Transmission, Distribution & Storage
Prospects for the Implementation of Underground Hydrogen Storage in the EU
Dec 2022
Publication
The hydrogen economy is one of the possible directions of development for the European Union economy which in the perspective of 2050 can ensure climate neutrality for the member states. The use of hydrogen in the economy on a larger scale requires the creation of a storage system. Due to the necessary volumes the best sites for storage are geological structures (salt caverns oil and gas deposits or aquifers). This article presents an analysis of prospects for large-scale underground hydrogen storage in geological structures. The political conditions for the implementation of the hydrogen economy in the EU Member States were analysed. The European Commission in its documents (e.g. Green Deal) indicates hydrogen as one of the important elements enabling the implementation of a climate-neutral economy. From the perspective of 2050 the analysis of changes and the forecast of energy consumption in the EU indicate an increase in electricity consumption. The expected increase in the production of energy from renewable sources may contribute to an increase in the production of hydrogen and its role in the economy. From the perspective of 2050 discussed gas should replace natural gas in the chemical metallurgical and transport industries. In the longer term the same process will also be observed in the aviation and maritime sectors. Growing charges for CO2 emissions will also contribute to the development of underground hydrogen storage technology. Geological conditions especially wide-spread aquifers and salt deposits allow the development of underground hydrogen storage in Europe.
Potential of Salt Caverns for Hydrogen Storage in Southern Ontario, Canada
Jul 2023
Publication
Salt caverns produced by solution mining in Southern Ontario provide ideal spaces for gas storage due to their low permeability. Underground hydrogen storage (UHS) is an important part of the future renewable energy market in Ontario in order to achieve global carbon neutrality and to fill the gap left by retiring nuclear power plants. However large-scale hydrogen storage is still restricted by limited storage space on the ground’s surface. In this study hydrogen’s physical and chemical properties are first introduced and characterized by low molecular weight high diffusivity low solubility and low density. Then the geological conditions of the underground reservoirs are analyzed especially salt caverns. Salt caverns with their inert cavity environments and stable physical properties offer the most promising options for future hydrogen storage. The scales heights and thicknesses of the roof and floor salt layers and the internal temperatures and pressures conditions of salt caverns can affect stabilities and storage capacities. Finally several potential problems that may affect the safe storage of hydrogen in salt caverns are discussed. Through the comprehensive analysis of the influencing factors of hydrogen storage in salt caverns this study puts forward the most appropriate development strategy for salt caverns which provides theoretical guidance for UHS in the future and helps to reduce the risk of large-scale storage design.
The Necessity and Feasibility of Hydrogen Storage for Large-Scale, Long-Term Energy Storage in the New Power System in China
Jun 2023
Publication
In the process of building a new power system with new energy sources as the mainstay wind power and photovoltaic energy enter the multiplication stage with randomness and uncertainty and the foundation and support role of large-scale long-time energy storage is highlighted. Considering the advantages of hydrogen energy storage in large-scale cross-seasonal and cross-regional aspects the necessity feasibility and economy of hydrogen energy participation in long-time energy storage under the new power system are discussed. Firstly power supply and demand production simulations were carried out based on the characteristics of new energy generation in China. When the penetration of new energy sources in the new power system reaches 45% long-term energy storage becomes an essential regulation tool. Secondly by comparing the storage duration storage scale and application scenarios of various energy storage technologies it was determined that hydrogen storage is the most preferable choice to participate in large-scale and long-term energy storage. Three long-time hydrogen storage methods are screened out from numerous hydrogen storage technologies including salt-cavern hydrogen storage natural gas blending and solid-state hydrogen storage. Finally by analyzing the development status and economy of the above three types of hydrogen storage technologies and based on the geographical characteristics and resource endowment of China it is pointed out that China will form a hydrogen storage system of “solid state hydrogen storage above ground and salt cavern storage underground” in the future.
Storage Integrity During Underground Hydrogen Storage in Depleted Gas Reservoirs
Nov 2023
Publication
The transition from fossil fuels to renewable energy sources particularly hydrogen has emerged as a central strategy for decarbonization and the pursuit of net-zero carbon emissions. Meeting the demand for large-scale hydrogen storage a crucial component of the hydrogen supply chain has led to the exploration of underground hydrogen storage as an economically viable solution to global energy needs. In contrast to other subsurface storage options such as salt caverns and aquifers which are geographically limited depleted gas reservoirs have garnered increasing attention due to their broader distribution and higher storage capacity. However the safe storage and cycling of hydrogen in depleted gas reservoirs require the preservation of high stability and integrity in the caprock reservoir and wellbore. Nevertheless there exists a significant gap in the current research concerning storage integrity in underground hydrogen storage within depleted gas reservoirs and a systematic approach is lacking. This paper aims to address this gap by reviewing the primary challenges associated with storage integrity including geochemical reactions microbial activities faults and fractures and perspectives on hydrogen cycling. The study comprehensively reviews the processes and impacts such as abiotic and biotic mineral dissolution/precipitation reactivation and propagation of faults and fractures in caprock and host-rock wellbore instability due to cement degradation and casing corrosion and stress changes during hydrogen cycling. To provide a practical solution a technical screening tool has been developed considering controlling variables risks and consequences affecting storage integrity. Finally this paper highlights knowledge gaps and suggests feasible methods and pathways to mitigate these risks facilitating the development of large-scale underground hydrogen storage in depleted gas reservoirs.
How a Grid Company Could Enter the Hydrogen Industry through a New Business Model: A Case Study in China
Mar 2023
Publication
The increasing penetration of renewable and distributed resources signals a global boom in energy transition but traditional grid utilities have yet to share in much of the triumph at the current stage. Higher grid management costs lower electricity prices fewer customers and other challenges have emerged along the path toward renewable energy but many more opportunities await to be seized. Most importantly there are insufficient studies on how grid utilities can thrive within the hydrogen economy. Through a case study on the State Grid Corporation of China we identify the strengths weaknesses opportunities and threats (SWOT) of grid utilities within the hydrogen economy. Based on these factors we recommend that grids integrate hydrogen into the energy-as-a-service model and deliver it to industrial customers who are under decarbonization pressure. We also recommend that grid utilities fund a joint venture with pipeline companies to optimize electricity and hydrogen transmissions simultaneously.
The Potential Role of Ammonia for Hydrogen Storage and Transport: A Critical Review of Challenges and Opportunities
Aug 2023
Publication
Hydrogen is being included in several decarbonization strategies as a potential contributor in some hard-to-abate applications. Among other challenges hydrogen storage represents a critical aspect to be addressed either for stationary storage or for transporting hydrogen over long distances. Ammonia is being proposed as a potential solution for hydrogen storage as it allows storing hydrogen as a liquid chemical component at mild conditions. Nevertheless the use of ammonia instead of pure hydrogen faces some challenges including the health and environmental issues of handling ammonia and the competition with other markets such as the fertilizer market. In addition the technical and economic efficiency of single steps such as ammonia production by means of the Haber–Bosch process ammonia distribution and storage and possibly the ammonia cracking process to hydrogen affects the overall supply chain. The main purpose of this review paper is to shed light on the main aspects related to the use of ammonia as a hydrogen energy carrier discussing technical economic and environmental perspectives with the aim of supporting the international debate on the potential role of ammonia in supporting the development of hydrogen pathways. The analysis also compares ammonia with alternative solutions for the long-distance transport of hydrogen including liquefied hydrogen and other liquid organic carriers such as methanol.
Underground Hydrogen Storage Safety: Experimental Study of Hydrogen Diffusion through Caprocks
Jan 2024
Publication
Underground Hydrogen Storage (UHS) provides a large-scale and safe solution to balance the fluctuations in energy production from renewable sources and energy consumption but requires a proper and detailed characterization of the candidate reservoirs. The scope of this study was to estimate the hydrogen diffusion coefficient for real caprock samples from two natural gas storage reservoirs that are candidates for underground hydrogen storage. A significant number of adsorption/desorption tests were carried out using a Dynamic Gravimetric Vapor/Gas Sorption System. A total of 15 samples were tested at the reservoir temperature of 45 °C and using both hydrogen and methane. For each sample two tests were performed with the same gas. Each test included four partial pressure steps of sorption alternated with desorption. After applying overshooting and buoyancy corrections the data were then interpreted using the early time approximation of the solution to the diffusion equation. Each interpretable partial pressure step provided a value of the diffusion coefficient. In total more than 90 estimations of the diffusion coefficient out of 120 partial pressure steps were available allowing a thorough comparison between the diffusion of hydrogen and methane: hydrogen in the range of 1 × 10−10 m2 /s to 6 × 10−8 m2 /s and methane in the range of 9 × 10−10 m2 /s to 2 × 10−8 m2 /s. The diffusion coefficients measured on wet samples are 2 times lower compared to those measured on dry samples. Hysteresis in hydrogen adsorption/desorption was also observed.
Modelling Hydrogen Storage and Filling Systems: A Dynamic and Customizable Toolkit
Aug 2023
Publication
Hydrogen plays a vital role in decarbonizing the mobility sector. With the number of hydrogen vehicles expected to drastically increase a network of refuelling stations needs to be built to keep up with the hydrogen demand. However further research and development on hydrogen refuelling infrastructure storage and standardization is required to overcome technical and economic barriers. Simulation tools can reduce time and costs during the design phase but existing models do not fully support calculations of complete and arbitrary system layouts. Therefore a flexible simulation toolbox for rapid investigations of hydrogen refuelling and extraction processes as well as development of refuelling infrastructure vehicle tank systems and refuelling protocols for non-standardized applications was developed. Our model library H2VPATT comprises of typical components found in refuelling infrastructure. The key component is the hydrogen tank model. The simulation model was successfully validated with measurement data from refuelling tests of a 320 l type III tank.
Impact of Experimentally Measured Relative Permeability Hysteresis on Reservoir-scale Performance of Undergound Hydrogen Storage (UHS)
Jan 2024
Publication
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.
Underground Hydrogen Storage: Integrated Surface Facilities and Fluid Flow Modelling for Depleted Gas Reservoirs
Aug 2023
Publication
We report a new techno-economic model to assess performance and capital costs for large-scale underground hydrogen storage in depleted gas reservoirs. A simulation toolbox is developed to model surface facilities and to simulate the hydrogen flow in geological formations in an integrated fashion.<br/>Integrated modelling revealed the following key insights: 1) A buffer system is highly desirable to absorb inherent variability in upstream hydrogen production; 2) hydrogen mixing with existing gases in the reservoir together with gravity segregation and diffusion results in a decline in hydrogen purity at the wellhead over time and can require increased purification; 3) the capital cost is dominated by the cost of cushion gas (hydrogen) and the compression system where about 9% of the total energy content of the hydrogen is consumed for compression. The scenarios modelled in our study result in a levelized cost of storage in Australia ranging from 2.3 to 4.29 A$/(kg).
Evaluation of Hydrogen Transportation Networks - A Case Study on the German Energy System
May 2023
Publication
Not only due to the energy crisis European policymakers are exploring options to substitute natural gas with renewable hydrogen. A condition for the application of hydrogen is a functioning transportation infrastructure. However the most efficient transport of large hydrogen quantities is still unclear and deeper analyses are missing. A promising option is converting the existing gas infrastructure. This study presents a novel approach to develop hydrogen networks by applying the Steiner tree algorithm to derive candidates and evaluate their costs. This method uses the existing grid (brownfield) and is compared to a newly built grid (Greenfield). The goal is the technical and economic evaluation and comparison of hydrogen network candidates. The methodology is applied to the German gas grid and demand and supply scenarios covering the industry heavy-duty transport power and heating sector imports and domestic production. Five brownfield candidates are compared to a greenfield candidate. The candidates differ by network length and pipeline diameters to consider the transported volume of hydrogen. The economic evaluation concludes that most brownfield candidates’ cost is significantly lower than those of the greenfield candidate. The candidates can serve as starting points for flow simulations and policymakers can estimate the cost based on the results.
Hydrogen Liquefaction: A Review of the Fundamental Physics, Engineering Practice and Future Opportunities
Apr 2022
Publication
Hydrogen is emerging as one of the most promising energy carriers for a decarbonised global energy system. Transportation and storage of hydrogen are critical to its large-scale adoption and to these ends liquid hydrogen is being widely considered. The liquefaction and storage processes must however be both safe and efficient for liquid hydrogen to be viable as an energy carrier. Identifying the most promising liquefaction processes and associated transport and storage technologies is therefore crucial; these need to be considered in terms of a range of interconnected parameters ranging from energy consumption and appropriate materials usage to considerations of unique liquid-hydrogen physics (in the form of ortho–para hydrogen conversion) and boil-off gas handling. This study presents the current state of liquid hydrogen technology across the entire value chain whilst detailing both the relevant underpinning science (e.g. the quantum behaviour of hydrogen at cryogenic temperatures) and current liquefaction process routes including relevant unit operation design and efficiency. Cognisant of the challenges associated with a projected hydrogen liquefaction plant capacity scale-up from the current 32 tonnes per day to greater than 100 tonnes per day to meet projected hydrogen demand this study also reflects on the next-generation of liquid-hydrogen technologies and the scientific research and development priorities needed to enable them.
A Review of Gas Phase Inhibition of Gaseous Hydrogen Embrittlement in Pipeline Steels
Feb 2024
Publication
The addition of small amounts of certain gases such as O2 CO and SO2 may mitigate hydrogen embrittlement in high-pressure gas transmission pipelines that transport hydrogen. To practically implement such inhibition in gas transmission pipelines a comprehensive understanding and quantification of this effect are essential. This review examines the impact of various added gases to hydrogen including typical odorants on gaseous hydrogen embrittlement of steels and evaluates their inhibition effectiveness. O2 CO and SO2 were found to be effective inhibitors of hydrogen embrittlement. Yet the results in the literature have not always been consistent partly because of the diverse range of mechanical tests and their parameters. The absence of systematic studies hinders the evaluation of the feasibility of using gas phase inhibitors for controlling gaseous hydrogen embrittlement. A method to quantify the effectiveness of gas phase inhibition is proposed using gas phase permeation studies.
Liquefied Hydrogen Value Chain: A Detailed Techno-economic Evaluation for its Application in the Industrial and Mobility Sectors
Oct 2023
Publication
Green hydrogen can be efficiently produced in regions rich in renewable sources far from the European largeproduction sites and delivered to the continent for utilization in the industrial and mobility sectors. In this work the transportation of hydrogen from North Africa to North Italy in its liquefied form is considered. A technoeconomic assessment is performed on its value chain which includes liquefaction storage maritime transport distribution regasification and compression. The calculated transport cost for the industrial application (delivery to a hydrogen valley) ranges from 6.14 to 9.16 €/kg while for the mobility application (delivery to refueling stations) the range is 10.96–17.71 €/kg. In the latter case the most cost-effective configuration involves the distribution of liquefied hydrogen and regasification at the refueling stations. The liquefaction process is the cost driver of the value chain in all the investigated cases suggesting the importance of its optimization to minimize the overall transport cost.
Preventing Hydrogen Embrittlement: The Role of Barrier Coatings for the Hydrogen Economy
May 2023
Publication
Hydrogen barrier coatings are protective layers consisting of materials with a low intrinsic hydrogen diffusivity and solubility showing the potential to delay reduce or hinder hydrogen permeation. Hydrogen barrier coatings are expected to enable steels which are susceptible to hydrogen embrittlement specifically cost-effective low alloy-steels or light-weight high-strength steels for applications in a hydrogen economy. Predominantly ceramic coating materials have been investigated for this purpose including oxides nitrides and carbides. In this review the state of the art with respect to hydrogen permeation is discussed for a variety of coatings. Al2O3 TiAlN and TiC appear to be the most promising candidates from a large pool of ceramic materials. Coating methods are compared with respect to their ability to produce layers with suitable quality and their potential for scaling up for industrial use. Different setups for the characterisation of hydrogen permeability are discussed using both gaseous hydrogen and hydrogen originating from an electrochemical reaction. Finally possible pathways for improvement and optimisation of hydrogen barrier coatings are outlined.
Subsurface Renewable Energy Storage Capcity for Hydrogen, Methane and Compress Air - A Performance Assessment Study from the North German Basin
Jul 2021
Publication
The transition to renewable energy sources to mitigate climate change will require large-scale energy storage to dampen the fluctuating availability of renewable sources and to ensure a stable energy supply. Energy storage in the geological subsurface can provide capacity and support the cycle times required. This study investigates hydrogen storage methane storage and compressed air energy storage in subsurface porous formations and quantifies potential storage capacities as well as storage rates on a site-specific basis. For part of the North German Basin used as the study area potential storage sites are identified employing a newly developed structural geological model. Energy storage capacities estimated from a volume-based approach are 6510 TWh and 24544 TWh for hydrogen and methane respectively. For a consistent comparison of storage capacities including compressed air energy storage the stored exergy is calculated as 6735 TWh 25795 TWh and 358 TWh for hydrogen methane and compressed air energy storage respectively. Evaluation of storage deliverability indicates that high deliverability rates are found mainly in two of the three storage formations considered. Even accounting for the uncertainty in geological parameters the storage potential for the three considered storage technologies is significantly larger than the predicted demand and suitable storage rates are achievable in all storage formations.
Modelling Underground Hydrogen Storage: A State-of-the-art Review of Fundamental Approaches and Findings
Dec 2023
Publication
This review presents a state-of-the-art of geochemical geomechanical and hydrodynamic modelling studies in the Underground Hydrogen Storage (UHS) domain. Geochemical modelling assessed the reactivity of hydrogen and res pective fluctuations in hydrogen losses using kinetic reaction rates rock mineralogy brine salinity and the integration of hydrogen redox reactions. Existing geomechanics studies offer an array of coupled hydromechanical models suggesting a decline in rock failure during the withdrawal phase in aquifers compared to injection phase. Hydrodynamic modelling evaluations indicate the critical importance of relative permeability hysteresis in determining the UHS performance. Solubility and diffusion of hydrogen gas appear to have minimal impact on UHS. Injection and production rates cushion gas deployment and reservoir heterogeneity however significantly affect the UHS performance stressing the need for thorough modelling and experimental studies. Most of the current UHS modelling efforts focus on assessing the hydrodynamic aspects which are crucial for understanding the viability and safety of UHS. In contrast the lesser-explored geochemical and geomechanical considerations point to potential research gaps. A variety of modelling software tools such as CMG Eclipse COMSOL and PHREEQC evaluated those UHS underlying effects along with a few recent applications of datadriven-based Machine Learning (ML) techniques for enhanced accuracy. This review identified several unresolved challenges in UHS modelling: pronounced lack of expansive datasets leading to a gap between model predictions and their practical reliability; need robust methodologies capable of capturing natural subsurface heterogeneity while upscaling from precise laboratory data to field-scale conditions; demanding intensive computational resources and novel strategies to enhance simulation efficiency; and a gap in addressing geological uncertainties in subsurface environments suggesting that methodologies from oil reservoir simulations could be adapted for UHS. This comprehensive review offers a critical synthesis of the prevailing approaches challenges and research gaps in the domain of UHS thus providing a valuable reference document for further modelling efforts facilitating the informed advancements in this critical domain towards the realization of sustainable energy solutions.
On the Bulk Transport of Green Hydrogen at Sea: Comparison Between Submarine Pipeline and Compressed and Liquefied Transport by Ship
Jan 2023
Publication
This paper compares six (6) alternatives for green hydrogen transport at sea. Two (2) alternatives of liquid hydrogen (LH2) by ship two (2) alternatives of compressed hydrogen (cH2) by ship and two (2) alternatives of hydrogen by pipeline. The ship alternatives study having hydrogen storage media at both end terminals to reduce the ships’ time at port or prescinding of them and reduce the immobilized capital. In the case of the pipeline new models are proposed by considering pressure costs. One scenario considers that there are compression stations every 500 km and the other one considers that there are none along the way. These alternatives are assessed under nine different scenarios that combine three distances: 100 km 2500 km and 5000 km; and three export rates of hydrogen 100 kt/y 1 Mt/y and 10 Mt/y. The results show including uncertainty bands that for the 100 km of distance the best alternative is the pipeline. For 2500 km and 100 kt/y the top alternative is cH2 shipping without storage facilities at the port terminals. For 2500 km and 1 Mt/y and for 5000 km and 100 kt/y the best alternatives are cH2 or LH2 shipping. For the remaining scenarios the best alternative is LH2 shipping.
Benchmark Study for the Simulation of Underground Hydrogen Storage Operations
Aug 2022
Publication
While the share of renewable energy sources increased within the last years with an ongoing upward trend the energy sector is facing the problem of storing large amounts of electrical energy properly. To compensate daily and seasonal fluctuations a sufficient storage system has to be developed. The storage of hydrogen in the subsurface referred to as Underground Hydrogen Storage (UHS) shows potential to be a solution for this problem. Hydrogen produced from excess energy via electrolysis is injected into a subsurface reservoir and withdrawn when required. As hydrogen possesses unique thermodynamic properties many commonly used correlations can not be simply transferred to a system with a high hydrogen content. Mixing processes with the present fluids are essential to be understood to achieve high storage efficiencies. Additionally in the past microbial activity e.g. by methanogenic archaea was observed leading to a changing fluid composition over time. To evaluate the capability of reservoir simulators to cover these processes the present study establishes a benchmark scenario of an exemplary underground hydrogen storage scenario. The benchmark comprises of a generic sandstone gas reservoir and a typical gas storage schedule is defined. Based on this benchmark the present study assesses the capabilities of the commercial simulator Schlumberger ECLIPSE and the open-source simulator DuMux to mimic UHS related processes such as hydrodynamics but also microbial activity. While ECLIPSE offers a reasonable mix of user-friendliness and computation time DuMux allows for a better adjustment of correlations and the implementation of biochemical reactions. The corresponding input data (ECLIPSE format) and relevant results are provided in a repository to allow this simulation study’s reproduction and extension.
Hydrogen Export Competitiveness Index for a Sustainable Hydrogen Economy
May 2023
Publication
The transition to cleaner energy sources including renewables introduces the need for versatile and transportable energy carriers such as hydrogen. This paper aims to quantify the hydrogen export competitiveness of all countries using a newly developed comprehensive index. The developed competitiveness index includes 21 indicators under four main categories: resource availability and potential economic and financial potential political and regulatory status and industrial knowledge. Expert interviews and surveys are conducted to properly identify choose and modify the categories and indicators and to calculate the appropriate weight for each. Top-ranking countries include the United States Australia Canada United Kingdom China Norway India Russia Netherlands and Germany and they are poised to be significant players in the hydrogen market. Policy recommendations for growing the hydrogen production and export sector are given based on each category.
Prediction of Mixing Uniformity of Hydrogen Injection in Natural Gas Pipeline Based on a Deep Learning Model
Nov 2022
Publication
It is economical and efficient to use existing natural gas pipelines to transport hydrogen. The fast and accurate prediction of mixing uniformity of hydrogen injection in natural gas pipelines is important for the safety of pipeline transportation and downstream end users. In this study the computational fluid dynamics (CFD) method was used to investigate the hydrogen injection process in a T-junction natural gas pipeline. The coefficient of variation (COV) of a hydrogen concentration on a pipeline cross section was used to quantitatively characterize the mixing uniformity of hydrogen and natural gas. To quickly and accurately predict the COV a deep neural network (DNN) model was constructed based on CFD simulation data and the main influencing factors of the COV including flow velocity hydrogen blending ratio gas temperature flow distance and pipeline diameter ratio were taken as input nodes of the DNN model. In the model training process the effects of various parameters on the prediction accuracy of the DNN model were studied and an accurate DNN architecture was constructed with an average error of 4.53% for predicting the COV. The computational efficiency of the established DNN model was also at least two orders of magnitude faster than that of the CFD simulations for predicting the COV.
Technical and Economic Viability of Underground Hydrogen Storage
Nov 2023
Publication
Considering the mismatch between the renewable source availability and energy demand energy storage is increasingly vital for achieving a net-zero future. The daily/seasonal disparities produce a surplus of energy at specific moments. The question is how can this “excess” energy be stored? One promising solution is hydrogen. Conventional hydrogen storage relies on manufactured vessels. However scaling the technology requires larger volumes to satisfy peak demands enhance the reliability of renewable energies and increase hydrogen reserves for future technology and infrastructure development. The optimal solution may involve leveraging the large volumes of underground reservoirs like salt caverns and aquifers while minimizing the surface area usage and avoiding the manufacturing and safety issues inherent to traditional methods. There is a clear literature gap regarding the critical aspects of underground hydrogen storage (UHS) technology. Thus a comprehensive review of the latest developments is needed to identify these gaps and guide further R&D on the topic. This work provides a better understanding of the current situation of UHS and its future challenges. It reviews the literature published on UHS evaluates the progress in the last decades and discusses ongoing and carried-out projects suggesting that the technology is technically and economically ready for today’s needs.
Optimizing Underground Hydrogen Storage in Aquifers: The Impact of Cushion Gas Type
Aug 2023
Publication
This study investigated the impact of cushion gas type and presence on the performance of underground hydrogen storage (UHS) in an offshore North Sea aquifer. Using numerical simulation the relationship between cushion gas type and UHS performance was comprehensively evaluated providing valuable insights for designing an efficient UHS project delivery. Results indicated that cushion gas type can significantly impact the process's recovery efficiency and hydrogen purity. CO2 was found to have the highest storage capacity while lighter gases like N2 and CH4 exhibited better recovery efficiency. Utilising CH4 as a cushion gas can lead to a higher recovery efficiency of 80%. It was also determined that utilising either of these cushion gases was always more beneficial than hydrogen storage alone leading to an incremental hydrogen recovery up to 7%. Additionally hydrogen purity degraded as each cycle progressed but improved over time. This study contributes to a better understanding of factors affecting UHS performance and can inform the selection of cushion gas type and optimal operational strategies.
Small-Scale High-Pressure Hydrogen Storage Vessels: A Review
Feb 2024
Publication
Nowadays high-pressure hydrogen storage is the most commercially used technology owing to its high hydrogen purity rapid charging/discharging of hydrogen and low-cost manufacturing. Despite numerous reviews on hydrogen storage technologies there is a relative scarcity of comprehensive examinations specifically focused on high-pressure gaseous hydrogen storage and its associated materials. This article systematically presents the manufacturing processes and materials used for a variety of high-pressure hydrogen storage containers including metal cylinders carbon fiber composite cylinders and emerging glass material-based hydrogen storage containers. Furthermore it introduces the relevant principles and theoretical studies showcasing their advantages and disadvantages compared to conventional high-pressure hydrogen storage containers. Finally this article provides an outlook on the future development of high-pressure hydrogen storage containers.
Implementation of Formic Acid as a Liquid Organic Hydrogen Carrier (LOHC): Techno-Economic Analysis and Life Cycle Assessment of Formic Acid Produced via CO2 Utilization
Sep 2022
Publication
To meet the global climate goals agreed upon regarding the Paris Agreement governments and institutions around the world are investigating various technologies to reduce carbon emissions and achieve a net-negative energy system. To this end integrated solutions that incorporate carbon utilization processes as well as promote the transition of the fossil fuel-based energy system to carbon-free systems such as the hydrogen economy are required. One of the possible pathways is to utilize CO2 as the base chemical for producing a liquid organic hydrogen carrier (LOHC) using CO2 as a mediating chemical for delivering H2 to the site of usage since gaseous and liquid H2 retain transportation and storage problems. Formic acid is a probable candidate considering its high volumetric H2 capacity and low toxicity. While previous studies have shown that formic acid is less competitive as an LOHC candidate compared to other chemicals such as methanol or toluene the results were based on out-of-date process schemes. Recently advances have been made in the formic acid production and dehydrogenation processes and an analysis regarding the recent process configurations could deem formic acid as a feasible option for LOHC. In this study the potential for using formic acid as an LOHC is evaluated with respect to the state-of-the-art formic acid production schemes including the use of heterogeneous catalysts during thermocatalytic and electrochemical formic acid production from CO2 . Assuming a hydrogen distribution system using formic acid as the LOHC each of the production transportation dehydrogenation and CO2 recycle sections are separately modeled and evaluated by means of techno-economic analysis (TEA) and life cycle assessment (LCA). Realistic scenarios for hydrogen distribution are established considering the different transportation and CO2 recovery options; then the separate scenarios are compared to the results of a liquefied hydrogen distribution scenario. TEA results showed that while the LOHC system incorporating the thermocatalytic CO2 hydrogenation to formic acid is more expensive than liquefied H2 distribution the electrochemical CO2 reduction to formic acid system reduces the H2 distribution cost by 12%. Breakdown of the cost compositions revealed that reduction of steam usage for thermocatalytic processes in the future can make the LOHC system based on thermocatalytic CO2 hydrogenation to formic acid to be competitive with liquefied H2 distribution if the production cost could be reduced by 23% and 32% according to the dehydrogenation mode selected. Using formic acid as a LOHC was shown to be less competitive compared to liquefied H2 delivery in terms of LCA but producing formic acid via electrochemical CO2 reduction was shown to retain the lowest global warming potential among the considered options.
Exploring Hydrogen Storage Potentital in Depleted Western Australian Hydrocarbon Reservoirs: A Petrophysical and Petrographic Analysis
Oct 2023
Publication
Hydrogen recognised as a clean and sustainable energy carrier with excellent transportation fuel properties drives numerous countries towards a hydrogen-based economy due to its high utilisation efficiency and minimal environmental impact. However the gaseous nature of hydrogen necessitates larger storage surface areas. Underground Hydrogen Storage (UHS) has emerged as a promising and efficient method to overcome this challenge. Currently only a handful of UHS locations exist globally due to the novelty of this field. With its abundant depleted hydrocarbon reservoirs boasting significant storage capacity Western Australia presents a suitable region for hydrogen storage. This paper comprehensively analyses petrophysical and petrographic characteristics employing XRD MIP and Micro-CT techniques on sandstone and claystone samples obtained from several fields in Western Australia. The suitability of these samples for hydrogen storage is evaluated based on mineral composition and porosity. The analysis reveals that more than 96% of Quartz is present in the sandstone samples. The claystone samples exhibit a mineral composition comprising Quartz Calcite K-feldspar Kaolinite Pyrite Albite and Muscovite. The study suggests that hydrogen storage in formation rock is favourable due to the low reactivity of hydrogen with silicate minerals but interactions with cap rock minerals should be considered. Micro-CT results indicate the connected porosity in the 17.23–4.67% range. Pore distribution in sandstones ranges from nanometers to millimetres with a substantial proportion of connected pores in the intermediate range which is conducive to hydrogen storage. This is particularly advantageous as the hydrogen-water system is highly water-wet with hydrogen primarily occupying medium and larger pores minimising hydrogen trapping. In claystone most pores were below 3 nm but instrumental constraints limited their quantification. In conclusion the petrophysical and petrographic analysis underscores the potential of Western Australian depleted hydrocarbon reservoirs for hydrogen storage. Understanding the mineralogical reactions with cap rock minerals is crucial while the favourable pore distribution in sandstones further supports the viability of hydrogen storage.
Subsurface Porous Media Hydrogen Storage - Scenario Development and Simulation
Aug 2015
Publication
Subsurface porous media hydrogen storage could be a viable option to mitigate shortages in energy supply from renewable sources. In this work a scenario for such a storage is developed and the operation is simulated using a numerical model. A hypothetical storage site is developed based on an actual geological structure. The results of the simulations show that the storage can supply about 20 % of the average demand in electrical energy of the state of Schleswig-Holstein Germany for a week-long period.
Integration of Different Storage Technologies towards Sustainable Development—A Case Study in a Greek Island
Mar 2024
Publication
The necessity for transitioning to renewable energy sources and the intermittent nature of the natural variables lead to the integration of storage units into these projects. In this research paper wind turbines and solar modules are combined with pumped hydro storage batteries and green hydrogen. Energy management strategies are described for five different scenarios of hybrid renewable energy systems based on single or hybrid storage technologies. The motivation is driven by grid stability issues and the limited access to fresh water in the Greek islands. A RES-based desalination unit is introduced into the hybrid system for access to low-cost fresh water. The comparison of single and hybrid storage methods the exploitation of seawater for the simultaneous fulfillment of water for domestic and agricultural purposes and the evaluation of different energy economic and environmental indices are the innovative aspects of this research work. The results show that pumped hydro storage systems can cover the energy and water demand at the minimum possible price 0.215 EUR/kWh and 1.257 EUR/m3 while hybrid storage technologies provide better results in the loss of load probability payback period and CO2 emissions. For the pumped hydro– hydrogen hybrid storage system these values are 21.40% 10.87 years and 2297 tn/year respectively.
Assessing Opportunities and Weaknesses of Green Hydrogen Transport via LOHC through a Detailed Techno-economic Analysis
Aug 2023
Publication
In the transition towards a more sustainable energy system hydrogen is seen as the key low-emission energy source. However the limited H2 volumetric density hinders its transportation. To overcome this issue liquid organic hydrogen carriers (LOHCs) molecules that can be hydrogenated and upon arrival dehydrogenated for H2 release have been proposed as hydrogen transport media. Considering toluene and dibenzyltoluene as representative carriers this work offers a systematic methodology for the analysis and the comparison of LOHCs in view of identifying cost-drivers of the overall value-chain. A detailed Aspen Plus process simulation is provided for hydrogenation and dehydrogenation sections. Simulation results are used as input data for the economic assessment. The process economics reveals that dehydrogenation is the most impactful cost-item together with the carrier initial loading the latter related to the LOHC transport distance. The choice of the most suitable molecule as H2 carrier ultimately is a trade-off between its hydrogenation enthalpy and cost.
Economic and Environmental Potential of Green Hydrogen Carriers (GHCs) Produced via Reduction of Amine-capture CO2
Jun 2023
Publication
Hydrogen is deemed as a crucial component in the transition to a carbon-free energy system and researchers are actively working to realize the hydrogen economy. While hydrogen derived from renewable energy sources is a promising means of providing clean energy to households and industries its practical usage is currently hindered by difficulties in transportation and storage. Due to the extreme operating conditions required for liquefying hydrogen various hydrogen carriers are being considered which can be transported and stored at mild operating conditions and provide hydrogen at the site of usage. Among various candidates green hydrogen carriers obtained via carbon dioxide utilization have been proposed as an economically and environmentally feasible option. Herein the potential of using methanol and formic acid as green hydrogen carriers are evaluated regarding various production and dehydrogenation pathways within a hydrogen distribution system including the recycle of carbon dioxide. Recent progress in carbon dioxide utilization processes especially conversion of carbon dioxide captured in amine solutions have demonstrated promising results for methanol and formic acid production. This study analyzes seven scenarios that consider carbon dioxide utilization-based thermocatalytic and electrochemical methanol and formic acid production as well as different dehydrogenation pathways and compares them to the scenario of delivering liquefied hydrogen. The scenarios are thoroughly analyzed via techno-economic analysis and life cycle assessment methods. The results of the study indicate that methanol-based options are economically viable reducing the cost up to 43% compared to liquefied hydrogen delivery. As for formic acid only the electrochemical production method is profitable retaining 10% less cost compared to liquefied hydrogen delivery. In terms of environmental impact all of the scenarios show higher global warming impact values than liquefied hydrogen distribution. However results show that in an optimistic case where wind electricity is widely used electrochemical formic acid production is competitive with liquefied hydrogen distribution retaining 39% less global warming impact values. This is because high conversion can be achieved at mild operating conditions for the production and dehydrogenation reactions of formic acid reducing the input of utilities other than electricity. This study suggests that while methanol can be a shortterm solution for hydrogen distribution electrochemical formic acid production may be a viable long-term option.
Hydrogen Balloon Transportation: A Cheap and Efficiency Mode to Transport Hydrogen
Nov 2023
Publication
The chances of a global hydrogen economy becoming a reality have increased significantly since the COVID pandemic and the war in Ukraine and for net zero carbon emissions. However intercontinental hydrogen transport is still a major issue. This study suggests transporting hydrogen as a gas at atmospheric pressure in balloons using the natural flow of wind to carry the balloon to its destination. We investigate the average wind speeds atmospheric pressure and temperature at different altitudes for this purpose. The ideal altitudes to transport hydrogen with balloons are 10 km or lower and hydrogen pressures in the balloon vary from 0.25 to 1 bar. Transporting hydrogen from North America to Europe at a maximum 4 km altitude would take around 4.8 days on average. Hydrogen balloon transportation cost is estimated at 0.08 USD/kg of hydrogen which is around 12 times smaller than the cost of transporting liquified hydrogen from the USA to Europe. Due to its reduced energy consumption and capital cost in some locations hydrogen balloon transportation might be a viable option for shipping hydrogen compared to liquefied hydrogen and other transport technologies.
Review on the Thermal Neutrality of Application-orientated Liquid Organic Hydrogen Carrier for Hydrogen Energy Storage and Delivery
Aug 2023
Publication
The depletion and overuse of fossil fuels present formidable challenge to energy supply system and environment. The human society is in great need of clean renewable and sustainable energy which can guarantee the long-term utilization without leading to escalation of greenhouse effect. Hydrogen as an extraordinary secondary energy is capable of realizing the target of environmental protection and transferring the intermittent primary energy to the application terminal while its nature of low volumetric energy density and volatility need suitable storage method and proper carrier. In this context liquid organic hydrogen carrier (LOHC) among a series of storage methods such as compressed and liquefied hydrogen provokes a considerable amount of research interest since it is proven to be a suitable carrier for hydrogen with safety and stability. However the dehydrogenation of hydrogen-rich LOHC materials is an endothermic process and needs large energy consumption which hampers the scale up of the LOHC system. The heat issue is thus essential to be addressed for fulfilling the potential of LOHC. In this work several strategies of heat intensification and management for LOHC system including the microwave irradiation circulation of exhaust heat and direct LOHC fuel cell are summarized and analyzed to provide suggestions and directions for future research.
Evaluation of the Impact of Gaseous Hydrogen on Pipeline Steels Utilizing Hollow Specimen Technique and μCT
Feb 2024
Publication
The high potential of hydrogen as a key factor on the pathway towards a climate neutral economy leads to rising demand in technical applications where gaseous hydrogen is used. For several metals hydrogen-metal interactions could cause a degradation of the material properties. This is especially valid for low carbon and highstrength structural steels as they are commonly used in natural gas pipelines and analyzed in this work. This work provides an insight to the impact of hydrogen on the mechanical properties of an API 5L X65 pipeline steel tested in 60 bar gaseous hydrogen atmosphere. The analyses were performed using the hollow specimen technique with slow strain rate testing (SSRT). The nature of the crack was visualized thereafter utilizing μCT imaging of the sample pressurized with gaseous hydrogen in comparison to one tested in an inert atmosphere. The combination of the results from non-conventional mechanical testing procedures and nondestructive imaging techniques has shown unambiguously how the exposure to hydrogen under realistic service pressure influences the mechanical properties of the material and the appearance of failure.
Geomechanics of Hydrogen Storage in a Depleted Gas Field
Feb 2024
Publication
We perform a simulation study of hydrogen injection in a depleted gas reservoir to assess the geomechanical impact of hydrogen storage relative to other commonly injected gases (methane CO2). A key finding is that the differences in hydrogen density compressibility viscosity and thermal properties compared to the other gases result in significantly less thermal perturbation at reservoir level. The risks of fault reactivation and wellbore fractures due to thermally-induced stress changes are significantly lower when storing hydrogen compared to results observed in CO2 scenarios. This implies that hydrogen injection and production has a much smaller geomechanical footprint with benefits for operational safety. We also find that use of nitrogen cushion gas ensures efficient deliverability and phase separation in the reservoir. However in this study a large fraction of cushion gas was back-produced in each cycle demonstrating the need for further studies of the surface processing requirements and economic implications.
An Overview on the Technologies Used to Storage Hydrogen
Aug 2023
Publication
Hydrogen energy has a significant potential in mitigating the intermittency of renewable energy generation by converting the excess of renewable energy into hydrogen through many technologies. Also hydrogen is expected to be used as an energy carrier that contribute to the global decarbonization in transportation industrial and building sectors. Many technologies have been developed to store hydrogen energy. Hydrogen can be stored to be used when needed and thus synchronize generation and consumption. The current paper presents a review on the different technologies used to store hydrogen. The storage capacity advantages drawbacks and development stages of various hydrogen storage technologies were presented and compared.
Geochemical Effects on Storage Gases and Reservoir Rock during Underground Hydrogen Storage: A Depleted North Sea Oil Reservoir Case Study
May 2023
Publication
In this work geochemical modelling using PhreeqC was carried out to evaluate the effects of geochemical reactions on the performance of underground hydrogen storage (UHS). Equilibrium exchange and mineral reactions were considered in the model. Moreover reaction kinetics were considered to evaluate the geochemical effect on underground hydrogen storage over an extended period of 30 years. The developed model was first validated against experimental data adopted from the published literature by comparing the modelling and literature values of H2 and CO2 solubility in water at varying conditions. Furthermore the effects of pressure temperature salinity and CO2% on the H2 and CO2 inventory and rock properties in a typical sandstone reservoir were evaluated over 30 years. Results show that H2 loss over 30 years is negligible (maximum 2%) through the studied range of conditions. The relative loss of CO2 is much more pronounced compared to H2 gas with losses of up to 72%. Therefore the role of CO2 as a cushion gas will be affected by the CO2 gas losses as time passes. Hence remedial CO2 gas injections should be considered to maintain the reservoir pressure throughout the injection and withdrawal processes. Moreover the relative volume of CO2 increases with the increase in temperature and decrease in pressure. Furthermore the reservoir rock properties porosity and permeability are affected by the underground hydrogen storage process and more specifically by the presence of CO2 gas. CO2 dissolves carbonate minerals inside the reservoir rock causing an increase in the rock’s porosity and permeability. Consequently the rock’s gas storage capacity and flow properties are enhanced
Hydrogen Impact: A Review on Diffusibility, Embrittlement Mechanisms, and Characterization
Feb 2024
Publication
Hydrogen embrittlement (HE) is a broadly recognized phenomenon in metallic materials. If not well understood and managed HE may lead to catastrophic environmental failures in vessels containing hydrogen such as pipelines and storage tanks. HE can affect the mechanical properties of materials such as ductility toughness and strength mainly through the interaction between metal defects and hydrogen. Various phenomena such as hydrogen adsorption hydrogen diffusion and hydrogen interactions with intrinsic trapping sites like dislocations voids grain boundaries and oxide/matrix interfaces are involved in this process. It is important to understand HE mechanisms to develop effective hydrogen resistant strategies. Tensile double cantilever beam bent beam and fatigue tests are among the most common techniques employed to study HE. This article reviews hydrogen diffusion behavior mechanisms and characterization techniques.
Optimizing the Operational Efficiency of the Underground Hydrogen Storage Scheme in a Deep North Sea Aquifer through Compositional Simulations
Aug 2023
Publication
In this study we evaluate the technical viability of storing hydrogen in a deep UKCS aquifer formation through a series of numerical simulations utilising the compositional simulator CMG-GEM. Effects of various operational parameters such as injection and production rates number and length of storage cycles and shut-in periods on the performance of the underground hydrogen storage (UHS) process are investigated in this study. Results indicate that higher H2 operational rates degrade both the aquifer's working capacity and H2 recovery during the withdrawal phase. This can be attributed to the dominant viscous forces at higher rates which lead to H2 viscous fingering and gas gravity override of the native aquifer water resulting in an unstable displacement of water by the H2 gas. Furthermore analysis of simulation results shows that longer and less frequent storage cycles lead to higher storage capacity and decreased H2 retrieval. We conclude that UHS in the studied aquifer is technically feasible however a thorough evaluation of the operational parameters is necessary to optimise both storage capacity and H2 recovery efficiency.
Hydrogen Pipelines vs. HVDC Lines: Should We Transfer Green Molecules or Electrons?
Nov 2023
Publication
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.
Thermal Design and Heat Transfer Optimisation of a Liquid Organic Hydrogen Carrier Batch Reactor for Hydrogen Storage
Aug 2023
Publication
Liquid organic hydrogen carriers (LOHCs) are considered a promising hydrogen storage technology. Heat must be exchanged with an external medium such as a heat transfer fluid for the required chemical reactions to occur. Batch reactors are simple but useful solutions for small-scale storage applications which can be modelled with a lumped parameter approach adequately reproducing their dynamic performance. For such reactors power is consumed to circulate the external heat transfer fluid and stir the organic liquid inside the reactor and heat transfer performance and power consumption are two key parameters in reactor optimisation. Therefore with reference to the hydrogen release phase this paper describes a procedure to optimise the reactor thermal design based on a lumped-parameter model in terms of heat transfer performance and minimum power consumption. Two batch reactors are analysed: a conventional jacketed reactor with agitation nozzles and a half-pipe coil reactor. Heat transfer performance is evaluated by introducing a newly defined dimensionless parameter the Heat Transfer Ratio (HTR) whose value directly correlates to the heat rate required by the carrier's dehydrogenation reaction. The resulting model is a valid tool for adequately reproducing the hydrogen storage behaviour within dynamic models of complex and detailed energy systems.
OIES Podcast - Hydrogen Pipelines vs. HVDC Lines
Nov 2023
Publication
In this podcast David Ledesma talks to Aliaksei Patonia and Veronika Lenivova about Hydrogen pipelines and high-voltage direct current (HVDC) transmission lines and how Hydrogen pipelines offer the advantage of transporting larger energy volumes but existing projects are dwarfed by the vast networks of HVDC transmission lines. The podcast discusses how 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.
The podcast can be found on their website.
The podcast can be found on their website.
Optimal Design and Analysis of a Hybrid Hydrogen Energy Storage System for an Island-Based Renewable Energy Community
Oct 2023
Publication
Installations of decentralised renewable energy systems (RES) are becoming increasing popular as governments introduce ambitious energy policies to curb emissions and slow surging energy costs. This work presents a novel model for optimal sizing for a decentralised renewable generation and hybrid storage system to create a renewable energy community (REC) developed in Python. The model implements photovoltaic (PV) solar and wind turbines combined with a hybrid battery and regenerative hydrogen fuel cell (RHFC). The electrical service demand was derived using real usage data from a rural island case study location. Cost remuneration was managed with an REC virtual trading layer ensuring fair distribution among actors in accordance with the European RED(III) policy. A multi-objective genetic algorithm (GA) stochastically determines the system capacities such that the inherent trade-off relationship between project cost and decarbonisation can be observed. The optimal design resulted in a levelized cost of electricity (LCOE) of 0.15 EUR/kWh reducing costs by over 50% compared with typical EU grid power with a project internal rate of return (IRR) of 10.8% simple return of 9.6%/year and return on investment (ROI) of 9 years. The emissions output from grid-only use was reduced by 72% to 69 gCO2 e/kWh. Further research of lifetime economics and additional revenue streams in combination with this work could provide a useful tool for users to quickly design and prototype future decentralised REC systems.
Influence of Capillary Threshold Pressure and Injection Well Location on the Dynamic CO2 and H2 Storage Capacity for the Deep Geological Structure
Jul 2021
Publication
The subject of this study is the analysis of influence of capillary threshold pressure and injection well location on the dynamic CO2 and H2 storage capacity for the Lower Jurassic reservoir of the Sierpc structure from central Poland. The results of injection modeling allowed us to compare the amount of CO2 and H2 that the considered structure can store safely over a given time interval. The modeling was performed using a single well for 30 different locations considering that the minimum capillary pressure of the cap rock and the fracturing pressure should not be exceeded for each gas separately. Other values of capillary threshold pressure for CO2 and H2 significantly affect the amount of a given gas that can be injected into the reservoir. The structure under consideration can store approximately 1 Mt CO2 in 31 years while in the case of H2 it is slightly above 4000 tons. The determined CO2 storage capacity is limited; the structure seems to be more prospective for underground H2 storage. The CO2 and H2 dynamic storage capacity maps are an important element of the analysis of the use of gas storage structures. A much higher fingering effect was observed for H2 than for CO2 which may affect the withdrawal of hydrogen. It is recommended to determine the optimum storage depth particularly for hydrogen. The presented results important for the assessment of the capacity of geological structures also relate to the safety of use of CO2 and H2 underground storage space.
CFD Simulations of Hydrogen Tank Fuelling: Sensitivity to Turbulence Model and Grid Resolution
Dec 2023
Publication
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.
Review of Common Hydrogen Storage Tanks and Current Manufacturing Methods for Aluminium Tank Liners
Aug 2023
Publication
With the growing concern about climate issues and the urgent need to reduce carbon emissions hydrogen has attracted increasing attention as a clean and renewable vehicle energy source. However the storage of flammable hydrogen gas is a major challenge and it restricts the commercialisation of fuel cell electric vehicles (FCEVs). This paper provides a comprehensive review of common on-board hydrogen storage tanks possible failure mechanisms and typical manufacturing methods as well as their future development trends. There are generally five types of hydrogen tanks according to different materials used with only Type III (metallic liner wrapped with composite) and Type IV (polymeric liner wrapped with composite) tanks being used for vehicles. The metallic liner of Type III tank is generally made from aluminium alloys and the associated common manufacturing methods such as roll forming deep drawing and ironing and backward extrusion are reviewed and compared. In particular backward extrusion is a method that can produce near net-shape cylindrical liners without the requirement of welding and its tool designs and the microstructural evolution of aluminium alloys during the process are analysed. With the improvement and innovation on extrusion tool designs the extrusion force which is one of the most demanding issues in the process can be reduced significantly. As a result larger liners can be produced using currently available equipment at a lower cost.
Multi-criteria Site Selection Workflow for Geological Storage of Hydrogen in Depleted Gas Fields: A Case for the UK
Oct 2023
Publication
Underground hydrogen storage (UHS) plays a critical role in ensuring the stability and security of the future clean energy supply. However the efficiency and reliability of UHS technology depend heavily on the careful and criteria-driven selection of suitable storage sites. This study presents a hybrid multi-criteria decision-making framework integrating the Analytical Hierarchy Process (AHP) and Preference Ranking Organisation Method for Enrichment of Evaluations (PROMETHEE) to identify and select the best hydrogen storage sites among depleted gas reservoirs in the UK. To achieve this a new set of site selection criteria is proposed in light of the technical and economic aspects of UHS including location reservoir rock quality and tectonic characteristics maximum achievable hydrogen well deliverability rate working gas capacity cushion gas volume requirement distance to future potential hydrogen clusters and access to intermittent renewable energy sources (RESs). The framework is implemented to rank 71 reservoirs based on their potential and suitability for UHS. Firstly the reservoirs are thoroughly evaluated for each proposed criterion and then the AHP-PROMETHEE technique is employed to prioritise the criteria and rank the storage sites. The study reveals that the total calculated working gas capacity based on single-well plateau withdrawal rates is around 881 TWh across all evaluated reservoirs. The maximum well deliverability rates for hydrogen withdrawal are found to vary considerably among the sites; however 22 % are estimated to have deliverability rates exceeding 100 sm3 /d and 63 % are located within a distance of 100 km from a major hydrogen cluster. Moreover 70 % have access to nearby RESs developments with an estimated cumulative RESs capacity of approximately 181 GW. The results highlight the efficacy of the proposed multicriteria site selection framework. The top five highest-ranked sites for UHS based on the evaluated criteria are the Cygnus Hamilton Saltfleetby Corvette and Hatfield Moors gas fields. The insights provided by this study can contribute to informed decision-making sustainable development and the overall progress of future UHS projects within the UK and globally.
Comprehensive Review of Geomechanics of Underground Hydrogen Storage in Depleted Reservoirs and Salt Caverns
Sep 2023
Publication
Hydrogen is a promising energy carrier for a low-carbon future energy system as it can be stored on a megaton scale (equivalent to TWh of energy) in subsurface reservoirs. However safe and efficient underground hydrogen storage requires a thorough understanding of the geomechanics of the host rock under fluid pressure fluctuations. In this context we summarize the current state of knowledge regarding geomechanics relevant to carbon dioxide and natural gas storage in salt caverns and depleted reservoirs. We further elaborate on how this knowledge can be applied to underground hydrogen storage. The primary focus lies on the mechanical response of rocks under cyclic hydrogen injection and production fault reactivation the impact of hydrogen on rock properties and other associated risks and challenges. In addition we discuss wellbore integrity from the perspective of underground hydrogen storage. The paper provides insights into the history of energy storage laboratory scale experiments and analytical and simulation studies at the field scale. We also emphasize the current knowledge gaps and the necessity to enhance our understanding of the geomechanical aspects of hydrogen storage. This involves developing predictive models coupled with laboratory scale and field-scale testing along with benchmarking methodologies.
Exploring Decentralized Ammonia Synthesis for Hydrogen Storage and Transport: A Comprehensive CFD Investigation with Experimental Validation and Parametric Study
Sep 2023
Publication
Hydrogen energy plays a vital role in the transition towards a carbon-neutral society but faces challenges in storage and transport as well as in production due to fluctuations in renewable electricity generation. Ammonia (NH3 ) as a carbon-neutral hydrogen carrier offers a promising solution to the energy storage and transport problem. To realize its potential and support the development of a hydrogen economy exploring NH3 synthesis in a decentralized form that integrates with distributed hydrogen production systems is highly needed. In this study a computational fluid dynamics (CFD) model for the Ruthenium (Ru) catalysts-based Haber– Bosch reactor is developed. First a state-of-the-art kinetic model comprehensively describing the complex catalytic reaction is assessed for its sensitivity and applicability to temperature pressure and conversion. Then the kinetic model is integrated into the CFD model and its accuracy is verified through comparison with experimental data obtained from different Ru-based catalysts and operation conditions. Detailed CFD results for a given case are presented offering a visual understanding of thermal gradients and species distributions inside the reactor. Finally a CFD-based parametric study is performed to reveal the impacts of key operation parameters and optimize the NH3 synthesis reactor. The results show that the NH3 production rate is predominantly influenced by temperature with a two-fold difference observed for every 30 ◦C variation while pressure primarily affects the equilibrium. Additionally the affecting mechanism of space velocity is thoroughly discussed and the best value for efficient NH3 synthesis is found to be 180000 h−1. In conclusion the CFD model and simulation results provide valuable insights for the design and control of decentralized NH3 synthesis reactor and operation contributing to the advancement of sustainable energy technologies.
Roles of Bioenergy and Green Hydrogen in Large Scale Energy Storage for Carbon Neutrality
Aug 2023
Publication
A new technical route to incorporate excess electricity (via green hydrogen generation by electrolysis) into a biorefinery to produce modern bioenergy (advanced biofuels) is proposed as a promising alternative. This new route involves storing hydrogen for mobile and stationary applications and can be a three-bird-one-stone solution for the storage of excess electrical energy storage of green hydrogen and high-value utilization of biomass.
The Potential of Hydrogen-battery Storage Systems for a Sustainable Renewable-based Electrification of Remote Islands in Norway
Oct 2023
Publication
Remote locations and off-grid regions still rely mainly on diesel generators despite the high operating costs and greenhouse gas emissions. The exploitation of local renewable energy sources (RES) in combination with energy storage technologies can be a promising solution for the sustainable electrification of these areas. The aim of this work is to investigate the potential for decarbonizing remote islands in Norway by installing RES-based energy systems with hydrogen-battery storage. A national scale assessment is presented: first Norwegian islands are characterized and classified according to geographical location number of inhabitants key services and current electrification system. Then 138 suitable installation sites are pinpointed through a multiple-step sorting procedure and finally 10 reference islands are identified as representative case studies. A site-specific methodology is applied to estimate the electrical load profiles of all the selected reference islands. An optimization framework is then developed to determine the optimal system configuration that minimizes the levelized cost of electricity (LCOE) while ensuring a reliable 100% renewable power supply. The LCOE of the RES-based energy systems range from 0.21 to 0.63 €/kWh and a clear linear correlation with the wind farm capacity factor is observed (R2 equal to 0.87). Hydrogen is found to be crucial to prevent the oversizing of the RES generators and batteries and ensure long-term storage capacity. The techno-economic feasibility of alternative electrification strategies is also investigated: the use of diesel generators is not economically viable (0.87–1.04 €/kWh) while the profitability of submarine cable connections is highly dependent on the cable length and the annual electricity consumption (0.14–1.47 €/kWh). Overall the cost-effectiveness of RES-based energy systems for off-grid locations in Northern Europe can be easily assessed using the correlations derived in this analysis.
Development of Liquid Organic Hydrogen Carriers for Hydrogen Storage and Transport
Jan 2024
Publication
The storage and transfer of energy require a safe technology to mitigate the global environmental issues resulting from the massive application of fossil fuels. Fuel cells have used hydrogen as a clean and efficient energy source. Nevertheless the storage and transport of hydrogen have presented longstanding problems. Recently liquid organic hydrogen carriers (LOHCs) have emerged as a solution to these issues. The hydrogen storage technique in LOHCs is more attractive than those of conventional energy storage systems like liquefaction compression at high pressure and methods of adsorption and absorption. The release and acceptance of hydrogen should be reversible by LOHC molecules following favourable reaction kinetics. LOHCs comprise liquid and semi-liquid organic compounds that are hydrogenated to store hydrogen. These hydrogenated molecules are stored and transported and finally dehydrogenated to release the required hydrogen for supplying energy. Hydrogenation and dehydrogenation are conducted catalytically for multiple cycles. This review elaborates on the characteristics of different LOHC molecules based on their efficacy as energy generators. Additionally different catalysts used for both hydrogenation and dehydrogenation are discussed.
Hydrogen Storage Capacity of Salt Caverns and Deep Aquifers Versus Demand for Hydrogen Storage: A Case Study of Poland
Nov 2023
Publication
Geological structures in deep aquifers and salt caverns can play an important role in large-scale hydrogen storage. However more work needs to be done to address the hydrogen storage demand for zero-emission energy systems. Thus the aim of the article is to present the demand for hydrogen storage expressed in the number of salt caverns in bedded rock salt deposits and salt domes or the number of structures in deep aquifers. The analysis considers minimum and maximum hydrogen demand cases depending on future energy system configurations in 2050. The method used included the estimation of the storage capacity of salt caverns in bedded rock salt deposits and salt domes and selected structures in deep aquifers. An estimation showed a large hydrogen storage potential of geological structures. In the case of analyzed bedded rock salt deposits and salt domes the average storage capacity per cavern is 0.05–0.09 TWhH2 and 0.06–0.20 TWhH2 respectively. Hydrogen storage capacity in analyzed deep aquifers ranges from 0.016 to 4.46 TWhH2. These values indicate that in the case of the upper bound for storage demand there is a need for the 62 to 514 caverns depending on considered bedded rock salt deposits and salt domes or the 9 largest analyzed structures in deep aquifers. The results obtained are relevant to the discussion on the global hydrogen economy and the methodology can be used for similar considerations in other countries.
Recent Developments in Materials for Physical Hydrogen Storage: A Review
Jan 2024
Publication
The depletion of reliable energy sources and the environmental and climatic repercussions of polluting energy sources have become global challenges. Hence many countries have adopted various renewable energy sources including hydrogen. Hydrogen is a future energy carrier in the global energy system and has the potential to produce zero carbon emissions. For the non-fossil energy sources hydrogen and electricity are considered the dominant energy carriers for providing end-user services because they can satisfy most of the consumer requirements. Hence the development of both hydrogen production and storage is necessary to meet the standards of a “hydrogen economy”. The physical and chemical absorption of hydrogen in solid storage materials is a promising hydrogen storage method because of the high storage and transportation performance. In this paper physical hydrogen storage materials such as hollow spheres carbon-based materials zeolites and metal– organic frameworks are reviewed. We summarize and discuss the properties hydrogen storage densities at different temperatures and pressures and the fabrication and modification methods of these materials. The challenges associated with these physical hydrogen storage materials are also discussed.
Current and Future Role of Natural Gas Supply Chains in the Transition to a Low-Carbon Hydrogen Economy: A Comprehensive Review on Integrated Natural Gas Supply Chain Optimisation Models
Nov 2023
Publication
Natural gas is the most growing fossil fuel due to its environmental advantages. For the economical transportation of natural gas to distant markets physical (i.e. liquefaction and compression) or chemical (i.e. direct and indirect) monetisation options must be considered to reduce volume and meet the demand of different markets. Planning natural gas supply chains is a complex problem in today’s turbulent markets especially considering the uncertainties associated with final market demand and competition with emerging renewable and hydrogen energies. This review study evaluates the latest research on mathematical programming (i.e. MILP and MINLP) as a decisionmaking tool for designing and planning natural gas supply chains under different planning horizons. The first part of this study assesses the status of existing natural gas infrastructures by addressing readily available natural monetisation options quantitative tools for selecting monetisation options and single-state and multistate natural gas supply chain optimisation models. The second part investigates hydrogen as a potential energy carrier for integration with natural gas supply chains carbon capture utilisation and storage technologies. This integration is foreseen to decarbonise systems diversify the product portfolio and fill the gap between current supply chains and the future market need of cleaner energy commodities. Since natural gas markets are turbulent and hydrogen energy has the potential to replace fossil fuels in the future addressing stochastic conditions and demand uncertainty is vital to hedge against risks through designing a responsive supply chain in the project’s early design stages. Hence hydrogen supply chain optimisation studies and the latest works on hydrogen–natural gas supply chain optimisation were reviewed under deterministic and stochastic conditions. Only quantitative mathematical models for supply chain optimisation including linear and nonlinear programming models were considered in this study to evaluate the effectiveness of each proposed approach.
A Review on Underground Gas Storage Systems: Natural Gas, Hydrogen and Carbon Sequestration
May 2023
Publication
The concept of underground gas storage is based on the natural capacity of geological formations such as aquifers depleted oil and gas reservoirs and salt caverns to store gases. Underground storage systems can be used to inject and store natural gas (NG) or hydrogen which can be withdrawn for transport to end-users or for use in industrial processes. Geological formations can additionally be used to securely contain harmful gases such as carbon dioxide deep underground by means of carbon capture and sequestration technologies. This paper defines and discusses underground gas storage highlighting commercial and pilot projects and the behavior of different gases (i.e. CH4 H2 and CO2) when stored underground as well as associated modeling investigations. For underground NG/H2 storage the maintenance of optimal subsurface conditions for efficient gas storage necessitates the use of a cushion gas. Cushion gas is injected before the injection of the working gas (NG/H2). The behavior of cushion gas varies based on the type of gas injected. Underground NG and H2 storage systems operate similarly. However compared to NG storage several challenges could be faced during H2 storage due to its low molecular mass. Underground NG storage is widely recognized and utilized as a reference for subsurface H2 storage systems. Furthermore this paper defines and briefly discusses carbon capture and sequestration underground. Most reported studies investigated the operating and cushion gas mixture. The mixture of operating and cushion gas was studied to explore how it could affect the recovered gas quality from the reservoir. The cushion gas was shown to influence the H2 capacity. By understanding and studying the different underground system technologies future directions for better management and successful operation of such systems are thereby highlighted.
OIES Podcast - Renewable Hydrogen Import Routes into the EU
Jun 2023
Publication
In this podcast David Ledesma talks to Martin Lambert and Abdurahman Alsulaiman about the potential hydrogen import market particularly focusing on the EU which currently holds the largest and earliest hydrogen target. The podcast explores the emerging hydrogen trade market and considers numerous possibilities for its open up providing better clarity on policy statements and balance them against project announcements.
Throughout the podcast Martin and Abdulrahman delve into various key points – they shed light on the primary areas of focus for projects set to be completed by or before 2030 as well as the distinction between announcements and tangible progress such as projects currently at the Final Investment Decision stage or under construction.
Additionally they explore the EU’s role as one of the few countries to have publicly announced its requirements for hydrogen imports and its ambitious hydrogen import target. The EU is currently establishing a benchmark for the future hydrogen market. However in order for the EU to succeed in establishing future hydrogen supply lines with future trade partners it will be crucial to engage in open dialogues covering a wide range of topics.
Join us in this podcast as we uncover the potential of the hydrogen import market with a specific focus on the EU and discuss the necessary steps for its success.
The podcast can be found on their website.
Throughout the podcast Martin and Abdulrahman delve into various key points – they shed light on the primary areas of focus for projects set to be completed by or before 2030 as well as the distinction between announcements and tangible progress such as projects currently at the Final Investment Decision stage or under construction.
Additionally they explore the EU’s role as one of the few countries to have publicly announced its requirements for hydrogen imports and its ambitious hydrogen import target. The EU is currently establishing a benchmark for the future hydrogen market. However in order for the EU to succeed in establishing future hydrogen supply lines with future trade partners it will be crucial to engage in open dialogues covering a wide range of topics.
Join us in this podcast as we uncover the potential of the hydrogen import market with a specific focus on the EU and discuss the necessary steps for its success.
The podcast can be found on their website.
Revolutionising Energy Storage: The Latest Breakthrough in Liquid Organic Hydrogen Carriers
Mar 2024
Publication
Liquid organic hydrogen carriers (LOHC) can be used as a lossless form of hydrogen storage at ambient conditions. The storage cycle consists of the exothermic hydrogenation of a hydrogen-lean molecule at the start of the transport usually the hydrogen production site becoming a hydrogen-rich molecule. This loaded molecule can be transported long distances or be used as long-term storage due to its ability to not lose hydrogen over long periods of time. At the site or time of required hydrogen production the hydrogen can be released through an endothermic dehydrogenation reaction. LOHCs show similar properties to crude oils such as petroleum and diesel allowing easy handling and possibilities of integration with current infrastructure. Using this background this paper reviews a variety of aspects of the LOHC life cycle with a focus on currently studied materials. Important factors such as the hydrogenation and dehydrogenation requirements for each material are analysed to determine their ability to be used in current scenarios. Toluene and dibenzyltoluene are attractive options with promising storage attributes however their dehydrogenation enthalpies remain a problem. The economic feasibility of LOHCs being used as a delivery device were briefly analysed. LOHCs have been shown to be the cheapest option for long distance transport (>200 km) and are cheaper than most at shorter distances in terms of specifically transport costs. The major capital cost of an LOHC delivery chain remains the initial investment for the raw materials and the cost of equipment for performing hydrogenation and dehydrogenation. Finally some studies in developing the LOHC field were discussed such as microwave enhancing parts of the process and mixing LOHCs to acquire more advantageous properties.
Levelised Cost of Transmission Comparison for Green Hydrogen and Ammonia in New-build Offshore Energy Infrastructure: Pipelines, Tankers, and HVDC
Mar 2024
Publication
As the global market develops for green hydrogen and ammonia derived from renewable electricity the bulk transmission of hydrogen and ammonia from production areas to demand-intensive consumption areas will increase. Repurposing existing infrastructure may be economically and technically feasible but increases in supply and demand will necessitate new developments. Bulk transmission of hydrogen and ammonia may be effected by dedicated pipelines or liquefied fuel tankers. Transmission of electricity using HVDC lines to directly power electrolysers producing hydrogen near the demand markets is another option. This paper presents and validates detailed cost models for newly-built dedicated offshore transmission methods for green hydrogen and ammonia and carries out a techno-economic comparison over a range of transmission distances and production volumes. New pipelines are economical for short distances while new HVDC interconnectors are suited to medium-large transmission capacities over a wide range of distances and liquefied gas tankers are best for long distances.
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