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.