion risks were quantitatively analyzed. The key findings indicate the following: (1) Downward leaks (−Z direction) from storage tanks tend to form large-area ground-hugging hydrogen clouds representing the highest explosion risk (overpressure peak: 0.25 barg; flame temperature: >2500 K). Leakage from compressors (±X/−Z directions) readily affects adjacent equipment. Dispenser leaks pose relatively lower risks but specific directions (−Y direction) coupled with wind fields may drive significant hydrogen dispersion toward station buildings. (2) Southeast/south winds during spring/summer promote outward migration of hydrogen clouds reducing overall station risk but causing localized accumulation near storage tanks. Conversely north/northwest winds in autumn/winter intensify hydrogen concentrations in compressor and station building areas. (3) An empirical formula integrating climatic parameters leakage conditions and spatial coordinates was proposed to predict hydrogen concentration (error < 20%). This model provides theoretical and data support for optimizing sensor placement dynamically adjusting ventilation strategies and enhancing safety design in HRSs.

In South Korea securing ground space for installing hydrogen refueling stations in urban areas is challenging due to limited ground space and high-density development. Safety concerns for hydrogen systems in enclosed urban environments also require careful consideration. To address this issue this study explored a method of undergrounding hydrogen infrastructure as a solution for urban hydrogen charging stations. This study examined the characteristics of hydrogen diffusion and concentration reduction under leakage conditions within a confined hydrogen infrastructure focusing on key safety systems including emergency shut-off valves (ESVs) and ventilation fans. We discovered that the ESV reduced hydrogen concentration by over 80%. Installing two or more ventilation fans arranged horizontally improves airflow and enhances ventilation efficiency. Moreover increasing the number of fans reduces stagnant zones within the space effectively lowering the average hydrogen concentration.

Hydrogen fuel cell electric trucks and battery electric trucks can significantly contribute to the decarbonisation of the heavy-duty vehicles transport segment. Nonetheless a paucity of hydrogen refuelling and fast-charging stations can represent a hindrance to the development of zero-emission vehicles. This work aims to provide a techno-economic analysis with a view to comparing the costs of hydrogen refuelling and electric charging and evaluating their effects on the total cost of ownership of zero-emission trucks. Thus a comprehensive analysis has been conducted on off-site compressed (CH2) cryo-compressed subcooled hydrogen refuelling stations in conjunction with a fast-charging station. The resulting levelized costs of hydrogen and charging have been incorporated into the total cost of ownership analysis. Thus it has been demonstrated that battery electric trucks are more costeffective than hydrogen-fuel cell electric trucks. The findings of this study indicate that the costs associated with electric charging and hydrogen refuelling are comparable and the economic profitability is contingent upon a number of techno-economic variables. Therefore it is not possible to determine a priori whether one solution is more economically competitive than the other. A mixed infrastructure can represent an opportunity for the transport sector decarbonisation whereby electric-charging and hydrogen-refuelling are not mutually exclusive.

Hydrogen is a promising environmentally friendly fuel with the potential for zero-carbon emissions particularly in maritime applications. However owing to its wide flammability range (4–75%) significant safety concerns persist. In confined spaces hydrogen leaks can lead to explosions posing a risk to both lives and assets. This study conducts a numerical analysis to investigate hydrogen flow within hydrogen storage rooms aboard ships with the goal of developing efficient ventilation strategies. Through simulations performed using ANSYS-CFX this research evaluates hydrogen diffusion stratification and ventilation performance. A vertex angle of 120◦ at the ceiling demonstrated superior ventilation efficiency compared to that at 177◦ while air inlets positioned on side-wall floors or mid-sections proved more effective than those located near the ceiling. The most efficient ventilation occurred at a velocity of 1.82 m/s achieving 20 air exchanges per hour. These findings provide valuable insights for the design of safer hydrogen vessel operations.

This study evaluates the technoeconomic impacts of direct and indirect electrification on the EU's net-zero emissions target by 2050. By linking the JRC-EU-TIMES long-term energy system model with PLEXOS hourly resolution power system model this research offers a detailed analysis of the interactions between electricity hydrogen and synthetic fuel demand production technologies and their effects on the power sector. It highlights the importance of high temporal resolution power system analysis to capture the synergistic effects of these components often overlooked in isolated studies. Results indicate that direct electrification increases significantly and unimpacted by biomass CCS and nuclear energy assumptions. However indirect electrification in the form of hydrogen varies significantly between 1400 and 2200 TWhH2 by 2050. Synthetic fuels are essential for sector coupling making up 6–12% of total energy consumption by 2050 with the power sector supplying most hydrogen and CO2 for their production. Varying levels of indirect electrification impact electrolysers renewable energy and firm capacities. Higher indirect electrification increases electrolyser capacity factors by 8% leading to more renewable energy curtailment but improves system reliability by reducing 11 TWh unserved energy and increasing flexibility options. These insights inform EU energy policies stressing the need for a balanced approach to electrification biomass use and CCS to achieve a sustainable and reliable net-zero energy system by 2050. We also explore limitations and sensitivities.

Nickel-based catalysts recognized for their cost-efficiency and availability play a critical role in advancing hydrogen production technologies. This study evaluates their optimization in water electrolysis to improve efficiency and system stability. Key findings highlight the enhancement of these catalysts with nickel-iron oxyhydroxide and nickel-molybdenum co-catalysts. Technological innovations such as Perovskite Solar Cells integration for solar-to-hydrogen conversion are explored. The use of nickel foam enhances electrode durability offering valuable insights into designing sustainable and efficient hydrogen production systems.

The fuel cell electric vehicle (FCEV) is a promising transportation technology for resolving the air pollution and climate change issues in the United States. However a large-scale penetration of FCEVs would require a sustained supply of hydrogen which does not exist now. Water electrolysis can produce hydrogen reliably and sustainably if the electricity grid is clean but the impacts of FCEVs on the electricity grid are unknown. In this paper we develop a comprehensive framework to model FCEV-driving and -refueling behaviors the water electrolysis process and electricity grid operation. We chose the Western Electricity Coordinating Council (WECC) region for this case study. We modeled the existing WECC electricity grids and accounted for the additional electricity loads from FCEVs using a Production Cost Model (PCM). Additionally the hydrogen need for five million FCEVs leads to a 3% increase in electricity load for WECC. Our results show that an inflexible hydrogen-producing process leads to a 1.55% increase to the average cost of electricity while a flexible scenario leads to only a 0.9% increase. On the other hand oversized electrolyzers could take advantage of cheaper electricity generation opportunities thus lowering total system costs.

The shift to renewable energy sources requires systems that are not only environmentally sustainable but also cost-effective and reliable. Mitigating the inherent intermittency of renewable energy optimally managing the hybrid energy storage efficiently integrating the microgrid with the power grid and maximizing the lifespan of system components are the significant challenges that need to be addressed. With this aim the paper proposes an economic viability assessment framework with an optimized dynamic operation approach to determine the most stable cost-effective and environmentally sound system for a specific location and demand. The green integrated hybrid microgrid combines photovoltaic (PV) generation battery storage an electrolyzer a hydrogen tank and a fuel cell tailored for deployment in remote areas with limited access to conventional infrastructure. The study’s control strategy focuses on managing energy flows between the renewable energy resources battery and hydrogen storage systems to maximize autonomy considering real-time changes in weather conditions load variations and the state of charge of both the battery and hydrogen storage units. The core system’s components include the interlinking converter which transfers power between AC and DC grids and the decentralized droop control approach which adjusts the converter’s output to ensure balanced and efficient power sharing particularly during overload conditions. A cloud-based Internet of Things (IoT) platform has been employed allowing continuous monitoring and data analysis of the green integrated microgrid to provide insights into the system's health and performance during the dynamic operation. The results presented in this paper confirmed that the proposed framework enabled the strategic use of energy storage particularly hydrogen systems. The optimal operational control of green hydrogen-integrated microgrid can indeed mitigate voltage and frequency fluctuations caused by variable solar input ensuring stable power delivery without reliance on the main grid or fossil fuel backups.

The study presents a complete one-dimensional model to evaluate the parameters that describe the operation of a Proton Exchange Membrane (PEM) electrolyzer and PEM fuel cell. The mathematical modeling is implemented in Matlab/Simulink® software to evaluate the influence of parameters such as temperature pressure and overpotentials on the overall performance. The models are further merged into an integrated electrolyzer-fuel cell system for electrical power generation. The operational description of the integrated system focuses on estimating the overall efficiency as a novel indicator. Additionally the study presents an economic assessment to evaluate the cost-effectiveness based on different economic metrics such as capital cost electricity cost and payback period. The parametric analysis showed that as the temperature rises from 30 to 70 C in both devices the efficiency is improved between 5-20%. In contrast pressure differences feature less relevance on the overall performance. Ohmic and activation overpotentials are highlighted for the highest impact on the generated and required voltage. Overall the current density exhibited an inverse relation with the efficiency of both devices. The economic evaluation revealed that the integrated system can operate at variable load conditions while maintaining an electricity cost between 0.3-0.45 $/kWh. Also the capital cost can be reduced up to 25% while operating at a low current density and maximum temperature. The payback period varies between 6-10 years for an operational temperature of 70 C which reinforces the viability of the system. Overall hydrogen-powered systems stand as a promising technology to overcome energy transition as they provide robust operation from both energetic and economic viewpoints.

Adverse climate change has forced a deeper reflection on the scale of pollution related to human activity including in the aviation industry. As a result fundamental questions have arisen about the characteristics of these pollutants the mechanisms of their formation and potential strategies for reducing them. This paper provides a comprehensive overview of key technical solutions to minimize the environmental impact of aircraft engines. The solutions presented range from fuel innovations to advanced design changes and drive concepts. Particular attention was paid to sustainable aviation fuels (SAFs) which are currently an important element of the environmental strategy regulated by the European Union. It also discusses the potential use of hydrogen as a potential alternative fuel to replace traditional aviation fuels in the long term. The analysis in the article made it possible to characterize in detail possible modifications in the functioning of aircraft engines based both on the current state of technical knowledge and on the anticipated directions of its development which has not been a frequent issue in comprehensive research so far. The analysis shows that the type of raw material used to create SAF has a strong impact on its physical and chemical parameters and the degree of greenhouse gas emissions. This necessitates a broader analysis of the legitimacy of using a given type of fuel from the SAF group in the direction of selected air operations and areas with a higher risk of severe atmospheric pollution. These results provide the basis for further research into sustainable solutions in the aviation sector that can contribute to significantly reducing its impact on climate change.

Hydrogen is seen as a key energy carrier to reduce CO2 emissions. Two main production options for hydrogen with low CO2 intensity are water electrolysis and natural gas reforming with Carbon Capture and Storage known as green and blue hydrogen. Northern Norway has a surplus of renewable energy and natural gas availability from the Barents Sea which can be used to produce hydrogen. However exports are challenging due to the large distances to markets and lack of energy infrastructure. This study explores the profitability of hydrogen exports from this Arctic region. It considers necessary investments in hydrogen technology and capacity expansions of wind farms and the power grid. Various scenarios are investigated with different assumptions for investment decisions. The critical question is how exogenous factors shape future regional hydrogen production and export. The results show that production for global export may be profitable above 90 €/MWh excluding costs for storage and transport with blue hydrogen being cheaper than green. Depending on the assumptions a combination of liquid hydrogen and ammonia export might be optimal for seaborne transport. Exports to Sweden can be profitable at prices above 60 €/MWh transported by pipelines. Expanding power generation capacity can be crucial and electricity and hydrogen exports are unlikely to co-exist.

The global shift toward a green hydrogen economy requires diversifying production beyond the Middle East and North Africa where political logistical and water constraints limit long-term supply. This study provides a comparative socio-economic assessment of Sub-Saharan African and South American countries focusing on their readiness for large-scale green hydrogen development. A Green Economy Index (GEI) was developed integrating political/regulatory efficiency socio-economic status infrastructure and sustainability indicators. In addition public perception was examined through a survey conducted in Nigeria. Results show GEI scores ranging from 0.328 to 0.744 with Germany as the benchmark. Brazil Uruguay and Namibia emerge as the most promising cases due to strong renewable energy potential socio-economic stability and supportive policies though each faces specific challenges such as transport logistics (Brazil and Uruguay) or water scarcity (Namibia). Nigeria demonstrates significant potential but is constrained by weak infrastructure and public safety concerns. Cameroon Angola and Gabon display moderate performance but require policy and investment reforms. By combining macro-level readiness analysis with social acceptance insights the study highlights opportunities and barriers for diversifying global hydrogen supply chains and advancing sustainable energy transitions in emerging regions.

Hydrogen (H2) admixing in Reactivity Controlled Compression Ignition (RCCI) technology engines is touted to enhance indicated efficiency (ITE>50%) optimize combustion and reduce greenhouse gas emissions. However many pending issues remain regarding engine durability nitrogen oxide (NOX) emissions and blending limits. These issues are addressed by employing a novel performance-oriented model which simulates under 3 min combustion physics with similar predictivity (>95% accuracy) as computational fluid dynamic results. This socalled multizone model is parameterized to real-world operating cycles from a dual-fuel mid-speed marine engine. By considering port-fuel injected H2 the simulations show that combustion phasing advances at an average rate of 0.3⁰CA/% H2 accompanied by a peak reduction in methane slip of 80% achievable at 25% H2 energy share. Also engine control oriented issues are addressed by demonstrating either intake temperature or diesel fuel share optimization to negate the drawbacks of combustion harshness and NOX emissions while improving ITE 1–1.5pp over baseline operation.

The present study aims to conduct a thermodynamic analysis of a novel concept that synergistically integrates clean hydrogen and power production with a liquified natural gas (LNG) regasification system. The designed integrated energy system aims to achieve hydrogen production power production liquified natural gas regasification carbon capture storage and in situ recirculation. Hydrogen sulfide (H2S) from industrial waste streams is used as a major feedstock and filtration combustion of H2S is employed as a hydrogen production method. CO2 obtained from the combustion process is liquified and pumped at a high pressure to recirculated back to the CO2 cycle power generation combustion process. The flu gas obtained after expansion on the turbine is condensed and CO2 is captured and pressurized. The entire plant is simulated in the Aspen Plus simulation environment and a comprehensive thermodynamic assessment including the energy and exergy analysis is conducted. Additionally several parametric studies and assessments of various factors influencing the system's performance are conducted. From the sensitivity analyses it is found that at 20% CO2 recirculation the hydrogen production rate decreases by 31.81% when the operating pressure is increased from 0.05 bar to 3 bar. The adiabatic temperature is reduced by 39.72% 35.37% and 32.85% when 50% 60% and 70% CO2 is recirculated in the oxidant stream at an oxygen to natural gas (ONG) ratio of 0.5. The energy and exergy efficiencies of the system are found to be 71.48% and 60.69% respectively. The present system avoids 2571.94 tons/yr of CO2 emissions for clean hydrogen production and 1426.27 tons/yr of CO2 for clean power production which would otherwise be emitted from steam methane reforming and coal gasification.

The temperature rises hydrogen tanks during the fast-filling process could threaten the safety of the hydrogen fuel cell vehicle. In this paper a 2D axisymmetric model of a type III hydrogen for the bus was built to investigate the temperature evolution during the fast-filling process. A test rig was carried out to validate the numerical model with air. It was found significant temperature rise occurred during the filling process despite the temperature of the filling air being cooled down due to the throttling effect. After verification the 2D model of the hydrogen tank was employed to study the temperature distribution and evolution of hydrogen during the fast-filling process. Thermal stratification was observed along the axial direction of the tank. Then the effects of filling parameters were examined and a formula was fitted to predict the final temperature based on the simulated results. At last an effort was paid on trying the improve the temperature distribution by increasing the injector length of the hydrogen tank. The results showed the maximal temperature and mass averaged temperature decreased by 2 K and 3.4 K with the length of the injector increased from 50 mm to 250 mm.

Hydrogen holds an important strategic position in the energy systems of many countries. Many studies have analyzed the acceptance of hydrogen energy technology from the public’s perspective but few have examined it from the corporate perspective. This paper establishes a technology acceptance model and employs structural equation modeling to investigate the factors affecting the acceptance of hydrogen energy technology within enterprises. After conducting questionnaire surveys among employees of energy enterprises electric power companies and new energy vehicle manufacturers the results indicate that while most of the interviewed enterprises have positive attitudes towards hydrogen technology their willingness to develop hydrogen business does not appear to be correspondingly positive. In addition government trust perceived benefit and social influence positively impact corporate acceptability indirectly whereas perceived risk exhibits a negative indirect effect on corporate acceptance. Finally this paper discusses the results of the above studies and makes corresponding policy recommendations.

The article examines the role of green hydrogen in reducing CO2 emissions in the transition to climate neutrality highlighting both its benefits and challenges. It starts by discussing the production of green hydrogen from renewable sources and provides a brief analysis of primary resource structures for energy production in European countries including Romania. Despite progress there remains a significant reliance on fossil fuels in some countries. Economic technologies for green hydrogen production are explored with a note that its production alone does not solve all issues due to complex and costly compression and storage operations. The concept of impure green hydrogen derived from biomass gasification pyrolysis fermentation and wastewater purification is also discussed. Economic efficiency and future trends in green hydrogen production are outlined. The article concludes with an analysis of hydrogen-methane mixture combustion technologies offering a conceptual framework for economically utilizing green hydrogen in the transition to a green hydrogen economy.

This study proposes the SMR Smart Net-Zero City (SSNC) framework—a scalable model for achieving carbon neutrality by integrating Small Modular Reactors (SMRs) renewable energy sources and sector coupling within a microgrid architecture. As deploying renewables alone would require economically and technically impractical energy storage systems SMRs provide a reliable and flexible baseload power source. Sector coupling systems—such as hydrogen production and heat generation—enhance grid stability by absorbing surplus energy and supporting the decarbonization of non-electric sectors. The core contribution of this study lies in its real-time data emulation framework which overcomes a critical limitation in the current energy landscape: the absence of operational data for future technologies such as SMRs and their coupled hydrogen production systems. As these technologies are still in the pre-commercial stage direct physical integration and validation are not yet feasible. To address this the researchers leveraged real-time data from an existing commercial microgrid specifically focusing on the import of grid electricity during energy shortfalls and export during solar surpluses. These patterns were repurposed to simulate the real-time operational behavior of future SMRs (ProxySMR) and sector coupling loads. This physically grounded simulation approach enables highfidelity approximation of unavailable technologies and introduces a novel methodology to characterize their dynamic response within operational contexts. A key element of the SSNC control logic is a day–night strategy: maximum SMR output and minimal hydrogen production at night and minimal SMR output with maximum hydrogen production during the day—balancing supply and demand while maintaining high SMR utilization for economic efficiency. The SSNC testbed was validated through a seven-day continuous operation in Busan demonstrating stable performance and approximately 75% SMR utilization thereby supporting the feasibility of this proxy-based method. Importantly to the best of our knowledge this study represents the first publicly reported attempt to emulate the real-time dynamics of a net-zero city concept based on not-yet-commercial SMRs and sector coupling systems using live operational data. This simulation-based framework offers a forward-looking data-driven pathway to inform the development and control of next-generation carbon-neutral energy systems.

This study conducts a life cycle assessment and exergoenvironmental evaluation of a double-effect vapor absorption chiller (DEAC) with a cooling capacity of 352 kW employing three different energy sources: natural gas biomethane and green hydrogen. The main objectives of this paper are as follows: (i) provide an exergoenvironmental model for DEAC technologies (ii) evaluation of a case-study where a DEAC is used to cover the cooling demand of a specific university building in the Northeast of Brazil and (iii) evaluate the scenario where the DEAC is fed by green hydrogen (GH2) and compare it with conventional energy resources (natural gas and biomethane). In order to develop the exergoenvironmental model two methodologies are essential: a thermodynamic analysis and a Life Cycle Assessment (LCA). The thermodynamic analysis was carried out using the Engineering Equation Solver (EES: 10.998) software. The LCA has been developed through the open-source software openLCA version 1.10.3 with the Ecoinvent 3.7.1 life cycle inventory database whereas the chosen life cycle inventory assessment (LCIA) method was the ReCiPe Endpoint LCA method (Humanitarian medium weighting–H A). The main results indicate that green hydrogen provides a 99.84% reduction in environmental impacts compared to natural gas during the operational phase while biomethane reduces these impacts by 54.21% relative to natural gas. In the context of life cycle assessment (LCA) green hydrogen decreases fossil resource depletion by 18% and climate change-related emissions by 33.16% compared to natural gas. This study contributes to enhancing the understanding of the environmental and exergoenvironmental impacts of a double-effect vapor absorption chiller by varying the fuel usage during the operational phase.

Côte d’Ivoire has substantially neglected crop residues from farms in rural areas so this study aimed to provide strategies for the sustainable conversion of these products to hydrogen. The use of existing data showed that in the Côte d’Ivoire there were up to 16801306 tons of crop residues from 11 crop types in 2019 from which 1296424.84 tons of hydrogen could potentially be derived via theoretical gasification and dark fermentation approaches. As 907497.39 tons of hydrogen is expected annually the following estimations were derived. The three hydrogen-project implementation scenarios developed indicate that Ivorian industries could be supplied with 9026635 gigajoules of heat alongside 17910 cars and 4732 buses in the transport sector. It was estimated that 817293.95 tons of green ammonia could be supplied to farmers. According to the study 5727992 households could be expected to have access to 1718.40 gigawatts of electricity. Due to these changes in the transport energy industry and agricultural sectors a reduction of 1644722.08 tons of carbon dioxide per year could theoretically be achieved. With these scenarios around 263276.87 tons of hydrogen could be exported to other countries. The conversion of crop residues to hydrogen is a promising opportunity with environmental and socio-economic impacts. Therefore this study requires further extensive research.

Combustion of hydrogen-enriched natural gas is a valuable short-term strategy for reducing CO2 emissions from high temperature industrial heating. This paper presents several experiments on combustion characteristics and the formation of nitrogen oxides. The experiments included hydrogen contents up to 100% and fuel heat inputs up to 75 kW. Water-cooled lances were used to influence the furnace temperature. The analysis includes the distribution of furnace temperatures the composition of flue gas the cooling capacity of the lances under steady-state operating conditions and OH*-chemiluminescence imaging of the near burner region. The presented results demonstrate the dependence of furnace conditions and NOX formation on various factors such as different air inlet fluxes furnace temperature and fuel composition for constant heat inputs. Efficiency increased by up to 5.5% and significant changes in flame shaped along with a maximum increase in NOX emissions when comparing natural gas to hydrogen was measured at 167%.

The optimization of hybrid renewable multi-generation systems is crucial for enhancing energy efficiency reducing costs and ensuring sustainable power generation. These factors can be significantly affected by system designs optimization methods climate changes and varying energy demands. The optimization of a stand-alone hybrid renewable energy system (HRES) that integrates various combinations of electricity heating cooling hydrogen and freshwater needs has not been reported in a single comprehensive study. Additionally there has been insufficient attention given to the impact of temporal resolution the recovery of excess energy usage and aligning these efforts with the sustainable development goals (SDGs). This study reviews the recent state-of-theart studies on the stand-alone HRES options for meeting electric heating cooling hydrogen electric vehicles and freshwater demands with various combinations. This study further contributes by examining contemporary literature on sizing optimization reliability analysis sensitivity analysis control techniques detailed modelling and techno-environmental-economic features. It also provides justification for selecting configurations suitable for specific geographical locations along with an analysis of the choice of algorithms and power management systems required to meet the various load demands of a self-sufficient community. By highlighting the im provements and potentials of HRES to achieve various United Nations SDGs this review study aims to bridge existing research gaps.

Green hydrogen is a promising energy vector for industrial applications. However hydrogen leaks can occur causing greenhouse effects and posing safety risks for operators and local communities potentially leading to legal liabilities. Industry 4.0 focuses on digital industrial modernization while Industry 5.0 emphasizes collaborative humancentered and sustainable processes. This study developed and analyzed an Industry 5.0 proof of concept as an additional safety layer for hydrogen leak management. The proof of concept was implemented using Raspberry Pi microcomputers integrated computer vision and OpenAI GPT-3 for dynamic email communication. A legal liability analysis for Chile and Spain identified potential challenges in transitioning the system into a marketready product. The findings suggest the system should act as a complementary safety layer rather than a primary detection system to mitigate legal liability risks as operational deployment without full certification and validation could lead to malfunctions. This study illustrated how hydrogen detection and management can be integrated into Industry 5.0 smart systems. With growing global interest in sustainable engineering and AI regulation as reflected in Regulation (EU) 2024/1689 legal considerations over technologies like the one presented in this study are becoming increasingly relevant.

Temporal decomposition methods aim to solve optimisation problems by converting one problem over a large time series into a series of subproblems over shorter time series. This paper introduces one such method where subproblems are defined over a window that moves back and forth repeatedly over the length of the large time series creating a convergent sequence of solutions and mitigating some of the boundary considerations prevalent in other temporal decomposition methods. To illustrate this moving window method it is applied to two models: an energy storage facility trading electricity in a market; and a hydrogen electrolyser powered by renewable electricity produced and potentially stored onsite. The method is simple to implement and it is found that for large optimisation problems it consistently requires less computation time than the base optimisation algorithm used in this study (by factors up to 100 times). In addition it is analytically demonstrated that decomposition methods in which a minimum is attained for each subproblem need not attain a minimum for the overall problem.

The European Union continues to lead global efforts toward climate neutrality by developing a cohesive regulatory and market framework for alternative fuels including renewable hydrogen. This review article critically examines the recent evolution of the EU’s policy landscape specifically for hydrogen as a renewable fuel of non-biological origin (RFNBO) highlighting its growing importance in hard-to-abate sectors such as industry and transportation. We assess the interplay of market-based mechanisms (e.g. EU ETS II) direct mandates (e.g. FuelEU Maritime RED III) and support auction-based measures (e.g. the European Hydrogen Bank) that collectively shape both the demand and the supply of hydrogen as RFNBO fuel. The article also addresses emerging cost capacity and technical barriers—ranging from constrained electrolyzer deployment to complex certification requirements—that hinder large-scale adoption and market rollout. The article aims to discuss advancing and changing regulatory and market environment for the development of infrastructure and market for hydrogen as RFNBO fuel in the EU in 2019–2024. Synthesizing current research and policy developments we propose targeted recommendations including enhanced cross-border coordination and capacity-based incentives to accelerate investment and infrastructure development. This review informs policymakers industry stakeholders and researchers on critical success factors for integrating hydrogen as a cornerstone of the EU’s climate neutrality efforts.

Accidental hydrogen releases from pipelines pose significant risks particularly with the expanding deployment of hydrogen infrastructure. Despite this there has been a lack of thorough investigation into hydrogen leakage from pipelines especially under complex real-world conditions. This study addresses this gap by modeling hydrogen gas dispersion jet fires and explosions based on practical scenarios. Various factors influencing accident consequences such as leak hole size wind speed wind direction and trench presence were systematically examined. The findings reveal that both hydrogen dispersion distance and jet flame thermal radiation distance increase with leak hole size and wind speed. Specifically the longest dispersion and radiation distances occur when the wind direction aligns with the trench which is 110 m where the hydrogen concentration is 4% and 76 m where the radiation is 15.8 kW/m2 in the case of a 325 mm leak hole and wind under 10 m/s. Meanwhile pipelines lacking trenching exhibit the shortest distances 0.17 m and 0.98 m at a hydrogen concentration of 4% and 15.8 kW/m2 radiation with a leak hole size of 3.25 mm and no wind. Moreover under relatively higher wind speeds hydrogen concentration stratification occurs. Notably the low congestion surrounding the pipeline results in an explosion overpressure too low to cause damage; namely the highest overpressure is 8 kPa but this lasts less than 0.2 s. This comprehensive numerical study of hydrogen pipeline leakage offers valuable quantitative insights serving as a vital reference for facility siting and design considerations to eliminate the risk of fire incidents.

China’s coal chemical sector uses coal as both a fuel and feedstock and its increasing greenhouse gas (GHG) emissions are hard to abate by electrification alone. Here we explore the GHG mitigation potential and costs for onsite deployment of green H2 and O2 in China’s coal chemical sector using a lifecycle assessment and techno-economic analyses. We estimate that China’s coal chemical production resulted in GHG emissions of 1.1 gigaton CO2 equivalent (GtCO2eq) in 2020 equal to 9% of national emissions. We project GHG emissions from China’s coal chemical production in 2030 to be 1.3 GtCO2eq ~50% of which can be reduced by using solar or wind power-based electrolytic H2 and O2 to replace coal-based H2 and air separation-based O2 at a cost of 10 or 153 Chinese Yuan (CNY)/tCO2eq respectively. We suggest that provincial regions determine whether to use solar or wind power for water electrolysis based on lowest cost options which collectively reduce 53% of the 2030 baseline GHG emissions at a cost of 9 CNY/tCO2eq. Inner Mongolia Shaanxi Ningxia and Xinjiang collectively account for 52% of total GHG mitigation with net cost reductions. These regions are well suited for pilot policies to advance demonstration projects.

The transition from fossil fuels to the renewable energies (wind solar) is a key factor to face climate change and build a sustainable reliable and secure energy system. To balance the intermittent energy demand and supply affecting the renewable sources the surplus of electrical energy may be converted in hydrogen and then storage in geological formations. While the risks associated to the natural gas storage in the sub-surface are well known from decades those associated with hydrogen underground storage (UHS) are relatively underexplored. This paper presents an inventory of risks related to large H2-storage in depleted gas and oil fields salt caverns and aquifers. Different issues such as integrity and durability of materials H2 leakages and interaction with the reservoir H2 uncontrolled outflow from the wellhead with potential combustion of air-hydrogen mixture (fire and explosion) soil subsidence and induced seismicity are analyzed.

This paper presents work undertaken by the HSE as part of the Hytunnel-CS project a consortium investigating safety considerations for fuel cell hydrogen (FCH) vehicles in tunnels and similar confined spaces. The sudden failure of a pressurised hydrogen vessel was identified as a scenario of concern due to the severity of the consequences associated with such an event. In order to investigate this scenario experimentally HSE designed a bespoke and reusable ‘sudden release’ vessel. This paper presents an overview of the vessel and the results of a series of 13 tests whereby hydrogen was released from the bespoke vessel into a tunnel at pressures up to 65 MPa. The starting pressure and the volume of hydrogen in the vessel were altered throughout the campaign. Four of the tests also included congestion in the tunnel. The tests reliably autoignited. Overpressure measurements and flame arrival times measured with exposed-tip thermocouples enabled analysis of the severity of the events. A high-pressure fast-acting pressure transducer in the body of the vessel showed the pressure decay in the vessel which shows that 90% of the hydrogen was evacuated in between 1.8 and 3.2 ms (depending on the hydrogen inventory). Schlieren flow imagery was also used at the release point of the hydrogen showing the progression of the shock front following initiation of the tests. An assessment of the footage shows an estimated initial velocity of Mach 3.9 at 0.4 m from the release point. Based on this an ignition mechanism is proposed based upon the temperature behind the initial shock front.

Industry emits around a quarter of global greenhouse gas (GHG) emissions. This paper presents the first comprehensive review to identify the main decarbonization options for this sector and their abatement potentials. First we identify the important GHG emitting processes and establish a global average baseline for their current emissions intensity and energy use. We then quantify the energy and emissions reduction potential of the most significant abatement options as well as their technology readiness level (TRL). We find that energy-intensive industries have a range of decarbonization technologies available with medium to high TRLs and mature options also exist for decarbonizing low-temperature heat across a wide range of industrial sectors. However electrification and novel process change options to reduce emissions from high-temperature and sector-specific processes have much lower TRLs in comparison. We conclude by highlighting important barriers to the deployment of industrial decarbonization options and identifying future research development and demonstration needs.