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![Figure 3-Simple phase diagram for hydrogen [5]](profile/Stathis-Peteves/publication/255636014/figure/fig3/AS:667780588261415@1536222707960/Simple-phase-diagram-for-hydrogen-5_Q320.jpg)
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... normal conditions hydrogen molecules are present both in ortho-state (75%) and para- state (25%) 4 ; this equilibrium composition is referred to as normal hydrogen. However, this equilibrium composition of hydrogen states varies with temperature, see Figure 2. As temperature decreases, ortho-hydrogen transforms into para-hydrogen and finally at the liquid state, hydrogen is present practically exclusively in the para-state (99.8%). ...
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... P 1 and P 3 are the suction and the discharge pressures and P 2 is the optimal intermediate pressure, being of such a value (P 2 = 3 1 .P P ) so that the pressure ratio is the same in each compression stage; a necessary requirement to achieve the conditions of minimum work. Figure 12 shows the calculated electrical work required for compressing hydrogen with multi-stage compressors. Two families of cases were examined, differentiated by the suction pressure being 2 bar and 35 bar respectively. ...
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... graph also highlights the importance of the suction pressure in the energy required to achieve a desired discharge pressure. Figure 12 -Electrical work required for the compression of hydrogen, based on multi- stage compression. Assumptions for the calculation: Ideal intercooling, T=25°C, isentropic =75%, electrical =90%. ...
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... was mentioned earlier, with the reduction of temperature, ortho-hydrogen transforms into para-hydrogen with a concurrent release of energy. If ortho-hydrogen remains after liquefaction in concentrations above the equilibrium concentration, see Figure 2, it will eventually be converted into para-hydrogen, releasing energy, thus increasing the temperature of the liquid hydrogen and resulting in losses due to evaporation. To overcome this difficulty, catalysts are used in the liquefaction process (typically embedded in the heat exchangers) such as iron oxides, rare earth metals and oxides, etc. to promote the hydrogen transformation during liquefaction. ...
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... terms of their storage capacity, curved structures such as carbon nanotubes appear to be more efficient as compared to high surface area graphite (25% extra at low temperatures) ( Figure 20). This behaviour is due to their structure interacting with the hydrogen molecule and to the greater attractive forces acting compared to the open flat surface structures [5,28]. ...
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... a similar performance, 8 kg hydrogen are needed for the ICE version or 4 kg hydrogen for an electric car with a fuel cell. In this case, hydrogen will occupy a volume of 45 m 3 (at room temperature and atmospheric pressure), requiring a tank with considerable storage space ( Figure 21). So the big challenge is to find a solution for compacting hydrogen; issues such as materials, technology and safety should also be addressed ( Figure 21) [28]. ...
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... this case, hydrogen will occupy a volume of 45 m 3 (at room temperature and atmospheric pressure), requiring a tank with considerable storage space ( Figure 21). So the big challenge is to find a solution for compacting hydrogen; issues such as materials, technology and safety should also be addressed ( Figure 21) [28]. In general, the optimal hydrogen storage solution involves lightweight storage systems with conformable tank shapes adaptable to the space available in various vehicle structures. ...
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... in partnership with North America and the Pacific Rim, as well as with the developing world, will speed up the introduction of sustainable energy technologies by co-operating on technology bottlenecks, codes and standards, and technology transfer. Finally, in their report the HLG members are presenting a preliminary, skeleton proposal for the main elements and timescales of the European roadmap on the production and distribution of hydrogen, hydrogen systems, and fuel cells -see Figure 22. . Under this programme, road maps have been drawn and strategic steps have been decided. ...
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... to US DoE and taking into consideration this classification, hydrogen storage media should by 2010 demonstrate the following performance characteristics - Table 7 [72]. Nevertheless, according to General Motors even these DoE targets for energy densities may still be low (see Figure 24) as recently indicated and could soon be revised [49,74]. ...
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... example, the daily losses of 50 m 3 , 100 m 3 and 20,000 m 3 containers are about 0.4%, 0.2% and 0.04% respectively [5]. Cylindrical containers are also available (see Figure 26) as they cost less to manufacture. ...
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... example, the Linde liquefaction plant in Germany stores the produced hydrogen in a 270 m 3 vessel, with a capacity of 19,000 kg [84]. The largest liquid storage tank in the world is spherical with a diameter of 20 m, volume of 3,800 m 3 and capacity of about 230,000 kg and is located at the Kennedy Space (KSC) Center of NASA, where it is used to provide liquid hydrogen to the Space Transportation System (Space Shuttle), see Figure 27. Its evaporation rate is 0.1 to 1% per day [81]. ...
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... storage of hydrogen in metal hydrides for stationary applications, although it has not yet seen any commercial application or large-scale demonstration because it is still in the research stage, may play an important role in the future. Figure 28 shows a conceptual picture of such a storage facility, where hydrides are stored in cylindrical containers. ...
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... selection of the most appropriate type of compressor is based on process variables such as capacity, suction and discharge pressure. Given that the required pressure for hydrogen storage applications exceeds 150 bar, the state-of-the-art in hydrogen compressors is the use of reciprocating piston engines for large applications, such as for pipeline transportation, and piston or diaphragm compressors for smaller applications, such as refuelling stations (see Figure 29). From an engineering point of view, the most appropriate type is the one that accomplishes the required compression with the minimum input of work. ...
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... higher discharge pressures, lubricating systems are used. Schematics of lubricated and unlubricated piston compressors are shown in Figure 32. Another issue, common for all types of hydrogen compressors, is the selection of materials to avoid hydrogen-induced damage (see chapter 1). ...
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... the costs of maintenance and of electricity are major contributors to the variable costs associated with compressors. The electricity consumption is calculated based on the efficiency of the compressor (70-85% based on its type and operating conditions) and the efficiency of the motor (90%), see Figure 12, chapter 1. ...
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... large and optimised plants, the cost of liquid hydrogen can be as low as $0.7/kg. The results are summarized in Figure 42. Figure 42 -Cost of hydrogen liquefaction, as calculated in Ref. [19] ...
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Citations
... To store gaseous hydrogen, it is compressed from the electrolyzer's outlet pressure to a significantly higher pressure level. This compression substantially reduces the required specific storage volume per kilogram of hydrogen [43,44]. Such high-pressure levels impose stringent material requirements for the pressure vessels, which are typically made of solid steel, steel composites, or plastic composites, depending on the necessary strength. ...
... Typically, piston or diaphragm compressors are employed for hydrogen compression. These are classified as high-pressure compressors, capable of reaching outlet pressures well above 1000 bar [25,44,51,52]. ...
... To store or transport gaseous hydrogen, it is compressed from the outlet pressure of the electrolysis unit to up to 425 bar for stationary buffer storage or up to 250 bar for filling the SBs. The calculation of the specific compressor work w s was based on the assumption of an isentropic process [32,44,52]. ...
Green hydrogen is a cornerstone in the global quest for a carbon-neutral future, offering transformative potential for decarbonizing transportation. This study investigates its role by assessing the feasibility of a large-scale hydrogen refueling station in Germany, focusing on integrating renewable energy sources. A hydrogen demand model with a 10-min time resolution to refuel 30 trucks and 20 vans (1019 kg/day) is combined with a techno-economic optimization model to evaluate a hybrid energy system utilizing wind, solar, and grid electricity. Scenario-based analysis reveals that Levelized Cost of Hydrogen ranges from 13.92 to 18.12 €/kg, primarily influenced by electricity costs. Excess electricity sales can reduce this cost to 13.34–16.92 €/kg. On-site wind energy reduces storage and grid reliance, achieving the lowest hydrogen cost. Unlike prior studies, this work combines temporally resolved hydrogen demand profiles with comprehensive techno-economic modeling, offering unprecedented insights into decentralized green hydrogen systems for heavy-duty transport. By bridging critical gaps in the scalability and economic feasibility of Power-to-Hydrogen systems, it provides viable strategies for advancing green hydrogen infrastructure.
... On the other hand, the ortho-to-para transition requires a nuclear spin flip making the conversion process inherently slow. These features have important technological consequences, especially for liquid H 2 energy storage technologies [51], implying the necessity of developing efficient ortho-para catalysts. Research on ortho-para conversion is also important from a basic-physics perspective, as it enables studies of the magnetic properties and structural composition of solid surfaces [52], processes on nonmagnetic surfaces of noble metals [53] or various physical properties of solid hydrogen [54]. ...
Spectrometers based on high-finesse optical cavities have proven to be powerful tools for applied and fundamental studies. Extending this technology to the deep cryogenic regime is beneficial in many ways: Doppler broadening is reduced, peak absorption is enhanced, the Boltzmann distribution of rotational states is narrowed, all unwanted molecular species disturbing the spectra are frozen out, and dense spectra of complex polyatomic molecules become easier to assign. We demonstrate a cavity-enhanced spectrometer fully operating in the deep cryogenic regime down to 4 K. We solved several technological challenges that allowed us to uniformly cool not only the sample but also the entire cavity, including the mirrors and cavity length actuator, which ensures the thermodynamic equilibrium of a gas sample. Our technology well isolates the cavity from external noise and cryocooler vibrations. This instrument enables a variety of fundamental and practical applications. We demonstrate a few examples based on accurate spectroscopy of cryogenic hydrogen molecules: accurate test of the quantum electrodynamics for molecules; realization of the primary SI standards for temperature, concentration and pressure in the deep cryogenic regime; measurement of the H phase diagram; and determination of the ortho-para spin isomer conversion rate.
... Conversely, salt cavern storage presents a more economical option at $$0.14/kg of H 2 . 83 Tzimas et al. 84 note higher long-term storage expenses, especially for compressed gaseous and liquid hydrogen. On-board storage systems exhibit varied costs, predominantly influenced by carbon fiber expenses. ...
The paper provides a comprehensive examination of resources available for the deployment of green hydrogen in Serbia. The assessment encompasses various aspects, including renewable energy potentials, technological advancements, and future projections. The evaluation considers factors such as solar and wind power capacities, which are pivotal for green hydrogen production. Additionally, the study delves into the policy landscape, addressing initiatives aimed at fostering the integration of green hydrogen into Serbia's energy matrix. The analysis combines quantitative data on energy production capacities with qualitative insights into the economic and environmental implications of green hydrogen utilization. While the nation boasts abundant renewable energy resources, challenges such as high production costs and infrastructure limitations hinder widespread adoption. However, with strategic initiatives and technological advancements, Serbia can overcome these hurdles and pave the way for a sustainable hydrogen economy. Assessing Serbia's green hydrogen potential, driven by over 24 095 MWp from solar and 10 750 MWp from wind, highlights the nation's capacity to harness renewable resources, with hydrogen production set to grow from 1915 tons in 2019 to 37 ,123 tons by 2040. The findings aim to contribute to the ongoing discourse on sustainable energy transitions and the role of green hydrogen in Serbia's evolving energy landscape.
... This may encourage energy saving and emission reduction even further. Finally, hydrogen is adjustable in terms of storage and transportation since its volume may alter substantially during phase transition (Tzimas et al., 2003). ...
This chapter, centered on hydrogen phase equilibrium and solubility data, provides a comprehensive overview of hydrogen’s physical and thermodynamic properties in different phases and their interactions with other materials. The fundamental principles of phase equilibrium, including the effects of temperature, pressure, and composition on the phase behavior of hydrogen, are reviewed. The solubility of hydrogen in various materials, including hydrocarbons, metals, and polymers, is also discussed. Particular attention is given to metals and alloys, as hydrogen solubility in metals has significant implications for nuclear power systems and hydrogen storage. The various experimental methods used to measure hydrogen solubility, such as gravimetric and volumetric techniques, are also discussed. In short, the chapter summarizes the current state of knowledge on hydrogen phase equilibrium and solubility data, highlighting the remaining challenges and open questions. The authors conclude by emphasizing the importance of accurate and reliable data on hydrogen properties for developing hydrogen-based technologies and the transition toward a more sustainable energy system.
... Hydrogen is a chemical element with symbol H with a gas density of 0.09 g/L at 0°C and 1.013 bar of pressure, which means 14 times lighter than air, and it has a great ability to spread outside the atmosphere [24]; however, it exists in combination with other elements. While hydrogen is not a primary source of energy, it becomes an attractive energy carrier when separated from other elements using alternative energy sources. ...
Renewable energy sources are essential for mitigating the greenhouse effect and supplying energy to resource-scarce regions. However, their intermittent nature necessitates efficient storage solutions to enhance system efficiency and manage energy costs. This paper investigates renewable and clean storage systems, specifically examining the storage of electricity generated from renewable sources using hydropower plants and hydrogen, both of which are highly efficient and promising for future energy production and storage. The study utilizes extensive literature data to analyze the impact of various parameters on the cost per kWh of electricity production in hybrid renewable systems incorporating hydropower and hydrogen storage plants. Results indicate that these hybrid systems can store electricity efficiently and cost-effectively, with production costs ranging from 0.126 to 0.3 /kWh for renewable-hydrogen systems, with expected cost reductions over the next decade due to technological advancements and increased market adoption. The novelty of this study lies in its comprehensive comparison of hybrid renewable systems integrating hydropower and hydrogen storage, providing detailed cost analysis and future projections. It identifies key parameters influencing the cost and efficiency of these systems, offering insights into optimizing storage solutions for renewable energy. Moreover, this research underscores the potential of hybrid systems to reduce dependency on fossil fuels, particularly during peak demand periods, and emphasizes the importance of seasonal and geographic considerations in selecting energy sources. The study highlights the importance of policy support and investment in hybrid renewable systems and calls for further research into optimizing these systems for different seasonal and geographic conditions. Overall, the integration of renewable energy sources with hydropower and hydrogen storage offers a promising pathway to a sustainable, economical, and resilient energy future.
... This distinction arises from its significant hydrogen content and its safe and ecofriendly nature. [25]. Two approaches exist for generating hydrogen from water. ...
Water is a potential green source for the generation of clean elemental hydrogen without contaminants. One of the most convenient methods for hydrogen generation is based on the oxidation of different metals by water. The inspection of the catalytic activity toward hydrogen formation from water performed in this study was carried out using four different metals, namely, zinc, magnesium, iron, and manganese. The process is catalyzed by in situ-generated nickel nanoparticles. The zinc–water system was found to be the most effective and exhibited 94% conversion in 4 h. The solid phase in the latter system was characterized by PXRD and SEM techniques. Several blank tests provided a fundamental understanding of the role of each constituent within the system, and a molecular mechanism for the catalytic cycle was proposed.
... If the water vapor is in the vapor phase, the energy release is referred to as LHV or net calorific value. If the water vapor is in the form of liquid water, the energy release is referred to as HHV or gross calorific value [65]. ...
The inherent intermittency of renewable energy sources frequently leads to variable power outputs, challenging the reliability of our power supply. An evolving approach to mitigate these inconsistencies is the conversion of excess energy into hydrogen. Yet, the pursuit of safe and efficient hydrogen storage methods endures. In this perspective paper, we conduct a comprehensive evaluation of the potential of lined rock caverns (LRCs) for hydrogen storage. We provide a detailed exploration of all system components and their associated challenges. While LRCs have demonstrated effectiveness in storing various materials, their suitability for hydrogen storage remains a largely uncharted territory. Drawing from empirical data and practical applications, we delineate the unique challenges entailed in employing LRCs for hydrogen storage. Additionally, we identify promising avenues for advancement and underscore crucial research directions to unlock the full potential of LRCs in hydrogen storage applications. The foundational infrastructure and associated risks of large-scale hydrogen storage within LRCs necessitate thorough examination. This work not only highlights challenges but also prospects, with the aim of accelerating the realization of this innovative storage technology on a practical, field-scale level.
... However, to maintain a high pressure, modifications to the container material are required, and safety issues owing to hydrogen leakage cannot be avoided, leading to an uneconomical outcome [11,13,[15][16][17][18][19]. In contrast, transporting hydrogen in the form of a cryogenic liquid has an advantage of an 800 times higher storage density compared to gaseous hydrogen, and it can be readily liquefied and transported without complicated processes [20]. However, this mode of transportation requires a highly efficient insulation system to maintain the extremely low temperature of − 253 • C, the boiling point of hydrogen. ...
... where α * and a 1 are the model coefficients; s is the mean strain-rate tensor; and F 2 is the blending function calculated using Eq. (20). ...
The present study aimed to analyze and compare vacuum insulation systems suitable for a type C liquid hydrogen storage tank. Multiphase thermal analysis was conducted via computational fluid dynamics, and experimental results for the boil-off rate (BOR) of a type C liquid nitrogen storage tank were obtained to verify the simulation technique. The simulation results showed a maximum error of 0.941 % compared to experimental results. Three insulation systems with superior thermal performance were selected and compared in a 3D system. The Vacuum+MLI Mylar-net insulation system showed the best thermal performance, with a result of 0.189 %/day. An analysis of the parts vulnerable to heat loss was conducted. These findings contribute to the development of high-performance insulation systems for the safe and economic transportation of liquid hydrogen. The study is an important resource for assessing insulation performance during the design phase and preventing local heat loss during operation.
... Additionally, utilization of existing power grid and infrastructure (as well as heavy transportation) makes GH2 at pressure ranges up to 350 bar, economically favorable. High-pressure hydrogen up to 750 bar for automotive solutions requires advanced cooling technologies and more sophisticated processing [8], which makes the high-pressure technology in direct comparison with batteries, less competitive in the opinion of the authors. Reciprocating compressors are key technology and developed for high-pressure hydrogen compression [9]. ...
Hydrogen technology can be one key for a transition to sustainable energy necessary to achieve climate targets and limit global warming to 1.5 °C since the beginning of the industrial revolution. Hydrogen as a CO2 neutral energy carrier must replace fossil fuels from the existing natural gas grid and infrastructure to enable an environmentally friendly and circular economy in future societies. Batteries and e-fuels are practicable technologies for short term and quantitatively limited energy provision, with disadvantages including raw material demands and technologically complex transformation cycles. Utilizing advanced power-to-gas concepts, hydrogen will not only be most efficient technology in energy storage, but also allows adaption and reuse of existing energy transportation infrastructure.To provide volatile hydrogen gas in the required flow and energy densities, advanced compression technology needs to be developed inspired by conventional gas compression systems. Reciprocating piston compressors are developed for high-pressure hydrogen applications, providing high pressure levels and flow rates. Compression equipment must be designed for non-lubricated dry-running conditions, as high gas purity standards of hydrogen do not allow for oil-based lubricants to be introduced into the process gas. High-strength carbon fiber reinforced composites are developed as piston and packing ring materials to withstand extreme pressure differences under harsh thermo-mechanically loaded operation conditions.Promising candidates with high strength and wear resistance in the form of PPS-polymers, are developed with PTFE solid lubricants and different carbon fiber fractions to combine high strength, with low friction and wear, improve pressure operation range, and limit down times of hydrogen piston compressors. The current work describes tribological testing of advanced PPS-polymers with 10 to 30 wt.% carbon fibers in a high-velocity tribometer under hydrogen gas atmosphere. Supporting thermo-mechanical tests give new insights in deformation mechanisms of fiber reinforced polymer composites and allow conclusions on their applicability for hydrogen compression.
... It has the potential to serve as a clean energy carrier for generating electricity and heat. Nevertheless, the lack of efficient and safe storage systems remains a major challenge impeding the widespread adoption of hydrogen [2], [3]. ...
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 (Metal-organic 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.
