On-board Hydrogen Storage Research Articles

Kinetic Enhancement of Direct Hydrogenation of MgB2 to Mg(BH4 )2 upon Mechanical Milling with THF, MgH2 , and/or Mg.

Modification of magnesium diboride, MgB2 , by mechanical milling with THF, MgH2 , and/or Mg results in a lowering of the conditions required for its direct, bulk hydrogenation to magnesium borohydride, Mg(BH4 )2 , by 300 bar and 100 °C. Following mechanical milling with MgH2 or THF and Mg, MgB2 can be hydrogenated to Mg(BH4 )2 at 300 °C under 700 bar of H2 while achieving ∼54-71 % conversion to the borohydride. The discovery of a means of dramatically lowering the conditions required for the hydrogenation of MgB2 is an important step towards the development of a practical onboard hydrogen storage system based on hydrogen cycling between Mg(BH4 )2 and MgB2 . We suggest that mechano-milling with THF, Mg, and/or MgH2 may possibly introduce defects in the MgB2 structure which enhance hydrogenation. The ability to activate the MgB2 through the introduction of structural defects transcends its relevance to hydrogen storage, as a method of overcoming its chemical inertness provides the key to harnessing other interesting properties of this material.

Computer-aided prediction of structure and hydrogen storage properties of tetrakis(4-aminophenyl)silsesquioxane based covalent-organic frameworks

With the aid of computer simulation, we have designed four covalent-organic frameworks based on tetrakis(4-aminophenyl)silsesquioxane (taps-COFs) and their hydrogen storage properties were predicted with grand canonical Monte Carlo (GCMC) simulation. The structural parameters and physical properties were investigated after the geometrical optimization. The accessible surface for H2 molecule (5564.68–6754.78 m2/g) were estimated using the numerical Monte Carlo integration and the pore volume (4.06–10.74 cm3/g) was evaluated by the amounts of the containable nonadsorbing helium molecules at low pressures and room temperature. GCMC simulation reveals that at 77 K, tapsCOF1 has the highest gravimetric H2 adsorption capacity of 51.43 wt% and tapsCOF3 possesses the highest volumetric H2 adsorption capacity of 58.51 g/L. Excitedly, at room temperature of 298 K, the gravimetric hydrogen adsorption capacities of tapsCOF1 (8.58 wt%) and tapsCOF2 (8.20 wt%) have exceeded the target (5.5 wt%) of onboard hydrogen storage system for 2025 set by the U.S Department of Energy.

GASTEF: The high pressure gas tank testing facility of the European commission joint research centre

This article portrays the European Commission's High Pressure Gas Tank Testing Facility (GasTeF), which is located at the Joint Research Centre in Petten (the Netherlands). GasTeF is one of the few facilities in Europe where research is conducted on on-board compressed hydrogen storage systems. The GasTeF facility is designed to carry out pneumatic hydrogen cycle and permeation tests according to the procedures prescribed by type approval regulations. GasTeF is as well suited for performing experiments replicating the refuelling of on-board hydrogen tanks also simulating out-of-specification operating conditions of a hydrogen fuelling station. With this research, the Gas Tank Testing Facility supports JRC's mission to provide policy makers and stakeholders with independent assessments of hydrogen technologies in terms of performance efficiency, safety and reliability.

Application of hydrides in hydrogen storage and compression: Achievements, outlook and perspectives

Metal hydrides are known as a potential efficient, low-risk option for high-density hydrogen storage since the late 1970s. In this paper, the present status and the future perspectives of the use of metal hydrides for hydrogen storage are discussed. Since the early 1990s, interstitial metal hydrides are known as base materials for Ni – metal hydride rechargeable batteries. For hydrogen storage, metal hydride systems have been developed in the 2010s [1] for use in emergency or backup power units, i. e. for stationary applications.With the development and completion of the first submarines of the U212 A series by HDW (now Thyssen Krupp Marine Systems) in 2003 and its export class U214 in 2004, the use of metal hydrides for hydrogen storage in mobile applications has been established, with new application fields coming into focus.In the last decades, a huge number of new intermetallic and partially covalent hydrogen absorbing compounds has been identified and partly more, partly less extensively characterized.In addition, based on the thermodynamic properties of metal hydrides, this class of materials gives the opportunity to develop a new hydrogen compression technology. They allow the direct conversion from thermal energy into the compression of hydrogen gas without the need of any moving parts. Such compressors have been developed and are nowadays commercially available for pressures up to 200 bar. Metal hydride based compressors for higher pressures are under development. Moreover, storage systems consisting of the combination of metal hydrides and high-pressure vessels have been proposed as a realistic solution for on-board hydrogen storage on fuel cell vehicles.In the frame of the “Hydrogen Storage Systems for Mobile and Stationary Applications” Group in the International Energy Agency (IEA) Hydrogen Task 32 “Hydrogen-based energy storage”, different compounds have been and will be scaled-up in the near future and tested in the range of 500 g to several hundred kg for use in hydrogen storage applications.

Heat transfer analysis for fast filling of on-board hydrogen tank

The heat transfer analysis in the filling process of compressed on-board hydrogen storage tank has been the focus of hydrogen storage research. The initial conditions, mass flow rate and heat transfer coefficient have certain influence on the hydrogen filling performance. In this paper, the effects of mass flow rate and heat transfer coefficient on hydrogen filling performance are mainly studied. A thermodynamic model of the compressed hydrogen storage tank was established by Matlab/Simulink. This 0D model is utilized to predict the hydrogen temperature, hydrogen pressure, tank wall temperature and SOC (State of Charge) during filling process. Comparing the simulated results with the experimental data, the practicability of the model can be verified. The simulated results have certain meaning for improving the hydrogenation parameters in real filling process. And the model has a great significance to the study of hydrogen filling and purification.

Study on reversible hydrogen uptake and release of 1,2-dimethylindole as a new liquid organic hydrogen carrier

Indole derivatives have been considered as promising liquid organic hydrogen carriers (LOHCs) for onboard hydrogen storage applications. Here a new member of indole family, 1,2-dimethylindole (1,2-DMID), was reported as a potential liquid organic hydrogen carrier with a hydrogen storage content of 5.23 wt%, a meting point of 55 °C and a boiling point of 260 °C. Full hydrogenation and dehydrogenation of 1,2-DMID can be achieved with fast kinetics under mild conditions. The hydrogenation of 1,2-DMID followed the first order kinetics with an apparent activation energy of 85.1 kJ/mol. Dehydrogenation of fully hydrogenated product, octahydro-1,2-DMID was conducted over 5 wt% Pd/Al2O3 at 170–200 °C. The stored hydrogen can be completely released at 180 °C in 3 h and at 200 °C in 1 h. The energy barrier of dehydrogenation of octahydro-1,2-DMID was calculated to be 111.9 kJ/mol 3 times cycles of hydrogenation and dehydrogenation were employed to test the recycle ability of 1,2-DMID. The structures of intermediates were also discussed by means of Material Studio calculations.

Physical model of onboard hydrogen storage tank thermal behaviour during fuelling

A physical model to simulate thermal behaviour of an onboard storage tank and parameters of hydrogen inside the tank during fuelling is described. The energy conservation equation, Abel-Noble real gas equation of state, and the entrainment theory are applied to calculate the dynamics of hydrogen temperature inside the tank and distribution of temperature through the wall to satisfy requirements of the regulation. Convective heat transfer between hydrogen, tank wall and the atmosphere are modelled using Nusselt number correlations. An original methodology, based on the entrainment theory, is developed to calculate changing velocity of the gas inside the tank during the fuelling. Conductive heat transfer through the tank wall, composed of a load-bearing carbon fibre reinforced polymer and a liner, is modelled by employing one-dimensional unsteady heat transfer equation. The model is validated against experiments on fuelling of Type III and Type IV tanks for hydrogen onboard storage. Hydrogen temperature dynamics inside a tank is simulated by the model within the experimental non-uniformity of 5 °C. The calculation procedure is time efficient and can be used for the development of automated hydrogen fuelling protocols and systems.

Reversible Hydrogen Uptake/Release over a Sodium Phenoxide-Cyclohexanolate Pair.

Hydrogen uptake and release in arene-cycloalkane pairs provide an attractive opportunity for on-board and off-board hydrogen storage. However, the efficiency of arene-cycloalkane pairs currently is limited by unfavorable thermodynamics for hydrogen release. It is shown here that the thermodynamics can be optimized by replacement of H in the -OH group of cyclohexanol and phenol with alkali or alkaline earth metals. The enthalpy change upon dehydrogenation decreases substantially, which correlates with the delocalization of the oxygen electron to the benzene ring in phenoxides. Theoretical calculations reveal that replacement of H with a metal leads to a reduction of the HOMO-LUMO energy gap and elongation of the C-H bond in the α site in cyclohexanolate, which indicates that the cyclohexanol is activated upon metal substitution. The experimental results demonstrate that sodium phenoxide-cyclohexanolate, an air- and water-stable pair, can desorb hydrogen at ca. 413 K and 373 K in the solid form and in an aqueous solution, respectively. Hydrogenation, on the other hand, is accomplished at temperatures as low as 303 K.

Enhanced hydrogen storage properties and mechanisms of magnesium hydride modified by transition metal dissolved magnesium oxides

Magnesium hydride (MgH2) is a promising on-board hydrogen storage material due to its high capacity, low cost and abundant Mg resources. Nevertheless, the practical application of MgH2 is hindered by its poor dehydrogenation ability and cycling stability. Herein, the influences and mechanisms of thin pristine magnesium oxide (MgO) and transition metals (TM) dissolved Mg(TM)O layers (TM = Ti, V, Nb, Fe, Co, Ni) on hydrogen desorption and reversible cycling properties of MgH2 were investigated using first-principles calculations method. The results demonstrate that either thin pristine MgO or Mg(TM)O layer weakens the MgH bond strength, leading to the decreased structural stability and hydrogen desorption energy of MgH2. Among them, the Mg(Nb)O layer exhibits the most pronounced destabilization effect on MgH2. Moreover, the Mg(Nb)O layer presents a long-acting confinement effect on MgH2 due to the stronger interfacial bonding strength of Mg(Nb)O/MgH2 and the lower brittleness of Mg(Nb)O itself. Further analyses of electronic structures indicate that these thin oxide layers coating on MgH2 surface reduce the bonding electron number of MgH2, which essentially accounts for the weakened MgH bond strength and enhanced hydrogen desorption properties of modified MgH2 systems. These findings provide a new avenue for enhancing the hydrogen desorption and reversible cycling properties of MgH2 by designing and adding suitable MgO based oxides with high catalytic activity and low brittleness.

The theoretical study of the bimetallic Ni/Pd, Ni/Pt and Pt/Pd catalysts for hydrogen spillover on penta-graphene

The catalytic property of the bimetallic Ni/Pd, Ni/Pt and Pt/Pd particles for hydrogen spillover on penta-graphene (PG) are studied by using the first-principles and kinetic Monte Carlo (KMC) calculations. The bimetallic Ni/Pd, Ni/Pt and Pt/Pd particles can be stably decorated on PG surface with binding energies in the range of 4.15–5.52 eV. The adsorption enthalpies of H2 molecules on bimetallic particles are in the range of −11.56–−15.35 kcal/mol. The H atom can migrate from the bimetallic particles to PG with the migration barriers range from 0.67 to 0.95 eV. The KMC simulations show that the hydrogen spillover reactions can occur at a suitable temperature (260–361 K), which meet DOE target for onboard hydrogen storage systems applied to light-duty vehicles. In the study, the highest occupied molecular orbital and electric field analysis shows that the bimetal mixing can reduce the hydrogen adsorption enthalpy, and thereby reduce the H migration barrier, which displays a synergistic effect for hydrogen spillover.

Numerical validation of pressure peaking from an ignited hydrogen release in a laboratory-scale enclosure and application to a garage scenario

This work focuses on the overpressures arising from the rapid ignited release of hydrogen in an enclosure, specifically the peak in overpressure that may result in the initial period of the release, dependent on the level of ventilation. Two volumes are considered: a 1 m3 laboratory scale enclosure for which experimental data exists, and a real scale residential garage. Various vent configurations are considered for each scenario for leak rates typical of those from a fuel cell (laboratory scale enclosure) and from onboard hydrogen storage tanks through a thermally activated pressure relief device (TPRD) in the garage-like enclosure. A validation study has been performed for the laboratory scale enclosure and the modelling approach which gives optimum results has been identified. The influence of heat transfer on the pressure peak has been highlighted, particularly, the importance of radiation in predicting the pressure peak. The validated modelling approach has been applied to a range of experiments and garage scenarios. Both the laboratory and real scale simulations demonstrate the complex relationship between vent size and release rate and indicate the significant overpressures that can result through pressure peaking following an ignited release in an enclosure. The magnitude of the pressure peak as a result of an ignited release has been found to be two orders of magnitude greater than that for the corresponding unignited release. The work indicates that TPRDs currently available for hydrogen-powered vehicles may result in a dangerous situation for the specific scenario considered which should be accounted for in regulations, codes and standards. The application of this work extends beyond TPRDs and is relevant where there is a rapid, ignited release of hydrogen in an enclosure with ventilation.

Pressure effects of an ignited release from onboard storage in a garage with a single vent

A numerical study has been performed comparing the hazards, in particular overpressures, arising from the sustained unignited and ignited release from an onboard hydrogen storage tank at 700 bar through a 3.34 mm diameter orifice, representing a thermally activated pressure relief device (TPRD) in a small garage with a single vent equivalent in area to small window. It has been demonstrated how the overpressure predicted in the case of an unignited release using both CFD and an analytical model is in the region of 0.55 kPa and thus unlikely to cause structural damage. However, the overpressure predicted for the ignited release is two orders of magnitude greater, reaching over 55 kPA in less than 1 s and thus potentially causing destruction of the structure.It has been shown that whilst the overpressures resulting from the unignited release are unlikely to cause harm, the garage is engulfed by a flammable atmosphere in less than 1 s and the oxygen is depleted to levels dangerous to people within this time. In the case of the ignited release, whilst the resultant overpressures are the primary safety concern, it has been shown how the thermal effects resulting from the release extend almost 9 m from the jet in 1.5 s.

Energy Science & Engineering: Looking ahead

Professor Yun Hang Hu, Editor-in-Chief It is my pleasure to have the honor of succeeding Tomas Kaberger as Editor-in-Chief of Energy Science & Engineering. Under Tomas's guidance, the effort of editorial board members and journal staff, and the contribution of all authors, ESE has become a leading open access energy journal in the world. It received an Impact Factor of 3.553 in the 2018 release of the Journal Citations Reports® from Thomson Reuters. Providing sufficient energy to meet the requirements of a growing population with rising living standards is a critical challenge of the 21st century. Our current major source of energy comes from fossil fuels, including oil, coal, and natural gas, which are associated with two issues: the insufficient source for use and the climate change caused by CO2 emission. Technological innovation is expected to play a critical role in facilitating the transition to low-carbon and renewable energies. Several technologies have been developed for sequestration of CO2, such as oceanic injection, geological injection, and scrubbing and mineral carbonation. However, their intrinsic issues would limit their applications. For example, although injection of a pure CO2 stream deep in the ocean is widely considered by engineers, CO2 injection may have some negative effects on deep sea biota. Industrial CO2 can also be injected into deep geological strata. The cost and leakage are its principal issues. For those reasons, the utilization of CO2 is being considered as a more attractive solution to solve CO2 issues. Solar cells provide an efficient technology to convert solar energy into electricity. However, the cost of electricity produced from commercial silicon photovoltaics is several times higher than that produced from fossil fuels, generating a prohibition for widespread adaptation of solar energy. Therefore, low-cost solar cells are necessary, but the efficiency of lower cost solar cells (such as ones based on polymers or quantum dots) started low, and climbed slowly to reach about 10%. In contrast, perovskite solar cells (PSC) have quickly achieved a high efficiency over 20% in 5 years. It is a high expectation that PSCs will be commercialized in near future. Hydrogen is being considered as a promising clean fuel for future transportation, which requires innovative technologies to produce, store, and utilize hydrogen. It is ideal to use solar energy for hydrogen production from water, which requires a breakthrough for the photocatalytic process with over 10% energy conversion efficiency. Developing efficient on-board hydrogen storage technology with high reversible capacity at low cost is still a challenge for hydrogen vehicles. Fuel cells are important devices for hydrogen utilizations. However, more efficient electrode materials are necessary to increase their efficiencies and reduce their cost. Batteries, such as ion rechargeable batteries, are the most important type of energy storage technologies widely used in portable electrical devices and electrical vehicles. However, their long recharging time and small capacity need to be improved. Other types of renewable energies are also attracting attentions. For example, wind energy has been experiencing dramatic cost reduction, but it still suffers some issues (such as low-energy density and intermittency). Technical Innovations to solve the energy issues require global collaborations between scientists and engineers. ESE aims to facilitate the collaborations and spark innovations in energy research and development by publishing high-quality research papers, which are accessible to a broad readership. With my experience of the journal as an editorial board member, a reader, an author, and a reviewer, I am delighted to now be assuming the role of Editor-in-Chief. My vision for ESE is not only to retain the leading position among open access energy journals but also to become a very high impact journal. We will take steps to reduce the time from manuscript submission to acceptance, to increase further the impact factor of the journal, and to produce special issues for increasing exposure of articles on common themes. I would like to again acknowledge Tomas Kaberger, editorial board members, and journal staff, for their diligent work over 5 years to make ESE the important journal. I also appreciate the support from Wiley and SCI (Society of Chemical Industry). Without doubt, the future of ESE is really in your hands as our readers, authors, and reviewers. We look forward to receiving and publishing your high-quality manuscripts.

Supercritical cryo-compressed hydrogen storage for fuel cell electric buses

Liquid hydrogen (LH2) truck delivery and storage at dispensing sites is likely to play an important role in an emerging H2 infrastructure. We analyzed the performance of single phase, supercritical, on-board cryo-compressed hydrogen storage (CcH2) with commercially-available LH2 pump enabled single-flow refueling for application to fuel cell electric buses (FCEB). We conducted finite-element stress analyses of Type 3 CcH2 tanks using ABAQUS for carbon fiber requirement and Fe-Safe for fatigue life. The results from these analyses indicate that, from the standpoint of weight, volume and cost, 2-mm 316 stainless steel liner is preferred to aluminium 6061 alloy in meeting the required 15,000 charge-discharge cycles for 350–700 bar storage pressures. Compared to the Type 3, 350 bar, ambient-temperature H2 storage systems in current demonstration FCEBs, 500-bar CcH2 storage system is projected to achieve 91% improvement in gravimetric capacity, 175% improvement in volumetric capacity, 46% reduction in carbon fiber composite mass, and 21% lower system cost, while exceeding >7 day loss-free dormancy with initially 85%-full H2 tank.

Study of hydrogenation and dehydrogenation of 1-methylindole for reversible onboard hydrogen storage application

Abstracts We report a new candidate of liquid organic hydrogen carrier, 1-methylindole, with a hydrogen content of 5.76 wt% and a low melting point of below −20 °C. The hydrogenation of 1-methylindole and the dehydrogenation of octahydro-1-methylindole were investigated in details. Full hydrogenation of 1-methylindole was realized over a 5 wt% Ru/Al2O3 catalyst at 130 °C and 6.0 MPa, and both conversion and selectivity of 100% towards octahydro-1-methylindole were achieved. The catalytic dehydrogenation of octahydro-1-methylindole was carried out over a 5 wt% Pd/Al2O3 catalyst. By using a combined experimental and density functional theory approach, the mechanism of octahydro-1-methylindole dehydrogenation to 1-methylindole and the two stable isomers of octahydro-1-methylindole were analyzed. The effect of reaction temperature and dosage of catalyst on the hydrogen release content were systematically studied. In addition, the dehydrogenation of octahydro-1-methylindole at 160–190 °C on Pd/Al2O3 was well described by a first-order stepwise dehydrogenation reaction with the apparent activation energy of 122.99 kJ/mol. The purity of released H2 was higher than 99.99% with no detectable impurity.

Risk assessment methodology for onboard hydrogen storage

A quantitative risk assessment of onboard hydrogen-powered vehicle storage, exposed to a fire, is performed. The risk is defined twofold as a cost of human life per vehicle fire, and annual fatality rate per vehicle. The increase of fire resistance rating of the storage tank is demonstrated to drastically reduce the risk to acceptable level. Hazard distances are calculated by validated engineering tools for blast wave and fireball, which follow catastrophic tank rupture in a fire, act in all directions and have larger hazard distances compared to jet fire. The fatality cash value, probabilities of vehicle fire and failure of thermally activated pressure relief device are taken from published sources. A vulnerability probit function is employed to calculate probability of emergency operations' failure to control fire and prevent tank rupture. The risk is presented as a function of fire resistance rating of onboard storage.

Nanomechanics and modelling of hydrogen stored carbon nanotubes under compression for PEM fuel cell applications

Compressive strength of single walled carbon nanotubes (SWCNTs) filled with hydrogen molecules is analysed in this work utilising molecular dynamics simulation. Understanding mechanical characteristics of SWCNTs with hydrogen interactions are urgently important for providing solid groundwork to design robust and effective on-board hydrogen storage systems for proton exchange membrane fuel cell (PEMFC). This study analyses impact of SWNCTs’ geometry, weight percentage of hydrogen storage, temperature variation and vacancy defects. It is obtained that effect of hydrogen storage increases compressive resistance of SWCNTs. Furthermore, temperature increase and presence of defects negatively impacts compressive strength of SWCNTs. The compressive resistance of hydrogen stored SWCNTs were also found to depend on inter-molecular spacing of hydrogen molecules. It is expected that this work could provide important fundamentals in understanding mechanical behaviour of hydrogen stored SWNCTs subjected to compression that could assist in the development of effective on-board hydrogen storage systems for fuel cells.

Validation of the Localized Fire Test Method for On-board Hydrogen Storage Systems

Validation of the Localized Fire Test Method for On-board Hydrogen Storage Systems

Pt4, Pd4, Ni4, and Ti4 catalyzed hydrogen spillover on penta-graphene for hydrogen storage: The first-principles and kinetic Monte Carlo study

Penta-graphene is a new 2D allotrope of carbon exclusively consists of pentagons in a planar sheet geometry. In this work, we explored that if it can be a substrate for hydrogen spillover. The density-functional theory (DFT) studies show that the H atom can stably adsorb on sp2 carbons. The saturation hydrogen storage density of penta-graphene is estimated to be 5.3 wt%. The Pt4, Pd4 Ni4, and Ti4 clusters are used as the catalyst for hydrogen spillover, and the migration barriers are 1.25, 1.07, 1.03 and 1.35 eV, respectively. The kinetic Monte Carlo simulations are performed to study the migration process for massive H atoms. The results show that the optimal reaction temperatures are 467, 405, 390, and 504 K for Pt4, Pd4, Ni4, and Ti4 catalyst, respectively. For Pd4 and Ni4 catalysts, the spillover reaction can occur at the appropriate temperature (355 and 340 K, respectively) for onboard hydrogen storage systems applied to light-duty vehicles.

Hydrogen Storage Technologies for Future Energy Systems.

Future energy systems will be determined by the increasing relevance of solar and wind energy. Crude oil and gas prices are expected to increase in the long run, and penalties for CO2 emissions will become a relevant economic factor. Solar- and wind-powered electricity will become significantly cheaper, such that hydrogen produced from electrolysis will be competitively priced against hydrogen manufactured from natural gas. However, to handle the unsteadiness of system input from fluctuating energy sources, energy storage technologies that cover the full scale of power (in megawatts) and energy storage amounts (in megawatt hours) are required. Hydrogen, in particular, is a promising secondary energy vector for storing, transporting, and distributing large and very large amounts of energy at the gigawatt-hour and terawatt-hour scales. However, we also discuss energy storage at the 120-200-kWh scale, for example, for onboard hydrogen storage in fuel cell vehicles using compressed hydrogen storage. This article focuses on the characteristics and development potential of hydrogen storage technologies in light of such a changing energy system and its related challenges. Technological factors that influence the dynamics, flexibility, and operating costs of unsteady operation are therefore highlighted in particular. Moreover, the potential for using renewable hydrogen in the mobility sector, industrial production, and the heat market is discussed, as this potential may determine to a significant extent the future economic value of hydrogen storage technology as it applies to other industries. This evaluation elucidates known and well-established options for hydrogen storage and may guide the development and direction of newer, less developed technologies.