Transmission, Distribution & Storage

The growing need for hydrogen indicates that there is likely to be a demand for transporting hydrogen. Hydrogen pipelines are an economical option but the issue of hydrogen damage to pipeline steels needs to be studied and investigated. So far limited research has been dedicated to determining how the choice of inspection method for pipeline integrity management changes depending on the presence of a coating. Thus this review aims to evaluate the effectiveness of inspection methods specifically for detecting the defects formed uniquely in coated hydrogen pipelines. The discussion will begin with a background of hydrogen pipelines and the common defects seen in these pipelines. This will also include topics such as blended hydrogen-natural gas pipelines. After which the focus will shift to pipeline integrity management methods and the effectiveness of current inspection methods in the context of standards such as ASME B31.12 and BS 7910. The discussion will conclude with a summary of newly available inspection methods and future research directions.

This study investigated the pressure-dependent CO2 effect on the hydrogen embrittlement of X80 and GB20# pipeline steels by combining experiments and first-principles calculations. Results revealed that the CO2 effect enhanced the fatigue crack growth for GB20# steel in 10 MPa CO₂-enriched hydrogen mixtures. However the improved degree by the CO₂ effect at 10 MPa was less pronounced than at 0.4 MPa which was found for the first time. This was attributed to the decreased adsorption rate of CO₂ on iron as hydrogen pressure increased. Therefore in high-pressure CO₂-enriched hydrogen mixtures CO2 could not significantly accelerate the inherent rapid hydrogen uptake at high pressure.

In recent years there has been a significant increase in research on hydrogen due to the urgent need to move away from carbon-intensive energy sources. This transition highlights the critical role of hydrogen storage technology where hydrogen tanks are crucial for achieving cleaner energy solutions. This paper aims to provide a general overview of hydrogen treatment from a mechanical viewpoint and to create a comprehensive review that integrates the concepts of hydrogen safety and storage. This study explores the potential of hydrogen applications as a clean energy alternative and their role in various sectors including industry automotive aerospace and marine fields. The review also discusses design technologies safety measures material improvements social impacts and the regulatory landscape of hydrogen storage tanks and safety technology. This work provides a historical literature review up to 2014 and a systematic literature review from 2014 to the present to fill the gap between hydrogen storage and safety. In particular a fundamental feature of this work is leveraging systematic procedural techniques for performing an unbiased review study to offer a detailed analysis of contemporary advancements. This innovative approach differs significantly from conventional review methods since it involves a replicable scientific and transparent process which culminates in minimizing bias and allows for highlighting the fundamental issues about the topics of interest and the main conclusions of the experts in the field of reference. The systematic approach employed in the paper was used to analyze 55 scientific articles resulting in the identification of six primary categories. The key findings of this review work underline the need for improved materials enhanced safety protocols and robust infrastructure to support hydrogen adoption. More importantly one of the fundamental results of the present review analysis is pinpointing the central role that composite materials will play during the transition toward hydrogen applications based on thin-walled industrial vessels. Future research directions are also proposed in the paper thereby emphasizing the importance of interdisciplinary collaboration to overcome existing challenges and facilitate the safe and efficient use of hydrogen.

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.

Accurate evaluation of thermo‑fluid dynamic characteristics in tanks is critically important for designing liquid hydrogen tanks for small‑scale hydrogen liquefiers to minimize heat leakage into the liquid and ullage. Due to the high costs most future liquid hydrogen storage tank designs will have to rely on predictive computational models for minimizing pressurization and heat leakage. Therefore in this study to improve the storage efficiency of a small‑scale hydrogen liquefier a three‑ dimensional CFD model that can predict the boil‑off rate and the thermo‑fluid characteristics due to heat penetration has been developed. The prediction performance and accuracy of the CFD model was validated based on comparisons between its results and previous experimental data and a good agreement was obtained. To evaluate the insulation performance of polyurethane foam with three different insulation thicknesses the pressure changes and thermo‑fluid characteristics in a partially liquid hydrogen tank subject to fixed ambient temperature and wind velocity were investigated nu‑ merically. It was confirmed that the numerical simulation results well describe not only the temporal variations in the thermal gradient due to coupling between the buoyance and convection but also the buoyancy‑driven turbulent flow characteristics inside liquid hydrogen storage tanks with differ‑ ent insulation thicknesses. In the future the numerical model developed in this study will be used for optimizing the insulation systems of storage tanks for small‑scale hydrogen liquefiers which is a cost‑effective and highly efficient approach.

In this study a theoretical–experimental methodology for determining the stress–strain state in pipeline systems taking into account the hydrogen environment was developed. A complex of theoretical and experimental studies was conducted to determine the specific energy of destruction as an invariant characteristic of the material’s resistance to strain at different hydrogen concentrations. The technique is based on the construction of complete diagrams of the destruction of the material based on the determination of true strains and stresses in the local volume using the method involving the optical–digital correlation of speckle images. A complex of research was carried out and true diagrams of material destruction were constructed depending on the previous elastic–plastic strain and the action of the hydrogen environment. The change in the concentration of hydrogen absorbed by the material was estimated depending on the value of the specific energy of destruction. A study was conducted on tubular samples and the degree of damage to the material of the inner wall under the action of hydrogen and stress from the internal pressure was evaluated according to the change in specific energy depending on the value of the true strain established with the help of an optical–digital correlator on the outer surface and the degree of damage was determined. It has been established that the specific fracture energy of 17G1S steel decreases by 70–90% under the influence of hydrogen. The effect of the change in the amount of strain energy on the thickness of the pipe wall is illustrated.

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.

One of the major challenges in harnessing energy from renewable sources like wind and solar is their intermittent nature. Energy production from these sources can vary based on weather conditions and time of day making it essential to store surplus energy for later use when there is a shortfall. Energy storage systems play a crucial role in addressing this intermittency issue and ensuring a stable and reliable energy supply. Green hydrogen sourced from renewables emerges as a promising solution to meet the rising demand for sustainable energy addressing the depletion of fossil fuels and environmental crises. In the present study underground hydrogen storage in various geological formations (aquifers depleted hydrocarbon reservoirs salt caverns) is examined emphasizing the need for a detailed geological analysis and addressing potential hazards. The paper discusses challenges associated with underground hydrogen storage including the requirement for extensive studies to understand hydrogen interactions with microorganisms. It underscores the importance of the issue with a focus on reviewing the the various past and present hydrogen storage projects and sites as well as reviewing the modeling studies in this field. The paper also emphasizes the importance of incorporating hybrid energy systems into hydrogen storage to overcome limitations associated with standalone hydrogen storage systems. It further explores the past and future integrations of underground storage of green hydrogen within this dynamic energy landscape.

One such technology is hydrogen-based which utilizes hydrogen to generate energy without emission of greenhouse gases. The advantage of such technology is the fact that the only by-product is water. Efficient storage is crucial for the practical application of hydrogen. There are several techniques to store hydrogen each with certain advantages and disadvantages. In gaseous hydrogen storage hydrogen gas is compressed and stored at high pressures requiring robust and expensive pressure vessels. In liquid hydrogen storage hydrogen is cooled to extremely low temperatures and stored as a liquid which is energy-intensive. Researchers are exploring advanced materials for hydrogen storage including metal hydrides carbonbased materials metal–organic frameworks (MOFs) and nanomaterials. These materials aim to enhance storage capacity kinetics and safety. The hydrogen economy envisions hydrogen as a clean energy carrier utilized in various sectors like transportation industry and power generation. It can contribute to decarbonizing sectors that are challenging to electrify directly. Hydrogen can play a role in a circular economy by facilitating energy storage supporting intermittent renewable sources and enabling the production of synthetic fuels and chemicals. The circular economy concept promotes the recycling and reuse of materials aligning with sustainable development goals. Hydrogen availability depends on the method of production. While it is abundant in nature obtaining it in a clean and sustainable manner is crucial. The efficiency of hydrogen production and utilization varies among methods with electrolysis being a cleaner but less efficient process compared to other conventional methods. Chemisorption and physisorption methods aim to enhance storage capacity and control the release of hydrogen. There are various viable options that are being explored to solve these challenges with one option being the use of a multilayer film of advanced metals. This work provides an overview of hydrogen economy as a green and sustainable energy system for the foreseeable future hydrogen production methods hydrogen storage systems and mechanisms including their advantages and disadvantages and the promising storage system for the future. In summary hydrogen holds great promise as a clean energy carrier and ongoing research and technological advancements are addressing challenges related to production storage and utilization bringing us closer to a sustainable hydrogen economy.

With rising demand for clean energy global focus turns to finding ideal sites for large-scale underground hydrogen storage (UHS) in depleted petroleum reservoirs. A thorough preliminary reservoir evaluation before hydrogen (H2) injection is crucial for UHS success and safety. Recent criteria for UHS often emphasize economics and chemistry neglecting key reservoir attributes. This study introduces a comprehensive framework for the reservoir-scale preliminary assessment specifically tailored for long-term H2 storage within depleted gas reservoirs. The evaluation criteria encompass critical components including reservoir geometry petrophysical properties tectonics and formation fluids. To illustrate the practical application of this approach we assess the Barnett shale play reservoir parameters. The assessment unfolds through three key stages: (1) A systematic evaluation of the reservoir's properties against our comprehensive screening criteria determines its suitability for H2 storage. (2) Using both homogeneous and multilayered gas reservoir models we explore the feasibility and efficiency of H2 storage. This phase involves an in-depth examination of reservoir behavior during the injection stage. (3) To enhance understanding of UHS performance sensitivity analyses investigate the impact of varying reservoir dimensions and injection/production pressures. The findings reveal the following: (a) Despite potential challenges associated with reservoir compaction and aquifer support the reservoir exhibits substantial promise as an H2 storage site. (b) Notably a pronounced increase in reservoir pressure manifests during the injection stage particularly in homogeneous reservoirs. (c) Furthermore optimizing injection-extraction cycle efficiency can be achieved by augmenting reservoir dimensions while maintaining a consistent thickness. To ensure a smooth transition to implementation further comprehensive investigations are advised including experimental and numerical studies to address injectivity concerns and explore storage site development. This evaluation framework is a valuable tool for assessing the potential of depleted gas reservoirs for large-scale hydrogen storage advancing global eco-friendly energy systems.

The effective storage of hydrogen is a critical challenge that needs to be overcome for it to become a widely used and clean energy source. Various methods exist for storing hydrogen including compression at high pressures liquefaction through extreme cooling (i.e. -253 °C) and storage with chemical compounds. Each method has its own advantages and disadvantages. MAST3RBoost (Maturing the Production Standards of Ultraporous Structures for High Density Hydrogen Storage Bank Operating on Swinging Temperatures and Low Compression) is a European funded Project aiming to establish a reliable benchmark for cold-adsorbed H2 storage (CAH2) at low compression levels (100 bar or below). This is achieved through the development of advanced ultraporous materials suitable for mobility applications such as hydrogen-powered vehicles used in road railway air and water transportation. The MAST3RBoost Project utilizes cutting-edge materials including Activated Carbons (ACs) and high-density MOFs (Metalorganic Frameworks) which are enhanced by Machine Learning techniques. By harnessing these materials the project seeks to create a groundbreaking path towards meeting industry goals. The project aims to develop the world's first adsorption-based demonstrator at a significant kg-scale. To support the design of the storage tank the project employs Computational Fluid Dynamics (CFD) software which allows for numerical investigations. In this paper a preliminary analysis of the tank refilling process is presented with a focus on the impact of the effect of the tank and hydrogen temperatures on quantity of hydrogen adsorbed.

To cope with climate change emerging fuels- hydrogen ammonia and methanol- have been proposed as promising energy carriers that will replace part of the liquefied natural gas (LNG) in future maritime scenarios. Energy efficiency is an important indicator for evaluating the system but the maritime supply system for emerging fuels has yet to be revealed. In this study the energy efficiency of the maritime supply chain of hydrogen ammonia methanol and natural gas is investigated considering processes including production storage loading transport and unloading. A sensitivity analysis of parameters such as ambient temperature storage time pipeline length and sailing time is also carried out. The results show that hydrogen (2.366%) has the highest daily boil-off gas (BOG) rate and wastes more energy than LNG (0.413%) with ammonia and methanol both being lower than LNG. The recycling of BOG is of great importance to the hydrogen supply chain. When produced from renewable energy sources methanol (98.02%) is the most energy efficient followed by ammonia with hydrogen being the least (89.10%). This assessment shows from an energy efficiency perspective that ammonia and methanol have the potential to replace LNG as the energy carrier of the future and that hydrogen requires efficient BOG handling systems to increase competitiveness. This study provides some inspirations for the design of global maritime supply systems for emerging fuels.

This article analyzes the processes of compressing hydrogen in the gaseous state an aspect considered important due to its contribution to the greater diffusion of hydrogen in both the civil and industrial sectors. This article begins by providing a concise overview and comparison of diverse hydrogen-storage methodologies laying the groundwork with an in-depth analysis of hydrogen’s thermophysical properties. It scrutinizes plausible configurations for hydrogen compression aiming to strike a delicate balance between energy consumption derived from the fuel itself and the requisite number of compression stages. Notably to render hydrogen storage competitive in terms of volume pressures of at least 350 bar are deemed essential albeit at an energy cost amounting to approximately 10% of the fuel’s calorific value. Multi-stage compression emerges as a crucial strategy not solely for energy efficiency but also to curtail temperature rises with an upper limit set at 200 ◦C. This nuanced approach is underlined by the exploration of compression levels commonly cited in the literature particularly 350 bar and 700 bar. The study advocates for a three-stage compression system as a pragmatic compromise capable of achieving high-pressure solutions while keeping compression work below 10 MJ/kg a threshold indicative of sustainable energy utilization.

Using high-resolution micro-CT imaging at 2.98 μm/voxel we compared the percolation of hydrogen in gas injection with gas expansion for a hydrogen-brine system in Bentheimer sandstone at 1 MPa and 20 ◦C representing hydrogen storage in an aquifer. We introduced dimensionless numbers to quantify the contribution of advection and expansion to displacement. We analysed the 3D spatial distribution of gas and its displacement in both cases and demonstrated that in gas injection hydrogen can only advance from a connected cluster in an invasion-percolation type process while in gas expansion hydrogen can access more of the pore space even from disconnected clusters. The average gas saturation in the sample increased from 30% to 50% by gas expansion and we estimated that 10% of the expanded volume is attributed to hydrogen exsolution from the brine. This work emphasises the importance of studying the combined effects of pressure decline and gas withdrawal in hydrogen storage to assess the influence of gas expansion on remobilising trapped gases.

High-pressure hydrogen tanks which are composed of an aluminum alloy liner and a carbon fiber wound layer are currently the most popular means to store hydrogen on vehicles. Nevertheless the aluminum alloy is easily affected by high-pressure hydrogen which leads to the appearance of hydrogen embrittlement (HE). Serious HE of hydrogen tank represents a huge dangers to the safety of vehicles and passengers. It is critical and timely to outline the mainstream approach and point out potential avenues for further investigation of HE. An analysis including the mechanism (including hydrogen-enhanced local plasticity model hydrogen-enhanced decohesion mechanism and hydrogen pressure theory) the detection (including slow strain rate test linearly increasing stress test and so on) and methods for the prevention of HE on aluminum alloys of hydrogen vehicles (such as coating) are systematically presented in this work. Moreover the entire experimental detection procedures for HE are expounded. Ultimately the prevention measures are discussed in detail. It is believed that further prevention measures will rely on the integration of multiple prevention methods. Successfully solving this problem is of great significance to reduce the risk of failure of hydrogen storage tanks and improve the reliability of aluminum alloys for engineering applications in various industries including automotive and aerospace.

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.

In the advancing landscape of sustainable energy the development of efficient and reversible hydrogen storage materials operable under ambient conditions remains a critical challenge for material scientists and the broader research community. Hydrogen owing to its exceptionally high energy density is regarded as a leading candidate for facilitating the transition from conventional fossil fuels to cleaner renewable energy systems. However alongside its production the safe and efficient storage of hydrogen presents a significant bottleneck due to its low volumetric density and associated safety concerns.<br/>Conventional storage techniques such as high-pressure compression and cryogenic liquefaction though widely used demand complex infrastructure and carry substantial safety risks. These limitations have steered growing interest toward solid-state hydrogen storage systems that rely on physisorption or chemisorption mechanisms preferably operating near ambient conditions. Consequently the pursuit of materials with favourable thermodynamics and kinetics for reversible hydrogen uptake and release has become imperative. Among the emerging candidates MXenes a class of two-dimensional (2D) materials comprising transition metal carbides nitrides or carbonitrides have garnered significant attention due to their high surface area tuneable surface chemistry and excellent conductivity.<br/>Despite the growing body of literature on hydrogen storage using MXenes a comprehensive evaluation that bridges the gap between theoretical predictions and experimental realities remains limited. This review addresses that gap by critically examining current strategies for solid-state hydrogen storage with a particular emphasis on MXene-based materials. It highlights the influence of synthesis techniques on structural properties discusses the mechanisms of hydrogen interaction with MXene surfaces and evaluates their practical implications in real-world applications. While the potential of MXenes in hydrogen storage is considerable it is not yet fully realized. This article provides an in-depth assessment of the current advancements challenges and future directions for MXene-based materials in the context of hydrogen storage offering valuable insights for both fundamental research and applied energy systems.

This narrative document sets out the main rationale for hydrogen storage development at scale in the UK: - To meet net zero the UK will need considerable energy storage - Hydrogen storage will be a major and essential part of this - Physical hydrogen storage is needed in the UK - Only geological hydrogen storage can deliver at the scale needed within the timescales for net zero - Geological hydrogen storage should be supported through a viable business model now to ensure it comes online in the 2030s.

: The global demand for energy and the need to mitigate climate change require a shift from traditional fossil fuels to sustainable and renewable energy alternatives. Hydrogen is recognized as a significant component for achieving a carbon-neutral economy. This comprehensive review examines the underground hydrogen storage and particularly laboratory-scale studies related to rock– hydrogen interaction exploring current knowledge. Using bibliometric analysis of data from the Scopus and Web of Science databases this study reveals an exponential increase in scientific publications post-2015 which accounts for approximately 85.26% of total research output in this field and the relevance of laboratory experiments to understand the physicochemical interactions of hydrogen with geological formations. Processes in underground hydrogen storage are controlled by a set of multi-scale parameters including solid properties (permeability porosity composition and geomechanical properties) and fluid properties (liquid and gas density viscosity etc.) together with fluid–fluid and solid–fluid interactions (controlled by solubility wettability chemical reactions etc.). Laboratory experiments aim to characterize these parameters and their evolution simulating real-world storage conditions to enhance the reliability and applicability of findings. The review emphasizes the need to expand research efforts globally to comprehensively address the currently existing issues and knowledge gaps.

Hydrogen globally recognized as the most efficient and clean energy carrier holds the potential to transform future energy systems through its use as a fuel and chemical resource. Although progress has been made in reversible hydrogen adsorption and release challenges in storage continue to impede widespread adoption. This review explores recent advancements in hydrogen storage materials and synthesis methods emphasizing the role of nanotechnology and innovative synthesis techniques in enhancing storage performance and addressing these challenges to drive progress in the field. The review provides a comprehensive overview of various material classes including metal hydrides complex hydrides carbon materials metal-organic frameworks (MOFs) and porous materials. Over 60 % of reviewed studies focused on metal hydrides and alloys for hydrogen storage. Additionally the impact of nanotechnology on storage performance and the importance of optimizing synthesis parameters to tailor material properties for specific applications are summarized. Various synthesis methods are evaluated with a special emphasis on the role of nanotechnology in improving storage performance. Mechanical milling emerges as a commonly used and cost-effective method for fabricating intermetallic hydrides capable of adjusting hydrogen storage properties. The review also explores hydrogen storage tank embrittlement mechanisms particularly subcritical crack growth and examines the advantages and limitations of different materials for various applications supported by case studies showcasing real-world implementations. The challenges underscore current limitations in hydrogen storage materials highlighting the need for improved storage capacity and kinetics. The review also explores prospects for developing materials with enhanced performance and safety providing a roadmap for ongoing advancements in the field. Key findings and directions for future research in hydrogen storage materials emphasize their critical role in shaping future energy systems.

A new model is presented to predict hydrogen-assisted fatigue. The model combines a phase field description of fracture and fatigue stress-assisted hydrogen diffusion and a toughness degradation formulation with cyclic and hydrogen contributions. Hydrogen-assisted fatigue crack growth predictions exhibit an excellent agreement with experiments over all the scenarios considered spanning multiple load ratios H2 pressures and loading frequencies. These are obtained without any calibration with hydrogen-assisted fatigue data taking as input only mechanical and hydrogen transport material properties the material’s fatigue characteristics (from a single test in air) and the sensitivity of fracture toughness to hydrogen content. Furthermore the model is used to determine: (i) what are suitable test loading frequencies to obtain conservative data and (ii) the underestimation made when not pre-charging samples. The model can handle both laboratory specimens and large-scale engineering components enabling the Virtual Testing paradigm in infrastructure exposed to hydrogen environments and cyclic loading.

This paper introduces a general criterion for the optimal design and operation of hydrogen storage tanks. Specifically the proposed procedure identifies the optimal delivery schedule that minimizes the capacity of material storage systems. Indeed many manufacturing processes need some buffer storage to administer mass flows appropriately according to the operating needs (one class above all: Power-to-X processes) and have one of their highest expenditures right in those tanks when proving not sufficiently flexible. Hence the novelty of the proposed method lies in a rigorous mathematical formulation that converts arbitrarily fluctuating inlet streams into optimally fluctuating outlet streams that minimize the storage volume and comply with different operating requirements. The criterion is validated by considering the techno-economic assessment of a chemical plant featuring a dedicated green hydrogen production facility that feeds the process. Specifically the required capacity of the “Flexible” hydrogen buffer storage which connects the green hydrogen generation system to the conversion process significantly decreases by 91.31%–99.31% (depending on the flexibility ranges enabled by the downstream conversion process) compared to the “Rigid” storage alternative based on a constant outlet mass flow withdrawal coinciding with the hydrogen consumption rate at nominal operating conditions. Correspondingly the resulting levelized cost of hydrogen benefits accordingly ranging from 4.19 to 6.03 USD/kg (California 2023).

Hydrogen has emerged as a key element in the transition to a sustainable energy model. Among hydrogen storage and transport technologies liquid organic hydrogen carriers (LOHCs) stand out as a promising alternative for large-scale long-term use. Catalysts essential in these systems are usually composed of platinum group metals (PGMs) over alumina known for their high cost and scarcity. This study analyzes the overall environmental impact of the LOHC benzyltoluene/perhydro-benzyltoluene-based hydrogen supply chain by means of the life cycle assessment (LCA) focusing on the synthesis processes of novel low-PGM catalysts which remain under explored in existing literature. The results identify dehydrogenation as the most impactful step due to significant heat consumption and highlight the substantial environmental footprint associated with the use of platinum in catalyst production. This research provides crucial insights into the environmental implications of LOHC systems particularly the role of novel low-PGM catalysts and offers guidance for their future large-scale applications.

Metal hydride-based hydrogen storage (MHHS) has been used for several purposes including mobile and stationary applications. In general the overall MHHS performance for both applications depends on three main factors which are the appropriate selection of metal hydride material uses design configurations of the MHHS based on the heat exchanger and overall operating conditions. However there are different specific requirements for the two applications. The weight of the overall MHHS is the key requirement for mobile applications while hydrogen storage capacity is the key requirement for stationary applications. Based on these requirements several techniques have been recently used to enhance MHHS performance by mostly considering the faster hydrogen absorption/desorption reaction. Considering metal hydride (MH) materials their low thermal conductivity significantly impacts the hydrogen absorption/desorption reaction. For this purpose a comprehensive understanding of these three main factors and the hydrogen absorption/desorption reaction is critical and it should be up to date to obtain the suitable MHHS performance for all related applications. Therefore this article reviews the key techniques which have recently been applied for the enhancement of MHHS performance. In the review it is demonstrated that the design and layout of the heat exchanger greatly affect the performance of the internal heat exchanger. The initial temperature of the heat transfer fluid and hydrogen supply pressure are the main parameters to increase the hydrogen sorption rate and specific heating power. The higher supply pressure results in the improvement in specific heating power. For the metal hydride material selection under the consideration of mobile applications and stationary applications it is important to strike trade-offs between hydrogen storage capacity weight material cost and effective thermal conductivity.

Hydrogen is an ideal energy carrier in future applications due to clean byproducts and high efciency. However many challenges remain in the application of hydrogen including hydrogen production delivery storage and conversion. In terms of hydrogen storage two compression modes (mechanical and non-mechanical compressors) are generally used to increase volume density in which mechanical compressors with several classifcations including reciprocating piston compressors hydrogen diaphragm compressors and ionic liquid compressors produce signifcant noise and vibration and are expensive and inefcient. Alternatively non-mechanical compressors are faced with issues involving large-volume requirements slow reaction kinetics and the need for special thermal control systems all of which limit large-scale development. As a result modular safe inexpensive and efcient methods for hydrogen storage are urgently needed. And because electrochemical hydrogen compressors (EHCs) are modular highly efcient and possess hydrogen purifcation functions with no moving parts they are becoming increasingly prominent. Based on all of this and for the frst time this review will provide an overview of various hydrogen compression technologies and discuss corresponding structures principles advantages and limitations. This review will also comprehensively present the recent progress and existing issues of EHCs and future hydrogen compression techniques as well as corresponding containment membranes catalysts gas difusion layers and fow felds. Furthermore engineering perspectives are discussed to further enhance the performance of EHCs in terms of the thermal management water management and the testing protocol of EHC stacks. Overall the deeper understanding of potential relationships between performance and component design in EHCs as presented in this review can guide the future development of anticipated EHCs.