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13 pages, 2520 KiB

Open AccessArticle

Techno-Economic Analysis of Solar Thermal Hydrogen Production in the United Arab Emirates

by Abdulrahman Joubi, Yutaro Akimoto and Keiichi Okajima

Hydrogen 2022, 3(4), 389-401; https://doi.org/10.3390/hydrogen3040024 - 10 Oct 2022

Cited by 8 | Viewed by 4200

Abstract

Solar thermal technology can provide the United Arab Emirates and the Middle East region with abundant clean electricity to mitigate the rising levels of carbon dioxide and satisfy future demand. Hydrogen can play a key role in the large-scale application of solar thermal [...] Read more.

Solar thermal technology can provide the United Arab Emirates and the Middle East region with abundant clean electricity to mitigate the rising levels of carbon dioxide and satisfy future demand. Hydrogen can play a key role in the large-scale application of solar thermal technologies, such as concentrated solar plants, in the region by storing the surplus electricity and exporting it to needed countries for profit, placing the Middle East and the United Arab Emirates as major future green hydrogen suppliers. However, a hydrogen supply chain comparison between hydrogen from CSP and other renewable under the UAE’s technical and economic conditions for hydrogen export is yet to be fully considered. Therefore, in this study we provide a techno-economic analysis for well-to-ship solar hydrogen supply chain that compares CSP and PV technologies with a solid oxide water electrolyzer for hydrogen production, assuming four different hydrogen delivery pathways based on the location of electrolyzer and source of electricity, assuming the SOEC can be coupled to the CSP plant when placed at the same site or provided with electric heaters when placed at PV plant site or port sites. The results show that the PV plant achieves a lower levelized cost of electricity than that of the CSP plant with 5.08 ¢/kWh and 8.6 ¢/kWh, respectively. Hydrogen production results show that the scenario where SOEC is coupled to the CSP plant is the most competitive scenario as it achieves the payback period in the shortest period compared to the other scenarios, and also provides higher revenues and a cheaper LCOH of 7.85 $/kg_H2. Full article

(This article belongs to the Special Issue Feature Papers in Hydrogen)

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21 pages, 4708 KiB

Open AccessArticle

Hybrid Renewable Hydrogen Energy Solution for Remote Cold-Climate Open-Pit Mines

by Hosein Kalantari and Seyed Ali Ghoreishi-Madiseh

Hydrogen 2022, 3(3), 312-332; https://doi.org/10.3390/hydrogen3030019 - 12 Aug 2022

Cited by 1 | Viewed by 2539

Abstract

Contemporary off-grid mining operations rely on diesel fuel for the provision of their total energy including electricity, heat, and haulage. Given the high cost of diesel and its imposed greenhouse gas emissions, mining companies are looking for more affordable and cleaner sources of [...] Read more.

Contemporary off-grid mining operations rely on diesel fuel for the provision of their total energy including electricity, heat, and haulage. Given the high cost of diesel and its imposed greenhouse gas emissions, mining companies are looking for more affordable and cleaner sources of energy for their operations. Although renewable energy systems, such as solar photovoltaic and wind provide efficient solutions to address this challenge, full decarbonization has shown to be very challenging, mainly due to the high cost of battery storage along with the inability to meet total site energy demand. Integrating hydrogen and thermal storage with battery banks can facilitate a full transitioning off diesel. In this sense, the present study intends to offer an innovative decarbonized solution by integrating wind turbines with a multi-storage system (battery, hydrogen, and thermal storage) to supply the total energy (electricity, heat, and haulage) for remote open-pit mines. Among the different proposed fully decarbonized configurations in this study, it is shown that a renewable system with a hydrogen-powered fleet and hybridized battery/hydrogen storage configuration can present the most economically viable case for open-pit mines with a considerably less life-of-mine cost. Full article

(This article belongs to the Special Issue Feature Papers in Hydrogen)

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9 pages, 2768 KiB

Open AccessArticle

Methods to Improve the First Hydrogenation of the Vanadium-Rich BCC Alloy Ti₁₆V₆₀Cr₂₄

by Francia Ravalison, Eugen Rabkin and Jacques Huot

Hydrogen 2022, 3(3), 303-311; https://doi.org/10.3390/hydrogen3030018 - 22 Jul 2022

Cited by 3 | Viewed by 2277

Abstract

In this paper we report the effect of three different preparation methods on the first hydrogenation of the vanadium-rich BCC alloy Ti₁₆V₆₀Cr₂₄: one-time cold rolling, 5 min ball milling and addition of 4 wt.% of Zr. All [...] Read more.

In this paper we report the effect of three different preparation methods on the first hydrogenation of the vanadium-rich BCC alloy Ti₁₆V₆₀Cr₂₄: one-time cold rolling, 5 min ball milling and addition of 4 wt.% of Zr. All samples were synthesized by arc melting. Without Zr addition the alloy was single phase, but when 4 wt.% Zr was added, a secondary zirconium-rich phase was present. However, X-ray diffraction patterns only showed a single-body-centred cubic phase before hydrogenation for all samples. The crystal structure of the fully hydrogenated samples was body-centred tetragonal. The highest hydrogen capacity (3.8 wt.%) was measured for the Zr-doped alloy. The ball-milled alloy also exhibited a high storage capacity and fast kinetics. However, the maximum hydrogen storage capacity slightly decreased after cold rolling. It was found that air exposure increases incubation time for the first hydrogenation. The incubation time was shortened by cold rolling which, however, reduced the hydrogen storage capacity. The Pressure-Composition isotherms of Ti₁₆V₆₀Cr₂₄ + 4 wt.% Zr at 297, 303 and 323 K were determined. The determined enthalpy and entropy of hydrides formation were −41 ± 5 kJ/mol and −134 ± 14 J/mol/K, respectively. Full article

(This article belongs to the Special Issue Feature Papers in Hydrogen)

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15 pages, 733 KiB

Open AccessArticle

Reducing Hydrogen Boil-Off Losses during Fuelling by Pre-Cooling Cryogenic Tank

by Fardin Ghaffari-Tabrizi, Jan Haemisch and Daniela Lindner

Hydrogen 2022, 3(2), 255-269; https://doi.org/10.3390/hydrogen3020015 - 1 Jun 2022

Cited by 7 | Viewed by 10432

Abstract

Boil-off losses occur when gaseous hydrogen has to be released from a cryogenic tank due to liquid hydrogen evaporating. These are a substantial drawback for all areas in which liquid hydrogen is discussed as a potential fuel to limit the climate impact. Especially [...] Read more.

Boil-off losses occur when gaseous hydrogen has to be released from a cryogenic tank due to liquid hydrogen evaporating. These are a substantial drawback for all areas in which liquid hydrogen is discussed as a potential fuel to limit the climate impact. Especially boil-off losses during fuelling are one of the most significant source of losses along the liquid hydrogen pathway. To analyse and minimize such losses, simulations of the filling process are performed with the simulation tool “EcoSimPro”. The simulations are validated with an analytical solution. The results show that boil-off losses can be significantly reduced by pre-cooling the cryogenic tank with liquid nitrogen. This method is most effective for relatively small tanks that could be used e.g., in small air crafts or air taxis. Full article

(This article belongs to the Special Issue Feature Papers in Hydrogen)

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18 pages, 7085 KiB

Open AccessArticle

Repetitive Bathing and Skin Poultice with Hydrogen-Rich Water Improve Wrinkles and Blotches Together with Modulation of Skin Oiliness and Moisture

by Yoshiharu Tanaka and Nobuhiko Miwa

Hydrogen 2022, 3(2), 161-178; https://doi.org/10.3390/hydrogen3020011 - 1 Apr 2022

Cited by 3 | Viewed by 14022

Abstract

Hydrogen-rich warm water (HW) has not been verified yet for skin anti-aging effects. Daily 10 min HW (dissolved hydrogen: 338–682 μg/mL, 41 °C) bathing and skin poultice with HW-impregnated towels for 11–98 days were demonstrated to improve wrinkle degrees (29 skin-loci) from 3.14 [...] Read more.

Hydrogen-rich warm water (HW) has not been verified yet for skin anti-aging effects. Daily 10 min HW (dissolved hydrogen: 338–682 μg/mL, 41 °C) bathing and skin poultice with HW-impregnated towels for 11–98 days were demonstrated to improve wrinkle degrees (29 skin-loci) from 3.14 ± 0.52 to 1.52 ± 0.74 (p < 0.001) and blotch degrees (23 loci) from 3.48 ± 0.67 to 1.74 ± 0.92 (p < 0.001) in five healthy subjects (49–66 years old), by densito-/planimetrically evaluating with an Image-J software, and ranking into six hierarchies (0, 1–5). Meanwhile, skin oiliness was evaluated to increase for the oil-poor skins, but inversely decrease for excessively oily skins, suggesting the HW’s function as skin-oiliness modulation, with an appreciably negative correlation in prior oiliness contents versus change after HW application (r = −0.345, 23 loci). Skin moisture increased upon HW application, with a negative correlation (r = −0.090, 23 loci) in prior moisture contents versus post-HW-application moisture-changing rates, meaning that HW application compensated moisture for water-deficient skins (27.5–40% moisture), but not for wet skins (>41% moisture). Thus, the HW bath together with HW poultice exerted beneficial effects on skin appearances such as wrinkles, blotches and moisture/oiliness, some of which might ensue from enhanced antioxidant ability in blood, as was previously demonstrated for the HW bath. Full article

(This article belongs to the Special Issue Feature Papers in Hydrogen)

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38 pages, 4560 KiB

Open AccessArticle

Blocking Hydrogen Diffusion in Palladium Cathode i—Analyzed by Electrochemistry; ii—Analyzed by Chaos

by Gilbert Bellanger

Hydrogen 2022, 3(1), 123-160; https://doi.org/10.3390/hydrogen3010010 - 17 Mar 2022

Cited by 1 | Viewed by 14071

Abstract

Electrochemical chaos is caused when, during diffusion, hydrogen and, at worst, tritium is trapped in palladium after the formation of adsorbates. The mechanism leads to cracking corrosion, as seen by scanning electron microscopy. The instabilities were apprehended from voltammetry and electrochemical impedance spectroscopy [...] Read more.

Electrochemical chaos is caused when, during diffusion, hydrogen and, at worst, tritium is trapped in palladium after the formation of adsorbates. The mechanism leads to cracking corrosion, as seen by scanning electron microscopy. The instabilities were apprehended from voltammetry and electrochemical impedance spectroscopy in the active potential where the cathodic hydrogen is charged from two models of transients. Tests performed using an electrochemical chaos analyzer simplify the expertise of the palladium cathode in focusing on the blocking diffusion of hydrogen. A complex electrical circuit of chaos is considered for adsorption and the blocking diffusion. Depending on the active potential, distinct behavior such as the transformation of transients and limited diffusion can occur. Phase-space spectra are obtained, and synchronization has been developed to clarify the chaos leading to the cracking of palladium. By applying these different analytical tests for the restricted diffusion, it is possible to interpret the processes from the power spectra, autocorrelation function, or the divergence coefficient in the region of active potentials. Analyzers can detect flaws in this hydrogen diffusion process and suggest corrective measures. Full article

(This article belongs to the Special Issue Feature Papers in Hydrogen)

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11 pages, 4826 KiB

Open AccessArticle

Mechanochemical Synthesis and Hydrogen Sorption Properties of a V-Ni Alloy

by Oriele Palumbo, Nicholas Carboni, Francesco Trequattrini, Sergio Brutti and Annalisa Paolone

Hydrogen 2022, 3(1), 112-122; https://doi.org/10.3390/hydrogen3010009 - 2 Mar 2022

Cited by 1 | Viewed by 2619

Abstract

Vanadium can store large quantities of hydrogen (about 4 mass%). However, only half of it can be reversibly absorbed. To avoid this issue, various partial substitutions were previously proposed, such as Ni. In this work, we explore the synthesis of a V₈₅ [...] Read more.

Vanadium can store large quantities of hydrogen (about 4 mass%). However, only half of it can be reversibly absorbed. To avoid this issue, various partial substitutions were previously proposed, such as Ni. In this work, we explore the synthesis of a V₈₅Ni₁₅ alloy by means of ball milling, a simpler and more scalable method compared to arc or induction melting usually applied for metal alloys. After ball milling the powders of the pure metals for 15 h in argon, SEM–EDX measurements confirmed the stoichiometry of the synthesized material, which has a typical particle dimension of the order of a few microns and is composed from the coalescence of nanometric primary particles. XRD indicated a BCC crystalline structure with a typical grain size of ≈3 nm. Hydrogen can be absorbed without activation procedures at high temperatures. Up to H/M ≈ 0.08, one can observe the occurrence of a solid solution of hydrogen in the alloy, while at a higher hydrogen content, the formation of a hydride is likely to occur. The maximum hydrogen content is H/M ≈ 0.4 at the maximum investigated pressure in this study of p ≈ 45 bar. Both the hydrogenation enthalpy and entropy decrease as the hydrogen content increases, and the shape of the sorption isotherms is different from that of V₈₅Ni₁₅ produced by induction melting, possibly because of the nanometric dimensions of the particles produced by ball milling. Full article

(This article belongs to the Special Issue Feature Papers in Hydrogen)

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28 pages, 1166 KiB

Open AccessArticle

The Renewable Hydrogen–Methane (RHYME) Transportation Fuel: A Practical First Step in the Realization of the Hydrogen Economy

by John G. Ingersoll

Hydrogen 2022, 3(1), 84-111; https://doi.org/10.3390/hydrogen3010008 - 18 Feb 2022

Cited by 7 | Viewed by 15621

Abstract

The permanent introduction of green hydrogen into the energy economy would require that a discriminating selection be made of its use in the sectors where its value is optimal in terms of relative cost and life cycle reduction in carbon dioxide emissions. Consequently, [...] Read more.

The permanent introduction of green hydrogen into the energy economy would require that a discriminating selection be made of its use in the sectors where its value is optimal in terms of relative cost and life cycle reduction in carbon dioxide emissions. Consequently, hydrogen can be used as an energy storage medium when intermittent wind and solar power exceed certain penetration in the grid, likely above 40%, and in road transportation right away, to begin displacing gasoline and diesel fuels. To this end, the proposed approach is to utilize current technologies represented by PHEV in light-duty and HEV in heavy-duty vehicles, where a high-performance internal combustion engine is used with a fuel comprised of 15–20% green hydrogen and 85–89% green methane depending on vehicle type. This fuel, designated as RHYME, takes advantage of the best attributes of hydrogen and methane, results in lower life cycle carbon dioxide emissions than BEVs or FCEVs and offers a cost-effective and pragmatic approach, both locally as well as globally, in establishing hydrogen as part of the energy economy over the next ten to thirty years. Full article

(This article belongs to the Special Issue Feature Papers in Hydrogen)

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11 pages, 2940 KiB

Open AccessArticle

Hydrogen Gas Inhalation Prevents Erythrocyte Aggregation and Promotes Leukocyte Phagocytosis Together with Increases in Serum Antioxidant Activity

by Yuki Takada and Nobuhiko Miwa

Hydrogen 2022, 3(1), 72-82; https://doi.org/10.3390/hydrogen3010006 - 3 Feb 2022

Cited by 2 | Viewed by 6401

Abstract

Hydrogen gas inhalation has not yet been elucidated to improve blood behaviors or antioxidant activity in blood. In the present study, the PEM (proton-exchange-membrane)-/platinum-plated electrode-equipped electrolyzer was examined as a hydrogen gas inhaler, which was estimated to supply 3% hydrogen as rapidly as [...] Read more.

Hydrogen gas inhalation has not yet been elucidated to improve blood behaviors or antioxidant activity in blood. In the present study, the PEM (proton-exchange-membrane)-/platinum-plated electrode-equipped electrolyzer was examined as a hydrogen gas inhaler, which was estimated to supply 3% hydrogen as rapidly as post-operating 10–15 min, together with continuous 30 min retention of 20.8% oxygen being nearly equal to atmospheric oxygen contents. The 40 min inhalation of 3% hydrogen gas and thereafter 60 min rest were shown to enhance the antioxidant ability in human serum, as evaluated by ORAC (oxygen radical absorbing capacity)-based fluorometry, although scarcely enhanced for air dummy inhalation. Unexpectedly, antioxidant ability was 2.50-fold more enhanced for post-inhalational 0–60 min rest than during 40 min inhalation. Oxidative stress-suffering erythrocytes formed a rosary-chain-like aggregation composed of 3–6 cells, together with loss of a single hollow/biconcave-discoid structure in the cell central-part being necessary for erythrocyte passing through capillary vessels, both of which were prevented by 3% hydrogen gas inhalation. Hydrogen gas inhalation increased the intracellular foreign bodies, being distinguished from vacuole/cyst, in leucocytes, suggesting the hydrogen-activated leukocyte phagocytosis-associated events. Thus, 3%-hydrogen gas inhalation is suggested to potentially improve both the erythrocyte rheological/morphologic behaviors and the leucocyte phagocytosis-associated activity, concurrently with the enhanced antioxidant ability in blood. Full article

(This article belongs to the Special Issue Feature Papers in Hydrogen)

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11 pages, 3482 KiB

Open AccessArticle

Hydrogen-Rich Water Prevents Dehydration-Induced Cellular Oxidative Stress and Cell Death in Human Skin Keratinocytes

by Li Xiao and Nobuhiko Miwa

Hydrogen 2022, 3(1), 62-71; https://doi.org/10.3390/hydrogen3010005 - 28 Jan 2022

Cited by 5 | Viewed by 6966

Abstract

Hypohydration is linked to increased risk of a variety of diseases and can be life-threatening, especially in elderly populations. Dehydration induces cellular damage partially through the production of reactive oxygen species (ROS) in cells, tissues and organs. Hydrogen molecules are known to convert [...] Read more.

Hypohydration is linked to increased risk of a variety of diseases and can be life-threatening, especially in elderly populations. Dehydration induces cellular damage partially through the production of reactive oxygen species (ROS) in cells, tissues and organs. Hydrogen molecules are known to convert ROS to harmless water. Therefore, theoretically hydrogen-rich water (HW) might eliminate dehydration-induced ROS and reverse its harmful effects in cells. In this in vitro study, we demonstrated that air-drying for 5 min could induce ROS generation in both nucleus and cytoplasm of human keratinocytes HaCaT as quantified by CellROX^® Green/Orange reagents (Thermo Fisher Scientific, Waltham, Massachusetts, U.S.), respectively. Conversely, when the air-drying time was increased to 10 and 20 min, HaCaT cells lost the ability to produce ROS. Scanning electron microscopic (SEM) images showed that 10 min air-drying could induce severe membrane damage in HaCaT cells. PrestoBlue assay showed that, when HaCaT cells were air-dried for 20 min, cell viability was decreased to 27.6% of the control cells 48 h later. However, once HaCaT cells were pretreated with HW-prepared media, dehydration-induced intracellular ROS, cell membrane damage and cell death were significantly reduced as compared with double distilled water (DDW) under the same conditions. In conclusion, our data suggested that HW can decrease dehydration-induced harmful effects in human cells partially through its antioxidant capacity. Full article

(This article belongs to the Special Issue Feature Papers in Hydrogen)

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9 pages, 775 KiB

Open AccessArticle

Classical Thermodynamic Analysis of Deuterium-Based Fusion Reactions

by Silvano Tosti and Luigi Marrelli

Hydrogen 2022, 3(1), 53-61; https://doi.org/10.3390/hydrogen3010004 - 20 Jan 2022

Cited by 2 | Viewed by 5061

Abstract

The fusion reactions involving deuterium are of great interest for the exploitation of the fusion energy via magnetic-confinement devices. In classical thermodynamics, the spontaneity of a process is established through the assessment of the change in Gibbs free energy. So far, the feasibility [...] Read more.

The fusion reactions involving deuterium are of great interest for the exploitation of the fusion energy via magnetic-confinement devices. In classical thermodynamics, the spontaneity of a process is established through the assessment of the change in Gibbs free energy. So far, the feasibility of nuclear reactions has been characterized in terms of cross section and Q-value while the entropic term (T ΔS) has been neglected. Such an assumption is always justified for fission reactions where the term ΔS is positive. In the case of fusion reactions that operate at very high temperatures (10⁶–10⁷ K) and where ΔS is negative, the change in Gibbs free energy may be positive, making the reaction non-spontaneous. This paper proposes a classical thermodynamic analysis of D-based reactions of interest for the magnetic-confinement fusion applications. The entropy contribution was evaluated via the Sackur–Tetrode equation while the change in enthalpy was considered constant and as corresponding to the Q-value of the fusion reaction. The results of the thermodynamic analysis are compared with nuclear reaction feasibility criteria based on the reaction reactivity. The DT and D³He reactions show a high degree of spontaneity although the second one presents a lower reactivity. An increase in temperature could enhance the reactivity of the D³He reaction at the cost of decreasing its thermodynamic spontaneity. Both branches of the DD reaction are characterized by a much lower thermodynamic spontaneity than that of the DT and D³He reactions. Furthermore, at the temperature of their maximum cross section, the DD reactions exhibit a largely positive change in Gibbs free energy and, therefore, are not spontaneous. At the temperature of magnetic-confinement fusion machines (1.5 × 10⁸ K), among the D-based reactions studied, the DT one exhibits the highest degrees of spontaneity and reactivity. Full article

(This article belongs to the Special Issue Feature Papers in Hydrogen)

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10 pages, 2428 KiB

Open AccessArticle

Hydrogen Storage Mechanism in Sodium-Based Graphene Nanoflakes: A Density Functional Theory Study

by Hiroto Tachikawa, Heewon Yi, Tetsuji Iyama, Shuhei Yamasaki and Kazuhisa Azumi

Hydrogen 2022, 3(1), 43-52; https://doi.org/10.3390/hydrogen3010003 - 19 Jan 2022

Cited by 13 | Viewed by 3989

Abstract

Carbon materials, such as graphene nanoflakes, carbon nanotubes, and fullerene, can be widely used to store hydrogen, and doping these materials with lithium (Li) generally increases their H₂-storage densities. Unfortunately, Li is expensive; therefore, alternative metals are required to realize a [...] Read more.

Carbon materials, such as graphene nanoflakes, carbon nanotubes, and fullerene, can be widely used to store hydrogen, and doping these materials with lithium (Li) generally increases their H₂-storage densities. Unfortunately, Li is expensive; therefore, alternative metals are required to realize a hydrogen-based society. Sodium (Na) is an inexpensive element with chemical properties that are similar to those of lithium. In this study, we used density functional theory to systematically investigate how hydrogen molecules interact with Na-doped graphene nanoflakes. A graphene nanoflake (GR) was modeled by a large polycyclic aromatic hydrocarbon composed of 37 benzene rings, with GR-Na-(H₂)_n and GR-Na⁺-(H₂)_n (n = 0–12) clusters used as hydrogen storage systems. Data obtained for the Na system were compared with those of the Li system. The single-H₂ GR-Li and GR-Na systems (n = 1) exhibited binding energies (per H₂ molecule) of 3.83 and 2.72 kcal/mol, respectively, revealing that the Li system has a high hydrogen-storage ability. This relationship is reversed from n = 4 onwards; the Na systems exhibited larger or similar binding energies for n = 4–12 than the Li-systems. The present study strongly suggests that Na can be used as an alternative metal to Li in H₂-storage applications. The H₂-storage mechanism in the Na system is also discussed based on the calculated results. Full article

(This article belongs to the Special Issue Feature Papers in Hydrogen)

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15 pages, 7733 KiB

Open AccessArticle

Numerical Analysis for Hydrogen Flame Acceleration during a Severe Accident Initiated by SBLOCA in the APR1400 Containment

by Hyung-Seok Kang, Jongtae Kim and Seong-Wan Hong

Hydrogen 2022, 3(1), 28-42; https://doi.org/10.3390/hydrogen3010002 - 7 Jan 2022

Cited by 3 | Viewed by 2804

Abstract

We performed a hydrogen combustion analysis in the Advanced Power Reactor 1400 MWe (APR1400) containment during a severe accident initiated by a small break loss of coolant accident (SBLOCA) which occurred at a lower part of the cold leg using a multi-dimensional hydrogen [...] Read more.

We performed a hydrogen combustion analysis in the Advanced Power Reactor 1400 MWe (APR1400) containment during a severe accident initiated by a small break loss of coolant accident (SBLOCA) which occurred at a lower part of the cold leg using a multi-dimensional hydrogen analysis system (MHAS) to confirm the integrity of the APR1400 containment. The MHAS was developed by combining MAAP, GASFLOW, and COM3D to simulate hydrogen release, distribution and combustion in the containment of a nuclear power plant during the severe accidents in the containment of a nuclear power reactor. The calculated peak pressure due to the flame acceleration by the COM3D, using the GASFLOW results as an initial condition of the hydrogen distribution, was approximately 555 kPa, which is lower than the fracture pressure 1223 kPa of the APR1400 containment. To induce a higher peak pressure resulted from a strong flame acceleration in the containment, we intentionally assumed several things in developing an accident scenario of the SBLOCA. Therefore, we may judge that the integrity of the APR1400 containment can be maintained even though the hydrogen combustion occurs during the severe accident initiated by the SBLOCA. Full article

(This article belongs to the Special Issue Feature Papers in Hydrogen)

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27 pages, 6371 KiB

Open AccessArticle

Techno-Economic Analysis of a Process to Convert Methane to Olefins, Featuring a Combined Reformer via the Methanol Intermediate Product

by Abdulaziz Alturki

Hydrogen 2022, 3(1), 1-27; https://doi.org/10.3390/hydrogen3010001 - 30 Dec 2021

Cited by 1 | Viewed by 7632

Abstract

The substantial growth in shale-derived natural gas production in the US has caused significant changes in the chemical and petrochemical markets. Ethylene production of ethane and naphtha via steam cracking is one of the most energy- and emission-intensive activities in chemical manufacturing. High [...] Read more.

The substantial growth in shale-derived natural gas production in the US has caused significant changes in the chemical and petrochemical markets. Ethylene production of ethane and naphtha via steam cracking is one of the most energy- and emission-intensive activities in chemical manufacturing. High operating temperatures, high reaction endothermicity, and complex separation create high energy demands as well as considerable CO₂ emissions. In this study, a demonstration of a transformational methane-to-ethylene process that offers lower emissions using energy optimization and a CO₂ minimum-emission approach is presented. The comparisons of different reforming processes suggest that the dry reforming of methane has a negative carbon footprint at low syngas ratios of 1 and below, and that additional carbon emissions can be reduced using integrated heating and cooling utilities, resulting in a 99.24 percent decrease in CO₂. A process design implemented to convert methane into value-added chemicals with minimum CO₂ emissions is developed. Full article

(This article belongs to the Special Issue Feature Papers in Hydrogen)

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14 pages, 6232 KiB

Open AccessArticle

Hydrogen Diffusivity in Different Microstructures of 42CrMo4 Steel

by Atif Imdad, Alfredo Zafra, Victor Arniella and Javier Belzunce

Hydrogen 2021, 2(4), 414-427; https://doi.org/10.3390/hydrogen2040023 - 3 Nov 2021

Cited by 5 | Viewed by 4316

Abstract

It is well known that the presence of hydrogen decreases the mechanical properties of ferritic steels, giving rise to the phenomenon known as hydrogen embrittlement (HE). The sensitivity to HE increases with the strength of the steel due to the increase of its [...] Read more.

It is well known that the presence of hydrogen decreases the mechanical properties of ferritic steels, giving rise to the phenomenon known as hydrogen embrittlement (HE). The sensitivity to HE increases with the strength of the steel due to the increase of its microstructural defects (hydrogen traps), which eventually increase hydrogen solubility and decrease hydrogen diffusivity in the steel. The aim of this work is to study hydrogen diffusivity in a 42CrMo4 steel submitted to different heat treatments—annealing, normalizing and quench and tempering—to obtain different microstructures, with a broad range of hardness levels. Electrochemical hydrogen permeation tests were performed in a modified Devanathan and Stachursky double-cell. The build-up transient methodology allowed the determination of the apparent hydrogen diffusion coefficient, D_app, and assessment of its evolution during the progressive filling of the microstructural hydrogen traps. Consequently, the lattice hydrogen diffusion coefficient, D_L, was determined. Optical and scanning electron microscopy (SEM) were employed to examine the steel microstructures in order to understand their interaction with hydrogen atoms. In general, the results show that the permeation parameters are strongly related to the steel hardness, being less affected by the type of microstructure. Full article

(This article belongs to the Special Issue Feature Papers in Hydrogen)

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15 pages, 6165 KiB

Open AccessArticle

Hydrogen Sorption Properties of a Novel Refractory Ti-V-Zr-Nb-Mo High Entropy Alloy

by Anis Bouzidi, Laetitia Laversenne, Guilherme Zepon, Gavin Vaughan, Vivian Nassif and Claudia Zlotea

Hydrogen 2021, 2(4), 399-413; https://doi.org/10.3390/hydrogen2040022 - 27 Oct 2021

Cited by 14 | Viewed by 4333

Abstract

High entropy alloys belong to a new and promising class of functional materials for solid-state hydrogen storage. In this context, a novel single-phase body centered cubic (bcc) high entropy alloy Ti_0.30V_0.25Zr_0.10Nb_0.25Mo_0.10 was [...] Read more.

High entropy alloys belong to a new and promising class of functional materials for solid-state hydrogen storage. In this context, a novel single-phase body centered cubic (bcc) high entropy alloy Ti_0.30V_0.25Zr_0.10Nb_0.25Mo_0.10 was prepared. The physicochemical and hydrogen sorption properties have been determined by both laboratory and large-scale facilities. This alloy can quickly absorb hydrogen up to 2.0 H/M (2.8 wt.%) at room temperature and forms a face centered cubic (fcc) hydride, as proven by synchrotron X-ray diffraction. The Pressure–Composition Isotherm and in situ neutron diffraction during hydrogen/deuterium desorption reaction suggest that the alloy experiences a reversible single step phase transition (bcc↔fcc). PDF analysis from X-ray total scattering data points out that the hydride phase possesses an average fcc structure with random atoms distribution and small lattice distortion. Despite an initial small fading of the capacity, the alloy withstands 20 absorption/desorption cycling without phase decomposition, as demonstrated by kinetic measurements coupled with X-ray diffraction and microstructural study by SEM-EDS. Moreover, the complete hydrogen absorption occurs in less than 30 s at room temperature and the kinetic improves during cycling. Full article

(This article belongs to the Special Issue Feature Papers in Hydrogen)

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13 pages, 4715 KiB

Open AccessArticle

Performance of Hydrogen Storage Tanks of Type IV in a Fire: Effect of the State of Charge

by Sergii Kashkarov, Dmitriy Makarov and Vladimir Molkov

Hydrogen 2021, 2(4), 386-398; https://doi.org/10.3390/hydrogen2040021 - 23 Sep 2021

Cited by 10 | Viewed by 5923

Abstract

The use of hydrogen storage tanks at 100% of nominal working pressure (NWP) is expected only after refuelling. Driving between refuellings is characterised by the state of charge SoC <100%. There is experimental evidence that Type IV tanks tested in a fire at [...] Read more.

The use of hydrogen storage tanks at 100% of nominal working pressure (NWP) is expected only after refuelling. Driving between refuellings is characterised by the state of charge SoC <100%. There is experimental evidence that Type IV tanks tested in a fire at initial pressures below 1/3 NWP, leaked without rupture. This paper aims at understanding this phenomenon. The numerical research has demonstrated that the heat transfer from fire through the composite overwrap at storage pressures below NWP/3 is sufficient to melt the polymer liner. This melting initiates hydrogen microleaks through the composite before it loses the load-bearing ability. The fire-resistance rating (FRR) is defined as the time to rupture in a fire of a tank without or with blocked thermally activated pressure relief device. The dependence of a FRR on the SoC is demonstrated for the tanks with defined material properties and volumes in the range of 36–244 L. A composite wall thickness variation is shown to cause a safety issue by reducing the tank’s FRR and is suggested to be addressed by tank manufacturers and OEMs. The effect of a tank’s burst pressure ratio on the FRR is investigated. Thermal parameters of the composite wall, i.e., decomposition heat and temperatures, are shown in simulations of a tank failure in a fire to play an important role in its FRR. Full article

(This article belongs to the Special Issue Feature Papers in Hydrogen)

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9 pages, 2154 KiB

Open AccessArticle

Role of Ultrasonic Shot Peening in Environmental Hydrogen Embrittlement Behavior of 7075-T6 Alloy

by Mahdieh Safyari and Masoud Moshtaghi

Hydrogen 2021, 2(3), 377-385; https://doi.org/10.3390/hydrogen2030020 - 11 Sep 2021

Cited by 24 | Viewed by 3981

Abstract

The effect of ultrasonic shot peening on the environmental hydrogen embrittlement behavior of the 7075-T6 aluminum alloy is investigated. The 7075-T6 tensile specimens were treated by ultrasonic shot peening for 50 s. Surface residual stress and the depth of residual stress under the [...] Read more.

The effect of ultrasonic shot peening on the environmental hydrogen embrittlement behavior of the 7075-T6 aluminum alloy is investigated. The 7075-T6 tensile specimens were treated by ultrasonic shot peening for 50 s. Surface residual stress and the depth of residual stress under the surface were evaluated using an X-ray diffractometer. Then, the specimens were tensile tested in humid air and dry nitrogen gas by the slow strain rate technique. The results showed that the ultrasonic shot-peened specimen has a superior hydrogen embrittlement resistance. Further, the ultrasonic shot peening changes the fracture mode from an intergranular fracture mode to the transgranular one. It was suggested that ultrasonic shot-peening has two effects on hydrogen embrittlement behavior; the distribution of hydrogen inside the surface layer by introducing dislocations/vacancies as hydrogen traps and reducing the normalized amount of hydrogen trapped per unit length of the grain boundary. Full article

(This article belongs to the Special Issue Feature Papers in Hydrogen)

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16 pages, 2170 KiB

Open AccessArticle

Theoretical Prediction of the Efficiency of Hydrogen Production via Alkane Dehydrogenation in Catalytic Membrane Reactor

by Ekaterina V. Shelepova and Aleksey A. Vedyagin

Hydrogen 2021, 2(3), 362-376; https://doi.org/10.3390/hydrogen2030019 - 11 Sep 2021

Cited by 4 | Viewed by 3140

Abstract

The hydrogen economy is expected to dominate in the nearest future. Therefore, the most hydrogen-containing compounds are considered as potential pure hydrogen sources in order to achieve climate neutrality. On the other hand, alkanes are widely used to produce industrially important monomers via [...] Read more.

The hydrogen economy is expected to dominate in the nearest future. Therefore, the most hydrogen-containing compounds are considered as potential pure hydrogen sources in order to achieve climate neutrality. On the other hand, alkanes are widely used to produce industrially important monomers via various routes, including dehydrogenation processes. Hydrogen is being produced as a by-product of these processes, so the application of efficient separation of hydrogen from the reaction mixture can give double benefits. Implementation of the dehydrogenation processes in the catalytic membrane reactor is that case. Since the use of dense metal membranes, which possess the highest perm-selectivity towards hydrogen, is complicated in practice, the present research is aimed at the optimization of the porous membrane characteristics. By means of a mathematical modeling approach, the effects of pore diameter on the hydrogen productivity and purity for the cases of ethane and propane dehydrogenation processes were analyzed. The pore size value of 0.45 nm was found to be crucial as far as the diffusion of both the alkane and alkene molecules through the membrane takes place. Full article

(This article belongs to the Special Issue Feature Papers in Hydrogen)

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19 pages, 7030 KiB

Open AccessArticle

Hydrogen Jet Fire from a Thermally Activated Pressure Relief Device (TPRD) from Onboard Storage in a Naturally Ventilated Covered Car Park

by Harem Hussein, Síle Brennan and Vladimir Molkov

Hydrogen 2021, 2(3), 343-361; https://doi.org/10.3390/hydrogen2030018 - 17 Aug 2021

Cited by 16 | Viewed by 5958

Abstract

Hydrogen jet fires from a thermally activated pressure relief device (TPRD) on onboard storage are considered for a vehicle in a naturally ventilated covered car park. Computational Fluid Dynamics was used to predict behaviour of ignited releases from a 70 MPa tank into [...] Read more.

Hydrogen jet fires from a thermally activated pressure relief device (TPRD) on onboard storage are considered for a vehicle in a naturally ventilated covered car park. Computational Fluid Dynamics was used to predict behaviour of ignited releases from a 70 MPa tank into a naturally ventilated covered car park. Releases through TPRD diameters 3.34, 2 and 0.5 mm were studied to understand effect on hazard distances from the vehicle. A vertical release, and downward releases at 0°, 30° and 45° for TPRD diameters 2 and 0.5 mm were considered, accounting for tank blowdown. direction of a downward release was found to significantly contribute to decrease of temperature in a hot cloud under the ceiling. Whilst the ceiling is reached by a jet exceeding 300 °C for a release through a TPRD of 2 mm for inclinations of either 0°, 30° or 45°, an ignited release through a TPRD of 0.5 mm and angle of 45° did not produce a cloud with a temperature above 300 °C at the ceiling during blowdown. The research findings, specifically regarding the extent of the cloud of hot gasses, have implications for the design of mechanical ventilation systems. Full article

(This article belongs to the Special Issue Feature Papers in Hydrogen)

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18 pages, 521 KiB

Open AccessArticle

Aspects of Hydrogen and Biomethane Introduction in Natural Gas Infrastructure and Equipment

by Filipe M. Quintino, Nuno Nascimento and Edgar C. Fernandes

Hydrogen 2021, 2(3), 301-318; https://doi.org/10.3390/hydrogen2030016 - 10 Aug 2021

Cited by 40 | Viewed by 7328

Abstract

The injection of green hydrogen and biomethane is currently seen as the next step towards the decarbonization of the gas sector in several countries. However, the introduction of these gases in existent infrastructure has energetic, material and operational implications that should be carefully [...] Read more.

The injection of green hydrogen and biomethane is currently seen as the next step towards the decarbonization of the gas sector in several countries. However, the introduction of these gases in existent infrastructure has energetic, material and operational implications that should be carefully looked at. With regard to a fully blown green gas grid, transport and distribution will require adaptations. Furthermore, the adequate performance of end-use equipment connected to the grid must be accounted for. In this paper, a technical analysis of the energetic, material and operational aspects of hydrogen and biomethane introduction in natural gas infrastructure is performed. Impacts on gas transmission and distribution are evaluated and an interchangeability analysis, supported by one-dimensional Cantera simulations, is conducted. Existing gas infrastructure seems to be generally fit for the introduction of hydrogen and biomethane. Hydrogen content up to 20% by volume appears to be possible to accommodate in current infrastructure with only minor technical modifications. However, at the Distribution System Operator (DSO) level, the introduction of gas quality tracking systems will be required due to the distributed injection nature of hydrogen and biomethane. The different tolerances for hydrogen blending of consumers, depending on end-use equipment, may be critical during the transition period to a 100% green gas grid as there is a risk of pushing consumers off the grid. Full article

(This article belongs to the Special Issue Feature Papers in Hydrogen)

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28 pages, 1366 KiB

Open AccessArticle

The Key Techno-Economic and Manufacturing Drivers for Reducing the Cost of Power-to-Gas and a Hydrogen-Enabled Energy System

by George Bristowe and Andrew Smallbone

Hydrogen 2021, 2(3), 273-300; https://doi.org/10.3390/hydrogen2030015 - 27 Jul 2021

Cited by 37 | Viewed by 12607

Abstract

Water electrolysis is a process which converts electricity into hydrogen and is seen as a key technology in enabling a net-zero compatible energy system. It will enable the scale-up of renewable electricity as a primary energy source for heating, transport, and industry. However, [...] Read more.

Water electrolysis is a process which converts electricity into hydrogen and is seen as a key technology in enabling a net-zero compatible energy system. It will enable the scale-up of renewable electricity as a primary energy source for heating, transport, and industry. However, displacing the role currently met by fossil fuels might require a price of hydrogen as low as 1 $/kg, whereas renewable hydrogen produced using electrolysis is currently 10 $/kg. This article explores how mass manufacturing of proton exchange membrane (PEM) electrolysers can reduce the capital cost and, thus, make the production of renewable power to hydrogen gas (PtG) more economically viable. A bottom up direct manufacturing model was developed to determine how economies of scale can reduce the capital cost of electrolysis. The results demonstrated that (assuming an annual production rate of 5000 units of 200 kW PEM electrolysis systems) the capital cost of a PEM electrolysis system can reduce from 1990 $/kW to 590 $/kW based on current technology and then on to 431 $/kW and 300 $/kW based on the an installed capacity scale-up of ten- and one-hundred-fold, respectively. A life-cycle costing analysis was then completed to determine the importance of the capital cost of an electrolysis system to the price of hydrogen. It was observed that, based on current technology, mass manufacturing has a large impact on the price of hydrogen, reducing it from 6.40 $/kg (at 10 units units per year) to 4.16 $/kg (at 5000 units per year). Further analysis was undertaken to determine the cost at different installed capacities and found that the cost could reduce further to 2.63 $/kg and 1.37 $/kg, based on technology scale-up by ten- and one hundred-fold, respectively. Based on the 2030 (and beyond) baseline assumptions, it is expected that hydrogen production from PEM electrolysis could be used as an industrial process feed stock, provide power and heat to buildings and as a fuel for heavy good vehicles (HGVs). In the cases of retrofitted gas networks for residential or industrial heating solutions, or for long distance transport, it represents a more economically attractive and mass-scale compatible solution when compared to electrified heating or transport solutions. Full article

(This article belongs to the Special Issue Feature Papers in Hydrogen)

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11 pages, 1487 KiB

Open AccessArticle

Strength, Hardness, and Ductility Evidence of Solid Solution Strengthening and Limited Hydrogen Embrittlement in the Alloy System Palladium-Copper (Cu wt. % 5–25)

by Sebastian DiMauro, Gabrielle Legall, Coleman Lubinsky, Monica Nadeau, Renee Tait, William Miller, Abena Adutwum, Isabella Portal, Brandon Roy, Steve Nesbit and Andrew Craft

Hydrogen 2021, 2(3), 262-272; https://doi.org/10.3390/hydrogen2030014 - 16 Jul 2021

Cited by 2 | Viewed by 3525

Abstract

Strength, hardness, and ductility characteristics were determined for a series of palladium-copper alloys that compositionally vary from 5 to 25 weight percent copper. Alloy specimens subjected to vacuum annealing showed clear evidence of solid solution strengthening. These specimens showed, as a function of [...] Read more.

Strength, hardness, and ductility characteristics were determined for a series of palladium-copper alloys that compositionally vary from 5 to 25 weight percent copper. Alloy specimens subjected to vacuum annealing showed clear evidence of solid solution strengthening. These specimens showed, as a function of increasing copper content, increased yield strength, ultimate strength, and Vickers microhardness, while their ductility was little affected by compositional differences. Annealed alloy specimens subsequently subjected to exposure to hydrogen at 323 K and P_H2 = 1 atm showed evidence of hydrogen embrittlement up to a composition of ~15 wt. % Cu. The magnitude of the hydrogen embrittlement decreased with increasing copper content in the alloy. Full article

(This article belongs to the Special Issue Feature Papers in Hydrogen)

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Review

Jump to: Research

37 pages, 6420 KiB

Open AccessReview

Nanoengineering of Catalysts for Enhanced Hydrogen Production

by Jhonatan Luiz Fiorio, Maitê Lippel Gothe, Emerson Cristofer Kohlrausch, Maria Luísa Zardo, Auro Atsushi Tanaka, Roberto Batista de Lima, Anderson Gabriel Marques da Silva, Marco Aurélio Suller Garcia, Pedro Vidinha and Giovanna Machado

Hydrogen 2022, 3(2), 218-254; https://doi.org/10.3390/hydrogen3020014 - 23 May 2022

Cited by 17 | Viewed by 7043

Abstract

Hydrogen (H₂) has emerged as a sustainable energy carrier capable of replacing/complementing the global carbon-based energy matrix. Although studies in this area have often focused on the fundamental understanding of catalytic processes and the demonstration of their activities towards different strategies, [...] Read more.

Hydrogen (H₂) has emerged as a sustainable energy carrier capable of replacing/complementing the global carbon-based energy matrix. Although studies in this area have often focused on the fundamental understanding of catalytic processes and the demonstration of their activities towards different strategies, much effort is still needed to develop high-performance technologies and advanced materials to accomplish widespread utilization. The main goal of this review is to discuss the recent contributions in the H₂ production field by employing nanomaterials with well-defined and controllable physicochemical features. Nanoengineering approaches at the sub-nano or atomic scale are especially interesting, as they allow us to unravel how activity varies as a function of these parameters (shape, size, composition, structure, electronic, and support interaction) and obtain insights into structure–performance relationships in the field of H₂ production, allowing not only the optimization of performances but also enabling the rational design of nanocatalysts with desired activities and selectivity for H₂ production. Herein, we start with a brief description of preparing such materials, emphasizing the importance of accomplishing the physicochemical control of nanostructures. The review finally culminates in the leading technologies for H₂ production, identifying the promising applications of controlled nanomaterials. Full article

(This article belongs to the Special Issue Feature Papers in Hydrogen)

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17 pages, 935 KiB

Open AccessReview

Molecular Hydrogen as Medicine: An Assessment of Administration Methods

by Grace Russell, Alexander Nenov, Hesham Kisher and John T. Hancock

Hydrogen 2021, 2(4), 444-460; https://doi.org/10.3390/hydrogen2040025 - 25 Nov 2021

Cited by 14 | Viewed by 16023

Abstract

Since the late 18th century, molecular hydrogen (H₂) has been shown to be well tolerated, firstly in animals, and then in humans. However, although research into the beneficial effects of molecular hydrogen in both plant and mammalian physiology is gaining momentum, [...] Read more.

Since the late 18th century, molecular hydrogen (H₂) has been shown to be well tolerated, firstly in animals, and then in humans. However, although research into the beneficial effects of molecular hydrogen in both plant and mammalian physiology is gaining momentum, the idea of utilising this electrochemically neutral and non-polar diatomic compound for the benefit of health has yet to be widely accepted by regulatory bodies worldwide. Due to the precise mechanisms of H₂ activity being as yet undefined, the lack of primary target identification, coupled with difficulties regarding administration methods (e.g., dosage and dosage frequencies, long-term effects of treatment, and the patient’s innate antioxidant profile), there is a requirement for H₂ research to evidence how it can reasonably and most effectively be incorporated into medical practice. This review collates and assesses the current information regarding the many routes of molecular hydrogen administration in animals and humans, whilst evaluating how targeted delivery methods could be integrated into a modern healthcare system. Full article

(This article belongs to the Special Issue Feature Papers in Hydrogen)

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16 pages, 2081 KiB

Open AccessReview

Solid-State Hydrogen Storage for a Decarbonized Society

by Claudio Pistidda

Hydrogen 2021, 2(4), 428-443; https://doi.org/10.3390/hydrogen2040024 - 20 Nov 2021

Cited by 35 | Viewed by 6865

Abstract

Humanity is confronted with one of the most significant challenges in its history. The excessive use of fossil fuel energy sources is causing extreme climate change, which threatens our way of life and poses huge social and technological problems. It is imperative to [...] Read more.

Humanity is confronted with one of the most significant challenges in its history. The excessive use of fossil fuel energy sources is causing extreme climate change, which threatens our way of life and poses huge social and technological problems. It is imperative to look for alternate energy sources that can replace environmentally destructive fossil fuels. In this scenario, hydrogen is seen as a potential energy vector capable of enabling the better and synergic exploitation of renewable energy sources. A brief review of the use of hydrogen as a tool for decarbonizing our society is given in this work. Special emphasis is placed on the possibility of storing hydrogen in solid-state form (in hydride species), on the potential fields of application of solid-state hydrogen storage, and on the technological challenges solid-state hydrogen storage faces. A potential approach to reduce the carbon footprint of hydrogen storage materials is presented in the concluding section of this paper. Full article

(This article belongs to the Special Issue Feature Papers in Hydrogen)

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24 pages, 1763 KiB

Open AccessReview

Hydrogen Sulfide: A Robust Combatant against Abiotic Stresses in Plants

by Kanika Khanna, Nandni Sharma, Sandeep Kour, Mohd. Ali, Puja Ohri and Renu Bhardwaj

Hydrogen 2021, 2(3), 319-342; https://doi.org/10.3390/hydrogen2030017 - 11 Aug 2021

Cited by 14 | Viewed by 5306

Abstract

Hydrogen sulfide (H₂S) is predominantly considered as a gaseous transmitter or signaling molecule in plants. It has been known as a crucial player during various plant cellular and physiological processes and has been gaining unprecedented attention from researchers since decades. They [...] Read more.

Hydrogen sulfide (H₂S) is predominantly considered as a gaseous transmitter or signaling molecule in plants. It has been known as a crucial player during various plant cellular and physiological processes and has been gaining unprecedented attention from researchers since decades. They regulate growth and plethora of plant developmental processes such as germination, senescence, defense, and maturation in plants. Owing to its gaseous state, they are effectively diffused towards different parts of the cell to counterbalance the antioxidant pools as well as providing sulfur to cells. H₂S participates actively during abiotic stresses and enhances plant tolerance towards adverse conditions by regulation of the antioxidative defense system, oxidative stress signaling, metal transport, Na⁺/K⁺ homeostasis, etc. They also maintain H₂S-Cys-cycle during abiotic stressed conditions followed by post-translational modifications of cysteine residues. Besides their role during abiotic stresses, crosstalk of H₂S with other biomolecules such as NO and phytohormones (abscisic acid, salicylic acid, melatonin, ethylene, etc.) have also been explored in plant signaling. These processes also mediate protein post-translational modifications of cysteine residues. We have mainly highlighted all these biological functions along with proposing novel relevant issues that are required to be addressed further in the near future. Moreover, we have also proposed the possible mechanisms of H₂S actions in mediating redox-dependent mechanisms in plant physiology. Full article

(This article belongs to the Special Issue Feature Papers in Hydrogen)

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