Transmission, Distribution & Storage

Transporting hydrogen gas has long been identified as one of the key issues to scaling up the hydrogen economy. Among various means of transportation many countries are considering using the existing natural gas pipeline networks for hydrogen transmission. This paper examines the implications of transporting hydrogen on the operational metrics of the high-pressure natural gas networks. A model of the GB high-pressure gas network was developed which has a high granularity with 294 nodes 356 pipes and 24 compressor stations. The model was developed using Synergi Gas a hydraulic pipeline network simulation software. By performing unsteady-state analysis pressure levels linepack levels and compressor energy consumption were simulated with 10-minute time steps. Additionally component tracing analysis was utilised to examine the variations in gas composition when hydrogen is injected into the gas network. Five scenarios were developed: one benchmark scenario representing the network transporting natural gas in 2018; one scenario where demand and supply levels are projected for 2035 but no hydrogen was transported by the network; two hydrogen injection scenarios in 2035 considering different geographical locations for hydrogen injection into the gas network; and lastly one pure hydrogen transmission scenario for 2050. The studies found that the GB’s high-pressure gas network could accept 20% volumetric hydrogen injection without significantly impacting network operation. Pressure levels and compressor energy consumption remain within the operational range. The geographical distribution of hydrogen injection points would highly affect the percentage of hydrogen across the network. Pure hydrogen transportation will cause significant variations in network linepack and increase compressor energy consumption significantly compared to other case studies. The findings signal that operating a network with pure hydrogen is possible only when it is prepared for these changes.

Hydrogen has been studied extensively as a potential enabler of the energy transition from fossil fuels to renewable sources. It promises a feasible decarbonisation route because it can act as an energy carrier a heat source or a chemical reactant in industrial processes. Hydrogen can be produced via renewable energy sources such as solar hydro or geothermic routes and is a more stable energy carrier than intermittent renewable sources. If hydrogen can be stored efficiently it could play a crucial role in decarbonising industries. For hydrogen to be successfully implemented in industrial systems its impact on infrastructure needs to be understood quantified and controlled. If hydrogen technology is to be economically feasible we need to investigate and understand the retrofitting of current industrial infrastructure. Currently there is a lack of comprehensive knowledge regarding alloys and components performance in long-term hydrogen-containing environments at industrial conditions associated with high-temperature hydrogen processing/production. This review summarises insights into the gaps in hydrogen embrittlement (HE) research that apply to high-temperature high-pressure systems in industrial processes and applications. It illustrates why it is still important to develop characterisation techniques and methods for hydrogen interaction with metals and surfaces under these conditions. The review also describes the implications of using hydrogen in large-scale industrial processes.

Underground Hydrogen Storage (UHS) is an emerging large-scale energy storage technology. Researchers are investigating its feasibility and performance including its injectivity productivity and storage capacity through numerical simulations. However several ad-hoc relative permeability and capillary pressure functions have been used in the literature with no direct link to the underlying physics of the hydrogen storage and production process. Recent relative permeability measurements for the hydrogen-brine system show very low hydrogen relative permeability and strong liquid phase hysteresis very different to what has been observed for other fluid systems for the same rock type. This raises the concern as to what extend the existing studies in the literature are able to reliably quantify the feasibility of the potential storage projects. In this study we investigate how experimentally measured hydrogen-brine relative permeability hysteresis affects the performance of UHS projects through numerical reservoir simulations. Relative permeability data measured during a hydrogen-water core-flooding experiment within ADMIRE project is used to design a relative permeability hysteresis model. Next numerical simulation for a UHS project in a generic braided-fluvial water-gas reservoir is performed using this hysteresis model. A performance assessment is carried out for several UHS scenarios with different drainage relative permeability curves hysteresis model coefficients and injection/production rates. Our results show that both gas and liquid relative permeability hysteresis play an important role in UHS irrespective of injection/production rate. Ignoring gas hysteresis may cause up to 338% of uncertainty on cumulative hydrogen production as it has negative effects on injectivity and productivity due to the resulting limited variation range of gas saturation and pressure during cyclic operations. In contrast hysteresis in the liquid phase relative permeability resolves this issue to some extent by improving the displacement of the liquid phase. Finally implementing relative permeability curves from other fluid systems during UHS performance assessment will cause uncertainty in terms of gas saturation and up to 141% underestimation on cumulative hydrogen production. These observations illustrate the importance of using relative permeability curves characteristic of hydrogen-brine system for assessing the UHS performances.

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.

Salt caverns have great potential to store relevant amounts of hydrogen as part of the energy transition. However the durability and suitability of commonly used steels for piping in hydrogen salt caverns is still under research. In this work aging effects focusing on corrosion and cracking patterns of casing steel API 5CT J55 and “H2ready” pipeline steel API 5L X56 were investigated with scanning electron microscopy and energy dispersive X-ray spectroscopy after accelerated stress tests with pressure/temperature cycling under hydrogen salt cavern-like conditions. Compared to dry conditions significant more corrosion by presence of salt ions was detected. However compared to X56 only for J55 an intensification of corrosion and cracking at the surface due to hydrogen atmosphere was revealed. Pronounced surface cracks were observed for J55 over the entire samples. Overall the results strongly suggest that X56 is more resistant than J55 under the conditions of a hydrogen salt cavern.

Hydrogen embrittlement (HE) poses a significant challenge for high-strength steels. Although HE of wrought steels has been extensively studied it remains limited in steels processed by additive manufacturing (AM). The present work (i) compares the HE susceptibility of AISI 4340 ultra-high-strength steel fabricated by selective laser melting (SLM) with its wrought counterpart; (ii) investigates the predominant factors and possible HE mechanisms in the AM-fabricated material; and (iii) correlates microstructures produced with different SLM processing parameters to HE susceptibility of the steel. Generally conventionally processed AISI 4340 steel is used with a tempered martensitic structure to ensure the ultrahigh strength and therefore is susceptible to HE. In contrast SLM-fabricated 4340 exhibits a uniform refined bainitic microstructure. How this change of microstructure influences the HE susceptibility of the steel is unknown and needs investigation. Our results demonstrate that at the same level of strength the SLM-fabricated 4340 steel exhibits significantly lower HE susceptibility than its wrought counterpart. The SLM-fabricated steel showed a higher hydrogen diffusion rate. Furthermore the refined microstructure of the SLM-fabricated steel contributes to enhanced ductility even with hydrogen. These findings indicate that AM of high-strength steels has strong potential to improve HE resistance providing a pathway to solve this long-term problem. This study highlights the critical role of microstructure in influencing HE and offers valuable insights for developing steels for hydrogen applications.

In the future the development of a zero-carbon economy will require large-scale hydrogen storage. This article addresses hydrogen storage capacities a critical issue for large-scale hydrogen storage in geological structures. The aim of this paper is to present a methodology to evaluate the potential for hydrogen storage in depleted natural gas reservoirs and estimate the capacity and energy of stored hydrogen. The estimates took into account the recoverable reserves of the reservoirs hydrogen parameters under reservoir conditions and reservoir parameters of selected natural gas reservoirs. The theoretical and practical storage capacities were assessed in the depleted natural gas fields of N and NW Poland. Estimates based on the proposed methodology indicate that the average hydrogen storage potential for the studied natural gas fields ranges from 0.01 to 42.4 TWh of the hydrogen energy equivalent. Four groups of reservoirs were distinguished which differed in recovery factor and technical hydrogen storage capacity. The issues presented in the article are of interest to countries considering large-scale hydrogen storage geological research organizations and companies generating electricity from renewable energy sources.

Hydrogen embrittlement is a phenomenon that affects the mechanical properties of steels intended for hydrogen transportation. One affected by this embrittlement is the Ductile to Brittle Transition Temperature (DBTT) which characterizes the change in the failure mode of the steel from ductile to brittle. This temperature is conventionally defined and compared to the operating temperature as an acceptability criterion for codes. Transition temperature does not depend only on the material but also on specimen geometry particularly the thickness. Generally the transition temperature is defined for the conservative reason by Charpy impact test. Standard Charpy specimens are straight beams with a thickness of 10 mm. For thin pipes it is impossible to extract these standard specimens. One uses in this case Mini-Charpy specimens with a reduced thickness due to pipe curvature. This paper aims to quantify the effect of hydrogen embrittlement on the transition temperature of pipe steel (API 5L X65) using two types of Charpy specimens.

Low-carbon hydrogen is a promising option for energy security and decarbonization. Cooperation is needed to ensure the widespread use of low-carbon energy. Cooperation among hydrogen supply chain (HSC) agents is essential to overcome the high costs the lack of infrastructure that needs heavy financial support and the environmental failure risk. But how can cooperation be operationalized and its potential benefits be measured to evaluate the impact of different allocation schemes in low-carbon HSCs? This research works around this question and aims to analyze the potential of cooperation in a generalized low-carbon HSC with limited and critical resources using systems and cooperative game theory. This work is original in several aspects. It evaluates cooperation effects under different benefit allocation schemes while considering infrastructure agents’ dependencies (production transportation and storage) and specific traits. Additionally it provides a transparent replicable methodology adaptable to various case studies. It is highlighted that HSC coalitions form hierarchies with veto power pursuing common goals like maximizing decarbonization and demand fulfillment. A cooperative game theory toolbox is developed to evaluate display and compare the results of six allocation solutions. The toolbox does not aim to determine the best allocation scheme but rather to support smart decision-making in the bargaining process facilitating debate and agreement on a trade-off solution that ensures the viability and achievement of long-term coalition goals. It is built on three naïve and three game-theoretical allocation rules (Gately Nucleolus and Shapley value) applicable to peer group games with transferable utility. Results are presented for an 8-agent low-carbon HSC along with the total environmental benefit the allocated individual shares and numerical indicators (stability satisfaction propensity to disrupt) reflecting the acceptability of allocations. Numerical results show that the Nucleolus achieves the highest satisfaction among stable allocations while the Gately allocation minimizes disruption propensity. Naïve rules yield different outcomes: “equal distribution for producers” carries the highest risk whereas “equal shares for all agents” and “proportional to individual benefits” rules are stable but perform poorly on other criteria.

Chemical hydrogen storage is a key step for establishing hydrogen as a main energy vector. For this purpose liquid organic hydrogen carriers (LOHCs) present the outstanding advantage of allowing a safe efficient and high-density hydrogen storage being also highly compatible with existing transport infrastructures. Typical LOHCs are organic compounds able to be hydrogenated and dehydrogenated at mild conditions enabling the hydrogen storage and release respectively. In addition the physical properties of these chemicals are also critical for practical implementation. In this work key properties of potential LOHCs of three different chemical families (homoaromatics and Nand O-heteroaromatics) are estimated using molecular simulations. Thus density viscosity vapour pressure octanol-water coefficient melting point flash point dehydrogenation enthalpy and hydrogen content are estimated using the programs COSMO-RS and HYSYS. In addition we have also evaluated the performance of several binary mixtures as LOHCs using these methodologies. Considering the hydrogen content characteristic temperatures and previous experimental results of the cyclic process; our simulation results suggest that 1-methylnaphthalene/1-methyldecahydronaftalene and methylbenzylpyridine/perhydromethylbenzylpyridine pairs are appropriate candidates for chemical hydrogen storage. Binary mixtures of LOHCs are also relevant alternatives since substances with a great potential can be used as LOHCS when dissolved. That is the case of naphthalene and 1-methyl-naphthalene mixtures or indoles dissolved in benzene or benzylbenzene. Concerning O-compounds although several pairs could be used as LOHCs thermodynamic and kinetic feasibility of the hydrogenation/dehydrogenation cycles must be better studied.