Transmission, Distribution & Storage

Transmission pipelines are the safest and most economical solution for long-distance hydrogen delivery. However safety and reliability issues such as hydrogen’s impact on material properties including fracture toughness and fatigue crack growth could restrict pipeline development. This impact may also increase the risk of several pipeline failure causes including excavation damage corrosion earth movement material failures and other hydrogen damage mechanisms. While many quantitative risk assessment (QRA) studies exist for natural gas pipelines limited work focuses on hydrogen pipelines; the influence of hydrogen must be considered. This work presents a systematic causal model for hydrogen pipeline failures that incorporates multiple failure causes quantifying hydrogen influence on pipeline failures and analyzing how changes in hydrogen effects or operating conditions impact multiple failure causes. According to the results (1) hydrogen has a relatively minor impact on corrosion-related failure; (2) hydrogen greatly affects crack damage (the failure probability can increase by over 1000 times); (3) excavation damage is nearly independent of hydrogen’s effects; (4) earth movement damage shows increased susceptibility (the failure probability can increase by over 10 times). The hydrogen effects change the relative susceptibility of pipelines to these failure causes therefore to implement tailored safety measures under varying operating conditions.

The widespread use of hydrogen as an energy source relies on efficient large-scale storage techniques. Underground Hydrogen Storage (UHS) is a promising solution to balance the gap between renewable energy production and constant energy demand. UHS employs geological structures like salt caverns depleted reservoirs or aquifers for hydrogen storage enabling long-term and scalable storage capacity. Therefore robust and reliable predictive tools are essential to assess the risks associated with geological hydrogen storage. This paper presents a novel reactive transport model called “Underground Gas Flow simulAtions with Coupled bio-geochemical reacTions” or “UGFACT” designed for various gas injection processes accounting for geochemical and microbial reactions. The flow module and geochemical reactions in the UGFACT model were verified against two commercial reservoir simulators E300 and CMG-GEM showing excellent agreement in fluid flow variables and geochemical behaviour. A major step forward of this model is to integrate flow dynamics geochemical reactions and microbial activity. UGFACT was used to conduct a simple storage cycle in a 1D geometry across three different reservoirs each with different mineralogies and water compositions: Bentheimer sandstone Berea sandstone and Grey Berea sandstone under three microbial conditions (“No Reaction” “Moderate Rate” “High Rate”). The findings suggest that Bentheimer sandstone and Berea sandstone sites may experience severe effects from ongoing microbial and geochemical reactions whereas Grey Berea sandstone shows no significant H2 loss. Additionally the model predicts that under the high-rate microbial conditions the hydrogen consumption rate can reach to as much as 11 mmol of H2 per kilogram of water per day (mmol / kg⋅day) driven by methanogenesis and acetogenesis.

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.

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.

Though being attractive on railway decarbonisation for regional lines excessive cost caused by immature hydrogen supply chain is one of the significant hurdles for promoting hydrogen traction to rolling stocks. Therefore we conduct bespoke research on the UK’s hydrogen supply chain for railway concentrating on hydrogen transportation. Firstly a map for the planned hydrogen production plants and potential hydrogen lines is developed with the location capacity and usage. A spatially explicit model for the hydrogen supply chain is then introduced which optimises the existing grid-based methodology on accuracy and applicability. Compressed hydrogen at three pressures and liquid hydrogen are considered as the mediums incorporating by road and rail transport. Furthermore three scenarios for hydrogen rail penetration are simulated respectively to discuss the levelised cost and the most suitable national transport network. The results show that the developed model with mix-integer linear programming (MILP) can well design the UK’s hydrogen distribution for railway traction. Moreover the hydrogen transport medium and vehicle should adjust to suit for different era where the penetration of hydrogen traction varies. The levelised cost of hydrogen (LCOH) decreases from 6.13 £/kg to 5.13 £/kg on average from the conservative scenario to the radical scenario. Applying different transport combinations according to the specific situation can satisfy the demand while reducing cost for multi-supplier and multitargeting hydrogen transport.

Hydrogen plays a vital role in decarbonizing the mobility sector. With the number of hydrogen vehicles expected to drastically increase a network of refuelling stations needs to be built to keep up with the hydrogen demand. However further research and development on hydrogen refuelling infrastructure storage and standardization is required to overcome technical and economic barriers. Simulation tools can reduce time and costs during the design phase but existing models do not fully support calculations of complete and arbitrary system layouts. Therefore a flexible simulation toolbox for rapid investigations of hydrogen refuelling and extraction processes as well as development of refuelling infrastructure vehicle tank systems and refuelling protocols for non-standardized applications was developed. Our model library H2VPATT comprises of typical components found in refuelling infrastructure. The key component is the hydrogen tank model. The simulation model was successfully validated with measurement data from refuelling tests of a 320 l type III tank.

The depletion of reliable energy sources and the environmental and climatic repercussions of polluting energy sources have become global challenges. Hence many countries have adopted various renewable energy sources including hydrogen. Hydrogen is a future energy carrier in the global energy system and has the potential to produce zero carbon emissions. For the non-fossil energy sources hydrogen and electricity are considered the dominant energy carriers for providing end-user services because they can satisfy most of the consumer requirements. Hence the development of both hydrogen production and storage is necessary to meet the standards of a “hydrogen economy”. The physical and chemical absorption of hydrogen in solid storage materials is a promising hydrogen storage method because of the high storage and transportation performance. In this paper physical hydrogen storage materials such as hollow spheres carbon-based materials zeolites and metal– organic frameworks are reviewed. We summarize and discuss the properties hydrogen storage densities at different temperatures and pressures and the fabrication and modification methods of these materials. The challenges associated with these physical hydrogen storage materials are also discussed.

Considerable progress has been made recently in the use of nanoporous materials for hydrogen storage. In this article the current status of the field and future challenges are discussed ranging from important open fundamental questions such as the density and volume of the adsorbed phase and its relationship to overall storage capacity to the development of new functional materials and complete storage system design. With regard to fundamentals the use of neutron scattering to study adsorbed H2 suitable adsorption isotherm equations and the accurate computational modelling and simulation of H2 adsorption are discussed. The new materials covered include flexible metal–organic frameworks core–shell materials and porous organic cage compounds. The article concludes with a discussion of the experimental investigation of real adsorptive hydrogen storage tanks the improvement in the thermal conductivity of storage beds and new storage system concepts and designs.

In the transition towards a more sustainable energy system hydrogen is seen as the key low-emission energy source. However the limited H2 volumetric density hinders its transportation. To overcome this issue liquid organic hydrogen carriers (LOHCs) molecules that can be hydrogenated and upon arrival dehydrogenated for H2 release have been proposed as hydrogen transport media. Considering toluene and dibenzyltoluene as representative carriers this work offers a systematic methodology for the analysis and the comparison of LOHCs in view of identifying cost-drivers of the overall value-chain. A detailed Aspen Plus process simulation is provided for hydrogenation and dehydrogenation sections. Simulation results are used as input data for the economic assessment. The process economics reveals that dehydrogenation is the most impactful cost-item together with the carrier initial loading the latter related to the LOHC transport distance. The choice of the most suitable molecule as H2 carrier ultimately is a trade-off between its hydrogenation enthalpy and cost.

As an important energy source to achieve carbon neutrality green hydrogen has always faced the problems of high use cost and unsatisfactory environmental benefits due to its remote production areas. Therefore a liquid-gaseous cascade green hydrogen delivery scheme is proposed in this article. In this scheme green hydrogen is liquefied into high-density and low-pressure liquid hydrogen to enable the transport of large quantities of green hydrogen over long distances. After longdistance transport the liquid hydrogen is stored and then gasified at transfer stations and converted into high-pressure hydrogen for distribution to the nearby hydrogen facilities in cities. In addition this study conducted a detailed model evaluation of the scheme around the actual case of hydrogen energy demand in Chengdu City in China and compared it with conventional hydrogen delivery methods. The results show that the unit hydrogen cost of the liquid-gaseous cascade green hydrogen delivery scheme is only 51.58 CNY/kgH2 and the dynamic payback periods of long- and short-distance transportation stages are 13.61 years and 7.02 years respectively. In terms of carbon emissions this scheme only generates indirect carbon emissions of 2.98 kgCO2/kgH2 without using utility electricity. In sum both the economic and carbon emission analyses demonstrate the advantages of the liquidgaseous cascade green hydrogen delivery scheme. With further reductions in electricity prices and liquefication costs this scheme has the potential to provide an economically/environmentally superior solution for future large-scale green hydrogen applications.