United Kingdom

This paper provides an in-depth analysis of alternative fuels including liquefied natural gas (LNG) hydrogen ammonia and biofuels assessing their feasibility based on operational requirements availability safety concerns and the infrastructure needed for large-scale adoption. Moreover it examines hybrid and fully electric propulsion systems considering advancements in battery technology and the integration of renewable energy sources such as wind and solar power to further reduce SOV emissions. Key findings from this research indicate that LNG serves as a viable short- to medium-term solution for reducing GHG emissions in the SOV sector due to its relatively lower carbon content compared to MDO and HFO. This paper finally insists that while LNG presents an immediate opportunity for emission reduction in the SOV sector a combination of hydrogen ammonia and hybrid propulsion systems will be necessary to meet long-term decarbonisation goals. The findings underscore the importance of coordinated industry efforts technological innovation and supportive regulatory frameworks to overcome the technical economic and infrastructural challenges associated with decarbonising the maritime industry.

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

As part of executing 25 hydrogen-based Power to X (PtX) projects our team of Safety consultants has completed safety and risk assessments for a number of hydrogen production developments. Drawing on this experience we will present the importance of making comparisons between hydrogen specific data sources such as HyRAM and conventional oil and gas data sets and calculation methods to ensure that project design is carried out to the most appropriate data and provides a robust solution to demonstrate risks are managed. This presentation will be based on case studies where Fire and Explosion Risk Assessments (FERA) and Quantitative Risk Assessments (QRA) were conducted. The frequency calculations for these assessments used the release frequencies and ignition probabilities provided in HyRAM. However it is noted that the HyRAM ignition probabilities are derived from a correlation from oil and gas assessments in the 1990s. The oil and gas approach has moved on from this data source and now derives ignition probabilities based on the type of facility and fluid characteristics. To address this evolution a comparison was made between the leak frequencies for equipment in hydrogen service and established oil and gas release frequencies from IOGP. In addition a comparison between the HyRAM recommended ignition probabilities and the correlations used for oil and gas (from OEUK formerly UKOOA) was conducted. By taking this approach it was confirmed that the UKOOA data was more conservative and sensitivity calculations were carried out. It was also noted that as hydrogen technologies are emerging there is a level of uncertainty around the data and comparisons must be regularly made to ensure the most appropriate basis for calculations is used.

Alternative fuels of low or zero carbon content can decarbonise the shipping operations. This study aims at assessing the lifetime environmental-economic sustainability of ammonia and hydrogen as alternatives to diesel fuel for short sea shipping cargo vessels. A model is employed to calculate key performance indicators representing the lifetime financial sustainability and environmental footprint of the case ship using a realistic operating profile and considering several scenarios with different diesel substitution rates. Scenarios meeting the carbon emissions reduction targets set by the International Maritime Organisation (IMO) for 2030 are identified whereas policy measures for their implementation including the emissions taxation are discussed. The derived results demonstrate that the future implementation of carbon emissions taxation in the ranges of 136–965 €/t for hydrogen and 356–2647 €/t for ammonia can support these fuels financial sustainability in shipping. This study provides insights for adopting zero-carbon fuels and as such impacts the de-risking of shipping decarbonisation.

In a first-of-its-kind project for Alberta ATCO Gas and Pipelines Ltd. (ATCO) began delivering a 5% blend of hydrogen (H2) in natural gas into a subsection of the existing Fort Saskatchewan natural gas distribution system (approximately 2100 customers). The project was commissioned in October 2022 with the intention of increasing the blend to 20% H₂ in 2023. As part of project due diligence ATCO in partnership with DNV undertook Quantitative Risk Assessments (QRAs) to understand any risks associated with the introduction of blended gas into its existing distribution system and to its customers. This paper describes key findings from the QRAs through the comparison of risks associated with H2 blended natural gas at concentrations of 5% and 20% H₂ and the current natural gas configuration. The impact of operating pressure and hydrogen blend composition formed a sensitivity study completed as part of this work. To provide context and to help interpret the results an individual risk (IR) level of 1 × 10-6 per year was utilised as a reference threshold for the limit of the ‘broadly acceptable’ risk level and juxtaposed against comparable risk scenarios. Although adding hydrogen increases the IR of ignited releases from mains services meters regulators and end user appliances the ignited release IR was always well below the broadly acceptable reference criterion for all operating pressures and blend cases considered as part of the project. The IR associated with carbon monoxide poisoning dominates the overall IR and the results demonstrate that the reduction in carbon monoxide poisoning associated with the introduction of H₂ blended natural gas negates any incremental risk associated with ignited releases due to H₂ blended gas. The paper also explains how the results of the QRA were incorporated into Engineering Assessments as per the requirements of CSA Z662:19 [1] to justify the conversion of existing natural gas infrastructure to H₂ blended gas infrastructure.

The UK government’s plans to decarbonise residential heating will mean major changes to the energy system whatever the specific technology pathway chosen driving a range of impacts on users and suppliers. We use an energy system model (UK TIMES) to identify the potential energy system impacts of alternative pathways to low or zero carbon heating. We find that the speed of transitioning can affect the network investment requirements the overall energy use and emissions generated while the primary heating fuel shift will determine which sectors and networks require most investment. Crucially we identify that retail price differences between heating fuels in the UK particularly gas and electricity could erode or eliminate bill savings from switching to more efficient heating systems.

This report presents an analysis of how hydrogen and battery technologies are likely to be utilised in different sectors within the UK including transportation manufacturing the built environment and power. In particular the report compares the use of hydrogen and battery technology across these sectors. In addition it evaluates where these technologies will be in competition where one technology will dominate and where a combination of the two may be used. This sector analysis draws on DNV’s knowledge and experience within both the battery and hydrogen industries along with a review of studies available in the public domain. The analysis has been incorporated into DNV’s Energy Transition Outlook model an integrated system-dynamics simulation model covering the energy system which provides an independent view of the energy outlook from now until 2050. The modelling which includes data on costs demand supply policy population and economic indicators enables the non-linear interdependencies between different parameters to be considered so that decisions made in one sector influence the decision made in another.

Transportation is the sector responsible for the largest greenhouse gas emission in the UK. To mitigate its impact on the environment and move towards net-zero emissions by 2050 hydrogen-fuelled transportation has been explored through research and development as well as trials. This article presents an overview of relevant technologies and issues that challenge the supply use and marketability of hydrogen for transportation application in the UK covering on-road aviation maritime and rail transportation modes. The current development statutes of the different transportation modes were reviewed and compared highlighting similarities and differences in fuel cells internal combustion engines storage technologies supply chains and refuelling characteristics. In addition common and specific future research needs in the short to long term for the different transportation modes were suggested. The findings showed the potential of using hydrogen in all transportation modes although each sector faces different challenges and requires future improvements in performance and cost development of innovative designs refuelling stations standards and codes regulations and policies to support the advancement of the use of hydrogen.

This work formed part of the H21 programme whose objective is to reach the point whereby it is feasible to convert the existing natural gas (NG) distribution network to 100% hydrogen (H2) and provide a contribution to decarbonising the UK’s heat and power sectors with the focus on decarbonised fuel at point of use. Hydrogen has an ATEX Gas Group of IIC compared to IIA for natural gas which means further precautions are necessary to prevent the ignition of hydrogen during network operations. Both electrostatic and friction ignition risks were considered. Network operations considered include electrostatic precautions for polyethylene (PE) pipe and cutting and drilling of metallic pipes. As a result of the updated basis of safety from ignition considerations existing flow stopping methods were reviewed to see if they were compatible. Commonly used flow stopping methods were tested under laboratory conditions with hydrogen following the methodologies specified in the Gas Industry Standards (GIS). A new basis of safety for flow stopping has been proposed that looks at the flow past the secondary stop as double isolations are recommended for use with hydrogen.

A growing share of renewable energy production in the energy supply systems is key to reaching the European political goal of zero CO2 emission in 2050 highlighted in the green deal. Linked to the irregular production of solar and wind energies which have the highest potential for development in Europe massive energy storage solutions are needed as energy buffers. The European project HyPSTER [1] (Hydrogen Pilot STorage for large Ecosystem Replication) granted by the Clean Hydrogen Partnership addresses this topic by demonstrating a cyclic test in an experimental salt cavern filled with hydrogen up to 3 tons using hydrogen that is produced onsite by a 1 MW electrolyser. One specific objective of the project is the assessment of the risks and environmental impacts of cyclic hydrogen storage in salt caverns and providing guidelines for safety regulations and standards. This paper highlights the first outcome of the task WP5.5 of the HyPSTER project addressing the regulatory and normative frameworks for the safety of hydrogen storage in salt caverns from some selected European Countries which is dedicated to defining recommendations for promoting the safe development of this industry within Europe.

Coastal areas particularly islands are especially vulnerable to climate change due to their geographic and climate conditions. Reaching decarbonisation targets is a long process which will require radical changes and ‘out of the box’ thinking. In this context islands have become laboratories for the green transition by providing spaces for exploring possibilities and alternatives. Here we explore how hydrogen (H2) energy technologies can be a critical ally for island production of renewable electricity in part by providing a storage solution. However given the abundance of sunlight on many islands we also note the huge potential for a more profound engagement between renewables and hydrogen technologies via the co-generation of ‘green hydrogen’ using solar fuels technology. Solar hydrogen is a clean energy carrier produced by the direct or indirect use of solar irradiation for water-splitting processes such as photovoltaic systems coupled with electrolysers and photoelectrochemical cells. While this technology is fast emerging we question to what extent sufficient policy support exists for such initiatives and how they could be scaled up. We report on a case study of a pilot H2 plant in the Canary Islands and we offer recommendations on early-stage policy implications for hydrogen and other solar fuels in an island setting. The paper draws on the literature on islands as policy laboratories and the multi-level perspective on energy transitions. We argue that particular attention needs to be given to discrete issues such as research and planning and better synchronising between emerging local technology niches the various regulatory regimes for energy together with global trends.

Hydrogen refuelling is imperative for the emerging market of hydrogen vehicles. The pressure control valve (PCV) at the hydrogen refuelling station (HRS) plays a major role in ensuring that hydrogen delivery to the vehicle follows the prescribed refuelling protocols. A three-dimensional CFD model with a detailed resolution of PCV motion affecting heat and mass transfer is developed. The PCV motion controlling the mass flow rate is simulated using dynamic mesh. The CFD model captures refuelling from high-pressure tanks through entire HRS equipment to onboard tanks capturing pressure and temperature changes upstream and downstream of the PCV. The Joule-Thomson effect resulting in a hydrogen temperature increase at PCV is captured using the NIST real gas database. The model is validated against Test No.1 of NREL on refuelling through the entire equipment of HRS. The CFD model can be used to design HRS equipment parameters including PCV and develop efficient refuelling protocols.

Recent advances in hydrogen internal combustion technologies highlight its potential for high efficiency and zero carbon emissions offering a promising alternative to fossil fuels. This paper investigates the effects of valve timings and overlaps on engine performance combustion characteristics and emissions in a boosted directinjection single-cylinder spark ignition engine using both gasoline and hydrogen. Optimized direct hydrogen injection effectively eliminates backfires and hydrogen slip during positive cam overlaps significantly reducing the pumping mean effective pressure. The study’s primary finding demonstrates the potential of hydrogen to operate as a direct substitute for a gasoline engine without necessitating changes to the cam profiles at the high load operation. Furthermore the study demonstrates that hydrogen leads to much higher thermal efficiencies across a wider range of engine loads when operated at a lean air-to-fuel ratio of 2.75. The engine operating with such a lean-burn hydrogen mixture keeps the engine-out NOx emission at ultra-low levels. Compared to gasoline hydrogen exhibits greater stability and a reduced reliance on camshaft timing during engine operation.

The main aim of this study deals with the potential evaluation of a fluidized bed membrane reactor (FBMR) for hydrogen production as a clean fuel carrier via methanol steam reforming reaction comparing its performance with other reactors including packed bed membrane reactors (PBMR) fluidized bed reactors (FBR) and packed bed reactors (PBR). For this purpose a two-dimensional axisymmetric numerical model was developed using computational fluid dynamics (CFD) to simulate the reactor performances. Model accuracy was validated by comparing the simulation results for PBMR and PB with experimental data showing an accurate agreement within them. The model was then employed to examine the effects of key operating parameters including reaction temperature pressure steam-to-methanol molar ratio and gas volumetric space velocity on reactor performance in terms of methanol conversion hydrogen yield hydrogen recovery and selectivity. At 573 K 1 bar a feed molar ratio of 3/1 and a space velocity of 9000 h−1 the PBMR reached the best results in terms of methanol conversion hydrogen yield hydrogen recovery and hydrogen selectivity such as 67.6% 69.5% 14.9% and 97.1% respectively. On the other hand the FBMR demonstrated superior performance with respect to the latter reaching a methanol conversion of 98.3% hydrogen yield of 95.8% hydrogen recovery of 74.5% and hydrogen selectivity of 97.4%. These findings indicate that the FBMR offers significantly better performance than the other reactor types studied in this work making it a highly efficient method for hydrogen production through methanol steam reforming and a promising pathway for clean energy generation.

The iron and steel industry contributes approximately 25% of global industrial CO2 emissions necessitating substantial decarbonisation efforts. Hydrogen-based iron and steel plants (HISPs) which utilise hydrogen-based direct reduction of iron ore followed by electric arc furnace steelmaking have attracted substantial research interest. However commercialisation of HISPs faces economic feasibility issues due to the high electricity costs of hydrogen production. To improve economic feasibility HISPs are jointly powered by local renewable generators and bulk power grid i.e. by a grid-assisted renewable energy system. Given the variability of renewable energy generation and time-dependent electricity prices flexible scheduling of HISP production tasks is essential to reduce electricity costs. However cost-effectively scheduling of HISP production tasks is non-trivial as it is subject to critical operational constraints arising from the tight coupling and distinct operational characteristics of HISPs sub-processes. To address the above issues this paper proposes an integrated resource-task network (RTN) to elaborately model the critical operational constraints such as resource balance task execution and transfer time. More specifically each sub-process is first modelled as an individual RTN which is then seamlessly integrated through boundary dependency constraints. By embedding the formulated operational constraints into optimisation a cost-effective scheduling model is developed for HISPs powered by the grid-assisted renewable energy system. Numerical results demonstrate that compared to conventional scheduling approaches the proposed method significantly reduces total operational costs across various production scales.

The transport sector is considered to be a significant contributor to greenhouse gas emissions as this sector emits about one-fourth of global CO2 emissions. Transport emissions contribute toward climate change and have been linked to adverse health impacts. Therefore alternative and sustainable transport options are urgent for decarbonising the transport sector and mitigating those issues. Hydrogen fuel cell vehicles are a potential alternative to conventional vehicles which can play a significant role in decarbonising the future transport sector. This study critically analyses the recent works related to hydrogen fuel cell integration into vehicles modelling and experimental investigations of hydrogen fuel cell vehicles with various powertrains. This study also reviews and analyses the performance energy management strategies lifecycle cost and emissions of fuel cell vehicles. Previous literature suggested that the fuel consumption and well-to-wheel greenhouse gas emissions of hydrogen fuel cell-powered vehicles are significantly lower than that of conventional internal combustion vehicles. Hydrogen fuel cell vehicles consume about 29–66 % less energy and cause approximately 31–80 % less greenhouse gas emissions than conventional vehicles. Despite this the lifecycle cost of hydrogen fuel cell vehicles has been estimated to be 1.2–12.1 times higher than conventional vehicles. Even though there has been recent progress in energy management in hydrogen fuel cell electric vehicles there are a number of technical and economic challenges to the commercialisation of hydrogen fuel cell vehicles. This study presents current knowledge gaps and details future research directions in relation to the research advancement of hydrogen fuel cell vehicles.

The growing need for hydrogen indicates that there is likely to be a demand for transporting hydrogen. Hydrogen pipelines are an economical option but the issue of hydrogen damage to pipeline steels needs to be studied and investigated. So far limited research has been dedicated to determining how the choice of inspection method for pipeline integrity management changes depending on the presence of a coating. Thus this review aims to evaluate the effectiveness of inspection methods specifically for detecting the defects formed uniquely in coated hydrogen pipelines. The discussion will begin with a background of hydrogen pipelines and the common defects seen in these pipelines. This will also include topics such as blended hydrogen-natural gas pipelines. After which the focus will shift to pipeline integrity management methods and the effectiveness of current inspection methods in the context of standards such as ASME B31.12 and BS 7910. The discussion will conclude with a summary of newly available inspection methods and future research directions.

Of all the alternatives to hydrocarbon fuels hydrogen offers the greatest long-term potential to radically reduce the many problems inherent in fuel used for transportation. Hydrogen vehicles have zero tailpipe emissions and are very efficient. If the hydrogen is made from renewable sources such as nuclear power or fossil sources with carbon emissions captured and sequestered hydrogen use on a global scale would produce almost zero greenhouse gas emissions and greatly reduce air pollutant emissions. The aim of this work is to realise a traceability chain for hydrogen flow metering in the range typical for fuelling applications in a wide pressure range with pressures up to 875 bar (for Hydrogen Refuelling Station - HRS with Nominal Working Pressure of 700 bar) and temperature changes from −40 °C (pre-cooling) to 85 °C (maximum allowed vehicle tank temperature) in accordance with the worldwide accepted standard SAE J2601. Several HRS have been tested in Europe (France Netherlands and Germany) and the results show a good repeatability for all tests. This demonstrates that the testing equipment works well in real conditions. Depending on the installation configuration some systematic errors have been detected and explained. Errors observed for Configuration 1 stations can be explained by pressure differences at the beginning and end of fueling in the piping between the Coriolis Flow Meter (CFM) and the dispenser: the longer the distance the bigger the errors. For Configuration 2 where this distance is very short the error is negligible.

he use of hydrogen (H2) as a substitute for fossil fuel which accounts for the majority of the world’s energy is environmentally the most benign option for the reduction of CO2 emissions. his will require gigawatt-scale storage systems and as such H2 storage in porous rocks in the subsurface will be required. ccurate estimation of the thermodynamic and transport properties of H2 mixed with other gases found within the storage system is therefore essential for the efcient design for the processes involved in this system chain. In this study we used the established and regarded GERG-2008 Equation of State (EoS) and SuperRPP model to predict the thermo-physical properties of H2 mixed with CH4 N2 CO2 and a typical natural gas from the North-Sea. he data covers a wide range of mole fraction of H2 (10–90 Mole%) pressures (0.01–100MPa) and temperatures (200–500K) with high accuracy and precision. Moreover to increase ease of access to the data a user-friendly software (H2Themobank) is developed and made publicly available.

Low carbon hydrogen is essential to achieve the Government’s Clean Energy Superpower and Growth Missions. It will be a crucial enabler of a low carbon and renewables-based energy system and will help to deliver new clean energy industries which can support good jobs in our industrial heartlands and coastal communities. Hydrogen presents significant growth and economic opportunities across the UK by enhancing our energy security providing flexible cleaner energy for our power system and helping to decarbonise vital UK industries. Hydrogen has a critical role in helping to achieve our Clean Energy Superpower Mission. It can provide flexible low carbon power generation meaning we can use hydrogen to produce electricity during extended periods of low renewable output. Hydrogen can also provide interseasonal energy storage through conversion of electricity into hydrogen and then back into electricity at times of need using a combination of hydrogen production storage and hydrogen to power. To advance our Clean Energy and Growth Missions hydrogen also has a unique role in transitioning crucial UK industries away from oil and gas and towards a clean homegrown source of fuel. Hydrogen can decarbonise hard-to-abate sectors like chemicals and heavy transport complementing our wider electrification efforts and accelerating our progress to net zero. Using our strong domestic expertise and favourable geology geography and infrastructure backing UK hydrogen can unlock significant economic opportunities and new low carbon jobs of the future. Government has an ambitious range of policies in place to incentivise and support industry to invest in low carbon hydrogen. The recent Hydrogen Skills Workforce Assessment an industry-led study undertaken by the Hydrogen Skills Alliance estimated that the UK hydrogen economy could support 29000 direct jobs and 64500 indirect jobs by 2030. Since establishing in Summer 2024 this Government has already made significant progress in delivering the UK hydrogen economy. This includes confirming support for the 11 successful Hydrogen Allocation Round 1 projects announcing up to £21.7 billion of available funding to launch the UK’s new carbon capture utilisation and storage industry and publishing our hydrogen to power consultation response with an aim to establish a new hydrogen to power business model. We have also launched three new bodies – the National Energy System Operator Great British Energy and the National Wealth Fund – which will help to deliver a world-class energy system including for low carbon hydrogen. This December 2024 Hydrogen Strategy Update to the Market sets out the key milestones achieved by the Department for Energy Security and Net Zero in 2024 to deliver the hydrogen economy and an ambitious forward look at our next steps and upcoming opportunities. To achieve net zero and create a thriving and resilient energy landscape we are already working at considerable pace to deliver a world-leading UK hydrogen sector.

CO2 emissions have been identified as the main driver for climate change with devastating consequences for the global natural environment. The steel industry is responsible for ~7–11% of global CO2 emissions due to high fossil-fuel and energy consumption. The onus is therefore on industry to remedy the environmental damage caused and to decarbonise production. This desk research report explores the Bio Steel Cycle (BiSC) and proposes a seven-step-strategy to overcome the emission challenges within the iron and steel industry. The true levels of combined CO2 emissions from the blast-furnace and basic-oxygen-furnace operation at 4.61 t of CO2 emissions/t of steel produced are calculated in detail. The BiSC includes CO2 capture implementing renewable energy sources (solar wind green H2 ) and plantation for CO2 absorption and provision of biomass. The 7-step-implementation-strategy starts with replacing energy sources develops over process improvement and installation of flue gas carbon capture and concludes with utilising biogas-derived hydrogen as a product from anaerobic digestion of the grown agrifood in the cycle. In the past CO2 emissions have been seemingly underreported and underestimated in the heavy industries and implementing the BiSC using the provided seven-steps-strategy will potentially result in achieving net-zero CO2 emissions in steel manufacturing by 2030.

With the growing concern about climate issues and the urgent need to reduce carbon emissions hydrogen has attracted increasing attention as a clean and renewable vehicle energy source. However the storage of flammable hydrogen gas is a major challenge and it restricts the commercialisation of fuel cell electric vehicles (FCEVs). This paper provides a comprehensive review of common on-board hydrogen storage tanks possible failure mechanisms and typical manufacturing methods as well as their future development trends. There are generally five types of hydrogen tanks according to different materials used with only Type III (metallic liner wrapped with composite) and Type IV (polymeric liner wrapped with composite) tanks being used for vehicles. The metallic liner of Type III tank is generally made from aluminium alloys and the associated common manufacturing methods such as roll forming deep drawing and ironing and backward extrusion are reviewed and compared. In particular backward extrusion is a method that can produce near net-shape cylindrical liners without the requirement of welding and its tool designs and the microstructural evolution of aluminium alloys during the process are analysed. With the improvement and innovation on extrusion tool designs the extrusion force which is one of the most demanding issues in the process can be reduced significantly. As a result larger liners can be produced using currently available equipment at a lower cost.

Many simplified methods for estimating blast loads from a hydrogen or vapor cloud explosion are unable to take into account the accurate geometry of confining spaces obstacles or landscape that may significantly interact with the blast wave and influence the strength of blast loads. Computation fluid dynamics (CFD) software Viper::Blast which was originally developed for the simulation of the detonation of high explosives is able to quickly and easily model geometry for blast analyses however its use for vapor cloud explosions and deflagrations is not well established. This paper describes the results of an investigation into the suitability of Viper::Blast for use in modeling hydrogen deflagration and detonation events from various experiments in literature. Detonation events have been captured with a high degree of detail and relatively little uncertainty in inputs while deflagration events are significantly more complex. An approach is proposed that may allow for a reasonable bounding of uncertainty potentially leading to an approach to CFD-based Monte Carlo analyses that are able to address a problem’s true geometry while remaining reasonably pragmatic in terms of run-time and computational investment. This will allow further exploration of practical CFD application to inform hydrogen safety in the engineering design assessment and management of energy mobility and transport systems infrastructure and operations.

Hydrogen is a key pillar in the global Net Zero strategy. Rapid scaling up of hydrogen production transport distribution and utilization is expected. This entails that hydrogen which is traditionally an industrial gas will come into proximity of populated urban areas and in some situations handled by the untrained public. To realize all their benefits hydrogen and its technologies must be safely developed and deployed. The specific properties of hydrogen involving wide flammability range low ignition energy and fast flame speed implies that any accidental release of hydrogen can be easily ignited. Comparing with conventional fuels combustion systems fueled by hydrogen are also more prone to flame instability and abnormal combustion. This paper aims to provide a comprehensive review about combustion research related to hydrogen safety. It starts with a brief introduction which includes some overview about risk analysis codes and standards. The core content covers ignition fire explosions and deflagration to detonation transition (DDT). Considering that DDT leads to detonation and that detonation may also be induced directly under special circumstances the subject of detonation is also included for completeness. The review covers laboratory medium and large-scale experiments as well as theoretical analysis and numerical simulation results. While highlights are provided at the end of each section the paper closes with some concluding remarks highlighting the achievements and key knowledge gaps.

Hydrogen is anticipated to play a key role in global decarbonization and within the UK’s pathway to achieving net zero targets. However as the production of hydrogen expands in line with government strategies a key concern is where this hydrogen will be stored for later use. This study assesses the different large-scale storage options in geological structures available to the UK and addresses the surrounding uncertainties moving towards establishing a hydrogen economy. Currently salt caverns look to be the most favourable option considering their proven experience in the storage of hydrogen especially high purity hydrogen natural sealing properties low cushion gas requirement and high charge and discharge rates. However their geographical availability within the UK can act as a major constraint. Additionally a substantial increase in the number of new caverns will be necessary to meet the UK’s storage demand. Salt caverns have greater applicability as a good short-term storage solution however storage in porous media such as depleted hydrocarbon reservoirs and saline aquifers can be seen as a long-term and strategic solution to meet energy demand and achieve energy security. Porous media storage solutions are estimated to have capacities which far exceed projected storage demand. Depleted fields have generally been well explored prior to hydrocarbon extraction. Although many saline aquifers are available offshore UK geological characterizations are still required to identify the right candidates for hydrogen storage. Currently the advantages of depleted gas reservoirs over saline aquifers make them the favoured option after salt caverns.