High-pressure Hydrogen Storage Research Articles

Innovative Design of Solid-State Hydrogen Storage and Proton Exchange Membrane Fuel Cell Coupling System with Enhanced Cold Start Control Strategy

This paper presents an innovative thermally coupled system architecture with a parallel coolant-heated metal hydride tank (MHT) designed to satisfy the hydrogen supply requirements of proton exchange membrane fuel cell s(PEMFCs). This design solves a problem by revolutionising the cold start capability of PEMFCs at low temperatures. During the design process, LaNi5 was selected as the hydrogen storage material, with thermodynamic and kinetic properties matching the PEMFC operating conditions. Afterwards, the MHT and thermal management subsystem were customised to integrate with the 70 kW PEMFC system to ensure optimal performance. Given the limitations of conventional high-pressure gaseous hydrogen storage for cold starting, this paper provides insights into the challenges faced by the PEMFC-MH system and proposes an innovative cold start methodology that combines internal self-heating and externally assisted preheating techniques, aiming to optimise cold start time, energy consumption, and hydrogen utilisation. The results show that the PEMFC-MH system utilises the heat generated during hydrogen absorption by the MHT to preheat the PEMFC stack, and the cold start time is only 101 s, which is 59.3% shorter compared to that of the conventional method. Meanwhile, the cold start energy consumption is reduced by 62.4%, achieving a significant improvement in energy efficiency. In conclusion, this paper presents a PEMFC-MH system design that achieves significant progress in terms of time saving, energy consumption, and hydrogen utilisation.

Effect of layup sequence on cure deformation and accurate prediction of composite pressure vessels

The application of composite winding pressure vessels is becoming more and more widespread, and the magnitude of deformation during curing can have a significant impact on service performance, but there are fewer studies on the accurate prediction of the numerical and experimental validation of the deformation during the curing process of pressure vessels. To accurately predict the effect of different angles of layup on the curing deformation of high-pressure hydrogen storage vessels made of T700S-12 K/4251A4B2 carbon fiber/epoxy composites in cylindrical and dome sections. In this paper, WCM-ABAQUS segmented pressure vessel accurate modeling method is proposed for the first time, using the method of converting the chemical shrinkage coefficient of epoxy resin into thermal expansion coefficient equivalently, the finite element prediction of the deformation of the pressure vessel during the curing process in different layup sequences was carried out, and the deformation values of the pressure vessel in different layup sequences were analyzed comparatively. Finally, the winding curing experiments were carried out on pressure vessels with different layup sequences, and the curing deformation values of the experimental tests on pressure vessels with different layup sequences were compared with the finite element simulation values, respectively, and the minimum error value 13.07%. It provides a reliable basis for accurately predicting the deformation value of the pressure vessel curing process, and also provides a reference for subsequent experiments to reduce the curing deformation value.

Techno-economic feasibility of integrating hybrid battery-hydrogen energy storage system into an academic building

Green hydrogen production and storage are vital in mitigating carbon emissions and sustainable transition. However, the high investment cost and management requirements are the bottleneck of utilizing hybrid hydrogen-based systems in microgrids. Given the necessity of cost-effective and optimal design of these systems, the present study examines techno-economic feasibility of integrating hybrid hydrogen-based systems into an outdoor test facility. With this perspective, several solar-driven hybrid scenarios are introduced at two energy storage levels, namely the battery and hydrogen energy storage systems, including the high-pressure gaseous hydrogen and metal hydride storage tanks. Dynamic simulations are carried out to address subtle interactions in components of the hybrid system by establishing a TRNSYS model coupled to a Fortran code simulating the metal hydride storage system. The OpenStudio-EnergyPlus plugin is used to simulate the building load, validate against experimental data, according to the measured data and monitored operating conditions. Aimed at enabling efficient integration of energy storage systems, a techno-enviro-economic optimization algorithm is developed to simultaneously minimize the levelized cost of the electricity and maximize the CO2 mitigation in each proposed hybrid scenario. The results indicate that integrating the gaseous hydrogen and metal hydride storages into the photovoltaic-alone scenario enhances 22.6% and 14.4% of the annual renewable factor. Accordingly, the inclusion of battery system to these hybrid scenarios gives a 30.4% and 20.3 % boost to the renewable factor value, respectively. Although the inclusion of battery energy storage into the hybrid systems increases the renewable factor, the results imply that it reduces the hydrogen production rate via electrolysis. The optimized values of the levelized cost of electricity and CO2 emission for different scenarios vary in the range of 0.376–0.789 $/kWh and 6.57–9.75 ton, respectively. The multi-criteria optimizations improve the levelized cost of electricity and CO2 emission by up to 46.2% and 11.3%, with respect to their preliminary design.

Study on the Effect of Bifurcation Position on Spontaneous Ignition and Shock Wave Propagation Characteristics in High-pressure Hydrogen Leakage Tubes

Hydrogen safety issues constrain the development and diffusion of hydrogen energy technologies. The current research on tube types in high-pressure hydrogen storage and transportation links is insufficient. In this paper, the spontaneous combustion law and the propagation characteristics of the shock wave in the tube after accidental leakage of high-pressure hydrogen in a bifurcated tube with a blocking structure are investigated by experimental means. By changing the relative position of the bifurcation structure, it is found that moving the bifurcation position upstream can effectively reduce the intensity of the shock wave at the nozzle of the tube, the propagation velocity of the shock wave inside the tube and the critical ignition pressure. There are three ignition possibilities in the bifurcated tube with blocking structure, and quenching can be realized in the tube under lower pressure.

Research on active and passive schemes for safety improvement of nuclear energy hydrogen production system

Nuclear hydrogen production has the advantages of large-scale and low carbon emissions, and is expected to play an active role in the energy transition process. However, the storage and transportation of hydrogen pose potential risks of leakage and diffusion when connected to high-pressure hydrogen storage tanks and pipelines. To address this concern, this study focused on designing three distinct safety improvement schemes tailored for potential hydrogen leakage accidents. These schemes encompassed a passively distributed arrangement of obstacles (Scheme 1), a passively centralized arrangement of obstacles (Scheme 2), and an active fan array blowing (Scheme 3). Numerical simulation methods were applied on extensive spatial scales for relevant calculations. The results revealed that all three schemes effectively reduced the diffusion distance of combustible hydrogen. Specifically, at lower ambient wind speeds, Scheme 1, Scheme 2, and Scheme 3 achieved the shortest diffusion distances of 123 m, 56 m, and 46 m, respectively. Meanwhile, at higher ambient wind speeds, the corresponding distances were 282 m, 100 m, and 79 m. These results collectively offer valuable insights to mitigate the risk of leakage accidents in nuclear hydrogen production systems.

Multiscale analysis of composite pressure vessel structures wound with different fiber tensile force

The aim of this paper is the multiscale investigation of composite pressure vessel structures wound with varying fibre tension. The paper explores the potential of ”programming” the fibre tension force during the winding process of a high pressure hydrogen storage vessel. Two series of vessels were wound with two different tensions: Two series of vessels wound with forces of 3 N and 80 N respectively were experimentally investigated. Other technological factors, such as the type and weight of carbon fibre used, were kept constant throughout the study. Quasi-static burst tests were used to measure the elastic deformation of the vessel surface. Microscopic studies were also carried out to analyse the structure of the composite at different length scales. The fibre content, the geometric parameters of the voids and the distribution of the three main components of the composite – carbon fibre, technological defects and resin – were also determined. Representative RVE elementary cells were generated for both materials using statistical modelling. The composite was then homogenised and elasticity matrices were obtained for the fibre tensile forces in both materials.

Numerical simulation of leakage jet flame hazard of high-pressure hydrogen storage bottle in open space

The jet fire is a common type of fire accident in high-pressure hydrogen storage bottles. It is crucial to conduct research on the thermal radiation hazards resulting from on-board hydrogen storage bottle leaks, leading to jet fires within 35 MPa. Additionally, accurately and swiftly calculating the characteristic parameters of hydrogen jet flames, such as flame geometry and radiation heat flow, is of utmost importance. To study the jet fire hazard caused by high-pressure hydrogen storage cylinder leaks, a simplified model of the hydrogen storage cylinder was established using FLUENT software for numerical simulation analysis. The study analyzed the impact patterns of high-pressure hydrogen leakage jet flames under different scenarios, including leakage aperture, leakage pressure and ambient wind speed. The results demonstrate a positive correlation between the leakage aperture and pressure with the size of the jet flame and the extent of thermal radiation damage. The larger the leakage aperture and pressure, the larger the hydrogen jet flame size. The higher the peak value of the flame thermal radiation, the greater the hazard range. Additionally, the temperature of the stable axis of the jet flame rises with increasing leakage aperture. As the leakage pressure rises, the thermal radiation of the flame also increases. Conversely, as the ambient wind speed increases, the flame length, the burn radius, and the thermal radiation range decreases, but the high-temperature heat range expands. The empirical formula between flame length and leakage pressure and leakage aperture under different environmental wind speeds is obtained by data fitting, which can be used as a priori prediction of flame length under wind speed conditions.

Drop damage analysis of automotive high-pressure composite hydrogen storage cylinders

With the world facing an energy crisis today, hydrogen is attracting attention as a renewable and clean energy source.In this paper, a carbon fiber fully wound plastic liner hydrogen storage cylinder (type IV cylinder) was modeled by software. Then the model was subjected to drop simulation, and by changing the drop height, the drop angle and the residual pressure inside the cylinder, the curve and the cloud diagram of the maximum total stress over time as well as the cloud diagram of the positive stress in all directions and the shear stress in all planes of the cylinder were obtained during the drop process. Meanwhile, by comparing the data and images under each working condition, it can be known that the location where the maximum stress appears is always near the spherical end and the pole hole, but the maximum stress is not a single-valued function of the drop height, and it is also related to the drop angle; and the maximum stress as a whole increases with the increase of the residual pressure. At the end of the article, a drop simulation of the conceptual unlined composite high-pressure hydrogen storage cylinder (V-cylinder) is also carried out, and it is found that the maximum stress during the drop is basically equal to that of the lined high-pressure hydrogen storage cylinder, and the liner mainly plays the role of preventing leakage and corrosion, and does not bear the stress loads.

Numerical study on the shock wave and vortex and their coupling effect on the behavior of the flame induced by the spontaneous ignition of high-pressure hydrogen release

High-pressure hydrogen storage is currently the mainstream way of hydrogen storage. However, the risk of spontaneous ignition and subsequent jet flame are serious obstacles to the wide application of hydrogen energy. To further reveal the interaction of shock waves, vortices and flame induced by the spontaneous ignition of high-pressure hydrogen release under the effect of release process and burst pressure, a numerical study is conducted by employing LES, RNG, EDC models and detailed hydrogen/air combustion mechanism. The qualitative and quantitative comparison of flow field and flame splitting process outside the tube between this numerical study and previous experimental results validate the numerical results. It is found that an initial vortex is formed at the edge of the jet. Then, several vortices are generated at the edge of the jet and ahead of the Mach disk. The number of vortices in the outer side of the barrel shock is larger when the opening time is shorter. After moving out of the tube, the flame front becomes hemisphere and the lateral edge has a hemispherical bulge which is induced by the initial vortex. The temperature is low and the hydrogen concentration is high in the high-speed region which is induced by the reflected shock wave, leading to the splitting of the flame into two parts: the first and the second half of the flame. However, the flame cannot be formed at the initial stage when the opening time increases to 150 μs and the flame area is larger than with smaller opening times. After splitting, under the affection of the vortices generated at the lateral side, the first half of the flame rotates backward and gradually merges with the second half of the flame, finally forming a complete hydrogen jet flame.

An Integrated Risk Assessment Methodology of In-Service Hydrogen Storage Tanks Based on Connection Coefficient Algorithms and Quintuple Subtraction Set Pair Potential

At present, there have been a number of hydrogen storage tank explosions in hydrogen filling stations, causing casualties and property losses, and having a bad social impact. This has made people realize that the risk assessment and preventive maintenance of hydrogen storage tanks are crucial. Therefore, this paper innovatively proposes a comprehensive risk assessment model based on connection coefficient algorithms and quintuple subtractive set pair potential. First of all, the constructed index system contains five aspects of corrosion factors, material factors, environmental factors, institutional factors and human factors. Secondly, a combined weighting analysis method based on FAHP and CRITIC is proposed to determine the weight of each indicator. The basic indicators influencing hydrogen storage tanks are analyzed via the quintuple subtraction set pair potential and full partial connection coefficient. Finally, the risk level and development trend of hydrogen storage tanks in hydrogen filling stations are determined by a combination of the three-category connection coefficient algorithms and the risk level eigenvalue method. The results of our case analysis show that the proposed risk assessment model can identify the main weak indicators affecting the safety of hydrogen storage tanks, including installation quality, misoperation and material quality. At the same time, it is found that the risk of high-pressure hydrogen storage tanks is at the basic safety level, and the development trend of safety conditions holds a critical value. The evaluation results can help establish targeted countermeasures for the prevention and maintenance of hydrogen storage tanks.

Investigation of Hydrogen Transport Properties through the Liner Material of 70 MPa Type IV Composite Overwrapped Pressure Vessels

In zero-emission solutions for the hydrogen supply chain, high-pressure hydrogen storage in Type IV composite overwrapped pressure vessels (COPVs) is crucial for being safe and secure for a variety of stationary and transport applications. These COPVs consist of a polymeric liner material that works as a barrier for the stored hydrogen, while the carbon fiber-based composite provides the strength to hold the high-pressure hydrogen (of nominal working pressure more than 70 MPa to achieve the competitive driving range). Several experimental studies and simulation work have been performed on the viability of various polymers as low-permeability materials under low-pressure conditions. However, because of their proprietary nature and commercialized research, the characteristics of hydrogen permeation through polymers and their behavior at high pressure are still readily available in the literature. It is a major concern and the most crucial component of Type IV COPVs that these polymeric liners hold high pressure and maintain the necessary density of hydrogen (state of charge) toward operational requirements and safety concerns related to the cause of failures due to permeation (such as blistering, buckling, cracking, and so on). This paper investigates the role of polymeric liners on hydrogen permeation behavior using finite element modeling. For this, a UMATHT subroutine is developed within the Abaqus software to implement a new hydrogen permeation transport model with extended governing equations. Through the simulations and material modeling, the role of hydrogen transport properties (permeability, diffusivity, and solubility), structural characteristics (crystallinity, free volume, thickness) of plastic liners, and the role of operational parameters (concentration, pressure) are combined to validate the model from the experimental data in the literature to estimate the effective thickness required to maintain the permeation limit of the polymeric liner of 70 MPa Type IV COPVs.

Modeling and Simulation of a Renewable Energy PV/PEM with Green Hydrogen Storage

The introduction of green hydrogen-based energy storage in association with renewable energy constitutes a promising and sustainable solution to the increase in energy demand while reducing greenhouse gas emissions. However, these hybrid systems face technical, economic, and logistic challenges that require a new transport and distribution architecture. The technical-economic study of these expensive installations requires good modeling and optimal sizing of the system components. This study presents a global model for hydrogen production and storage stations using photovoltaics (PV) and integrating Proton Exchange Membrane Fuel Cell (PEMFC) modules for electric vehicles. The simulations and sizing were based on the implementation of an effective mathematical model capable of accurately simulating the real dynamic behavior of the installation, the electrical and energy yields, the power consumed and produced, and finally the mass of hydrogen stored and/or consumed by the fuel cell. In this model, the hybrid system integrates PV solar panels with a maximum power of 1.2 MW, followed by a 1.0 MW Proton Exchange Membrane (PEM) electrolyzer, a high-pressure hydrogen storage tank, and a PEMFC to convert hydrogen into electricity. The simulation results showed that the energy generated by the PV panels can produce around 200 kg/day of green hydrogen by electrolysis, which makes it possible to power 100 electric cars per day with a range of 250 km for each.

Small-Scale High-Pressure Hydrogen Storage Vessels: A Review.

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.

Development of a metal hydride hydrogen compressor with high-pressure hydrogen storage alloys

Single- and double-stage metal hydride hydrogen compressors (MHHC) were developed using two series of metal hydrides of AB5-based La0.5Ce0.5Ni5-xAlx (x = 0, 0.1, 0.2) alloys and AB2-based Ti1-yZryMn0.8Cr1.2 (y = 0.05, 0.1, 0.2) alloys. In single-stage mode, La0.5Ce0.5Ni5 and Ti0.9Zr0.1Mn0.8Cr1.2 alloys could produce hydrogen pressures of 117 atm and 132 atm, respectively, at 100 °C. When the temperature was raised to 140 °C, both alloys could produce hydrogen pressures of 200 atm. The Ti0.9Zr0.1Mn0.8Cr1.2 alloy exhibited higher hydrogen discharging pressure and faster kinetics than those of the La0.5Ce0.5Ni5 alloy. A pair of alloys were used for a double-stage MHHC (first stage: Ti0.9Zr0.1Mn0.8Cr1.2; second stage: Ti0.95Zr0.05Mn0.8Cr1.2). The initial hydrogen pressure of 50 atm increased to 245 atm when the working temperature was raised from 25 °C to 100 °C, which provides an opportunity for designing a compact and simple MHHC.

First principles and molecular dynamics simulations of effect of dopants on properties of high strength steel for hydrogen storage vessels

High-pressure gaseous hydrogen storage is an important way of hydrogen energy storage and transport at present, while high-strength steel material is one of the main materials used for hydrogen storage vessels. However, their internal doping elements and inherent defects often lead their mechanical properties to decrease, thus reducing the pressure-bearing capability and storage life of the vessel. At present, the mechanism of doping elements influencing the mechanical properties of high-strength steels is still unclear. In this work, a first-principles approach is used to study the influence of elemental doping (Cr, Mn, Mo, As, Sb, Bi, Sn, Pb) on the mechanical properties of Fe single crystals and Fe-C systems. The results show that among the above elements, Mn doping can increase the elastic modulus, bulk modulus, and shear modulus compared with those of pure Fe, while the doping by remaining elements will reduce the three moduli above, with the non-transition metal elements having a greater effect on the three moduli than the transition metal elements. Electronic structure analysis shows that the transition metal elements have better compatibility with the Fe lattice. Molecular dynamics results further show that the injection of H atoms significantly disrupts the lattice ordering of the Fe polycrystalline doped by C, Cr, and Mn elements, while the doping of Cr elements can significantly enhance the dislocation density of the system. The effects of doping elements on the mechanical properties of single-crystal and polycrystalline Fe, which are studied in this work, are of great significance in guiding the mechanistic study of the effects of doping and defects on the strength of Fe-based materials.

An investigation on enhancing the bonding properties of PA11-CFRP interface in type IV high pressure hydrogen storage vessel through nanosecond pulsed laser treatment and failure mechanism research

At present, several key technologies remain to be addressed in the development of type IV high-pressure hydrogen storage vessels, especially the prevention of plastic liner collapse, which demands urgent resolution. One major factor contributing to plastic liner collapse is the weak interfacial bonding between the plastic liner and carbon fiber reinforced polymer (CFRP). Therefore, enhancing the bonding properties of the plastic liner-CFRP interface can effectively reduce the risk of liner failure. Nanosecond pulsed laser surface treatment, known for its high efficiency, precise control, and automation capabilities, was employed in this study to modify the surface of the PA11 liner. The bonding properties of the PA11-CFRP interface were comprehensively investigated through climbing drum peel (CDP) tests, flatwise tensile (FWT) tests, and surface performance assessments. Utilizing the Optimization module within the Response Surface Method (RSM) software Design Expert for analysis, it was found that, under the optimal parameters of 400 mm/s, 20 kHz, and 12.7 W for nanosecond pulsed laser treatment, the CDP strength increased to 24.1 N mm/mm, which was 4.74-fold higher than that of untreated samples. The FWT strength reached 2.43 MPa, which was 8.35-fold higher than that of untreated samples. The increase in interfacial bonding strength after laser treatment primarily resulted from the formation of periodic grooves on the PA11 surface, along with an increase in surface roughness. This approach presents a promising direction for the surface treatment of plastic liners in type IV hydrogen storage vessels prior to winding and is poised to enhance the safety of such vessels.

Tank volume and energy consumption optimization of hydrogen cycle test system

The hydrogen cycle test is the most complex type test of high-pressure hydrogen storage cylinders for hydrogen fuel cell vehicles, and it is quite challenging to develop a hydrogen cycle test system for this test. The volume of gas source tank and recovery tank can be described on the basis of thermodynamic model with considering of hydrogen mass, pressure, and temperature. The optimal volumes for the tanks are determined by applying the objective function. The sum of pressure drops in each level of the source tanks is used to evaluate the test energy consumption and the optimal pressure at each stage of hydrogen charging and discharging is obtained to minimize the test energy consumption. The tank volume calculation method and energy consumption optimization method proposed in this paper not only reduce the hydrogen consumption and energy consumption during the operation of the hydrogen cycle test system, but also improve the safety and economy of the system.

Hydrogen-Based Energy Systems: Current Technology Development Status, Opportunities and Challenges

The use of hydrogen as an energy carrier within the scope of the decarbonisation of the world’s energy production and utilisation is seen by many as an integral part of this endeavour. However, the discussion around hydrogen technologies often lacks some perspective on the currently available technologies, their Technology Readiness Level (TRL), scope of application, and important performance parameters, such as energy density or conversion efficiency. This makes it difficult for the policy makers and investors to evaluate the technologies that are most promising. The present study aims to provide help in this respect by assessing the available technologies in which hydrogen is used as an energy carrier, including its main challenges, needs and opportunities in a scenario in which fossil fuels still dominate global energy sources but in which renewables are expected to assume a progressively vital role in the future. The production of green hydrogen using water electrolysis technologies is described in detail. Various methods of hydrogen storage are referred, including underground storage, physical storage, and material-based storage. Hydrogen transportation technologies are examined, taking into account different storage methods, volume requirements, and transportation distances. Lastly, an assessment of well-known technologies for harnessing energy from hydrogen is undertaken, including gas turbines, reciprocating internal combustion engines, and fuel cells. It seems that the many of the technologies assessed have already achieved a satisfactory degree of development, such as several solutions for high-pressure hydrogen storage, while others still require some maturation, such as the still limited life and/or excessive cost of the various fuel cell technologies, or the suitable operation of gas turbines and reciprocating internal combustion engines operating with hydrogen. Costs below 200 USD/kWproduced, lives above 50 kh, and conversion efficiencies approaching 80% are being aimed at green hydrogen production or electricity production from hydrogen fuel cells. Nonetheless, notable advances have been achieved in these technologies in recent years. For instance, electrolysis with solid oxide cells may now sometimes reach up to 85% efficiency although with a life still in the range of 20 kh. Conversely, proton exchange membrane fuel cells (PEMFCs) working as electrolysers are able to sometimes achieve a life in the range of 80 kh with efficiencies up to 68%. Regarding electricity production from hydrogen, the maximum efficiencies are slightly lower (72% and 55%, respectively). The combination of the energy losses due to hydrogen production, compression, storage and electricity production yields overall efficiencies that could be as low as 25%, although smart applications, such as those that can use available process or waste heat, could substantially improve the overall energy efficiency figures. Despite the challenges, the foreseeable future seems to hold significant potential for hydrogen as a clean energy carrier, as the demand for hydrogen continues to grow, particularly in transportation, building heating, and power generation, new business prospects emerge. However, this should be done with careful regard to the fact that many of these technologies still need to increase their technological readiness level before they become viable options. For this, an emphasis needs to be put on research, innovation, and collaboration among industry, academia, and policymakers to unlock the full potential of hydrogen as an energy vector in the sustainable economy.

Techno-Economic Analysis of a Physisorption-Based Hydrogen Storage System

Abstract Alternative long-term storage of energy is becoming increasingly important due to climate change. Hydrogen-based storage technologies have long been considered promising alternatives to batteries. However, the different forms of hydrogen storage have various disadvantages and are still comparatively expensive. As an alternative, this paper deals with a new concept for hydrogen storage, the Cryogenic Flux Capacitor (CFC). It is intended as an intermediate between high-pressure and liquid storage to exploit the advantages and reduce the disadvantages. This paper ranks the CFC technology against the others. For this purpose, it investigates the economic viability and the specific application as a grid-connected system. A complete system from hydrogen production and storage to conversion into electrical energy is considered. In detail, the costs for storage and storage time are compared, and the size scaling of a CFC-based system as a grid-connected system is examined. The Levelized Costs of Energy (LCOE) are calculated and compared as a benchmark. It turns out that a CFC-based storage system also requires a tremendous amount of energy in the form of liquid nitrogen and the associated operational costs for cooling down the hydrogen. Nevertheless, the overall operating costs are between high-pressure and liquid hydrogen storage. Most surprising is the LCOE, which, at 0.192 $/kWh–0.234 $/kWh, is well within the range of the other storage technologies. As a grid-connected storage system, CFC technology can be used as a small- to a medium-scale energy storage system, e.g., to serve smaller neighborhoods.

Numerical investigation on the influence of geometrical parameters on the temperature distribution in marine hydrogen storage tanks during filling

This paper established a two-dimensional axisymmetric model with a marine high-pressure hydrogen storage tank as the research object. Using numerical simulation, the effects of different aspect ratios, inlet diameters, and inlet pipe lengths on the temperature rise of the hydrogen storage tank during the filling process were studied. As the L/D ratio of the hydrogen storage tank increases, the momentum of the hydrogen gas reaching the bottom of the tank gradually decreases, making it easier to form localized high-temperature regions. For a hydrogen storage tank with an L/D of 6.0, the difference between the maximum and average temperature at the end of filling was 155.85 K. In contrast, the temperature difference of the tank with an L/D of 3.6 was only 32.81 K. In addition, the inlet pipe delivers the hydrogen deep into the tank and reduces the obstructing effect of the existing hydrogen in the tank on the newly filled hydrogen. For smaller L/D hydrogen storage tanks, the inlet pipe may backfire and create a high-temperature zone at the shoulder of the tank. In contrast, for larger L/D hydrogen storage tanks, a suitable length of inlet pipe can deliver the hydrogen deep into the tank. This will enhance the gas flow inside the tank, facilitating heat exchange and avoiding the formation of localized high-temperature areas at the bottom of the tank. However, excessively long inlet pipes can also lead to high-temperature areas on the shoulders. At a specific charge mass flow rate, the lower the inlet diameter, the higher the hydrogen flow rate. The larger flow rate helped promote uniform hydrogen mixing in the tank and made it challenging to form localized high-temperature regions.