United Kingdom

One of the major challenges in harnessing energy from renewable sources like wind and solar is their intermittent nature. Energy production from these sources can vary based on weather conditions and time of day making it essential to store surplus energy for later use when there is a shortfall. Energy storage systems play a crucial role in addressing this intermittency issue and ensuring a stable and reliable energy supply. Green hydrogen sourced from renewables emerges as a promising solution to meet the rising demand for sustainable energy addressing the depletion of fossil fuels and environmental crises. In the present study underground hydrogen storage in various geological formations (aquifers depleted hydrocarbon reservoirs salt caverns) is examined emphasizing the need for a detailed geological analysis and addressing potential hazards. The paper discusses challenges associated with underground hydrogen storage including the requirement for extensive studies to understand hydrogen interactions with microorganisms. It underscores the importance of the issue with a focus on reviewing the the various past and present hydrogen storage projects and sites as well as reviewing the modeling studies in this field. The paper also emphasizes the importance of incorporating hybrid energy systems into hydrogen storage to overcome limitations associated with standalone hydrogen storage systems. It further explores the past and future integrations of underground storage of green hydrogen within this dynamic energy landscape.

Reducing industrial emissions to achieve net-zero targets by the middle of the century will require profound and sustained changes to how energy intensive industries operate. Preliminary activity is now underway with governments of several developed economies starting to implement policy and providing funding to support the deployment of low carbon infrastructure into high emitting industrial clusters. While clusters appear to offer the economies of scale and institutional capacity needed to kick-start the industrial transition to date there has been little systematic assessment of the factors that may influence the success of these initiatives. Drawing from academic and grey literature this paper presents a rapid evidence assessment of the approaches being used to drive the development of low carbon industrial clusters internationally. Many projects are still at the scoping stage but it is apparent that current initiatives focus on the deployment of carbon capture technologies alongside hydrogen as a future secondary revenue stream. This model of decarbonisation funnels investment into large coastal clusters with access to low carbon electricity and tends to obscure questions about the integration of these technologies with other decarbonisation interventions such as material efficiency and electrification. The technology focus also omits the importance that a favourable location and shared history and culture appears to have played in helping progress the most advanced initiatives; factors that cannot be easily replicated elsewhere. If clusters are to kick-start the low-carbon industrial transition then greater attention is needed to the social and political dimensions of this process and to a broader range of decarbonisation interventions and cluster types than represented by current projects.

This study focuses on development of a CFD model able to simulate the experimentally observed critical nozzle diameter for hydrogen non-premixed flames. The critical diameter represents the minimum nozzle size through which a free jet flame will remain stable at all driving pressures. Hydrogen non-premixed flames will not blow-out at diameters equal to or greater than the critical diameter. Accurate simulation of this parameter is important for assessment of thermally activated pressure relief device (TPRD) performance during hydrogen blowdown from a storage tank. At TPRD diameters below the critical value there is potential for a hydrogen jet flame to blow-out as the storage tank vents potentially leading to hydrogen accumulation in an indoor release scenario. Previous experimental studies have indicated that the critical diameter for hydrogen is approximately 1 mm. In this study flame stability is considered across a range of diameters and overpressures from 0.1 mm to 2 mm and from 0.2 MPa to 20 MPa respectively. The impact of turbulent Schmidt number Sct which is the ratio of momentum diffusivity (kinematic viscosity) and mass diffusivity on the hydrogen concentration profile in the region near the nozzle exit and subsequent influence on critical diameter was investigated and discussed. For lower Sct values the enhanced mass mixing resulted in smaller predicted critical diameters. The use of value Sct=0.61 in the model demonstrated the best agreement with experimental values of the critical diameter. The model reproduced the critical diameter of 1 mm and then was applied to predict flame stability for under-expanded hydrogen jets.

National Nuclear Laboratory (NNL) is aiming to demonstrate through a research and development programme that nuclear enabled hydrogen can be used to support future clean energy systems. Demonstrating the safe operation of hydrogen facilities co-generating with a nuclear reactor will be key to enabling the deployment and success of nuclear enabled hydrogen technologies in the future. During the deployment continuity of supply will be paramount and possibly requires inter-seasonal storage. Co-generation is a means of using a source of energy in this case a nuclear reactor to efficiently produce power and thermal energy. Since a great deal of the heat energy is lost to the environment in a power plant making use of wasted energy for other useful output like the production of hydrogen and direct heating would be advantageous to plant economics and energy system flexibility. The civil nuclear industry is regulated around the world. This approach ensures that all the activities related to the production of power from nuclear and the hazards associated with ionising radiation are controlled in a manner which protects workers members of the public property and the environment. Nuclear safety assessments follow a rigorous process and are required as part of the Nuclear Site Licence. A fundamental requirement which is cited in the UK legislation is that the risks associated with all activities at the licensed site be reduced to As Low As Reasonably Practicable (ALARP). The principle places a requirement on duty holders to implement measures to reduce risk where doing so is considered reasonable and proportionate. The inclusion of risks for hazardous materials associated with the hydrogen production facilities need to be considered and this requires harmonisation of two different safety and regulatory governance regimes which have not previously interacted in this way. The safety demonstration for nuclear facilities is provided through the Safety Case.

The adoption of liquid hydrogen (LH2) as an energy carrier presents significant opportunities for distributing large quantities of hydrogen efficiently. However ensuring safety of LH2 transfer operations requires the evo lution of suitable technologies and regulatory framework. This study offers an extensive overview of technical considerations and safety aspects pertaining to liquid hydrogen installations and mobile applications. A signif icant lack of regulations specifically tailored for LH2 transfer operations is highlighted. Additionally experi mental findings and outcomes of the modelling activities carried out in previous research are presented shedding light on the combustion and ignition behaviour of liquid hydrogen during accident scenarios. The identification of research gaps and ongoing research projects underscores the importance of continued investigation and development of this critical area.

The introduction of hydrogen in natural gas pipeline systems introduces integrity challenges due to the nature of interactions between hydrogen and line pipe steel materials. However not every natural gas pipeline is equal in regards to the challenges potentially posed by the repurposing to hydrogen. Existing codes and practices penalise high-grade materials on the basis of a perceived higher susceptibility to hydrogen embrittlement in regards to their increased strength. This philosophy challenges the realisation of a hydrogen economy because it puts at economical and technical risk the conversion of almost half of the natural gas transmission systems in western countries.

The paper addresses the question whether pipe grade is actually a good proxy to strength and predictor to assess the performance of steel line pipes in hydrogen. Drivers that could affect the suitability of pipeline conversion in hydrogen from an integrity management perspective and industry experience of other hydrogen-charging applications are reviewed. In doing so the paper challenges the basis of the assumption that low-grade steels (up to X52 / L360) are automatically safer for hydrogen repurposing while at the other end of the spectrum higher-grade materials (>X52 / L360) are inevitably less suitable for hydrogen service.

Ultimately the paper discusses that materials sampling and testing of representative line pipes populations should be placed at the core of hydrogen repurposing strategies in order to safely address conversion and to maximize the hydrogen chain value. The paper addresses alternatives to make the sampling smart and cost-effective.

Decarbonising the global housing stock is imperative for reaching climate change targets. In the United Kingdom hydrogen is currently being tested as a replacement fuel for natural gas which could be used to supply low-carbon energy to parts of the country. Transitioning the residential sector towards a net-zero future will call for an inclusive understanding of consumer preferences for emerging technologies. In response this paper explores consumer attitudes towards domestic cooking and heating technologies and energy appliances of the future which could include a role for hydrogen hobs and boilers in UK homes. To access qualitative evidence on this topic we conducted ten online focus groups (N = 58) with members of the UK public between February and April 2022. The study finds that existing gas users wish to preserve the best features of gas cooking such as speed responsiveness and controllability but also desire the potential safety and aesthetic benefits of electric systems principally induction hobs. Meanwhile future heating systems should ensure thermal comfort ease of use energy efficiency and smart performance while providing space savings and noise reduction alongside demonstrable green benefits. Mixed-methods multigroup analysis suggests divergence between support levels for hydrogen homes which implies a degree of consumer heterogeneity. Foremost we find that domestic hydrogen acceptance is positively associated with interest and engagement with renewable energy and fuel poverty pressures. We conclude that internalising the perspectives of consumers is critical to enabling constructive socio-technical imaginaries for low-carbon domestic energy futures.

Green energy is at the forefront of current policy research and engineering but some of the potential fuels require either a lot of deeper research or a lot of infrastructure before they can be implemented. In the case of hydrogen both are true. This report aims to analyse the potential of hydrogen as a future fuel source by performing a life-cycle assessment. Through this the well-to-tank phase of fuel production and the usage phase of the system have been analysed. Models have also been created for traditional fuel systems to best compare results. The results show that hydrogen has great potential to convert marine transport to operating off green fuels when powered through low-carbon energy sources which could reduce a huge percentage of the international community’s greenhouse gas emissions. Hydrogen produced through wind powered alkaline electrolysis produced emission data 5.25 g of CO2 equivalent per MJ compared to the 210 g per MJ produced by a medium efficiency diesel equivalent system a result 40 times larger. However with current infrastructure in most countries not utilising a great amount of green energy production the effects of hydrogen usage could be more dangerous than current fuel sources owing to the incredible energy requirements of hydrogen production with even grid (UK) powered electrolysis producing an emission level of 284 g per MJ which is an increase against standard diesel systems. From this the research concludes that without global infrastructure change hydrogen will remain as a potential fuel rather than a common one.

If hydrogen fuel is available to support the transportation sector decarbonization its usage can be placed either directly onboard in a fuel cell vehicle or indirectly off-board by using a fuel cell power station to produce electricity to charge a battery electric vehicle. Therefore in this work the direct and indirect conversion scenarios of hydrogen to vehicle propulsion were investigated regarding energy efficiency. Thus in the first scenario hydrogen is the fuel for the onboard electricity production to propel a fuel cell vehicle while in the second hydrogen is the electricity source to charge the battery electric vehicle. When simulated for a drive cycle results have shown that the scenario with the onboard fuel cell consumed about 20% less hydrogen demonstrating higher energy efficiency in terms of driving range. However energy efficiency depends on the outside temperature when heat loss utilization is considered. For outside temperatures of − 5 ◦C or higher the system composed of the battery electric vehicle fueled with electricity from the off-board fuel cell was shown to be more energyefficient. For lower temperatures the system composed of the onboard fuel cell again presented higher total (heat + electricity) efficiency. Therefore the results provide valuable insights into how hydrogen fuel can be used for vehicle propulsion supporting the hydrogen economy development.

Porous carbons have been extensively investigated for hydrogen storage but to date appear to have an upper limit to their storage capacity. Here in an effort to circumvent this upper limit we explore the potential of oxygen-rich activated carbons. We describe cellulose acetate-derived carbons that combine high surface area (3800 m2 g−1 ) and pore volume (1.8 cm3 g−1 ) that arise almost entirely (>90%) from micropores with an oxygen-rich nature. The carbons exhibit enhanced gravimetric hydrogen uptake (8.1 wt% total and 7.0 wt% excess) at −196 °C and 20 bar rising to a total uptake of 8.9 wt% at 30 bar and exceptional volumetric uptake of 44 g l −1 at 20 bar and 48 g l −1 at 30 bar. At room temperature they store up to 0.8 wt% (excess) and 1.2 wt% (total) hydrogen at only 30 bar and their isosteric heat of hydrogen adsorption is above 10 kJ mol−1 .