Publications

Concerns related to climate change have shifted global attention towards advanced sustainable and decarbonized energy systems. While renewable resources such as wind and solar energy offer environmentally friendly alternatives their inherent variability and intermittency present significant challenges to grid stability and reliability. The integration of renewable energy sources requires innovative solutions to effectively balance supply and demand in the electricity grid. This review explores the critical role of electrolyzer systems in addressing these challenges by providing ancillary services to modern electricity grids. Electrolyzers traditionally used only for hydrogen production have now emerged as versatile tools capable of responding quickly to grid load variations. They can consume electricity during excess periods or when integrated with fuel cells generate electricity during peak demand contributing to grid stability. Therefore electrolyzer systems can fulfill the dual function of producing hydrogen for the end-user and offering grid balancing services ensuring greater economic feasibility. This review paper aims to provide a comprehensive view of the electrolyzer systems’ role in the provision of ancillary services including frequency control voltage control congestion management and black start. The technical aspects market projects challenges and future prospects of using electrolyzers to provide ancillary services in modern energy systems are explored.

Hydrogen presents the UK with a substantial opportunity to drive economic growth and secure skilled jobs by leveraging our natural geological and geographical advantages robust supply chain and existing energy expertise. Hydrogen UK’s most recent Economic Impact Assessment estimates that the hydrogen sector in the UK could support approximately 30000 direct jobs and contribute more than £7 billion gross value added annually by 2030. On a global scale the hydrogen market is projected to be worth $2.5 trillion by 2050.

With international competition increasing the UK must act now to capitalise on this potential. These projections are supported by a recognition that hydrogen is one of the key solutions to decarbonising the UK economy complementing other low-carbon solutions such as electrification carbon capture biofuels and energy efficiency. Additionally hydrogen will play a vital role in enhancing the UK’s energy security by storing domestically produced energy to balance intermittent renewable sources like wind and solar. As a critical component of the clean energy transition hydrogen is indispensable to achieving net zero.

As it stands the UK is well placed to capitalise on the hydrogen opportunity and emerge as a global leader. We have made early strides in establishing a framework for hydrogen development with various pilot projects and strategic investments already underway. However the next five years will be critical for the sector as we move from strategy and planning to development and delivery. It is imperative to get the first lowcarbon production projects over the line and into construction as a matter of urgency and then deliver substantial infrastructure development regulatory clarity and sustained financial support to scale-up production and distribution. A new Government presents an opportunity for policymakers to solidify commitments and accelerate the deployment of hydrogen technology ensuring the UK remains competitive in the global race.

Our manifesto outlines policy recommendations for the new UK Government to take across production distribution and storage infrastructure end use applications trade and beyond which will support a thriving British industrial base that creates jobs and growth for British people. To achieve this the UK hydrogen industry calls on policymakers to speed up the deployment of hydrogen through the recommendations set out in this Manifesto.

This report can be found on Hydrogen UK's website.

The affordability and availability of water and energy have a huge impact on food production. Research has shown that there exists a direct and indirect link between power production and clean water generation. Hence the inclusion/importance given to the energy-water-food (EWF) nexus in the United Nations’ sustainable development goals. Acknowledging the importance of decarbonization to the global future there exists a gap in literature on the development of models that can enhance the EWF nexus reduce energy poverty and achieve 100% renewable energy in the electricity sector. Therefore the technical and economic prospect of geothermal energy for bridging the aforementioned gaps in existing works of literature is presented in this study. The energy poverty/wealthy status of a country has been confirmed to have a significant impact on economic development as economic development is largely reflected in the food-water availability. Ditto this study is focused on the interconnectivity of the EWF nexus while incorporating global decarbonization targets. Geothermal energy is of the utmost significance in East Africa due to its abundant potential and distinctive geological features. Located in the Great Rift Valley the region has an abundance of geothermal reservoirs making it an ideal location for geothermal power generation. This study is novel as a comprehensive assessment framework for energy poverty is developed and innovative models utilizing primarily the geothermal resource in the East African region to mitigate this problem are proposed and analyzed. The role of hydrogen generation from critical excess electricity production is also analyzed. The East Africa region is considered the case study for implementing the models developed. A central renewable energy grid is proposed/modelled to meet the energy demand for seven East African countries namely; Ethiopia Tanzania Uganda Djibouti Comoros Eritrea and Rwanda. This study considers 2030 2040 and 2050 as the timestamp for the implementation of the proposed models. The hybrid mix of the biomass power plant solar photovoltaic (PV) pumped hydro storage system and onshore wind power is considered to furthermore show the potency of renewable energy resources in this region. Results showed that the use of geothermal energy to meet energy demands in the case study will mitigate energy poverty and enhance the region’s EWF.

Hydrogen is one of the key solutions to decarbonising the UK economy along with other carbon abatement solutions such as electrification CCUS biofuels and energy efficiency. It provides a low carbon alternative to fossil fuels that has many of the same desirable features such as burning with a high temperature flame without producing carbon emissions during combustion. Hydrogen will be particularly valuable in hard-to-decarbonise sectors that have few cost-effective alternatives including elements of industry heavy transport and dispatchable power generation. However it’s use could be much more widespread depending on how costs preferences and policy for different low carbon solutions develop. The Government’s Hydrogen Strategy estimates that based on analysis from the Climate Change Committee (CCC) in 2050 between 20% and 35% of the UK’s final energy demand could be met with low carbon hydrogen1 . While hydrogen provides a promising solution to reducing emissions current deployment of low carbon hydrogen is low with almost all hydrogen in the UK produced from unabated fossil fuels resulting in high emissions. In the UK hydrogen production must meet the Low Carbon Hydrogen Standard (LCHS) to access government support. This is currently set at 20g CO2 e/MJ(LHV) and will ensure that future deployment will deliver significant emissions reductions when switching from fossil fuels2. The period to 2030 will be a critical time for the UK to seize the economic opportunity presented by low carbon hydrogen sector. Internationally increasing attention has been placed on hydrogen as a solution to global emissions. In the USA the Inflation Reduction Act (IRA) has provided fixed rate tax credits of up to $3/kg (£2.4/kgII) for clean hydrogen production3. Closer to home the EU is targeting 10 million tonnes of domestic electrolytic production and an additional 10 million tonnes of electrolytic hydrogen imports by 20304. This will be achieved through a variety of policy levers including an auction for fixed price subsidy support for electrolytic production with a ceiling of €4.5/kg5 (£3.84/kgIII). In the UK Government have set an ambitious target of up to 10 GW of low carbon hydrogen production by 2030 with at least half of this from electrolytic sources6. This will be supported by the Hydrogen Production Business Model (HPBM) a two-way variable CfD which could potentially provide hydrogen for a price as low as the natural gas price7 . As global supply chains investment and skills are in international competition the UK must continue its ambitious hydrogen aspirations to ensure the decarbonisation and economic opportunity presented by low carbon hydrogen is captured. This study estimates the economic impact of the low carbon hydrogen sector in the UK by 2030. The impact is assessed by estimating the costs of hydrogen deployment and applying employment and GVA multipliers to these costs based on historic economic activity. These estimates are broken down by different forms of low carbon hydrogen production and end use as well as the enabling infrastructure required to connect production and demand namely hydrogen networks and storage. Both the employment and GVA are estimated for each of these value chain elements for every year between 2024 and 2030. Employment and economic growth from the hydrogen sector will be created across the UK with many benefits arising in regions that have faced historic underinvestment such as the industrial clusters and Scotland. Beyond the high-level economic benefits estimated in this study the hydrogen sector creates an opportunity for the hundreds of thousands oil and gas sector jobs in the UK to transition to a low carbon alternative.

This report can be found on Hydrogen UK's website.

Long-duration energy storage is the key challenge facing renewable energy transition in the future of well over 50% and up to 75% of primary energy supply with intermittent solar and wind electricity while up to 25% would come from biomass which requires traditional type storage. To this end chemical energy storage at grid scale in the form of fuel appears to be the ideal option for wind and solar power. Renewable hydrogen is a much-considered fuel along with ammonia. However these fuels are not only difficult to transport over long distances but they would also require totally new and prohibitively expensive infrastructure. On the other hand the existing natural gas pipeline infrastructure in developed economies can not only transmit a mixture of methane with up to 20% hydrogen without modification but it also has more than adequate long-duration storage capacity. This is confirmed by analyzing the energy economies of the USA and Germany both possessing well-developed natural gas transmission and storage systems. It is envisioned that renewable methane will be produced via well-established biological and/or chemical processes reacting green hydrogen with carbon dioxide the latter to be separated ideally from biogas generated via the biological conversion of biomass to biomethane. At the point of utilization of the methane to generate power and a variety of chemicals the released carbon dioxide would be also sequestered. An essentially net zero carbon energy system would be then become operational. The current conversion efficiency of power to hydrogen/methane to power on the order of 40% would limit the penetration of wind and solar power. Conversion efficiencies of over 75% can be attained with the on-going commercialization of solid oxide electrolysis and fuel cells for up to 75% penetration of intermittent renewable power. The proposed hydrogen/methane system would then be widely adopted because it is practical affordable and sustainable.

A gas turbine is usually installed inside an acoustic enclosure where the fuel gas supply system is also placed. It is common practice using CFD analysis to simulate the accidental fuel gas release inside the enclosure and the consequent dispersion. These numerical studies are used to properly design the gas detection system according to specific safety criteria which are well defined when the fuel gas is a conventional natural gas. Package design is done to prevent that any sparking items and hot surfaces higher than auto-ignition temperature could be a source of ignition in case of leak. Nevertheless it is not possible to exclude that a leakage from a theoretical point of view could be ignited and for this reason a robust design requires that the enclosure structure is able to withstand the overpressure generated by a gas cloud ignition. Moving to hydrogen as fuel gas makes this design constraint much more relevant for its known characteristics of reactiveness large range of flammability maximum burning velocity etc. In such context gas leak and dispersion analysis become even more crucial because a correct prediction of these scenarios can guide the design to a safe configuration. The present work shows a comparison of the dispersion of different leakages inside a gas turbine enclosure carried out with two different CFD tools Ansys CFX and FLACS. This verification is considered essential since dispersion analysis results are used as initial conditions for gas cloud ignition simulations strictly necessary to predict the consequence in term of overpressure without doing experimental tests.

Polymeric materials are widely used in hydrogen energy system such as FCEV and hydrogen refueling stations under high-pressure condition. The permeation property (coefficients of permeation diffusion and solubility) of polymers under high-pressure hydrogen condition should be discussed as parameters to develop those devices. Also the property should be determined to understand influence of the compression by the pressure on polymer materials. A device which can measure gas permeation property of polymer materials accurately in equilibrium state under high-pressure environment is developed and the reliability of the measurements is ensured. High-pressure hydrogen gas permeability characteristics up to 100 MPa are measured for high-density polyethylene. An advantage of the method is discussed comparing with the non-equilibrium state method focusing on the hydrostatic pressure effect. Deterioration of hydrogen permeability is observed along with the decrease of diffusion coefficient which is supposedly affected by hydrostatic compression effect with the increase of environment pressure.

Hydrogen can manage intermittent Renewable Energy Sources (RES) especially in high-RES share systems. The energy transition calls for mature low cost low space solutions bringing the attention to unitized items such as the reversible Solid Oxide Cell (rSOC). This device made of a single unit can work as an electrolyzer and as fuel cell with high efficiency fuel flexibility and producing combined heat. The objective of this review is to identify and classify rSOC applications to the building sector as an effective solution and to show how much this technology is near to its commercialisation. Research & Development projects were analysed and discussed for a comprehensive overview. Conclusions show an increasing interest in the reversible technology although it is still at pre industrialisation stage with few real applications in the building sector of which the majority is reported commented and compared in this paper for the first time.

Hydrogen is emerging as a critical component in the global energy transition providing a low-carbon alternative for sectors such as industry and transportation. This paper aims to comprehensively address water usage in hydrogen production by exploring the water demands of different production methods and their implications for water management particularly in Texas. Key variables influencing water consumption are identified and potential water demands under different hydrogen market scenarios are estimated. Using spatial analysis regions where hydrogen production may stress local water resources are identified alongside policy recommendations for sustainable water use.

This report explores how hydrogen could be taken up in the UK and how this in turn translates to each sector from both global and UK perspectives to understand the practical implications of global and UK targets and projections on hydrogen innovation opportunities:

♦ Assessing demand for hydrogen sets out the context and the approach taken in the assessment of global and UK sector hydrogen needs including the development of specific UK scenarios for hydrogen deployment and innovation across the energy system and supply chain.

♦ Key insights discusses the insights and an overview of the outputs from the implementation of the UK deployment scenarios in whole energy system modelling.

♦ Hydrogen production storage and distribution and demand explore these areas in more detail setting out the current state and potential trajectories for hydrogen in each sector both globally and in the UK up to 2050.

This report can also be downloaded free on the Hydrogen Innovation Initative website.

A viable green energy source for heavy industries and transportation is hydrogen. The internal combustion engine (ICE) when powered by hydrogen offers an economical and adaptable way to quickly decarbonize the transportation industry. In general two techniques are used to inject hydrogen into the ICE combustion chamber: port injection and direct injection. The present work examined direct injection technology highlighting the need to understand and manage hydrogen mixing within an ICE’s combustion chamber. Before combusting hydrogen it is critical to study its propagation and mixture behavior just immediately before burning. For this purpose the DI-CHG.2 direct injector model by BorgWarner was used. This injector operated at 35 barG and 20 barG as maximum and minimum upstream pressures respectively; a 5.8 g/s flow rate; and a maximum tip nozzle temperature of 250 ◦C. Experiments were performed using a high-pressure and hightemperature visualization vessel available at our facility. The combustion mixture prior to burning (spray) was visually controlled by the single-pass high-speed Schlieren technique. Images were used to study the spray penetration (S) and spray volume (V). Several parameters were considered to perform the experiments such as the injection pressure (Pinj) chamber temperature (Tch) and the injection energizing time (Tinj). With pressure ratio and injection time being the parameters commonly used in jet characterization the addition of temperature formed a more comprehensive group of parameters that should generally aid in the characterization of this type of gas jets as well as the understanding of the combined effect of the rate of injection on the overall outcome. It was observed that the increase in injection pressure (Pinj) increased the spray penetration depth and its calculated volume as well as the amount of mass injected inside the chamber according to the ROI results; furthermore it was also observed that with a pressure difference of 20 bar (the minimum required for the proper functioning of the injector used) cyclic variability increased. The variation in temperature inside the chamber had less of an impact on the spray shape and its penetration; instead it determined the velocity at which the spray reached its maximum length. In addition the injection energizing time had no effect on the spray penetration.

In recent years global efforts towards a future with sustainable energy have intensified the development of renewable energy sources (RESs) such as offshore wind solar photovoltaics (PVs) hydro and geothermal. Concurrently green hydrogen produced via water electrolysis using these RESs has been recognized as a promising solution to decarbonizing traditionally hard-to-abate sectors. Furthermore hydrogen storage provides a long-duration energy storage approach to managing the intermittency of RESs which ensures a reliable and stable electricity supply and supports electric grid operations with ancillary services like frequency and voltage regulation. Despite significant progress the hydrogen economy remains nascent with ongoing developments and persistent uncertainties in economic technological and regulatory aspects. This paper provides a comprehensive review of the green hydrogen value chain encompassing production transportation logistics storage methodologies and end-use applications while identifying key research gaps. Particular emphasis is placed on the integration of green hydrogen into both grid-connected and islanded systems with a focus on operational strategies to enhance grid resilience and efficiency over both the long and short terms. Moreover this paper draws on global case studies from pioneering green hydrogen projects to inform strategies that can accelerate the adoption and large-scale deployment of green hydrogen technologies across diverse sectors and geographies.

Liquid hydrogen has the potential to significantly reduce in-flight carbon emissions in the aviation industry. Among the most promising aircraft configurations for future hydrogen-powered aviation are the blended wing body and the pure flying wing configurations. However their tapered and flattened airframe designs pose a challenge in accommodating liquid hydrogen storage tanks. This paper presents a design guide to tapered conformable pressure tanks for liquid hydrogen storage. The proposed tank configurations feature a multi-bubble layout and are subject to low internal differential pressure. The objective is to provide tank designers with simple geometric rules and practical guidelines to simplify the design process of tapered multi-bubble pressure tanks. Various tank configurations are discussed starting with a simple tapered two-bubble tank and advancing to more complex tapered configurations with a multi-segment and multi-bubble layout. A comprehensive design methodology is established providing tank designers with a step-by-step design procedure and highlighting the practical guidelines in each step of the design process.

This study aims to elucidate the behavior of diffusible hydrogen and delayed fracture in martensitic steel with 1500 MPa strength during automotive painting process and under vehicle service conditions. A sequential process of automotive pretreatment line and vehicle service environment is simulated to evaluate the hydrogen pick up in each process. In case of the automotive painting line the absorption of hydrogen is within the common range in the process of phosphating treatment and electrodeposition. The baking process plays an effective role for desorbing the diffusible hydrogen absorbed during the automotive pre-treatment such as zinc-phosphating and electrodeposition process. In case of the corrosion environment under the automotive driving conditions hydrogen induced delayed fracture is accelerated as the exposure time increases. Further it is clarified that severe plastic deformation are the significant factors for hydrogen induced delayed fracture under with low pH value and present of chloride ion in a chemical solution parameter. In summary hydrogen is transported constantly during electrodeposition sequential line process of automobile manufacturing below the hydrogen content of 0.5 ppm which is not critical value for leading to hydrogen delayed fracture based on results of slow strain rate tensile tests. However exposure to extreme conditions under service environment of vehicle such as acidic solution and chloride chemistry solution that result in high level of hydrogen absorption severe plastic deformation in the sheared edge and constantly applied internal or external stresses can cause the hydrogen induced delayed fracture in the fully martensitic steels.

Water electrolysis is considered as an important technology for an increased renewable energy penetration. This perspective on low-temperature water electrolysis joins the dots between the interdisciplinary fields of fundamental science describing physicochemical processes engineering for the targeted design of cell components and the development of operation strategies. Within this aim the mechanisms of ion conduction gas diffusion corrosion and electrocatalysis are reviewed and their influence on the optimum design of separators electrocatalysts electrodes and other cell components are discussed. Electrocatalysts for the water splitting reactions and metals for system components are critically accessed towards their stability and functionality. On the basis of the broad scientific analysis provided challenges for the design of water electrolyzers are elucidated with special regard to the alkaline or acidic media of the electrolyte.

Renewable hydrogen has emerged as a potentially critical energy carrier for achieving climate change mitigation goals. International trade could play a key role in meeting hydrogen demand in a globally decarbonized energy system. To better understand this role we have developed a modelling framework that incorporates hydrogen supply and demand curves and a market equilibrium model to maximize social welfare. Applying this framework we investigate two scenarios: an unrestricted trade scenario where hydrogen trade is allowed between all regions globally and a regional independence scenario where trade is restricted to be intra-regional only. Under the unrestricted trade scenario global hydrogen demand could reach 234 Mt by 2050 with 31.2% met through international trade. Key trade routes identified include North Africa to Europe the Middle East to Developing Asia and South America to Japan and South Korea. In the regional independence scenario most regions could meet their demand domestically except for Japan and South Korea due to self-insufficiency. Finally this analysis reveals that producers in North Africa and South America are likely to gain more economic value from international trade compared to other producing regions. The results offer key insights for policymakers and investors for shaping future hydrogen trade policies and investment decisions.

Chapters:<br/>♦ Introduction by Rainer Quitzow and Yana Zabanova<br/>♦ The EU in the Global Hydrogen Race: Bringing Together Climate Action Energy Security and Industrial Policy by Yana Zabanova<br/>♦ Germany’s Hydrogen Strategy: Securing Industrial Leadership in a Carbon–Neutral Economy by Almudena Nunez and Rainer Quitzow<br/>♦ France’s Hydrogen Strategy: Focusing on Domestic Hydrogen Production to Decarbonise Industry and Mobility by Ines Bouacida<br/>♦ International Dimension of the Polish Hydrogen Strategy. Conditions and Potential for Future Development by Michał Smoleń and Wojciech Żelisko<br/>♦ Hydrogen Affairs in Hungary’s Politically Confined Ambition byJohn Szabo<br/>♦ Spain’s Hydrogen Ambition: Between Reindustrialisation and Export-Led Energy Integration with the EU by Ignacio Urbasos and Gonzalo Escribano<br/>♦  Italian Hydrogen Policy: Drivers Constraints and Recent Developments by Andrea Prontera<br/>♦  Hydrogen Policy in the Netherlands: Laying the Foundations for a Scalable Hydrogen Value Chain by Roelof Stam Coby van der Linde and Pier Stapersma<br/>♦ Hydrogen Strategy of Sweden: Unpacking the Multiple Drivers and Potential Barriers to Hydrogen Development by Stefan Ćetković and Janek Stockburger<br/>♦  Norway’s Hydrogen Strategy: Unveiling Green Opportunities and Blue Export Ambitions by Jon Birger Skjærseth Per Ove Eikeland Tor Håkon Jackson Inderberg and Mari Lie Larsen<br/>♦ The Geopolitics of Hydrogen in Europe: The Interplay between EU and Member State Policies by Rainer Quitzow and Yana Zabanova

Reducing the gap between the electrodes and diaphragm to zero is an often adopted strategy to reduce the ohmic drop in alkaline water electrolyzers for hydrogen production. We provide a thorough account of the current–voltage relationship in such a zero-gap configuration over a wide range of electrolyte concentrations and current densities. Included are voltage components that are not often experimentally quantified like those due to bubbles hydroxide depletion and dissolved hydrogen and oxygen. As is commonly found for zero-gap configurations the ohmic resistance was substantially larger than that of the separator. We find that this is because the relatively flat electrode area facing the diaphragm was not active likely due to separator pore blockage by gas the electrode itself and or solid deposits. Over an e-folding time-scale of ten seconds an additional ohmic drop was found to arise likely due to gas bubbles in the electrode holes. For electrolyte concentrations below 0.5 M an overpotential was observed associated with local depletion of hydroxide at the anode. Finally a high supersaturation of hydrogen and oxygen was found to significantly increase the equilibrium potential at elevated current densities. Most of these voltage losses are shown to be easily avoidable by introducing a small 0.2 mm gap greatly improving the performance compared to zero-gap.

A promising energy carrier and storage solution for integrating renewable energies into the power grid currently being investigated is hydrogen produced via electrolysis. It already serves various purposes but it might also enable the development of hydrogen-based electricity storage systems made up of electrolyzers hydrogen storage systems and generators (fuel cells or engines). The adoption of hydrogen-based technologies is strictly linked to the electrification of end uses and to multicarrier energy grids. This study introduces a generic method to integrate and optimize the sizing and operation phases of hydrogen-based power systems using an energy hub optimization model which can manage and coordinate multiple energy carriers and equipment. Furthermore the uncertainty related to renewables and final demands was carefully assessed. A case study on an urban microgrid with high hydrogen demand for mobility demonstrates the method’s applicability showing how the multi-objective optimization of hydrogen-based power systems can reduce total costs primary energy demand and carbon equivalent emissions for both power grids and mobility down to  −145%. Furthermore the adoption of the uncertainty assessment can give additional benefits allowing a downsizing of the equipment.

The current global energy environment is experiencing a substantial shift towards minimizing carbon emissions and enhancing sustainability due to persistent problems. Demand for sustainable end-to-end energy solutions has boosted green hydrogen as the solution to decarbonize the world. The current study has identified and evaluated 7 main criteria of 27 sub-criteria for enabling the hydrogen supply Chains for decarbonization using the Fuzzy DEMATEL technique. The results show that the most prominent enablers criteria under causal factors are: cluster-based approach for developing a green hub Cost and investment decisions Hydrogen trade policy and regulatory actions and Technology. The effect group factors include: Assessment of ecological concerns- Ecology effect Availability of Energy sources and Awareness and public outreach. This study offers insights to understand the dynamics of the hydrogen supply chains and its way ahead towards decarbonization and transition towards a low-carbon economy. This research helps various academic and industrial stakeholders to give pace to green hydrogen uptake as a vital decarbonization tool and act as a base for strategic and collaborative decisions for a resilient and responsible energy landscape.

Transitioning from carbon-intensive steam methane reforming to low-carbon hydrogen production is essential for decarbonizing the European industrial sector. However the employment impact of such a transition remains unclear. Here we estimate the effects using a transition pathways optimization model and industrial survey data. The results show that an electrolysis-based hydrogen sector transition would create 40000 jobs in the hydrogen sector by 2050. However these jobs are not equally distributed with Western Europe hosting the largest share (40%) and 20% of current hydrogen-producing regions experiencing net job decreases. Even after accounting for renewable energy jobs created by electrolysis-driven electricity demand growth the 2050 low-carbon hydrogen workforce would provide only 10% of the jobs currently offered by European fossil fuel production. Numerous uncertainties and regional development inequities suggest the need for sector-diversified workforce transition plans and training programs to foster skills suited to multiple low-carbon opportunities.

Natural gas (NG) is favored for transportation due to its availability and lower CO2 emissions than fossil fuels despite drawbacks like poor lean combustion ability and slow burning. According to a few recent studies using hydrogen (H2 ) alongside NG and diesel in Tri-fuel mode addresses these drawbacks while enhancing efficiency and reducing emissions making it a promising option for diesel engines. Due to the importance and novelty of this the continuation of ongoing research and insufficient literature studies on HNG–diesel engine emissions that are considered helpful to researchers this research has been conducted. This review summarizes the recent research on the HNG–diesel Tri-fuel engines utilizing hydrogen-enriched natural gas (HNG). The research methodology involved summarizing the effect of engine design operating conditions fuel mixing ratios and supplying techniques on the CO CO2 NOx and HC emissions separately. Previous studies show that using natural gas with diesel increases CO and HC emissions while decreasing NOx and CO2 compared to pure diesel. However using hydrogen with diesel reduces CO CO2 and HC emissions but increases NOx. On the other hand HNG–diesel fuel mode effectively mitigates the disadvantages of using these fuels separately resulting in decreased emissions of CO CO2 HC and NOx. The inclusion of hydrogen improves combustion efficiency reduces ignition delay and enhances heat release and in-cylinder pressure. Additionally operational parameters such as engine power speed load air–fuel ratio compression ratio and injection parameters directly affect emissions in HNG–diesel Tri-fuel engines. Overall the Tri-fuel approach offers promising emissions benefits compared to using natural gas or hydrogen separately as dual-fuels.

This study reviews existing simulation models and describes a selected model for analysing combustion dynamics in hydrogen and natural gas mixtures specifically within non-ferrous melting furnaces. The primary objectives are to compare the combustion characteristics of these two energy carriers and assess the impact of hydrogen integration on furnace operation and efficiency. Using computational fluid dynamics (CFD) simulations incorporating actual furnace geometries and a detailed combustion and NOx emission prediction model this research aims to accurately quantify the effects of hydrogen blending. Experimental tests on furnaces using only natural gas confirmed the validity of these simulations. By providing precise predictions for temperature distribution and NOx emissions this approach reduces the need for extensive laboratory testing facilitates broader exploration of design modifications accelerates the design process and ultimately lowers product development costs.

The dynamic response characteristics between the multiple energy flows of electricity-hydrogen-heat in the renewable energy DC off-grid hydrogen production system are highly coupled and nonlinear which leads to the complexity of its energy conversion and transmission law. This study proposes a model to describe the dynamic nonlinear energy conversion and transmission laws specific to such systems. The model develops a nonlinear admittance framework and a conversion characteristic matrix for multi-heterogeneous energy flow subsystems based on the operational characteristics of each subsystem within the DC off-grid hydrogen production system. Building upon this foundation an energy hub model for the hydrogen production system is established yielding the electrical thermal and hydrogen energy outputs along with their respective conversion efficiencies for each subsystem. By discretizing time the energy flow at each time node within the hydrogen production system is computed revealing the system’s dynamic energy transfer patterns. Experiments were conducted using measured wind speed and irradiance data from a specific location in eastern China. Results from selected typical days were analyzed and discussed revealing that subsystem characteristics exhibit nonlinear variation patterns. This highlights the limitations of traditional models in accurately capturing these dynamics. Finally a simulation platform incorporating practical control methods was constructed to validate the model’s accuracy. Validation results demonstrate that the model possesses high accuracy providing a solid theoretical foundation for further in-depth analysis of DC off-grid hydrogen production systems.

The conversion of solar to chemical energy is one of the central processes considered in the emerging renewable energy economy. Hydrogen production from water splitting over particulate semiconductor catalysts has often been proposed as a simple and a cost-effective method for largescale production. In this review we summarize the basic concepts of the overall water splitting (in the absence of sacrificial agents) using particulate photocatalysts with a focus on their synthetic methods and the role of the so-called “co-catalysts”. Then a focus is then given on improving light absorption in which the Z-scheme concept and the overall system efficiency are discussed. A section on reactor design and cost of the overall technology is given where the possibility of the different technologies to be deployed at a commercial scale and the considerable challenges ahead are discussed. To date the highest reported efficiency of any of these systems is at least one order of magnitude lower than that deserving consideration for practical applications.