Transmission, Distribution & Storage

A multi-scale modeling approach for simulating the tensile behavior of the corroded aluminum alloy 2024 T3 was developed accounting for both the geometrical features of corrosion damage and the effect of corrosion-induced hydrogen embrittlement (HE). The approach combines two Finite Element (FE) models: a model of a three-dimensional Representative Unit Cell (RUC) representing an exfoliated area and its correspondent hydrogen embrittled zone (HEZ) and a model of the tensile specimen. The models lie at the micro- and macro-scales respectively. The characteristics of the HEZ are determined from measurements of nanoindentation hardness conducted on pre-corroded specimens. Using the model of the RUC the local homogenized mechanical behavior of the corroded material is simulated. Then the behavior of the exfoliated areas is assigned into different areas (elements) of the tensile specimen and final analyses are performed to simulate the tensile behavior of the corroded material. The approach was applied to model specimens after 8 16 and 24 h exposure periods of the Exfoliation Corrosion (EXCO) test. For validation of the approach tensile tests were used. The numerical results show that this approach is suitable for accurately simulating the tensile behavior of pre-corroded experimental specimens accounting for both geometrical features of corrosion damage and corrosion-induced HE.

Overview of advances in the technology of solid state hydrogen storage methods applying different kinds of novel materials is provided. Metallic and intermetallic hydrides complex chemical hydride nanostructured carbon materials metal-doped carbon nanotubes metal-organic frameworks (MOFs) metal-doped metal organic frameworks covalent organic frameworks (COFs) and clathrates solid state hydrogen storage techniques are discussed. The studies on their hydrogen storage properties are in progress towards positive direction. Nevertheless it is believed that these novel materials will offer far-reaching solutions to the onboard hydrogen storage problems in near future. The review begins with the deficiencies of current energy economy and discusses the various aspects of implementation of hydrogen energy based economy.

Hydrogen has become a strong candidate to be a future energy storage medium but there are technological challenges both in its production and storage. For storage a search for lightweight abundant and non-toxic materials is on the way. An abundant natural material such as wood cellulose would make an ideal storage medium from a sustainability perspective. Here using a combination of static DFT calculations and ab initio molecular dynamics simulations at different temperatures it is shown that wood cellulose has the ability to uptake H2 via a physisorption mechanism based on dispersion interactions of the van der Waals type involving the O-atoms of the d-glucose rings. The absorption causes little to no disturbances on the cellulose structure and H2 is highly mobile in the material. At an external pressure of H2(g) of 0.09 atm and T = 25 °C cellulose has a theoretical gravimetric density of hydrogen storage of ≈1%.

Hydrogen storage is a materials science challenge because for all six storage methods currently being investigated materials with either a strong interaction with hydrogen or without any reaction are needed. Besides conventional storage methods i.e. high pressure gas cylinders and liquid hydrogen the physisorption of hydrogen on materials with a high specific surface area hydrogen intercalation in metals and complex hydrides and storage of hydrogen based on metals and water are reviewed.

Melt spinning was successfully utilized to prepare Mg₂₅−_xY_xNi₉Cu (x = 0 1 3 5 7) alloys producing nanocrystalline and amorphous structures with improved hydrogenation and dehydrogenation performances. The influence of spinning rate on hydrogenation and dehydrogenation thermodynamics and kinetics was studied in detail. XRD and TEM were utilized to characterize the alloy structures. Hydrogenation and dehydrogenation performances were investigated by Sievert apparatus DSC and TGA connected to a H₂ detector. Dehydrogenation activation energies were estimated using both Arrhenius and Kissinger methods. Results show that melt spinning significantly decreases thermodynamic parameters (ΔH and ΔS) and ameliorates desorption kinetics. Dehydrogenation activation energy markedly lowers with increase in spinning rate and is the real driver of amelioration of dehydrogenation kinetics caused by increasing Y content.

Press hardening steel (PHS) is widely applied in current automotive body design. The trend of using PHS grades with strengths above 1500 MPa raises concerns about sensitivity to hydrogen embrittlement. This study investigates the hydrogen delayed fracture sensitivity of steel alloy 32MnB5 with a 2000 MPa tensile strength and that of several alloy variants involving molybdenum and niobium. It is shown that the delayed cracking resistance can be largely enhanced by using a combination of these alloying elements. The observed improvement appears to mainly originate from the obstruction of hydrogen-induced damage incubation mechanisms by the solutes as well as the precipitates of these alloying elements.

Renewable electricity can be converted into hydrogen via electrolysis also known as power-to-H2 (P2H) which when injected in the gas network pipelines provides a potential solution for the storage and transport of this green energy. Because of the variable renewable electricity production the electricity end-user’s demand for “power when required” distribution and transmission power grid constrains the availability of renewable energy for P2H can be difficult to predict. The evaluation of any potential P2H investment while taking into account this consideration should also examine the effects of incorporating the produced green hydrogen in the gas network. Parameters including pipeline pressure drop flowrate velocity and most importantly composition and calorific content are crucial for gas network management. A simplified representation of the Irish gas transmission network is created and used as a case study to investigate the impact on gas network operation of hydrogen generated from curtailed wind power. The variability in wind speed and gas network demands that occur over a 24 h period and with network location are all incorporated into a case study to determine how the inclusion of green hydrogen will affect gas network parameters. This work demonstrates that when using only curtailed renewable electricity during a period with excess renewable power generation despite using multiple injection points significant variation in gas quality can occur in the gas network. Hydrogen concentrations of up to 15.8% occur which exceed the recommended permitted limits for the blending of hydrogen in a natural gas network. These results highlight the importance of modelling both the gas and electricity systems when investigating any potential P2H installation. It is concluded that for gas networks that decarbonise through the inclusion of blended hydrogen active management of gas quality is required for all but the smallest of installations.

Hydrogen embrittlement (HE) of metals has remained a mystery in materials science for more than a century. To try to clarify this mystery tensile tests were conducted at room temperature (RT) on a 316 stainless steel (SS) in air and hydrogen of 70 MPa. With an aim to directly observe the effect of hydrogen on ordering of 316 SS during deformation electron diffraction patterns and images were obtained from thin foils made by a focused ion beam from the fracture surfaces of the tensile specimens. To prove lattice contraction by ordering a 40% CW 316 SS specimen was thermally aged at 400 °C to incur ordering and its lattice contraction by ordering was determined using neutron diffraction by measuring its lattice parameters before and after aging. We demonstrate that atomic ordering is promoted by hydrogen leading to formation of short-range order and a high number of planar dislocations in the 316 SS and causing its anisotropic lattice contraction. Hence hydrogen embrittlement of metals is controlled by hydrogen-enhanced ordering during RT deformation in hydrogen. Hydrogen-enhanced ordering will cause the ordered metals to be more resistant to HE than the disordered ones which is evidenced by the previous observations where furnace-cooled metals with order are more resistant to HE than water-quenched or cold worked metals with disorder. This finding strongly supports our proposal that strain-induced martensite is a disordered phase.

Blending hydrogen into natural gas pipelines is a recent alternative adopted for hydrogen transportation as a mixture with natural gas. In this paper hydrogen embrittlement of steel pipelines originally designed for natural gas transportation is investigated. Solubility permeation and diffusion phenomena of hydrogen molecules into the crystalline lattice structure of the pipeline material are followed up based on transient evolution of internal pressure applied on the pipeline wall. The transient regime is created through changes of gas demand depending on daily consumptions. As a result the pressure may reach excessive values that lead to the acceleration of hydrogen solubility and its diffusion through the pipeline wall. Furthermore permeation is an important parameter to determine the diffusion amount of hydrogen inside the pipeline wall resulting in the embrittlement of the material. The numerical obtained results have shown that using pipelines designed for natural gas conduction to transport hydrogen is a risky choice. Actually added to overpressure and great fluctuations during transients that may cause fatigue and damage the structure also the latter pressure evolution is likely to induce the diffusion phenomena of hydrogen molecules into the lattice of the structure leading to brittle the pipe material. The numerical simulation reposes on solving partial differential equations describing transient gas flow in pipelines coupled with the diffusion equation for mass transfer. The model is built using the finite elements based software COMSOL Multiphysics considering different cases of pipe material; API X52 (base metal and nutrided) and API X80 steels. Obtained results allowed tracking the evolution with time of hydrogen concentration through the pipeline internal wall based on the pressure variation due to transient gas flow. Such observation permits to estimate the amount of hydrogen diffused in the metal to avoid leakage of this flammable gas. Thus precautions may be taken to prevent explosive risks due to hydrogen embrittlement of steel pipelines among other effects that can lead to alter safe conditions of gas conduction.

Some aspects of damage accumulation modelling and brittle fracture processes mechanisms under the combined effect of mechanical loading and hydrogen has been discussed in the article. New mechanism of brittle fracture for metallic materials based on dislocation and phonon structure fingerprints and lattice hydrogen content under the static and dynamic loading at low temperature condition has been proposed. The mechanism based on theoretical research and experimental and numerical studies. The experiments include the energy spectrum of internal friction determination and impact toughness testing for low-temperature brittle-ductile transition revealing. The numerical study based on damage accumulation modeling under the influence of up-hill diffusion in the elastic-plastic problem of solid state by finite element method. A new simple activation model of low temperature and hydrogen influence on damage accumulation process has been proposed. The model shows the rate of damage strong dependence of stress level and hydrogen content and test temperature. The combination of low temperature and high hydrogen content is most dangerous so the weld structures in extreme environment such as the Arctic and Subarctic regions have a high risk of breakage. So it is possible to estimate the energy and phonon spectrum of crystal lattice and predict the properties of microcrystalline and nanostructured materials with the high cold-short threshold on the base of such the approach. There are the recommendations propose to improve the cold resistance of steels and alloys by controlling the characteristics of the dislocation structure of new materials with polycrystalline and ultrafine-grained structure.

With the increase in renewable energy connected to the grid new challenges arise due to its variable supply of power. Therefore it is crucial to develop new methods of storing energy. Hydrogen can fulfil the role of energy storage and even act as an energy carrier since it has a much higher energetic density than batteries and can be easily stored. Considering that the offshore wind sector is facing significant growth and technical advances hydrogen has the potential to be combined with offshore wind energy to aid in overcoming disadvantages such as the high installation cost of electrical transmission systems and transmission losses. This paper aims to outline and discuss the main features of the integration of hydrogen solutions in offshore wind power and to offer a literature review of the current state of hydrogen production from offshore wind. The paper provides a summary of the technologies involved in hydrogen production along with an analysis of two possible hydrogen producing systems from offshore wind energy. The analysis covers the system components including hydrogen storage the system configuration (i.e. offshore vs. onshore electrolyzer) and the potential uses of hydrogen e.g. Power to Mobility Power to Power and Power to Gas.

Proton exchange membrane fuel cells (PEMFCs) are promising clean energy conversion devices in residential transportation and portable applications. Currently a high-pressure tank is the state-of-the-art mode of hydrogen storage; however the energy cost safety and portability (or volumetric hydrogen storage capacity) presents a major barrier to the widespread dissemination of PEMFCs. Here we show an ‘all-polymer type’ rechargeable PEMFC (RCFC) that contains a hydrogen-storable polymer (HSP) which is a solid-state organic hydride as the hydrogen storage media. Use of a gas impermeable SPP-QP (a polyphenylenebased PEM) enhances the operable time reaching up to ca. 10.2 s mg_HSP ⁻¹ which is more than a factor of two longer than that (3.90 s mg_HSP ⁻¹) for a Nafion NRE-212 membrane cell. The RCFCs are cycleable at least up to 50 cycles. The features of this RCFC system including safety ease of handling and light weight suggest applications in mobile light-weight hydrogen-based energy devices.

Integrated energy systems have become an area of interest as with growing energy demand globally means of producing sustainable energy from flexible sources is key to meet future energy demands while keeping carbon emissions low. Hydrogen is a potential solution for providing flexibility in the future energy mix as it does not emit harmful gases when used as an energy source. In this paper an integrated energy system including hydrogen as an energy vector and hydrogen storage is studied. The system is used to assess the behaviour of a hydrogen production and storage system under different renewable energy generation profiles. Two case studies are considered: a high renewable energy generation scenario and a low renewable energy generation scenario. These provide an understanding of how different levels of renewable penetration may affect the operation of an electrolyser and a fuel cell against an electricity import/export pricing regime. The mathematical model of the system under study is represented using the energy hub approach with system optimisation through linear programming conducted via MATLAB to minimise the total operational cost. The work undertaken showcases the unique interactions the fuel cell has with the hydrogen storage system in terms of minimising grid electricity import and exporting stored hydrogen as electricity back to the grid when export prices are competitive.

One alternative for the storage and transport of hydrogen is blending a low amount of hydrogen (up to 15 or 20%) into existing natural gas grids. When demanded hydrogen can be then separated close to the end users using membranes. In this work composite alumina carbon molecular sieves membranes (Al-CMSM) supported on tubular porous alumina have been prepared and characterized. Single gas permeation studies showed that the H₂/CH₄ separation properties at 30 °C are well above the Robeson limit of polymeric membranes. H₂ permeation studies of the H2–CH4 mixture gases containing 5–20% of H2 show that the H2 purity depends on the H₂ content in the feed and the operating temperature. In the best scenario investigated in this work for samples containing 10% of H₂ with an inlet pressure of 7.5 bar and permeated pressure of 0.01 bar at 30 °C the H₂ purity obtained was 99.4%.

Although hydrogen is considered to be one of the most promising green fuels its efficient and safe storage and use still raise several technological challenges. Physisorption in porous materials may offer an attractive means of  storage but the state-of-the-art capacity of these kinds of systems is still limited. To overcome the present drawbacks a deeper understanding of the adsorption and surface diffusion mechanism is required along with new types of adsorbents developed and/or optimised for this purpose. In the present study we compare the hydrogen adsorption behaviour of three carbon gels exhibiting different porosity and/or surface chemistry. In addition to standard adsorption characterisation techniques neutron spin-echo spectroscopy (NSE) has been also applied to explore the surface mobility of the adsorbed hydrogen. Our results reveal that both the porosity and surface chemistry of the adsorbent play a significant role in the adsorption of  in these systems.

Future low-carbon systems with very high shares of variable renewable generation require complex models to optimise investments and operations which must capture high degrees of sector coupling contain high levels of operational and temporal detail and when considering seasonal storage be able to optimise both investments and operations over long durations. Standard energy system models often do not adequately address all these issues which are of great importance when considering investments in emerging energy carriers such as Hydrogen. An advanced energy system model of the Irish power system is built in SpineOpt which considers a number of future scenarios and explores different pathways to the wide-scale adoption of Hydrogen as a low-carbon energy carrier. The model contains a high degree of both temporal and operational detail sector coupling via Hydrogen is captured and the optimisation of both investments in and operation of large-scale underground Hydrogen storage is demonstrated. The results highlight the importance of model detail and demonstrate how over-investment in renewables occur when the flexibility needs of the system are not adequately captured. The case study shows that in 2030 investments in Hydrogen technologies are limited to scenarios with high fuel and carbon costs high levels of Hydrogen demand (in this case driven by heating demand facilitated by large Hydrogen networks) or when a breakthrough in electrolyser capital costs and efficiencies occurs. However high levels of investments in Hydrogen technologies occur by 2040 across all considered scenarios. As with the 2030 results the highest level of investments occur when demand for Hydrogen is high albeit at a significantly higher level than 2030 with increases in investments of large-scale electrolysers of 538%. Hydrogen fuelled compressed air energy storage emerges as a strong investment candidate across all scenarios facilitating cost effective power-to-Hydrogen-to-power conversions.

The last twenty years of an intense research on metal hydroborates as solid hydrogen stores and solid electrolytes are reviewed. It is shown that from the most promising application in hydrogen storage due to their high gravimetric and volumetric capacities the focus has moved to solid electrolytes due to high cation mobility in disordered structures with rotating or tumbling anions-hydroborate clusters. Various strategies of overcoming the strong covalent bonding of hydrogen in hydroborates for hydrogen storage and disordering their structures at room temperature for solid electrolytes are discussed. The important role of crystal chemistry and crystallography knowledge in material design can be read in the cited literature.

Hydrogen has been identified as a fuel of choice for providing clean energy for transport and other applications across the world and the development of materials to store hydrogen efficiently and safely is crucial to this endeavour. Hydrogen has the largest scattering interaction with neutrons of all the elements in the periodic table making neutron scattering ideal for studying hydrogen storage materials. Simultaneous characterisation of the structure and dynamics of these materials during hydrogen uptake is straightforward using neutron scattering techniques. These studies will help us to understand the fundamental properties of hydrogen storage in realistic conditions and hence design new hydrogen storage materials.

Bi-directional solid oxide cell systems (Bi-SOC) are being increasingly considered as an electrical energy storage method and consequently as a means to boost the penetration of renewable energy (RE) and to improve the grid flexibility by power-to-gas electrochemical conversion. A major advantage of these systems is that the same SOC stack operates as both energy storage device (SOEC) and energy producing device (SOFC) based on the energy demand and production. SOEC and SOFC systems are now well-optimised as individual systems; this work studies the effect of using the bi-directionality of the SOC at a system level. Since the system performance is highly dependent on the cell-stack operating conditions this study improves the stack parameters for both operation modes. Moreover the year-round cumulative exergy method (CE) is introduced in the solid oxide cell (SOC) context for estimating the system exergy efficiencies. This method is an attempt to obtain more insightful exergy assessments since it takes into account the operational hours of the SOC system in both modes. The CE method therefore helps to predict more accurately the most efficient configuration and operating parameters based on the power production and consumption curves in a year. Variation of operating conditions configurations and SOC parameters show a variation of Bi-SOC system year-round cumulative exergy efficiency from 33% to 73%. The obtained thermodynamic performance shows that the Bi-SOC when feasible can prove to be a highly efficient flexible power plant as well as an energy storage system.

We investigate the implications of conducting hydrogen-assisted fatigue crack growth experiments in a hydrogen gas environment (in-situ hydrogen charging) or in air (following exposure to hydrogen gas). The study is conducted on welded 42CrMo4 steel a primary candidate for the future hydrogen transport infrastructure allowing us to additionally gain insight into the differences in behavior between the base steel and the coarse grain heat affected zone. The results reveal significant differences between the two testing approaches and the two weld regions. The differences are particularly remarkable for the comparison of testing methodologies with fatigue crack growth rates being more than one order of magnitude higher over relevant loading regimes when the samples are tested in a hydrogen-containing environment relative to the pre-charged samples. Aided by finite element modelling and microscopy analysis these differences are discussed and rationalized. Independent of the testing approach the heat affected zone showed a higher susceptibility to hydrogen embrittlement. Similar microstructural behavior is observed for both testing approaches with the base metal exhibiting martensite lath decohesion while the heat affected zone experienced both martensite lath decohesion and intergranular fracture.

After nearly 25 years of service some of the wires of the tendons of “La Arena” bridge (Spain) started to exhibit the effects of environmental degradation processes. “La Arena” is cable-stayed bridge with 6 towers and a reference span between towers of about 100 meters. After a maintenance inspection of the bridge evidences of corrosion were detected in some of the galvanized wires of the cables. A more in-deep analysis of these wires revealed that many of them exhibited loss of section due to the corrosion process. In order to clarify the causes of this degradation event and to suggest some remedial actions an experimental program was designed. This program consisted of tensile and fatigue tests on some strand samples of the bridge together with a fractographic analysis of the fracture surfaces of the wires its galvanized layer thickness and some hydrogen measurements (hydrogen embrittlement could be another effect of the environmental degradation process).Once the type and extension of the flaws in the wires was characterized a structural integrity assessment of the strands was performed with the aim of quantifying the margins until failure and establishing some maintenance recommendations.

As natural gas (NG) demand increases in China the question arises how the NG infrastructure fit into a low greenhouse gas (GHG) emissions future towards 2050. Herein the potential role of the NG infrastructure in supplying low-carbon gases during 2020–2050 for China at a provincial resolution was analyzed for different scenarios. In total four low-carbon gases were considered in this study: biomethane bio-synthetic methane hydrogen and low-carbon synthetic methane. The results show that the total potential of low-carbon gas production can increase from 1.21 EJ to 5.25 EJ during 2020–2050 which can replace 20%–67% of the imported gas. In particular Yunnan and Inner Mongolia contribute 17% of China’s low-carbon gas production. As the deployment of NG infrastructure can be very different three scenarios replacing imported pipeline NG were found to reduce the expansion of gas infrastructure by 35%–42% while the three scenarios replacing LNG imports were found to increase infrastructure expansion by 31%–53% as compared to the base case. The cumulative avoided GHG emissions for the 6 analyzed scenarios were 6.0–8.3 Gt CO2. The GHG avoidance costs were highly influenced by the NG price. This study shows that the NG infrastructure has the potential to supply low-carbon gases in China thereby significantly reducing GHG emissions and increasing both China’s short- and long-term gas supply independence.

Germany’s energy transition known as ‘Energiewende’ was always very progressive. However it came technically to a halt at the question of large-scale seasonal energy storage for wind and solar which was not available. At the end of the 2000s we combined our knowledge of both electrical and process engineering imitated nature by copying photosynthesis and developed Power-to-Gas by combining water electrolysis with CO2 -methanation to convert water and CO2 together with wind and solar power to synthetic natural gas. Storing green energy by coupling the electricity with the gas sector using its vast TWh-scale storage facility was the solution for the biggest energy problem of our time. This was the first concept that created the term ‘sector coupling’ or ‘sectoral integration’. We first implemented demo sites presented our work in research industry and ministries and applied it in many macroeconomic studies. It was an initial idea that inspired others to rethink electricity as well as eFuels as an energy source and energy carrier. We developed the concept further to include Power-to-Liquid Power-to-Chemicals and other ways to ‘convert’ electricity into molecules and climate-neutral feedstocks and named it ‘Power-to-X’ at the beginning of the 2010s.

Hydrogen can be used to enable decarbonisation of challenging applications such as provision of heat and as a fuel for heavy transport. The UK has set out a strategy for developing a new low carbon hydrogen sector by 2030. Underground storage will be a key component of any regional or national hydrogen network because of the variability of both supply and demand across different end-use applications. For storage of pure hydrogen salt caverns currently remain the only commercially proven subsurface storage technology implemented at scale. A new network of hydrogen storage caverns will therefore be required to service a low carbon hydrogen network. To facilitate planning for such systems this study presents a modelling approach used to evaluate the UK's theoretical hydrogen storage capacity in new salt caverns in bedded rock salt. The findings suggest an upper bound potential for hydrogen storage exceeding 64 million tonnes providing 2150 TWh of storage capacity distributed in three discrete salt basins in the UK. The modelled cavern capacity has been interrogated to identify the practical inter-seasonal storage capacity suitable for integration in a hydrogen transmission system. Depending on cavern spacing a peak load deliverability of between 957 and 1876 GW is technically possible with over 70% of the potential found in the East Yorkshire and Humber region. The range of geologic uncertainty affecting the estimates is approximately ±36%. In principle the peak domestic heating demand of approximately 170 GW across the UK can be met using the hydrogen withdrawn from caverns alone albeit in practice the storage potential is unevenly distributed. The analysis indicates that the availability of salt cavern storage potential does not present a limiting constraint for the development of a low-carbon hydrogen network in the UK. The general framework presented in this paper can be applied to other regions to estimate region-specific hydrogen storage potential in salt caverns.

The Poza de la Sal diapir is a closed circular depression with Cretaceous Mesozoic materials formed by gypsum Keuper clays and a large extension of salt in the center with intercalations of ophite. The low seismic activity of the area the reduced permeability and porosity of the salt caverns and the proximity to the Páramo de Poza wind park make it a suitable place for the construction of a facility for underground storage of green hydrogen obtained from surplus wind power. The design of a cavern for hydrogen storage at a depth of 1000 m takes into account the differences in stresses temperatures and confining pressures involved in the salt deformation process. During the 8 months of the injection phase 23.0 GWh can be stored in the form of hydrogen obtained from the wind energy surplus to be used later in the extraction phase. The injection and extraction ratio must be developed under the conditions of geomechanical safety of the cavity so as to minimize the risks to the environment and people by conditioning the gas pressure inside the cavity to remain within a given range.