Publications

With the world facing the twin pressures of a warming climate and an ever-increasing amount of waste it is becoming increasingly clear that we need to rethink the way we generate energy and use materials. Despite growing awareness our energy systems are still largely dependent on fossil fuels and characterized by a linear ‘take-make-dispose’ model. This leaves us vulnerable to supply disruptions rising greenhouse gas emissions and the depletion of critical raw materials. Hydrogen is emerging as a potential carbonfree energy vector that can overcome both challenges if it is produced sustainably from renewable sources. This study reviews hydrogen production from a circular economy perspective considering industrial agricultural and municipal solid waste as a resource rather than a burden. The focus is on the reuse of waste as a catalyst or catalyst support for hydrogen production. Firstly the role of hydrogen as a new energy carrier is explored along with possible routes of waste valorization in the process of hydrogen production. This is followed by an analysis of where and how catalysts from waste can be utilized within various hydrogen production processes namely those based on using fossil fuels as a source biomass as a source and electrocatalytic applications.

This research models a 20 MW PEM hydrogen plant. PEM units operate in the 60 to 80 ◦C range based on their location and size. This study aims to recover the waste heat from PEM modules to enhance the efficiency of the plant. In order to recover the heat two systems are implemented: (a) recovering the waste heat from each PEM module; (b) recovering the heat from hot water to produce electricity utilizing an organic refrigerant cycle (ORC). The model is made by ASPEN® V14. After modeling the plant and utilizing the ORC the module is optimized using Python to maximize the electricity produced by the turbine therefore enhancing the efficiency. The system is a closed-loop cycle operating at 25 ◦C and ambient pressure. The 20 MW PEM electrolyzer plant produces 363 kg/hr of hydrogen and 2877 kg/hr of oxygen. Based on the higher heating value of hydrogen the plant produces 14302.2 kWh of hydrogen energy equivalents. The ORC is maximized by increasing the electricity output from the turbine and reducing the pump work while maintaining energy conservation and mass balance. The results show that the electricity power output reaches 555.88 kW and the pump power reaches 23.47 kW.

Green hydrogen is gaining global attention as a zero-carbon energy carrier with the potential to drive sustainable energy transitions particularly in regions facing rising fossil fuel costs and resource depletion. In sub-Saharan Africa financing mechanisms and structured off-take agreements are critical to attracting investment across the green hydrogen value chain from advisory and pilot stages to full-scale deployment. While substantial funding is required to support a green economic transition success will depend on the effective mobilization of capital through smart public policies and innovative financial instruments. This review evaluates financing mechanisms relevant to sub-Saharan Africa including green bonds public–private partnerships foreign direct investment venture capital grants and loans multilateral and bilateral funding and government subsidies. Despite their potential current capital flows remain insufficient and must be significantly scaled up to meet green energy transition targets. This study employs a mixed-methods approach drawing on primary data from utility firms under the H2Atlas-Africa project and secondary data from international organizations and the peer-reviewed literature. The analysis identifies that transitioning toward Net-Zero emissions economies through hydrogen development in sub-Saharan Africa presents both significant opportunities and measurable risks. Specifically the results indicate an estimated investment risk factor of 35% reflecting potential challenges such as financing infrastructure and policy readiness. Nevertheless the findings underscore that green hydrogen is a viable alternative to fossil fuels in subSaharan Africa particularly if supported by targeted financing strategies and robust policy frameworks. This study offers practical insights for policymakers financial institutions and development partners seeking to structure bankable projects and accelerate green hydrogen adoption across the region.

The increasing global energy demand and the transition toward sustainable energy systems have highlighted the importance of energy storage technologies by ensuring efficiency reliability and decarbonization. This study reviews chemical and thermal energy storage technologies focusing on how they integrate with renewable energy sources industrial applications and emerging challenges. Chemical Energy Storage systems including hydrogen storage and power-to-fuel strategies enable long-term energy retention and efficient use while thermal energy storage technologies facilitate waste heat recovery and grid stability. Key contributions to this work are the exploration of emerging technologies challenges in large-scale implementation and the role of artificial intelligence in optimizing Energy Storage Systems through predictive analytics real-time monitoring and advanced control strategies. This study also addresses regulatory and economic barriers that hinder widespread adoption emphasizing the need for policy incentives and interdisciplinary collaboration. The findings suggest that energy storage will be a fundamental pillar of the sustainable energy transition. Future research should focus on improving material stability enhancing operational efficiency and integrating intelligent management systems to maximize the benefits of these technologies for a resilient and low-carbon energy infrastructure.

The burgeoning adoption of photovoltaic and wind energy has limitations of volatility and intermittency which hinder their application. Electro-hydrogen coupling energy storage systems emerge as a promising solution to address this issue. This technology combines renewable energy power generation with hydrogen production through water electrolysis and hydrogen fuel cell power generation effectively enabling the consumption and peak load management of renewable energy sources. This paper presents a power system with a 10 kW photovoltaic system and lithium battery energy storage system designed for hydrogen-electric coupled energy storage validated through the physical experiments. The results demonstrate the system's effectiveness in mitigating the impact of randomness and volatility in photovoltaic power generation. Moreover the energy management system can adjust bus power based on load demand. Testing the system in the absence of photovoltaic power generation reveals its capability to supply energy to the load for three hours with a minimum operating load power of 3 kW even under weather conditions unsuitable for photovoltaic power generation. These findings showed the potential of electro-hydrogen coupling energy storage systems in addressing the challenges associated with renewable energy integration paving the way for a reliable and sustainable energy supply.

The hydrogen fuel quality is critical to the efficiency and longevity of fuel cell electric vehicles (FCEVs) with ISO 14687:2019 grade D establishing stringent impurity limits. This study compared two different sampling techniques for assessing the hydrogen fuel quality focusing on the National Physical Laboratory hydrogen direct sampling apparatus (NPL DirSAM) from a 35 MPa heavy-duty (HD) dispenser and qualitizer sampling from a 70 MPa light-duty (LD) nozzle both of which were deployed on the same day at a local hydrogen refuelling station (HRS). The collected samples were analysed as per the ISO 14687:2019 contaminants using the NPL H2-quality laboratory. The NPL DirSAM was able to sample an HD HRS demonstrating the ability to realise such sampling on an HD nozzle. The comparison of the LD (H2 Qualitizer sampling) and HD (NPL DirSAM) devices showed good agreement but significant variation especially for sulphur compounds non-methane hydrocarbons and carbon dioxide. These variations may be related to the HRS difference between the LD and HD devices (e.g. flow path refuelling conditions and precooling for light duty versus no precooling for heavy duty). Further study of HD and LD H2 fuel at HRSs is needed for a better understanding.

In an effort to bridge the gap between academic research and industrial application this study investigates the integration potential of steam methane reforming and Co-electrolysis for the efficient conversion of refinery offgases into high-purity syngas. Experimental work was conducted under conditions representative of industrial environments using platinum- and nickel-based catalysts in steam reforming to assess methane conversion and H2 /CO ratio at varying temperatures and gas hourly space velocities (GHSV). Co-electrolysis was evaluated in solid oxide electrolysis cells (SOECs) across a range of gas compositions (H2O/CO2 /H2 /CO) including pure CO2 electrolysis as a strategy for pre-electrolysis hydrogen removal. Electrochemical performance was analyzed using impedance spectroscopy distribution of relaxation times (DRT) and current–voltage characterization. Results confirm the superior stability and performance of the Pt catalyst under high-throughput conditions while Ni-based systems were more sensitive to operational fluctuations. In the SOEC increased H2O content accelerated reaction kinetics whereas CO2 concentration governed polarization resistance. To enable optimal SOEC operation the addition of steam downstream of the reformer is proposed as a means of adjusting the reformate composition. The findings demonstrate that tuning reforming and electrolysis conditions in tandem offers a promising route for sustainable syngas production using renewable electricity. This work establishes a foundation for further development of integrated thermo-electrochemical systems tailored to industrial gas streams.

Demand for hydrogen is expected to increase in the coming years to defossilize hard-to-abate sectors. In the European Union the question remains in which quantities and at what cost hydrogen can be produced to satisfy the growing demand. This paper applies different approaches to model costs and potentials of off-grid hydrogen production within the European Union. The modeled approaches distinguish the effects of different spatial and technological resolutions on hydrogen production potentials costs and prices. According to the results the hydrogen potential within the European Union is above 6800 TWh. This figure far surpasses the expected demand range of 1423 to 1707 TWh in 2050. The cost of satisfying the demand exceeds 100 billion euro at marginal costs of hydrogen below 85 euro per megawatt-hour. Additionally the results show that an integrated European Union market would reduce the overall system costs notably compared to a setup in which each country covers its own hydrogen demand domestically. Just a few countries would be able to supply the entire European Union’s hydrogen demand in the case of an integrated market. This finding leads to the conclusion that an international hydrogen infrastructure seems advantageous.

Hydrogen storage in depleted gas reservoirs triggers geochemical and microbiological reactions at the caprockreservoir interface yielding significant implications on storage integrity. Acetogenesis is a microbial reaction observed during underground hydrogen storage (UHS) that produces acetate and converts it into acetic acid under protonation potentially impacting the UHS process integrity. For the first time this research explores the impact of the acetic acid + brine + caprock reaction on shale caprock mineralogy microstructure and physicochemical properties where this preliminary study has been conducted under ambient conditions to obtain an initial assessment of the impact. A comprehensive mineralogical and micro-structural characterization including scanning electron microscopy (SEM) energy dispersive X-ray spectroscopy (EDS) X-ray fluorescence (XRF) Xray diffraction (XRD) micro-computed tomography (micro-CT) and inductively coupled plasma mass spectrometry (ICP-MS) have been conducted to assess the mineralogical and microstructural changes in shale specimens saturated with brine solutions with a range of acetic acid percentages (5 % 10 % and 20 %) to find the maximum possible impact. According to the conducted mineralogical analysis (EDS XRF and XRD) there is a significant primary mineral dissolution during the acetic acid interaction where calcite and dolomite are the predominant minerals dissolved evidencing the significant impact of the acetic acid reaction on carbonate-rich caprock systems during UHS. However secondary mineral precipitation happened at high acidic concentrations (20 %). Interestingly other common minerals in reservoir rocks (e.g. mica pyrite) did not demonstrate rapid interactions with acetic acid compared to carbonates. The impact of these mineralogical changes on the caprock microstructure was then investigated through SEM and micro-CT and the results demonstrate substantial enhancements in porosity and microcracks in the rock matrix due to the calcite and dolomite dissolutions despite some microcracks being closed by secondary precipitations. This preliminary study evidences the significant impact of acidification on caprock integrity which may occur during the acetogenesis reaction in UHS environments. These effects should be carefully considered in field UHS projects to eliminate the risks.

This research presents a hierarchically synchronized Multi-Energy System (MES) designed for regional communities incorporating a network of small-scale Integrated Energy Microgrids (IEMs) to augment efficiency and collective advantages. The MES framework innovatively integrates energy complementarity pairing algorithms with efficient iterative optimization processes significantly curtailing operational expenditures for constituent microgrids and bolstering both community-wide benefits and individual microgrid autonomy. The MES encompasses electricity hydrogen and heat resources while leveraging controllable assets such as battery storage systems fuel cell combined heat and power units and electric vehicles. A comparative study of six IEMs demonstrates an operational cost reduction of up to 26.72% and a computation time decrease of approximately 97.13% compared to traditional methods like ADMM and IDAM. Moreover the system preserves data privacy by limiting data exchange to aggregated energy information thus minimizing direct communication between IEMs and the MES. This synergy of multi-energy complementarity iterative optimization and privacy-aware coordination underscores the potential of the proposed approach for scalable community-centered energy systems.

Fuel cell (FC) technologies are often regarded as a sustainable alternative to conventional combustion-based energy systems due to their low environmental impact and high efficiency. Thorough environmental assessments using Life Cycle Assessment (LCA) methodologies are needed to understand and mitigate their impacts. However there has been a lack of comprehensive reviews on LCA studies across all major types of FCs. This study reviews and synthesizes results from 44 peer-reviewed LCA studies from 2015 to 2024 covering six major FC types: alkaline (AFC) direct methanol (DMFC) molten carbonate (MCFC) proton- exchange membrane (PEMFC) solid oxide (SOFC) and phosphoric acid (PAFC). The review provides an updated overview of LCA practices and results over the past decade while identifying methodological inconsistencies and gaps. PEMFCs are the most frequently assessed FC typology covering 49 % of the studies followed by SOFCs at 38 % with no studies on DMFCs. Only 11 % of comparative studies carry out inter-comparison between FC types. Discrepancies in system boundary definitions across studies are identified highlighting the need for standardization to enhance comparability between studies. Global Warming Potential (GWP) evaluated in 100 % of the studies is the most assessed impact category. Fuel supply in the use phase a major contributor to greenhouse gas (GHG) emissions is under-assessed as it is usually aggregated with Operation and Maintenance (O&M) phase instead of discussed separately. GWP of energy production by all FC typologies spans from 0.026 to 1.76 kg CO₂-equivalent per kWh. Insufficient quantitative data for a meta-analysis and limited inter-comparability across FC types are noted as critical gaps. The study highlights the need for future research and policies focusing on green hydrogen supply and circular economy practices to improve FC sustainability.

Electric arc furnace slag is a major by-product of steelmaking yet its industrial utilization remains limited due to its complex chemical and mineralogical composition. This study presents a hydrogen-based approach to recover metallic components from EAF slag for potential reuse in steelmaking. Laboratory experiments were conducted by melting 50 g of industrial slag samples at 1600 ◦C and injecting hydrogen gas through a ceramic tube into the liquid slag. After cooling both the slag and the metallic phases were analyzed for their chemical and phase compositions. Additionally the reduction process was modeled using a combination of approaches including the thermochemical software FactSage 8.1 models for density surface tension and viscosity as well as a diffusion model. The injection of hydrogen resulted in the reduction of up to 40% of the iron oxide content in the liquid slag. In addition the fraction of reacted hydrogen gas was calculated.

The increasing demand for energy and the urgent need to reduce carbon emissions have positioned hydrogen as a promising alternative. This review paper explores the potential of hydrogen blending in natural gas pipelines focusing on the compatibility of pipeline materials and the associated safety challenges. Hydrogen blending can significantly reduce carbon emissions from homes and industries as demonstrated by various projects in Canada and globally. However the introduction of hydrogen into natural gas pipelines poses risks such as hydrogenassisted materials degradation which can compromise the integrity of pipeline materials. This study reviews the effects of hydrogen on the mechanical properties of both vintage and modern pipeline steels cast iron copper aluminum stainless steel as well as plastics elastomers and odorants that compose an active natural gas pipeline network. The review highlights the need for updated codes and standards to ensure safe operation and discusses the implications of hydrogen on material selection design and safety considerations. Overall this manuscript aims to provide a comprehensive resource on the current state of pipeline materials in the context of hydrogen blending emphasizing the importance of further research to address the gaps in current knowledge and to develop robust guidelines for the integration of hydrogen into existing natural gas infrastructure.

In this work a new modeling tool called DECAL (DEcarbonize CALifornia) is developed and used to evaluate what it will take to reach California’s climate mandate of net-zero emissions by 2045. DECAL is a scenario-based model that projects emissions society-wide costs and resource consumption in response to user-defined inputs. DECAL has sufficient detail to model true net-zero pathways and reveal fine-grain technology insights. Using DECAL we find the State can achieve 52 % of the emissions abatement needed to meet net-zero by 2045 using technologies that are already commercially available such as electric vehicles heat pumps and renewable electricity & storage. While these technologies are mature the speed and scale of deployment required will still pose significant practical challenges if not technical ones. In addition we find that 25 % of emissions abatement will come from technologies currently at early-stage deployment and 23 % from technologies at research scale motivating the continued research & development of these technologies including zero-emission heavy-duty vehicles carbon capture & sequestration clean industrial heating low global warming potential refrigerants and direct air capture. Significant carbon dioxide removal will also be needed for California to meet its net-zero target on time at least 45 Mt/yr and more likely up to 75 Mt/yr by 2045. Accelerating deployment of mature technologies can further reduce the need for carbon removal nevertheless establishing enforceable carbon removal targets and conducting policy planning to make said goals a reality will be needed if California is to meet its net-zero by 2045 goal.

Under the guidance of energy-saving and emission reduction goals a lowcarbon economic operation method for integrated energy systems (IES) has been proposed. This strategy aims to enhance energy utilization efficiency bolster equipment operational flexibility and significantly cut down on carbon emissions from the IES. Firstly a thorough exploration of the two-stage operational framework of Power-to-Gas (P2G) technology is conducted. Electrolyzers methane reactors and hydrogen fuel cells (HFCs) are introduced as replacements for traditional P2G equipment with the objective of harnessing the multiple benefits of hydrogen energy. Secondly a cogeneration and HFC operational strategy with adjustable heat-to-electricity ratio is introduced to further enhance the IES’s low-carbon and economic performance. Finally a step-by-step carbon trading mechanism is introduced to effectively steer the IES towards carbon emission control.

Hydrogen can play a significant role in Australian economy and Australia has set an ambitious goal to become a global leader in hydrogen industry as outlined in the National Hydrogen Strategy 2024. Hydrogen is an efficient energy carrier that can be used for both transporting and storing energy. Underground hydrogen storage (UHS) in aquifers depleted gas and oil reservoirs and salt caverns have been considered as a low-cost option for largescale storage of hydrogen. In this study a method for hydrogen storage in engineered (shallow) lenses is proposed where a lens is created in a very low permeability layered formation such as shales via opening the layers by a pressurised fluid. A preliminary overview of the Australian basins is presented focussing on the most suitable/obvious units for the purpose of creating engineered lenses for storage of hydrogen. Major engineering aspects of lenses such as size volume storage capacity storage time and hydrogen loss are reviewed followed by a Techno-Economic Analysis for the proposed hydrogen storage method. Initial modelling shows that up to 250 tonnes of hydrogen can be stored in shallow engineered lenses incurring a capital cost of 35.7 US$/kg and total annual operational cost of 7 US$/kg making the proposed storage method a competitive option against salt and lined rock caverns. Finally Monitoring and Verification (M&V) as part of storage assurance practice has been discussed and successful examples are presented.

In this study the electrolysis of water by using ammonium chloride (NH4Cl) as an electrolyte was investigated for the production of hydrogen gas. The assembled electrochemical cell consists mainly of twenty-one stainless-steel electrodes and a direct current from a battery ammonium chloride solution. In the electrolysis process hydrogen and oxygen are developed at the same time and collected as a mixture to be used as a fuel. This study explores a technic regarding the matching of oxyhydrogen (HHO) electrolyzers with photovoltaic (PV) systems to make HHO gas. The primary objective of the present research is to enable the electrolyzer to operate independently of other energy origins functioning as a complete unit powered solely by PV. Moreover the impact of using PWM on cell operation was investigated. The experimental data was collected at various time intervals NH4Cl concentrations. Additionally the hydrogen unit consists of two cells with a shared positive pole fixed between them. Some undesirable anodic reaction affects the efficiency of hydrogen gas production because of the corrosion of anode to ferrous hydroxide (Fe(OH)2). Polyphosphate Inhibitor was used to minimize the corrosion reaction of anode and keep the efficiency of hydrogen gas flow. The optimal concentration of 3M for ammonium chloride was identified balancing a gas flow rate of 772 ml/min with minimal anode corrosion. Without PWM conversion efficiency ranges between 93% and 96%. Therefore PWM increased conversion efficiency by approximately 5% leading to a corresponding increase in hydrogen gas production.

This study investigates the impact of delayed and accelerated expansion of the volatile renewable energy sources (vRES) onshore wind offshore wind and photovoltaics on Europe’s (EU27 United Kingdom Norway and Switzerland) demand for hydrogen imports and its derivatives to meet demand from final energy consumption sectors and to comply with European greenhouse gas (GHG) emission targets. Using the multi-energy system model ISAaR we analyze fourteen scenarios with different levels of vRES expansion including an evaluation of the resulting hydrogen prices. The load-weighted average European hydrogen price in the BASE scenario decreases from 4.1 €/kg in 2030 to 3.3 €/kg by 2050. Results show that delaying the expansion of vRES significantly increases the demand for imports of hydrogen and its derivatives and thus increases the risk of not meeting GHG emission targets for two reasons: (1) higher import volumes to meet GHG emission targets increase dependence on third parties and lead to higher risk in terms of security of supply; (2) at the same time lower vRES expansion in combination with higher import volumes leads to higher resulting hydrogen prices which in turn affects the economic viability of the energy transition. In contrast an accelerated expansion of vRES reduces dependency on imports and stabilizes hydrogen prices below 3 €/kg in 2050 which increases planning security for hydrogen off-takers. The study underlines the importance of timely and strategic progress in the expansion of vRES and investment in hydrogen production storage and transport networks to minimize dependence on imports and effectively meet the European climate targets.

The Middle East and North Africa region has not played a major role in climate action so far and several countries depend economically on fossil fuel exports. However this is a region with vast solar energy resources which can be exploited affordably for power generation and hydrogen production at scale to eventually reach carbon neutrality. In this paper we elaborate on the case of the United Arab Emirates and explore the aspirations and feasibility of its net-zero by 2050 target. While we affirm the concept per se we also highlight the technological complexity and economic dimensions that accompany such transformation. We expect the UAE’s electricity demand to triple between today and 2050 and the annual green hydrogen production is expected to reach 3.5 Mt accounting for over 40% of the electricity consumption. Green hydrogen will provide power-to-fuel solutions for aviation maritime transport and hard-to-abate industries. At the same time electrification will intensify—most importantly in road transport and low-temperature heat demands. The UAE can meet its future electricity demands primarily with solar power followed by natural gas power plants with carbon capture utilization and storage while the role of nuclear power in the long term is unclear at this stage.

Hydrogen is increasingly recognized as an element in the effort to decarbonize the energy sector. Within the development of large-scale supply chain the storage phase emerges as a significant challenge. This study reviews Life Cycle Assessment (LCA) literature focused exclusively on hydrogen as an energy vector aiming to identify areas for improvement highlight effective solutions and point out research gaps. The goal is to provide a comprehensive overview of hydrogen storage technologies from an environmental perspective. A systematic search was conducted in the SCOPUS database using a specific set of keywords resulting in the identification of 30 relevant studies. These works explore hydrogen storage across different scales and applications which were classified into five categories based on the type of storage application most of them related to stationary use. The majority of the selected studies focus on storing hydrogen in compressed gas tanks. Notably 33 % of the analyzed articles assess only greenhouse gas (GHG) emissions and 10 % evaluate only two environmental impact categories including GHGs. This reflects a limited understanding of broader environmental impacts with a predominant focus on CO₂eq emissions. When comparing different case studies storage methods associated with the lowest emissions include metal hydrides and underground hydrogen storage. Another important observation is the trend of decreasing CO₂eq emissions as the storage system scale increases. Future studies should adopt more comprehensive approaches by analyzing a wider range of hydrogen storage technologies and considering multiple environmental impact categories in LCA. Moreover it is crucial to integrate environmental economic and social dimensions of sustainability as multidimensional assessments are essential to support well-informed balanced decisions that align with the sustainable development of hydrogen storage systems.

Green hydrogen is a promising energy carrier for the decarbonization of hard-toabate sectors and supporting renewable energy integration aligning with carbon neutrality goals like the European Green Deal. Iceland’s abundant renewable energy and decarbonized electricity system position it as a strong candidate for green hydrogen production. Despite early initiatives its hydrogen economy has yet to significantly expand. This study evaluated Iceland’s hydrogen development through stakeholder interviews and a techno-economic analysis of alkaline and PEM electrolyzers. Stakeholders were driven by decarbonization goals economic opportunities and energy security but faced technological economic and governance challenges. Recommendations include building stakeholder confidence financial incentives and creating hydrogen-based chemicals to boost demand. Currently alkaline electrolyzers are more cost-effective (EUR 1.5–2.8/kg) than PEMs (EUR 2.1–3.6/kg) though the future costs for both could drop below EUR 1.5/kg. Iceland’s low electricity costs and high electrolyzer capacity provide a competitive edge. However this advantage may shrink as solar and wind costs decline globally particularly in regions like Australia. This work’s findings emphasize the need for strategic planning to sustain competitiveness and offer transferable insights for other regions introducing hydrogen into ecosystems lacking infrastructure.

A recent consensus to achieve carbon neutrality is promoting interest in the use of hydrogen and management of its production system. Among the several types of hydrogen green hydrogen is of most interest which is produced using power generated from renewable energy sources (RES). However several challenges are encountered in the stable operation of green hydrogen production systems (GHPS) owing to the inherent intermittent and variables characteristics of RES. Although the implementation of energy storage systems (ESS) can aid in compensating for this variability large-scale ESS installations can be economically infeasible. Thus this study seeks an operation strategy suitable for GHPS considering the expected variability of RES and the operational conditions of a relatively small-sized ESS. In particular as state-of-charge management is crucial for operating an ESS with limited capacity this study presents a method to conduct coordinated control between the ESS and electrolyzer. Furthermore considering the characteristics of the GHPS the expected short-term variability analyzed using the copula-based approach is utilized. The proposed method is validated based on various RES generation scenarios. By applying the developed method operational continuity to GHPS is expected to increase with efficiency.

Hydrogen is a key energy carrier in the global transition to low-carbon systems requiring scalable and secure storage solutions. While underground hydrogen storage (UHS) in salt caverns is proven its cost and limited geographic availability have led to growing interest in depleted oil and gas reservoirs. A critical factor in evaluating these reservoirs is the sealing capacity of the overlying caprock. This study presents a novel experimental protocol for assessing caprock integrity under UHS conditions using a custom-designed core-flooding apparatus integrated with a micro-capillary flow meter. This setup enables high-resolution measurements of ultra-low permeabilities (as low as 10 nano-Darcy) flow rates (down to 10 nano-liters/hour) threshold pressure and breakthrough pressure. Benchmark tests with nitrogen and methane were followed by hydrogen experiments across caprocks with a wide range of permeability and porosity. The results demonstrate clear trends between caprock properties and sealing performance providing a quantitative framework for evaluating UHS site suitability. Hydrogen showed slightly lower threshold and breakthrough pressures compared to other gases reinforcing the need for accurate site-specific caprock evaluation. The proposed method offers a robust approach for characterizing candidate storage sites in depleted reservoirs.

Industrial alkaline water electrolysis systems face challenges in maintaining hydrogenin-oxygen impurity within safe limits under fluctuating operating conditions. This study aims to characterize the dynamic response of hydrogen-in-oxygen concentration in an industrial 10 kW alkaline water electrolysis test platform (2 Nm3/h hydrogen output at 1.6 MPa and 90 ◦C) and to identify how operating parameters influence hydrogen-inoxygen behavior. We systematically varied the cell current system pressure and electrolyte flow rate while monitoring real-time hydrogen-in-oxygen levels. The results show that hydrogen-in-oxygen exhibits significant inertia and delay: during startup hydrogen-inoxygen remained below the 2% safety threshold and stabilized at 0.9% at full load whereas a step decrease to 60% load caused hydrogen-in-oxygen to rise to 1.6%. Furthermore reducing the pressure from 1.4 to 1.0 MPa lowered the hydrogen-in-oxygen concentration by up to 15% and halving the alkaline flow rate suppressed hydrogen-in-oxygen by over 20% compared to constant conditions. These findings provide new quantitative insights into hydrogen-in-oxygen dynamics and offer a basis for optimizing control strategies to keep gas purity within safe limits in industrial-scale alkaline water electrolysis systems.

This study comprehensively reviews the state-of-the-art laboratory-scale fracture mechanics testing methods to assess their suitability for investigating stress-induced critical cracks and geochemically induced subcritical cracks in caprock during underground hydrogen storage. Subcritical crack propagation is primarily examined using empirical techniques such as double torsion and constant stress-rate methods. Both methods determine stress intensity factors and crack velocities without requiring crack length measurements. Comparatively the double torsion method provides advantages such as simple sample preparation and pre-cracking process continuous data acquisition and fracture toughness measurements which makes it more reliable for caprockrelated studies. The International Society for Rock Mechanics recommends four standard methods for critical crack propagation to determine fracture toughness values. Chevron-notched specimens including the Chevron Bend specimen Short Rod specimen and Cracked Chevron Notched Brazilian Disk specimen exhibit higher uncertainty in fracture toughness data due to specimen size effects additional fixture requirements and undesirable crack formations. In contrast the Semi-Circular Bend specimen method is frequently employed due to its smaller specimen size simplified testing and well-balanced dynamic forces. Despite these advancements studies on multiple cracking behaviour in caprock under subsurface hydrogen storage conditions remain limited. The conventional methods discussed in this review are primarily designed to function at ambient conditions making it challenging to replicate subsurface geochemical interactions. Future studies should focus more on developing new laboratory techniques and enhancing existing specimen configurations by incorporating specialised apparatus such as high-pressure cells and reaction chambers to implement typical subsurface conditions observed during underground hydrogen storage. Additionally more parametric studies on caprock samples are recommended to generate a comprehensive dataset on subcritical and critical crack propagation and validate the reliability of these testing methods for underground hydrogen storage applications.