Transmission, Distribution & Storage

In response to the global climate change and the need for green and low-carbon development hydrogen energy has been recognized as a clean energy source that can achieve carbon neutrality unlike fossil fuels. As a country with a shortage of energy resources the development of hydrogen energy is of significant importance for China to adjust its energy structure and accelerate the new era of energy transformation. Based on the development of China’s hydrogen energy industry this paper elaborates on the current status and development trends of key technologies in the entire industrial chain of hydrogen energy in various stages including production storage transportation and application and identifies the problems and challenges of hydrogen energy development. The paper focuses on the analysis of hydrogen storage and transportation application scenarios and clarifies the selection of hydrogen storage and transportation technologies in different scenarios. To achieve healthy devel opment of China’s hydrogen energy industry it is necessary to strengthen top-level design make strategic planning encourage large-scale state-owned energy enterprises to play a leading role promote the development of the entire industry chain increase technological research and development efforts prevent the risk of core technology constraints and vigorously promote the application of hydrogen energy to realize the construction of a hydrogen energy society.

This study explores the integration and optimization of battery energy storage systems (BESSs) and hydrogen energy storage systems (HESSs) within an energy management system (EMS) using Kangwon National University’s Samcheok campus as a case study. This research focuses on designing BESSs and HESSs with specific technical specifications such as energy capacities and power ratings and their integration into the EMS. By employing MATLAB-based simulations this study analyzes energy dynamics grid interactions and load management strategies under various operational scenarios. Real-time data from the campus are utilized to examine energy consumption renewable energy generation grid power fluctuations and pricing dynamics providing key insights for system optimization. This study finds that a BESS manages energy fluctuations between 0.5 kWh and 3.7 kWh over a 24 h period with battery power remaining close to 4 W for extended periods. Grid power fluctuates between −5 kW and 75 kW while grid prices range from 75 to 120 USD/kWh peaking at 111 USD/kWh. Hydrogen energy storage varies from 1 kWh to 8 kWh with hydrogen power ranging from −40 kW to 40 kW. Load management keeps power stable at around 35 kW and PV power integration peaks at 48 kW by the 10th h. The findings highlight that BESSs and HESSs effectively manage energy distribution and storage improving system efficiency reducing energy costs by approximately 15% and enhancing grid stability by 20%. This study underscores the potential of BESSs and HESSs in stabilizing grid operations and integrating renewable energy. Future directions include advancements in storage technologies enhanced EMS capabilities through artificial intelligence and machine learning and the development of smart grid infrastructures. Policy recommendations stress the importance of regulatory support and stakeholder collaboration to drive innovation and scale deployment ensuring a sustainable energy future.

CFD modelling of compressed hydrogen fuelling provides information on the hydrogen and tank structure temperature dynamics required for onboard storage tank design and fuelling protocol development. This study compares five turbulence models to develop a strategy for costeffective CFD simulations of hydrogen fuelling while maintaining a simulation accuracy acceptable for engineering analysis: RANS models k-ε and RSM; hybrid models SAS and DES; and LES model. Simulations were validated against the fuelling experiment of a Type IV 29 L tank available in the literature. For RANS with wall functions and blended models with near-wall treatment the simulated average hydrogen temperatures deviated from the experiment by 1–3% with CFL ≈ 1–3 and dimensionless wall distance y + ≈ 50–500 in the tank. To provide a similar simulation accuracy the LES modelling approach with near-wall treatment requires mesh with wall distance y + ≈ 2–10 and demonstrates the best-resolved flow field with larger velocity and temperature gradients. LES simulation on this mesh however implies a ca. 60 times longer CPU time compared to the RANS modelling approach and 9 times longer compared to the hybrid models due to the time step limit enforced by the CFL ≈ 1.0 criteria. In all cases the simulated pressure histories and inlet mass flow rates have a difference within 1% while the average heat fluxes and maximum hydrogen temperature show a difference within 10%. Compared to LES the k-ε model tends to underestimate and DES tends to overestimate the temperature gradient inside the tank. The results of RSM and SAS are close to those of LES albeit of 8–9 times faster simulations.

H2 geo-storage has been suggested as a key technology with which large quantities of H2 can be stored and withdrawn again rapidly. One option which is currently explored is H2 storage in sedimentary geologic for mations which are geographically widespread and potentially provide large storage space. The mechanism which keeps the buoyant H2 in the subsurface is structural trapping where a caprock prevents the H2 from rising by capillary forces. It is therefore important to assess how much H2 can be stored via structural trapping under given geo-thermal conditions. This structural trapping capacity is thus assessed here and it is demonstrated that an optimum storage depth for H2 exists at a depth of 1100 m at which a maximum amount of H2 can be stored. This work therefore aids in the industrial-scale implementation of a hydrogen economy.

Transformation of energy supply systems into green intensifies the use of renewable energy sources. Renewables cannot continuously supply energy. Therefore energy storage systems are very important in the whole system of generation and distribution. Anyway energy storage systems have many issues in terms of sustainability. This paper classified energy storage and analyzed issues in their sustainability solutions. In addition it determines the key performance indicators that define the sustainability of energy storage systems. This analysis determined many sustainability problems presented by the information for each key performance indicator. The least negative impact is shown for the performance of mechanical energy storage and sensible/latent heat storage. The production of green hydrogen green ammonia and biogas showed some negative impact. The worst sustainability is related to energy storage technologies or electrochemical energy storage technologies.

This paper aims to present an overview of the current state of hydrogen storage methods and materials assess the potential benefits and challenges of various storage techniques and outline future research directions towards achieving effective economical safe and scalable storage solutions. Hydrogen is recognized as a clean secure and costeffective green energy carrier with zero emissions at the point of use offering significant contributions to reaching carbon neutrality goals by 2050. Hydrogen as an energy vector bridges the gap between fossil fuels which produce greenhouse gas emissions global climate change and negatively impact health and renewable energy sources which are often intermittent and lack sustainability. However widespread acceptance of hydrogen as a fuel source is hindered by storage challenges. Crucially the development of compact lightweight safe and cost-effective storage solutions is vital for realizing a hydrogen economy. Various storage methods including compressed gas liquefied hydrogen cryocompressed storage underground storage and solid-state storage (material-based) each present unique advantages and challenges. Literature suggests that compressed hydrogen storage holds promise for mobile applications. However further optimization is desired to resolve concerns such as low volumetric density safety worries and cost. Cryo-compressed hydrogen storage also is seen as optimal for storing hydrogen onboard and offers notable benefits for storage due to its combination of benefits from compressed gas and liquefied hydrogen storage by tackling issues related to slow refueling boil-off and high energy consumption. Material-based storage methods offer advantages in terms of energy densities safety and weight reduction but challenges remain in achieving optimal stability and capacities. Both physical and material-based storage approaches are being researched in parallel to meet diverse hydrogen application needs. Currently no single storage method is universally efficient robust and economical for every sector especially for transportation to use hydrogen as a fuel with each method having its own advantages and limitations. Moreover future research should focus on developing novel materials and engineering approaches in order to overcome existing limitations provide higher energy density than compressed hydrogen and cryo-compressed hydrogen storage at 70 MPa enhance costeffectiveness and accelerate the deployment of hydrogen as a clean energy vector.

The global transition towards clean energy sources is becoming essential to reduce reliance on conventional fuels and mitigate carbon emissions. In the future the clean energy storage landscape green hydrogen and green ammonia (powered by renewable energy sources) are emerging as key players. This study explores the prospectives and feasibility of producing and storing offshore green hydrogen and green ammonia. The potential power output of Hornsea one and Hornsea two winds farms in the United Kingdom was calculated using real wind data. The usable electricity from the Hornsea one wind farm was 5.83 TWh/year and from the Hornsea two wind farm it was 6.44 TWh/year harnessed to three different scenarios for the production and storage of green ammonia and green hydrogen. Scenario 1 fulfil the requirement of green hydrogen storage for flexible ammonia production but consumes more energy for green hydrogen compression. Scenario 2 does not offer any hydrogen storage which is not favourable in terms of flexibility and market demand. Scenario 3 offers both a direct routed supply of produced hydrogen for green ammonia synthesis and a storage facility for green hydrogen storage. Detailed mathematical calculations and sensitivity analysis was performed based on the total energy available to find out the energy storage capacity in terms of the mass of green hydrogen and green ammonia produced. Sensitivity analysis in the case of scenario 3 was conducted to determine the optimal percentage of green hydrogen going to the storage facility. Based on the cost evaluation of three different presented scenarios the levelized cost of hydrogen (LCOH) is between USD 5.30 and 5.97/kg and the levelized cost of ammonia (LCOA) is between USD 984.16 and USD 1197.11/tonne. These prices are lower compared to the current UK market. The study finds scenario 3 as the most appropriate way in terms of compression energy savings flexibility for the production and storage capacity that depends upon the supply and demand of these green fuels in the market and a feasible amount of green hydrogen storage.

Integrating renewable energy requires robust large-scale storage solutions to balance intermittent supply. Underground hydrogen storage (UHS) in geological formations such as salt caverns depleted hydrocarbon reservoirs or aquifers offers a promising way to store large volumes of energy for seasonal periods. This review focuses on the biological aspects of UHS examining the biogeochemical interactions between H2 reservoir minerals and key hydrogenotrophic microorganisms such as sulfate-reducing bacteria methanogens acetogens and iron-reducing bacteria within the gas–liquid–rock–microorganism system. These microbial groups use H2 as an electron donor triggering biogeochemical reactions that can affect storage efficiency through gas loss and mineral dissolution–precipitation cycles. This review discusses their metabolic pathways and the geochemical interactions driven by microbial byproducts such as H2S CH4 acetate and Fe2+ and considers biofilm formation by microbial consortia which can further change the petrophysical reservoir properties. In addition the review maps 76 ongoing European projects focused on UHS showing 71% target salt caverns 22% depleted hydrocarbon reservoirs and 7% aquifers with emphasis on potential biogeochemical interactions. It also identifies key knowledge gaps including the lack of in situ kinetic data limited field-scale monitoring of microbial activity and insufficient understanding of mineral–microbe interactions that may affect gas purity. Finally the review highlights the need to study microbial adaptation over time and the influence of mineralogy on tolerance thresholds. By analyzing these processes across different geological settings and integrating findings from European research initiatives this work evaluates the impact of microbial and geochemical factors on the safety efficiency and long-term performance of UHS.

Climate change is projected to have substantial economic social and environmental impacts worldwide. Currently the leading solutions for hydrogen storage are in salt caverns and depleted natural gas reservoirs. However the required geological formations are limited to certain regions. To increase alternatives for hydrogen storage this paper proposes storing hydrogen in pipes filled with gravel in lakes hydropower and pumped hydro storage reservoirs. Hydrogen is insoluble in water non-toxic and does not threaten aquatic life. Results show the levelized cost of hydrogen storage to be 0.17 USD kg−1 at 200 m depth which is competitive with other large scale hydrogen storage options. Storing hydrogen in lakes hydropower and pumped hydro storage reservoirs increases the alternatives for storing hydrogen and might support the development of a hydrogen economy in the future. The global potential for hydrogen storage in reservoirs and lakes is 3 and 12 PWh respectively. Hydrogen storage in lakes and reservoirs can support the development of a hydrogen economy in the future by providing abundant and cheap hydrogen storage.

Hydrogen as a zero-emission fuel produces only water when used in fuel cells making it a vital contributor to reducing greenhouse gas emissions across industries like transportation energy and manufacturing. Efficient hydrogen storage requires lightweight high-strength vessels capable of withstanding high pressures to ensure the safe and reliable delivery of clean energy for various applications. Type V composite pressure vessels (CPVs) have emerged as a preferred solution due to their superior properties thus this study aims to predict the performance of a Type V CPV by developing its numerical model and calculating numerical burst pressure (NBP). For the validation of the numerical model a Hydraulic Burst Pressure test is conducted to determine the experimental burst pressure (EBP). The comparative study between NBP and EBP shows that the numerical model provides an accurate prediction of the vessel’s performance under pressure including the identification of failure locations. These findings highlight the potential of the numerical model to streamline the development process reduce costs and accelerate the production of CPVs that are manufactured by prepreg hand layup process (PHLP) using carbon fiber/epoxy resin prepreg material.

Hydrogen (H2) has been recognized as a promising solution to reduce carbon dioxide (CO2) emissions. H2 is considered a green energy carrier for energy storage transport and usage and it can be produced from renewable energy resources (such as solar hydropower and wind energy). However H2 is a highly diffusive compound compared to other natural gases raising concerns about the possibility of H2 loss in geo-storage (e.g. in underground geological formations such as depleted oil/gas reservoirs aquifers or shale formations) or H2 leak via pipelines when blending H2 with natural gas in existing pipeline systems. Thus understanding H2 diffusion in subsurface formations and pipeline systems is vital. However despite its importance only limited data is available to assess the above situations. Therefore in this study molecular dynamics simulations were used to predict the self-diffusion coefficients of H2 in water and cushion gases (CH4 and N2) at relevant geothermal conditions (i.e. 300 K–373 K and pressures up to 50 MPa). The findings showed that H2 self-diffusion in methane and nitrogen increases with increasing temperature but decreases with increasing pressure. However H2 selfdiffusion in water increases with increasing temperature but is not impacted by increasing or decreasing pres sure. The results also indicated that the rate of H2 self-diffusion in cushion gas is faster than in water about exceeding two-digit times. Furthermore the outcomes reported extended or new data on H2 self-diffusion for the binary system of H2–H2O H2–CH4 and H2–N2. This study is beneficial and contributes to assessing efficiency and safety for executing H2 transportation and underground hydrogen storage (UHS) schemes.

Underground hydrogen storage in porous rocks is a promising method to stabilize renewable energy fluctuations. However data on the geochemical reactivity of hydrogen with reservoir rocks and its potential effects on reservoir performance are limited. This study investigates the geochemical reactivity of hydrogen with Bunt sandstein reservoir sandstones from northern Germany collected at a depth of about 2.5 km. Experiments were performed at 100 ◦C and 150 bar hydrogen partial pressure for four weeks examining scenarios with dry hydrogen synthetic saline fluid with hydrogen synthetic saline fluid with helium (as a control) and an oxidation environment (air). We measured permeability porosity magnetic susceptibility and fluid element concentration before and after the experiments. Results showed no significant mineral changes attributed to hydrogen. Mag netic susceptibility indicated no formation of magnetic minerals such as magnetite and pyrrhotite. Minor var iations in permeability and porosity were attributed to anhydrite dissolution from fluid chemistry nonequilibrium. Overall our findings suggest hydrogen interactions with Buntsandstein sandstone (no pyrite content) at temperatures up to 100 ◦C do not risk hydrogen loss or reservoir performance degradation.

Photovoltaic (PV) and wind energy generation result in low greenhouse gas footprints and can supply electricity to the grid or generate hydrogen for various applications including seasonal energy storage. Designing integrated wind–PV–electrolyzer underground hydrogen storage (UHS) projects is complex due to the interactions between components. Additionally the capacities of PV and wind relative to the electrolyzer capacity and fluctuating electricity prices must be considered in the project design. To address these challenges process modelling was applied using cost components and parameters from a project in Austria. The hydrogen storage part was derived from an Austrian hydrocarbon gas field considered for UHS. The results highlight the impact of the renewable energy source (RES) sizing relative to the electrolyzer capacity the influence of different wind-to-PV ratios and the benefits of selling electricity and hydrogen. For the case study the levelized cost of hydrogen (LCOH) is EUR 6.26/kg for a RES-to-electrolyzer capacity ratio of 0.88. Oversizing reduces the LCOH to 2.61 €/kg when including electricity sales revenues or EUR 4.40/kg when excluding them. Introducing annually fluctuating electricity prices linked to RES generation results in an optimal RES-to-electrolyzer capacity ratio. The RES-to-electrolyzer capacity can be dynamically adjusted in response to market developments. UHS provides seasonal energy storage in areas with mismatches between RES production and consumption. The main cost components are compression gas conditioning wells and cushion gas. For the Austrian project the levelized cost of underground hydrogen storage (LCHS) is 0.80 €/kg with facilities contributing EUR 0.33/kg wells EUR 0.09/kg cushion gas EUR 0.23/kg and OPEX EUR 0.16/kg. Overall the analysis demonstrates the feasibility of integrated RES–hydrogen generation-seasonal energy storage projects in regions like Austria with systems that can be dynamically adjusted to market conditions.

Hydrogen is used as a fuel in various fields such as aviation space and automobiles due to its high specific energy. Hydrogen can be stored as a compressed gas at high pressure and as a liquid at cryogenic temperatures. In order to keep liquid hydrogen at a cryogenic temperature the tanks for storing liquid hydrogen are required to have insulation to prevent heat leakage. When liquid hydrogen is vaporized by heat inflow a large pressure is generated inside the tank. Therefore a technology capable of predicting the tank pressure is required for cryogenic liquid hydrogen tanks. In this study a thermodynamic model was developed to predict the maximum internal pressure and pressure behavior of cryogenic liquid hydrogen fuel tanks. The developed model considers the heat inflow of the tank due to heat transfer the phase change from liquid to gas hydrogen and the fuel consumption rate. To verify the accuracy of the proposed model it was compared with the analyses and experimental results in the referenced literature and the model presented good results. A cryogenic liquid hydrogen fuel tank was simulated using the proposed model and it was confirmed that the storage time along with conditions such as the fuel filling ratio of liquid hydrogen and the fuel consumption rate should be considered when designing the fuel tanks. Finally it was confirmed that the proposed thermodynamic model can be used to sufficiently predict the internal pressure and the pressure behavior of cryogenic liquid hydrogen fuel tanks.

The hydrogen compatibility of two X65 pipeline steels for transport of hydrogen gas is investigated through microstructural characterization hydrogen permeation measurements and fracture mechanical testing. The investigated materials are a quenched and tempered pipeline steel with a fine-grained homogeneously distributed ferrite-bainite microstructure and hot rolled pipeline steel with a ferrite-pearlite banded microstructure. All tests are performed both under electrochemical and gaseous hydrogen charging conditions. A correlation between electrochemical hydrogen charging and gaseous charging is determined. The results point to inherent differences in the interaction between hydrogen and the two material microstructures. Further research is needed to unveil the influence of material microstructure on hydrogen embrittlement.

Hydrogen is gaining attention due to its potential to address key challenges in the sectors of energy transportation and industry since it is a much cleaner energy source when compared to fossil fuels. The transportation of hydrogen from the point of its production to the point of use can be performed by road rail sea pipeline networks or a combination of the abovementioned. Being in the preliminary stage of hydrogen use the utilization of the already existing natural gas pipeline networks for hydrogen mixtures transportation has been suggested as an efficient means of expanding hydrogen infrastructure. Yet exploring this alternative major challenges such as the pre-existence of cracks in the pipelines and the effect of hydrogen embrittlement on the material of the pipelines exist. In this paper the macroscopic numerical modeling of pipeline segments with the use of the finite element method is performed. In more details the structural integrity of intact and damaged pipeline segments of different geometry and mechanical properties was estimated. The effect of the pipeline geometry and material has been investigated in terms of stress contours with and without the influence of hydrogen. The results suggest that the structural integrity of the pipeline segments is more compromised by pre-existing longitudinal cracks which might lead to an increase in the maximum value of equivalent Von Mises stress by up to four times depending on their length-tothickness ratio. This effect becomes more pronounced with the existence of hydrogen in the pipeline network.

This article presents a comprehensive review of the current landscape and prospects of large-scale hydrogen storage technologies with a focus on both onshore and offshore applications and flexibility. Highlighting the evolving technological advancements it explores storage and compression techniques identifying potential research directions and avenues for innovation. Underwater hydrogen storage and hybrid metal hydride com pressed gas tanks have been identified for offshore buffer storage as well as exploration of using metal hydride slurries to transport hydrogen to/from offshore wind farms coupled with low pressure high flexibility elec trolyser banks. Additionally it explores the role of metal hydride hydrogen compressors and the integration of oxyfuel processes to enhance roundtrip efficiency. With insights into cost-effectiveness environmental and technology considerations and geographical factors this review offers insights for policymakers researchers and industry stakeholders aiming to advance the deployment of large-scale hydrogen storage systems in the transition towards sustainable energy.

To combat global temperature rise we need affordable clean and renewable energy that does not add carbon to the atmosphere. Hydrogen is a promising option because it can be used as a carbon-free energy source. However storing and transporting pure hydrogen in liquid or gaseous forms is challenging. To overcome the limitations associated with conventional compressed and liquefied hydrogen or physio-chemical adsorbents for bulk storage and transport hydrogen can be attached to other molecules known as hydrogen carriers. Circular carriers which involve the production of CO2 or nitrogen during the hydrogen recovery process include substances such as methanol ammonia or synthetic natural gas. These carriers possess higher gravimetric and volumetric hydrogen densities (i.e. 12.5 wt% and 11.88 MJ/L for methanol) than cyclic carriers (i.e. 6.1 wt% and 5.66 MJ/L for methylcyclohexane (MCH)) which produce cyclic organic chemicals during dehydrogenation. This makes circular carriers particularly appealing for the Australian energy export market. Furthermore the production-decomposition cycle of circular carriers can be made carbon-neutral if they are derived from renewable H2 sources and combined with atmospheric or biomass-based CO2 or nitrogen. The key parameters are investigated in this study focusing on circular hydrogen carriers relevant to Australia. The parameters are ranked from 0 (worst) to 10 (best) depending on the bandwidth of the parameter in this review. Methanol shows great potential as a cost-effective solution for long-distance transport of renewable energy being a liquid at standard conditions with a boiling point of 64.7 °C. Methane is also an important hydrogen carrier due to the availability of natural gas infrastructure and its role as a significant export product for Australia.

Underground hydrogen storage (UHS) in shale and tight reservoirs offers a promising solution for large-scale energy storage playing a critical role in the transition to a hydrogenbased economy. However the successful deployment of UHS in these low-permeability formations depends on a thorough understanding of the geomechanical and geochemical factors that affect storage integrity injectivity and long-term stability. This review critically examines the geomechanical aspects including stress distribution rock deformation fracture propagation and caprock integrity which govern hydrogen containment under subsurface conditions. Additionally it explores key geochemical challenges such as hydrogen-induced mineral alterations adsorption effects microbial activity and potential reactivity with formation fluids to evaluate their impact on storage feasibility. A comprehensive analysis of experimental studies numerical modeling approaches and field applications is presented to identify knowledge gaps and future research directions.

As the transport of gaseous hydrogen and its use as a low carbon-footprint energy vector become increasingly likely scenarios both the scientific literature and technical standards addressing the compatibility of pipeline steels with high-pressure hydrogen environments are rapidly expanding. This work presents a detailed review of the most relevant hydrogen embrittlement testing methodologies proposed in standards and the academic literature. The focus is placed on testing approaches that support design-oriented assessments rather than simple alloy qualification for hydrogen service. Particular attention is given to tensile tests (conducted on smooth and notched specimens) as well as to J-integral and fatigue tests performed following the fracture mechanics’ approach. The influences of hydrogen partial pressure and deformation rate are critically examined as these parameters are essential for ensuring meaningful comparisons across different studies.

The resilience and sustainable development of modern power distribution systems faces escalating challenges due to increasing renewable integration and extreme events. Traditional single-system approaches often overlook the spatiotemporal coordination of cross-domain restoration resources. In this paper we propose a multi-stage resilience enhancement method that employs transportation and hydrogen energy systems. This approach coordinates the pre-event preventive allocation and multi-stage collaborative scheduling of diverse restoration resources including remote-controlled switches (RCSs) mobile hydrogen emergency resources (MHERs) and hydrogen production and refueling stations (HPRSs). The proposed framework supports cross-stage dynamic optimization scheduling enabling the development of adaptive resource dispatch strategies tailored to the characteristics of different stages including prevention fault isolation and service restoration. The model is applicable to complex scenarios involving dynamically changing network topologies and is formulated as a mixed-integer linear programming (MILP) problem. Case studies based on the IEEE 33-bus system show that the proposed method can restore a distribution system’s resilience to approximately 87% of its normal level following extreme events.

The aim of this study is to review and identify H2 storage suitability in geological reservoirs of the Republic of Lithuania. Notably Lithuania can store clean H2 effectively and competitively because of its wealth of resources and well-established infrastructure. The storage viability in Lithuanian geological contexts is highlighted in this study. In addition when it comes to injectivity and storage capacity salt caverns and saline aquifers present less of a challenge than other kinds of storage medium. Lithuania possesses sizable subterranean reservoirs (Cambrian rocks) that can be utilized to store H2. For preliminary assessment the cyclic H2 injection and production simulation is performed. A 10-year simulation of hydrogen injection and recovery in the Syderiai saline aquifer demonstrated the feasibility of UHS though efficiency was reduced by nearly 50% when using a single well for both injection and production. The study suggests using separate wells to improve efficiency. However to guarantee economic injectivity and containment security a detailed assessment of the geological structures is required specifically at the pore scale level. The volumetric approach estimated a combined storage capacity of approximately 898.5 Gg H2 (~11 TWh) for the Syderiai and Vaskai saline aquifers significantly exceeding previous estimates. The findings underscore the importance of detailed geological data and further research on hydrogen-specific factors to optimize UHS in Lithuania. Addressing technical geological and environmental challenges through multidisciplinary research is essential for advancing UHS implementation and supporting Lithuania’s transition to a sustainable energy system. UHS makes it possible to maximize the use of clean energy reduce greenhouse gas emissions and build a more sustainable and resilient energy system. Hence intensive research and advancements are needed to optimize H2 energy for broader applications in Lithuania.

Underground hydrogen storage (UHS) in geological formations presents a viable option for long-term large-scale H2 storage. A physical coal model was constructed based on experimental tests and a MD simulation was used to investigate the potential of UHS in underground coal gasification (UCG) cavities. We investigated H2 behavior under various conditions including temperatures ranging from 278.15 to 348.15 K pressures in the range of 5–20 MPa pore sizes ranging from 1 to 20 nm and varying water content. We also examined the competitive adsorption dynamics of H2 in the presence of CH4 and CO2 . The findings indicate that the optimal UHS conditions for pure H2 involve low temperatures and high pressures. We found that coal nanopores larger than 7.5 nm optimize H2 diffusion. Additionally higher water content creates barriers to hydrogen diffusion due to water molecule clusters on coal surfaces. The preferential adsorption of CO2 and CH4 over H2 reduces H2 -coal interactions. This work provides a significant understanding of the microscopic behaviors of hydrogen in coal nanopores at UCG cavity boundaries under various environmental factors. It also confirms the feasibility of underground hydrogen storage (UHS) in UCG cavities.

Integrating microbial activity into underground hydrogen storage models is crucial for simulating longterm reservoir behavior. In this work we present a coupled framework that incorporates bio-geochemical reactions and compositional flow models within the Matlab Reservoir Simulation Toolbox (MRST). Microbial growth and decay are modeled using a double Monod formulation with populations influenced by hydrogen and carbon dioxide availability. First a refined Equation of State (EoS) is employed to accurately capture hydrogen dissolution thereby improving phase behavior and modeling of microbial activity. The model is then discretized using a cell-centered finite-volume method with implicit Euler time discretization. A fully coupled fully implicit strategy is considered. Our implementation builds upon MRST’s compositional module by incorporating the Søreide–Whitson EoS microbial reaction kinetics and specific effects such as bio-clogging and molecular diffusion. Through a series of 1D 2D and 3D simulations we analyze the effects of microbialinduced bio-geochemical transformations on underground hydrogen storage in porous media.These results highlight that accounting for bio-geochemical effects can substantially impact hydrogen loss purity and overall storage performance.

The UK net zero strategy aims to fully decarbonize the power system by 2035 anticipating a 40–60% increase in demand due to the growing electrification of the transport and heating sectors over the next thirteen years. This paper provides a detailed technical and economic analysis of the role of energy storage technologies and transmission lines in balancing the power system amidst large shares of intermittent renewable energy generation. The analysis is conducted using the cost-optimizing energy system modelling framework REMix developed by the German Aerospace Center (DLR). The obtained results of multiple optimization scenarios indicate that achieving the lowest system cost with a 73% share of electricity generated by renewable energy sources is feasible only if planning rules in England and Wales are flexible enough to allow the construction of 53 GW of onshore wind capacity. This flexibility would enable the UK to become a net electricity exporter assuming an electricity trading market with neighbouring countries. Depending on the scenario 2.4–11.8 TWh of energy storage supplies an average of 11% of the electricity feed-in with underground hydrogen storage representing more than 80% of that total capacity. In terms of storage converter capacity the optimal mix ranges from 32 to 34 GW of lithium-ion batteries 13 to 22 GW of adiabatic compressed air energy storage 4 to 24 GW of underground hydrogen storage and 6 GW of pumped hydro. Decarbonizing the UK power system by 2035 is estimated to cost $37–56 billion USD with energy storage accounting for 38% of the total system cost. Transmission lines supply 10–17% of the total electricity feed-in demonstrating that when coupled with energy storage it is possible to reduce the installed capacity of conventional power plants by increasing the utilization of remote renewable generation assets and avoiding curtailment during peak generation times.