Publications

This publication presents the results of a pre-feasibility study to introduce a green hydrogen (GH2) market in Trinidad and Tobago (T&T). The study analyzed the potential supply and competitiveness of producing GH2 in T&T and the actions needed to build a foundation for producing green ammonia and methanol. The study updated previous estimates of renewable energy generation potential in the country. The study also highlighted Trinidad and Tobago's comparative advantage to produce GH2 with its ability to capitalize on existing infrastructure its know-how and capabilities and its long-standing trade relations. Lastly the study identifies demonstration projects and created a roadmap for developing a low carbon hydrogen economy in Trinidad and Tobago.

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.

The paper shows the latest developments of Gexcon’s consequence modelling software EFFECTS with validation based on hydrogen experimental data for different storage conditions and scenarios including liquid hydrogen two-phase jet releases. The effect of atmospheric turbulence on the dispersion and potential worst-case scenarios of hydrogen which are very different from heavy gas releases are discussed. Beside validation for gaseous hydrogen releases a validation study for pressurised liquid hydrogen jet releases including a sensitivity analysis is performed and the results are compared with experimental data.

Ahead of a potential large-scale implementation of hydrogen as an energy carrier in society safety regulation systems should be in place to provide a systematic consideration of safety related concerns. Knowledge is essential for regulatory activities. At the same time it is challenging to obtain sufficient information when regulating emerging technologies – it may be difficult to address informational shortcomings in regulatory matters as analysts can be prone to under-communicate the significance of uncertainties. Furthermore Strength of Knowledge (SoK) has been developed to address the quality of background knowledge in risk analyses. An example of a SoK framework is based on the following four conditions that is used to assess whether knowledge can be considered weak or strong: the issue of simplifications availability and reliability of data consensus among experts and general understanding of the phenomena in question. In theory this concept seems relevant for the introduction of hydrogen as an energy carrier mainly because there is little historical data to develop sound analyses creating uncertainties. However there are no clear-cut guidelines as to how knowledge gaps should be handled in the development of regulatory requirements. In this paper we consider the relevance of a specific approach for SoK assessment in the context of safety and security regulation of hydrogen as an energy carrier in society. We conclude that there are some challenges with the proposed framework and argue that further research should be conducted to identify or develop a method for handling uncertainties in regulatory processes regarding hydrogen systems as energy carriers in societies.

Achieving the required decarbonisation targets by the shipping industry requires a transition to technologies with zero or near-zero greenhouse gas (GHG) emissions. One promising shipping fuel with zero emission of exhaust gases (including CO2) is green hydrogen. This type of fuel recognised as a 100% clean solution is being investigated for feasible use on a service offshore vessel (SOV) working for offshore wind farms. This study aims to examine whether hydrogen may be used on an SOV in terms of the technical and economic challenges associated with the design process and other factors. In the analyses a reference has been made to the current International Maritime Organization (IMO) guidelines and regulations. In this study it was assumed that hydrogen would be directly combusted in a reciprocating internal combustion engine. This engine type was reviewed. In further research hydrogen fuel cell propulsion systems will also be considered. The hydrogen demand was calculated for the assumed data of the SOV and then the volume and number of highpressure tanks were estimated. The analyses revealed that the SOV cannot undertake 14-day missions using hydrogen fuel stored in cylinders on board. These cylinders occupy 66% of the ship’s current volume and their weight including the modular system accounts for 62% of its deadweight. The costs are over 100% higher compared to MDO and LNG fuels and 30% higher than methanol. The actual autonomy of the SOV with hydrogen fuel is 3 days.

As the world races to decarbonize its energy systems the choice between transmitting green energy as electrons through high-voltage direct current (HVDC) lines or as molecules via hydrogen pipelines emerges as a critical decision. This paper considers this pivotal choice and compares the technoeconomic characteristics of these two transmission technologies. Hydrogen pipelines offer the advantage of transporting larger energy volumes but existing projects are dwarfed by the vast networks of HVDC transmission lines. Advocates for hydrogen pipelines see potential in expanding these networks capitalizing on hydrogen’s physical similarities to natural gas and the potential for cost savings. However hydrogen’s unique characteristics such as its small molecular size and compression requirements present construction challenges. On the other hand HVDC lines while less voluminous excel in efficiently transmitting green electrons over long distances. They already form an extensive global network and their efficiency makes them suitable for various applications. Yet intermittent renewable energy sources pose challenges for both hydrogen and electricity systems necessitating solutions like storage and blending. Considering these technologies as standalone competitors belies their complementary nature. In the emerging energy landscape they will be integral components of a complex system. Decisions on which technology to prioritize depend on factors such as existing infrastructure adaptability risk assessment and social acceptance. Furthermore while both HVDC lines and hydrogen pipelines are expected to proliferate other factors such as market maturity of the relevant energy vector government policies and regulatory frameworks around grid development and utilization are also expected to play a crucial role. Energy transition is a multifaceted challenge and accommodating both green molecules and electrons in our energy infrastructure may be the key to a sustainable future. This paper’s insights underline the importance of adopting a holistic perspective and recognising the unique strengths of each technology in shaping a resilient and sustainable energy ecosystem.

A new technical route to incorporate excess electricity (via green hydrogen generation by electrolysis) into a biorefinery to produce modern bioenergy (advanced biofuels) is proposed as a promising alternative. This new route involves storing hydrogen for mobile and stationary applications and can be a three-bird-one-stone solution for the storage of excess electrical energy storage of green hydrogen and high-value utilization of biomass.

CFD modelling of liquified hydrogen boiling and evaporation during the pressurised tank venting is presented. The model is based on the volume-of-fluid method for tracking liquid and gas phases and Lee’s model for phase change. The simulation results are compared against the liquid hydrogen evaporation experiment performed by Tani et al. (2021) in a large-scale pressurised storage tank using experimental pressure dynamics and temperatures measured in gas and liquid phases. The study focuses on tank pressure decrease and recovery phenomena during the first 15 s of the venting process. The model sensitivity have been studied applying different Lee’s model evaporisation-condensation coefficients. The CFD model provided reasonable agreement with the observed pressure and gas phase temperature dynamics during the liquid hydrogen storage depressurisation using Lee’s model coefficient =0.05 s-1. Experimentalists’ hypothesis about particularly intensive boiling in the proximity of thermocouples was supported by close agreement between simulated and experimental saturation temperatures obtained from pressure dynamics.

Widely available and low-cost solar photovoltaics and wind power can enable production of renewable electricity-based hydrogen at many locations throughout the world. Hydrogen is expected to emerge as an important energy carrier constituting some of the final energy demand; however its most important role will be as feedstock for further processing to e-fuels e-chemicals and e-steel. Apart from meeting their own hydrogen demand countries may have opportunities to export hydrogen to countries with area limitations or higher production costs. This paper assesses the feasibility of e-hydrogen imports to Germany and Finland from two case regions with a high availability of low-cost renewable electricity Chile and Morocco in comparison to domestic supply. Special attention is paid to the transport infrastructure which has a crucial impact on the economic viability of imports via two routes shipping and pipelines. This study has found that despite lower e-hydrogen production costs in Morocco and Chile compared to Germany and Finland additional transportation costs make imports of e-hydrogen economically unattractive. In early 2020s imported fuel costs are 39–79% and 34–100% higher than e-hydrogen produced in Germany and Finland respectively. In 2050 imported e-hydrogen is projected to be 39–70% more expensive than locally produced e-hydrogen in Germany and 43–54% in the case of Finland. e-Hydrogen may become a fuel that is mostly produced domestically and may be feasible for imports only in specific locations. Local e-hydrogen production may also lower dependence on imports enhance energy security and add jobs.

For widespread adoption of hydrogen fuel cell powered vehicles such vehicles need to be able to provide similar transportation capabilities as their gasoline/diesel powered counterparts. Meeting this requirement in many regions will necessitate access to tunnels. Previous work completed at Sandia National Laboratories provided high-fidelity consequence modeling of hydrogen vehicle tunnel crashes for a specific fire scenario in selected Massachusetts tunnels. To consider additional tunnels a generalized tunnel safety analysis framework is being developed. This framework aims to be broader than specific fire scenarios in specific tunnels allowing it to be applied to a range of tunnel geometries vehicle types and crash scenarios. Initial steps in the development of the generalized framework are reported within this work. Representative tunnel characteristics are derived based on data for tunnels in the U.S. Tunnel dimensions shapes and traffic levels are among the many characteristics reported within the data that can be used to inform crash scenario specification. Various crash scenario parameters are varied using lower-fidelity consequence modeling to quantify the impact on resulting safety hazards for time-dependent releases. These lower-fidelity models consider the unignited dispersion of hydrogen gas the thermal effects of jet fires and potential impacts of overpressures. Different sizes/classes of vehicles are considered as the total amount of hydrogen onboard may greatly affect scenario-specific consequences. The generalized framework will allow safety assessments to be both more agile and consistent when applied to different types of tunnels.

The economic operation of the integrated energy system faces the problems of coupling between energy production and conversion equipment in the system and the imbalance of various energy demands. Therefore taking system safety as the constraint and minimum economic cost as the objective function including fuel cost operation and maintenance cost this paper proposes the operation dispatching model of the integrated energy system based on hydrogen fuel cell (HFC) including HFC photovoltaic wind turbine electric boiler electric chiller absorption chiller electric energy storage and thermal energy storage equipment. On this basis a distributionally robust optimization (DRO) model is introduced to deal with the uncertainty of wind power and photovoltaic output. In the distributionally robust optimization model Kullback–Leibler (KL) divergence is used to construct an ambiguity set which is mainly used to describe the prediction errors of renewable energy output. Finally the DRO economic dispatching model of the HFC integrated energy system (HFCIES) is established. Besides based on the same load scenario the economic benefits of hybrid energy storage equipment are discussed. The dispatching results show that compared with the scenario of only electric energy storage and only thermal energy storage the economic cost of the scenario of hybrid electric and thermal storage can be reduced by 3.92% and 7.55% respectively and the use of energy supply equipment can be reduced and the stability of the energy storage equipment can be improved.

The energy transition from hydrocarbon-based energy sources to renewable and carbon-free energy sources such as wind solar and hydrogen is facing increasing demands. The decarbonization of global transportation could come true via applying carbon-free fuel such as ammonia especially for internal combustion engines (ICEs). Although ammonia has advantages of high hydrogen content high octane number and safety in storage it is uninflammable with low laminar burning velocity thus limiting its direct usage in ICEs. The purpose of this review paper is to provide previous studies and current research on the current technical advances emerging in assisted combustion of ammonia. The limitation of ammonia utilization in ICEs such as large minimum ignition energy lower flame speed and more NOx emission with unburned NH3 could be solved by oxygen-enriched combustion ammonia–hydrogen mixed combustion and plasma-assisted combustion (PAC). In dual-fuel or oxygen-enriched NH3 combustion accelerated flame propagation speeds are driven by abundant radicals such as H and OH; however NOx emission should be paid special attention. Furthermore dissociating NH3 in situ hydrogen by non-noble metal catalysts or plasma has the potential to replace dual-fuel systems. PAC is able to change classical ignition and extinction S-curves to monotonic stretching which makes low-temperature ignition possible while leading moderate NOx emissions. In this review the underlying fundamental mechanism under these technologies are introduced in detail providing new insight into overcoming the bottleneck of applying ammonia in ICEs. Finally the feasibility of ammonia processing as an ICE power source for transport and usage highlights it as an appealing choice for the link between carbon-free energy and power demand.

Conventional transportation systems are facing many challenges related to reducing fuel consumption noise and pollutants to satisfy rising environmental and economic criteria. These requirements have prompted many researchers and manufacturers in the transportation sector to look for cleaner more efficient and more sustainable alternatives. Powertrains based on fuel cell systems could partially or completely replace their conventional counterparts used in all modes of transport starting from small ones such as scooters to large mechanisms such as commercial airplanes. Since hydrogen fuel cells (HFCs) emit only water and heat as byproducts and have higher energy conversion efficiency in comparison with other conventional systems it has become tempting for many scholars to explore their potential for resolving the environmental and economic concerns associated with the transportation sector. This paper thoroughly reviews the principles and applications of fuel cell systems for the main transportation schemes including scooters bicycles motorcycles cars buses trains and aerial vehicles. The review showed that fuel cells would soon become the powertrain of choice for most modes of transportation. For commercial long-rage airplanes however employing fuel cells will be limited due to the replacement of the axillary power unit (APU) in the foreseeable future. Using fuel cells to propel such large airplanes would necessitate redesigning the airplane structure to accommodate the required hydrogen tanks which could take a bit more time.

The number of Fuel Cell Electric Vehicles (FCEVs) in circulation has undergone a significant increase in recent years. This trend is foreseen to be stronger in the near future. In correlation with the FCEVs market increase the hydrogen delivery infrastructure must be developed. With this aim many countries have announced ambitious projects. For example Spain has the objective of increasing the number of Hydrogen Refuelling Stations (HRS) with public access from three units in operation currently to about 150 by 2030. HRSs are complex systems with high variability in terms of layout design size of components operational strategy hydrogen generation method or hydrogen generation location. This paper is focused on on-site HRS with electrolysis-based hydrogen production which provides interesting advantages when renewable energy is utilized compared to off-site hydrogen production despite their complexity. To optimize HRS design and operation a simulation model must be implemented. This paper describes a generic on-site HRS with electrolysis-based hydrogen production a cascaded multi-tank storage system with multiple compressors renewable energy sources and multiple types of dispensing formats. A modelling approach of the layout is presented and tested with real-based parameters of an HRS currently under development which is capable of producing 11.34 kg/h of green H2 with irradiation at 1000 W/m2. For the operation an operational strategy is proposed. The modelled system is tested through several simulations. A sensitivity analysis of the effects of hydrogen demand and day-ahead hydrogen production objective on emissions demand satisfaction and variable costs is performed. Simulation results show how the operational strategy has achieved service up to 310 FCEVs refuelling events of heavy duty and light duty FCEVs bringing the total H2 sold up to almost 7200 H2kg in one month of winter. Additionally considering variable costs of the energy from the utility grid the model shows a profit in the range of 21–50 k€ for a daily demand of 60 H2kg/day and 100 H2kg/day respectively. In terms of emissions a year simulation with 60 H2kg/day of demand shows specific emissions in the production of H2 in Spain of 6.26 kgCO2eq/H2kg which represents a greenhouse gas emission intensity of 52.26 kgCO2eq/H2MJ.

Limiting global warming to 1.5 ◦C is crucial to prevent the worst effects of climate change. This entails also the decarbonization of the aviation sector which is considered to be a “hard-to-abate” sector and thus requires special attention regarding its sustainability transition. However transition pathways to a potentially climateneutral aviation sector are unclear with different stakeholders having diverse imaginations of the sector's future. This paper aims to analyze socio-technical imaginaries of climate-neutral aviation as different perceptions of various stakeholders on this issue have not been sufficiently explored so far. In that sense this work contributes to the current scientific debate on socio-technical imaginaries of energy transitions for the first time studying the case of the aviation sector. Drawing on six decarbonization reports composed by different interest groups (e.g. industry academia and environmental associations) three imaginaries were explored following the process of a thematic analysis: rethinking travel and behavioral change (travel innovation) radical modernization and technological progress (fleet innovation) and transition to alternative fuels and renewable energy sources (fuel innovation). The results reveal how different and partly conflicting socio-technical imaginaries are co-produced and how the emergence and enforceability of these imaginaries is influenced by the situatedness of their creators indicating that the sustainability transition of aviation also raises political issues. Essentially as socio-technical imaginaries act as a driver for change policymakers should acknowledge the existence of alternative and counter-hegemonic visions created by actors from civil society settings to take an inclusive and equitable approach to implementing pathways towards climate-neutral aviation.

As new sources of energy and advanced technologies are used there is a continuous evolution in energy supply demand and distribution. Advanced nuclear reactors and clean hydrogen have the opportunity to scale together and diversify the hydrogen production market away from fossil fuel-based production. Nevertheless the technical uncertainties surrounding nuclear hydrogen processes necessitate thorough research and a solid development effort. This paper aims to position pink hydrogen for nuclear hydrogen production at the forefront of sustainable energy-related solutions by offering a comprehensive review of recent advancements in nuclear hydrogen production covering both research endeavors and industrial applications. It delves into various pink hydrogen generation methodologies elucidating their respective merits and challenges. Furthermore this paper analyzes the evolving landscape of pink hydrogen in terms of its levelized cost by comparatively assessing different production pathways. By synthesizing insights from academic research and industrial practices this paper provides valuable perspectives for stakeholders involved in shaping the future of nuclear hydrogen production.

The global trend towards decarbonization and the demand for energy security have put hydrogen energy into the spotlight of industry politics and societies. Numerous governments worldwide are adopting policies and strategies to facilitate the transition towards hydrogen-based economies. To assess the determinants of such transition this study presents a comparative analysis of the technological innovation systems (TISs) for hydrogen technologies in Germany and South Korea both recognized as global front-runners in advancing and implementing hydrogen-based solutions. By providing a multi-dimensional assessment of pathways to the hydrogen economy our analysis introduces two novel and crucial elements to the TIS analysis: (i) We integrate the concept of ‘quality infrastructure’ given the relevance of safety and quality assurance for technology adoption and social acceptance and (ii) we emphasize the social perspective within the hydrogen TIS. To this end we conducted 24 semi-structured expert interviews applying qualitative open coding to analyze the data. Our results indicate that the hydrogen TISs in both countries have undergone significant developments across various dimensions. However several barriers still hinder the further realization of a hydrogen economy. Based on our findings we propose policy implications that can facilitate informed policy decisions for a successful hydrogen transition.

Power-to-gas technology can be used to convert excess power from renewable energies to hydrogen by means of water electrolysis. This hydrogen can serve as “chemical energy storage” and be converted back to electricity or fed into the natural gas grid. In the presented study a leak in a household pipe in a single-family house with a 13 KW heating device was experimentally investigated. An admixture of up to 40% hydrogen was set up to produce a scenario of burning leakage. Due to the outflow and mixing conditions a lifted turbulent diffusion flame was formed. This led to an additional examination point and expanded the aim and novelty of the experimental investigation. In addition to the fire safety experimental simulation of a burning leakage the resulting complex properties of the flame namely the lift-off height flame length shape and thermal radiation have also been investigated. The obtained results of this show clearly that as a consequence of the hydrogen addition the main properties of the flame such as lifting height flame temperature thermal radiation and total heat flux densities along the flame have been changed. To supplement the measurements with thermocouples imaging methods based on the Sobel gradient were used to determine the lifting height and the flame length. In order to analyze the determined values a probability density function was created.

One of the benefits of the direct use of hydrogen is its ability to be burned in a similar way to natural gas using appliances with which the community is already familiar. This is particularly true for applications where electrification is neither practicable nor desirable. One common example is domestic cooking stoves where the open flame offers numerous real and perceived benefits to the chef. Similarly many commercial and industrial appliances rely on the unique properties of combustion to achieve a desired purpose that cannot readily be replaced by an alternative to an open flame. Despite the enormous decarbonisation potential of the direct replacement of natural gas with hydrogen there are some operational constraints due to the different burning characteristics of hydrogen. One of the challenges is the low visible light emission from hydrogen flames. The change in visible radiation from the combustion of hydrogen compared with natural gas is a safety concern whereby visual observation of a flame may be difficult. This paper aims to provide clarity on the visual appearance of hydrogen flames via a series of measurements of flame visibility and emission spectra accompanied by the assessment of strategies to improve the safe use of hydrogen.

In order to promote low-carbon fuels such as hydrogen to decarbonize the maritime sector it is crucial to promote clean fuels and zero-emission propulsion systems in demonstrative projects and to showcase innovative technologies such as fuel cells in vessels operating in local public transport that could increase general audience acceptability thanks to their showcase potential. In this study a short sea journey ferry used in the port of Genova as a public transport vehicle is analyzed to evaluate a ”zero emission propulsion” retrofitting process. In the paper different types of solutions (batteries proton exchange membrane fuel cell (PEMFC) solid oxide fuel cell (SOFC)) and fuels (hydrogen ammonia natural gas and methanol) are investigated to identify the most feasible technology to be implemented onboard according to different aspects: ferry daily journey and scheduling available volumes and spaces propulsion power needs energy storage/fuel tank capacity needed economics etc. The paper presents a multi-aspect analysis that resulted in the identification of the hydrogen-powered PEMFC as the best clean power system to guarantee for this specific case study a suitable retrofitting of the vessel that could guarantee a zero-emission journey

Hydrogen has been at the centre of attention since the EU kicked-off its decarbonization agenda at full speed. Many consider it a silver bullet for the deep decarbonization of technically challenging sectors and industries but it is also an attractive option for the gas industry to retain and future-proof its well-developed infrastructure networks. The modelling methodology presented in this report systematically tests the feasibility and cost of different pipeline transportation methods – blending repurposing and dedicated hydrogen pipelines - under different decarbonization pathways and concludes that blending is not a viable solution and pipeline repurposing can lead to excessive investment outlays in the range of EUR 19–25 bn over the modelled period (2020–2050) for the EU-27.

The use of liquid hydrogen in maritime applications is expected to grow in the coming years in order to meet the decarbonisation goals that EU countries and countries worldwide have set for 2050. In this context The Norwegian Public Roads Administration commissioned large-scale LH2 dispersion and explosion experiments both indoors and outdoors which were conducted by DNG GL in 2019 to better understand safety aspects of LH2 in the maritime sector. In this work the DNV unignited outdoor and indoor tests have been simulated and compared with the experiments with the aim to validate the ADREA-HF Computational Fluid Dynamics (CFD) code in maritime applications. Three tests two outdoors and one indoors were chosen for the validation. The outdoor tests (test 5 and 6) involved liquid hydrogen release vertically downwards and horizontal to simulate an accidental leakage during bunkering. The indoor test (test 9) involved liquid hydrogen release inside a closed room to simulate an accident inside a tank connection space (TCS) connected to a ventilation mast.

HyCARE project supported by the Clean Hydrogen Partnership of the European Union deals with a prototype of hydrogen storage tank using a solid-state hydrogen carrier. Up to 40 kilograms of hydrogen are stored in twelve tanks at less than 50 barg and less than 100 °C. The innovative design is based on a standard twenty-foot container including twelve TiFe-based metal hydride (MH) hydrogen storage tanks coupled with a thermal energy storage in phase change materials (PCM). This article aims at showing the main risks related to hydrogen storage in a MH system and the safety barriers considered based on HyCARE’s specific risk analysis.<br/>Regarding the TiFe MH material used to store hydrogen experimental tests showed that the exposure of the MH to air or water did not cause spontaneous ignition. Furthermore an explosion within the solid MH cannot propagate due to internal pore size. Additionally in case of leakage the speed of hydrogen desorption from the MH is self-limited which is an important safety characteristic since it reduces the potential consequences from the hydrogen release scenario.<br/>Regarding the integrated system the critical scenarios identified during the risk analysis were: explosion due to release of hydrogen inside or outside the container internal explosion inside MH tanks due to accidental mix of hydrogen and air and asphyxiation due to inert gas accumulation in the container. This identification phase of the risk analysis allowed to pinpoint the most relevant safety barriers already in place and recommend additional ones if needed to further reduce the risk that were later implemented.<br/>The main safety barriers identified were: material and component selection (including the MH selected) safety interlocks safety valves ventilation gas detection and safety distances.<br/>The risk management process based on risk identification and assessment contributed to coherently integrate inherently safe design features and safety barriers.

This paper presents a comprehensive review of existing explosion mitigation techniques for tunnels and evaluates their applicability in scenarios of hydrogen tank rupture in a fire. The study provides an overview of the current state of the art in tunnel explosion mitigation and discusses the challenges associated with hydrogen explosions in the context of fire incidents. The review shows that there are several approaches available to decrease the effects of explosions including wrapping the tunnel with a flexible and compressible barrier and introducing energy-absorbing flexible honeycomb elements. However these methods are limited to the mitigation of the action and do not consider either the mitigation of the structural response or the effects on the occupants. The study highlights how the structural response is affected by the duration of the action and the natural period of the structural elements and how an accurate design of the element stiffness can be used in order to mitigate the structural vulnerability to the explosion. The review also presents various passive and active mitigation techniques aimed at mitigating the explosion effects on the occupants. Such techniques include tunnel branching ventilation openings evacuation lanes right-angled bends drop-down perforated plates or high-performance fibre-reinforced cementitious composite (HPFRCC) panels for blast shielding. While some of these techniques can be introduced during the tunnel's construction phase others require changes to the already working tunnels. To simulate the effect of blast wave propagation and evaluate the effectiveness of these mitigation techniques a CFD-FEM study is proposed for future analysis. The study also highlights the importance of considering these mitigation techniques to ensure the safety of the public and first responders. Finally the study identifies the need for more research to understand blast wave mitigation by existing structural elements in the application for potential accidents associated with hydrogen tank rupture in a tunnel.

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.