Metal Hydride Alloys Research Articles

Metal Hydride Storage Systems: Approaches to Improve Their Performances

AbstractMetal hydrides provide a safe and efficient way to store hydrogen. However, current metal hydride storage systems, i.e., hydrides incorporated within a storage tank, are far from efficient. Depending on the design, (dis)charging rates may be very long. However, this can be significantly improved by implementing strategies tackling the issue of heat management at the level of: i) the metal hydride bed, and ii) the overall storage system design. This review summarises recent progress in tackling heat management of hydride systems. In this respect, modeling has emerged as a powerful tool. In particular, simulation results show that the compaction of hydride powders with binders and the use of metal foams are both effective in lifting the poor thermal conductivity of hydride beds. For tank designs, cylindrical shapes remain the preferred choice because of the flexibility and ease of supplementing heat management with fins and tubular heat exchangers. The addition of phase change materials to the hydride tank can lead to further heat storage, but any add‐on to simple hydride tanks can only lead to cumbersome systems. It is still a fine art to tune the thermal conductivity of hydride beds while selecting a suitable metal hydride alloy composition.

Zirconium-Modified Medium-Entropy Alloy (TiVNb)85Cr15 for Hydrogen Storage.

In this study, we investigate the effect of small amounts of zirconium alloying the medium-entropy alloy (TiVNb)85Cr15, a promising material for hydrogen storage. Alloys with 1, 4, and 7 at.% of Zr were prepared by arc melting and found to be multiphase, comprising at least three phases, indicating that Zr addition does not stabilize a single-phase solid solution. The dominant BCC phase (HEA1) is the primary hydrogen absorber, while the minor phases HEA2 and HEA3 play a crucial role in hydrogen absorption/desorption. Among the studied alloys, Zr4 (TiVNb)81Cr15Zr4 shows the highest hydrogen storage capacity, ease of activation, and reversibly retrievable hydrogen. This alloy can absorb hydrogen at room temperature without additional processing, with a reversible capacity of up to 0.74 wt.%, corresponding to hydrogen-to-metal ratio H/M = 0.46. The study emphasizes the significant role of minor elemental additions in alloy properties, stressing the importance of tailored compositions for hydrogen storage applications. It suggests a direction for further research in metal hydride alloys for effective and safe hydrogen storage.

Numerical study of polymer embedded metal hydride-based self-sensing actuator

Metal hydride actuators have amassed increasing attention over the past decade owing to their desirable operational characteristics, such as a high power-to-weight ratio, noiseless and vibration-less operation, lightweight, safety and environmental friendliness. Essentially, there are two ways in which we can attain actuation using hydrides. Primarily, actuation force is generated by the hydrogen gas pressure changes associated with charge–discharge process. Alternatively, the incompressible volumetric changes in the hydride bed during sorption can also result in actuation. However the studies reported on this type of actuators are rare and mostly deal with bimorph actuators. The present study investigates the effect of soft silicone rubber composited metal hydride bed within a hollow stainless steel spring for its potential use as a self-sensing actuator element. LaNi5 is used as the metal hydride alloy. For an equivalent quantity of hydride by mass, the estimated actuation stroke and force for the composite bed actuator are better than their powder bed counterpart (12 mm and 100 N, respectively, in contrast to 5.84 mm and 60 N), due to improved heat transfer. Bed thickness, coil pitch and coil diameter are important geometric parameters which control the performance of the device. As previously reported, hydrogen supply pressure and heat transfer coefficient are found to be important operating parameters controlling the force –stroke characteristics of the actuating element. The simulation study has been executed using COMSOL Multiphysics™ commercial code.

Unraveling the synergistic effects and mechanisms of nano-carbon modification on metal hydride alloys for enhanced electrochemical performance in energy storage applications

Unraveling the synergistic effects and mechanisms of nano-carbon modification on metal hydride alloys for enhanced electrochemical performance in energy storage applications

A Newly Proposed Method for Hydrogen Storage in a Metal Hydride Storage Tank Intended for Maritime and Inland Shipping

The utilisation of hydrogen in ships has important potential in terms of achieving the decarbonisation of waterway transport, which produces approximately 3% of the world’s total emissions. However, the utilisation of hydrogen drives in maritime and inland shipping is conditioned by the efficient and safe storage of hydrogen as an energy carrier on ship decks. Regardless of the type, the constructional design and the purpose of the aforesaid vessels, the preferred method for hydrogen storage on ships is currently high-pressure storage, with an operating pressure of the fuel storage tanks amounting to tens of MPa. Alternative methods for hydrogen storage include storing the hydrogen in its liquid form, or in hydrides as adsorbed hydrogen and reformed fuels. In the present article, a method for hydrogen storage in metal hydrides is discussed, particularly in a certified low-pressure metal hydride storage tank—the MNTZV-159. The article also analyses the 2D heat conduction in a transversal cross-section of the MNTZV-159 storage tank, for the purpose of creating a final design of the shape of a heat exchanger (intensifier) that will help to shorten the total time of hydrogen absorption into the alloy, i.e., the filling process. Based on the performed 3D calculations for heat conduction, the optimisation and implementation of the intensifier into the internal volume of a metal hydride alloy will increase the performance efficiency of the shell heat exchanger of the MNTZV-159 storage tank. The optimised design increased the cooling power by 46.1%, which shortened the refuelling time by 41% to 2351 s. During that time, the cooling system, which comprised the newly designed internal heat transfer intensifier, was capable of eliminating the total heat from the surface of the storage tank, thus preventing a pressure increase above the allowable value of 30 bar.

Performance analysis of a metal hydride refrigeration system

The varying applications of metal hydride refrigeration systems, such as cold storage and space air conditioning, grant them important advantages over conventional ones. These advantages include being a low-grade heat driven, more environmentally friendly and renewable working fluid with greater compactness and fewer moving parts. However, a metal hydride refrigeration system always operates under unsteady conditions due to the cyclic hydriding and dehydriding processes involved. To analyse and optimise the metal hydride refrigeration system’s design and performance, in this paper, a comprehensive transient system model has been developed with a new and revised intrinsic kinetic correlation inclusive of the essential operating controls and applicable process conditions of regeneration, cooling and transitions in between. In addition, the correlative model on the characterisation process of pressure, concentration and temperature (PCT) profiles for the metal hydride alloys employed in the system has been developed and is introduced briefly in this paper. It is integrated in the system model and ensures the accurate prediction of maximum capacities for the metal hydride isothermal desorption and absorption processes. The developed transient system model has been validated through comparison with experimental results from literature on the medium-temperature cooling process of a metal hydride refrigeration system. The model simulation is conducted for a specially designed low-temperature metal hydride refrigeration system at different operating conditions and controls. In quantity, when the high-grade heat source temperature increases from 90 °C to 120 °C, the low-grade heat source temperature increases from −20 °C to 10 °C, the medium-grade heat sink temperature decreases from 30 °C to 15 °C, and the time period for regeneration or cooling process decreases from 10 min to 4 min, the cooling COP increases by 112.0%, 136.6%, 19.3% and 31.8% respectively. The optimisation strategies for the system operating conditions and controls are therefore recommended based on the detailed performance analyses of the system simulation results.

New Design of a Separator Unit with Metal Hydride and an Analysis of Its Potential Application in the Process of Hydrogen Separation from a Binary Mixture of Gases

Synthesis gases produced in the processes of the high-temperature gasification of otherwise unusable waste, with the use of technologically efficient and cost-effective separation methods, may represent a reliable source of hydrogen intended for applications in the industry and the transport segments. One of the possible solutions to the separation of hydrogen from a mixture of gases is the use of metal hydride (MH) alloys, which are capable of binding hydrogen into their structure. This is the subject of the present article, in which a new design is presented for a fully functional system and a hydrogen separator unit, and the potential application of a commonly available metal hydride alloy in the separation of hydrogen from a binary mixture containing carbon dioxide and hydrogen is discussed. Load testing of the selected type of metal hydride alloy with a high concentration of carbon dioxide in the mixture, representing 40 vol. % and 4 vol. %, was performed. In addition, testing the alloy’s ability to separate hydrogen from a mixture containing H2 and CO2 was conducted using small alloy samples and a newly designed hydrogen separator unit. The resulting higher purity of hydrogen after the separation was confirmed by an experiment, in which the hydrogen concentration in the resulting mixture increased by 2.7 vol. %. The purity of the desorbed hydrogen amounted to 99.4 vol. %. The testing also confirmed a high degree of degradation of the alloy, caused by the poisoning effect of CO2 on the selected alloy type. There was also a significant decrease in the absorption ability of the alloy—from 1.7 wt. % to 1.2 wt. %—and a significant extension of the absorption time caused by the slower kinetics of the hydrogen storage, which occurred as early as after ten absorption–desorption cycles.

Synergistic effect for improving the hydrogen storage capability and electrochemical performance of AB2 Laves phase alloys

The structure of a series AB2 Laves-type metal hydride alloys, in which Ce was doped into Ti0.24Zr0.76Ni1.15Mn0.7V0.15 and annealed the alloys, was studied and correlated to hydrogen storage properties and electrochemical performances. X-ray diffraction, scanning electron microscope, and energy-dispersive spectroscopy results revealed that Ce formed a CeNi3 secondary phase instead of entering the Laves phases. The synergistic effect of the CeNi3 and (Ti,Zr)Ni phase improved the hydrogen storage and electrochemical discharge properties of the Ce-doped (Ce0.02) alloy. Especially, the secondary phases could decrease the hydrogen absorption plateau, reduce the hysteresis phenomenon, and increase the hydrogen storage capacity (from 0.9 wt% to 1.4 wt% at 25 ℃). The formation of CeNi3Hx hydride on the surfaces of alloy electrodes led to a higher discharge capacity (∼500 mAh/g) and a faster activation rate. The Ce0.02 alloy also showed a good cyclic stability ∼82.08%, after 500 charge-discharge cycling, which could be ascribed to the good corrosion resistance of the CeNi3 phase on the surface of alloy. In addition, annealing treatment promoted the depletion of (Ti,Zr)Ni secondary phase and the transformation from the C14 to C15 phase. The Ce-doped AB2 alloy can be used as a hydrogen storage and hydride battery electrode material.

Sintesis dan Karakterisasi Fe₂TiO₅ dari Besi Oksida dan Titanium Dioksida dengan Metode Planetary Ball-Mill

The method of solid hydrogen storage through integration in metal hydride compounds is a new, promising method. This research has succeeded in synthesizing and characterizing the metal hydride alloy Fe-Ti system through a planetary ball-mill process. Based on the XRF analysis, it was found that the composition of Fe oxide content reached 56.22% while Ti oxide reached 43.78%. The FTIR study showed absorption at wavenumbers of 900 cm-1 and 500 cm-1. Both are typical absorptions for Ti-O and Fe-O groups, suggesting that the synthesized sample was successful. It can be seen from the XRD data that some of the diffractogram peaks of the resulting Fe-Ti compound match the peaks of the Fe2TiO5 and TiO2 compounds obtained from the Powder Diffraction File (PDF) database number 00-003-0374. After the refinement was performed, information was obtained that the synthesis of Fe-Ti alloy material using the planetary ball mill technique produced Fe2TiO5.

Effect of CO2 concentration on the kinetics of the hydralloy C5

The article discusses the effect of a high concentration of CO2 on the kinetics of the hydrogen absorption and desorption process in the metal hydride alloy Hydralloy C5, on which research is being carried out on the ability of the metal hydride (MH) alloy to separate hydrogen from unwanted synthesis gas components. The focus is on the contamination of the alloy by the carbon dioxide, which is the main gas found in the mixture of unwanted gases after SYNGAS has been modified to increase the percentage of hydrogen in the gas mixture. Carbon dioxide, as a significant oxidant, significantly affects the kinetics of the selected metal hydride alloy. With the increasing percentage representation of the given gas in the mixture with hydrogen, the rate of deterioration of the alloy’s properties increases. The process of contamination of the alloy with carbon dioxide occurs by its decomposition into carbon monoxide and oxygen and subsequent oxidation of the surface layers of the alloy grains, which prevents or significantly degrades the passage of hydrogen into the structure of the metal hydride alloy.

Performance tests on embedded cooling tube type metal hydride reactor for heating and cooling applications

• Heating and cooling traits of two AB 5 -type metal hydride alloys were investigated. • Heating performances of the alloys were found to be superior compared to cooling. • Peak heating rate of 3.5 kW was accomplished, producing 514 kJ heat within 361 s. • A decentralized heating cum H 2 storage system was suggested based on test results. The present work reports the heating and cooling characteristics of two AB 5 type metal hydride (MH) alloys commercially labelled as A3® and LCC1®. A cylindrical MH reactor configuration comprising 48 Embedded Cooling Tubes (ECT) in a circular pattern and an outer jacket was considered to accomplish the set objectives. Two identical reactors were each filled with 3.4 kg of one of the alloys. The reactor configuration allows MH alloy to be filled in the shell space while the heat transfer fluid (HTF) could flow through the tubes and the outer jacket. A set of parametric investigations was conducted on the aforementioned alloys by varying the operational parameters. During the absorption set of the parametric study, hydrogen supply pressure was varied from 10 bar to 30 bar, and HTF temperature was varied from 15 °C to 35 °C, while during the desorption study, HTF temperature was varied from 5 °C to 25 °C. At the absorption condition of 30 bar and 25 °C, the alloys A3® and LCC1® attained absorption capacity of 1.24 wt.% and 1.38 wt.%, respectively. At this condition, LCC1® was able to generate 514.5 kJ cumulative heat output in 361 s, yielding a maximum heating rate of 3.57 kW. The parametric study revealed that the absorption behaviour of A3® was more sensitive towards changes in supply pressure as well as HTF temperature compared to LCC1®. Compared to heating performance, the cooling performance of both the alloys was lower. Based on the outcomes of the experimental study, it was suggested to utilize LCC1® for decentralized hydrogen storage cum heating applications in the temperature range of 15–35 °C.

Elaboration and electrochemical characterization of CeZr2Ni4.5Al0.2Mn0.3Cr4-based metal hydride alloys

Elaboration and electrochemical characterization of CeZr2Ni4.5Al0.2Mn0.3Cr4-based metal hydride alloys

Design and performance analysis of an annular metal hydride reactor for large-scale hydrogen storage applications

The present study is focused on developing a modular design of a metal hydride reactor for large-scale hydrogen storage applications. In this perspective, an annular metal hydride reactor that is cooled/heated on both inner and outer surfaces is designed and analyzed. A numerical model is developed to study the absorption and desorption characteristics of the designed annular metal hydride reactor. Three configurations of the annular metal hydride reactor that could offer a weight ratio (i.e., mass of metal hydride alloy to mass of the reactor) of 2 are investigated. The first two configurations are of annular metal hydride reactor with only change in the heat transfer fluid's flow direction. The third configuration is the same as the second one, with extra radial fins inside the metal hydride bed. The main objective of studying the three configurations is to visualize the enhancement achieved in the reaction rate and outlet temperature. The results showed that the peak outlet temperature is enhanced by 3.6 °C with the second configuration. At the same time, the third configuration improved the absorption and desorption rates by a factor of 2.07 and 1.92, respectively, while the radial fins occupying only 4.6% of reactor volume. Further, a sensitivity analysis is conducted on the third configuration to analyze the influence of operating parameters on absorption and desorption times. Furthermore, the performance of the third configuration is compared with several designs present in the literature.

New arrangement of the metal hydride linear drive

A new arrangement of a metal hydride linear drive is presented, in which a thermoelectric sorber—hydrogen desorber using the Peltier effect is located inside the working chambers. Variants of different versions of a linear drive with a new arrangement and their advantages in comparison with known metal hydride linear drives are shown. Recommendations for their practical application are given. Keywords: metal hydride alloys and their application, metal hydride linear drive, thermoelectric sorber—hydrogen desorber. S.Sayapin@rambler.ru

Isotherm measurements of high-pressure metal hydrides for hydrogen compressors

Hydrogen absorption and desorption isotherms have been measured for several metal hydride alloys identified as possible candidates in the high-pressure (i.e. >80 MPa) stage of a two-stage hydrogen compressor. The isotherms were obtained using two independent Sieverts volumetric test systems built specifically for measuring hydrogen absorption and desorption parameters from 0.10 to 100 MPa. The results obtained enabled us to identify the alloy Ti0.8Zr0.2Fe1.6V0.4 as the most viable of the candidates investigated for use in the high-pressure stage of a prototype two-stage 80+ MPa compressor, as it produced the highest desorption pressures at moderate temperatures. Issues and challenges in determining reliable isotherms at pressures >50 MPa are also described.

Analysis of the Heat Balance of a Metal Hydride Separator Used for the Separation of Hydrogen from Syngas

The present article discusses the potential for hydrogen separation using a metal hydride separator, which facilitates the generation of hydrogen contained in syngas following the thermal recovery of wastes. The article provides a detailed description of the separator heat balance using analytical calculations and optimised calculations, and by applying numerical methods. The proposed concept of a separator intended for hydrogen separation from syngas offers a solution to a problem associated with the use of metal hydride alloy powders; in particular, their low thermal conductivity. In order to eliminate big temperature differences in the alloy, a heat transfer intensifier was implemented in the metal hydride alloy volume; the intensifier was made of metal and exhibited high thermal conductivity. For the purpose of comparing the thermal fields, the first stage comprised the creation of a numerical simulation of hydrogen absorption without the use of an intensifier. Subsequently, three different geometries were created for an intensifier intended to remove heat from the metal hydride alloy powder towards the separator cover, and the effects of these three geometries were analysed. The implementation of heat transfer intensifiers into the metal hydride alloy powder improved the heat removal by as much as 43.9% and increased the thermal field homogeneity by 77%. A result of the heat removal optimisation was an increase in the hydrogen absorption kinetics and the efficiency of the separator operation.

Hydrogen storage and electrochemical properties of annealed low-Co AB5 type intermetallic compounds

The structure, hydrogen storage and electrochemical properties of annealed low-Co AB5-type intermetallic compounds have been investigated. La-alloy, Nd-alloy and Cr-alloy are used to represent La0.8Ce0.2Ni4Co0.4Mn0.3Al0.3, La0.6Ce0.2Nd0.2Ni4Co0.4Mn0.3Al0.3 and La0.6Ce0.2Nd0.2Ni3.8Co0.4Mn0.3Al0.3Cr0.2, respectively. The XRD results indicated that annealed samples are all single-phase alloys with CaCu5 type structure. The maximum of both hydrogen content and discharge capacity is obtained for La-alloy 1.23 wt%H2 and 321.1 mA h/g, respectively. All the investigated alloys are quiet stable with ΔH of hydrogen desorption about 36–38 kJ/mol H2. Cycle life of alloy electrode has been improved by partial substitution of La for Nd and Ni for Cr. The highest capacity retention of 92.2% after 100 charge/discharge cycles at 1C has been observed for Nd-alloy. The hydrogen diffusion coefficient measured by PITT is higher at the start of charging process and dramatically reduces by 2–3 order of magnitude with saturation of β-hydride. The highest value 6.9 × 10−13 cm2/s is observed for La alloy at 100% SOC. Partial substitution La for Nd and Cr for Ni in low-Co AB5 metal hydride alloys slightly reduces maximum discharge capacity, HRD performance and hydrogen diffusion kinetics. Low-Co alloys show good overall electrochemical properties compared to high-Co alloys and might be perspective materials for various electrochemical applications.

Study of hydrogen storage properties of oxygen modified Ti- based AB2 type metal hydride alloy

A multi component AB2 type hydrogen storage intermetallic alloy (A = Ti0.85Zr0.15, B2 = Mn1.22Ni0.22Cr0.2V0.3Fe0.06; was investigated in this work. The intermetallic specified above was modified by oxygen to yield the composition AB2O0.05. The oxygen was introduced by adding TiO2 to the charge, with corresponding decrease of the Ti amount, followed by arc melting and annealing at the same conditions as for the oxygen free AB2-type alloy. The addition of oxygen to the alloy did not change much the PCT properties; the only difference was that the plateau pressure for the oxygen-modified alloy increased slightly. Both alloys have shown to be excellent candidates for H2 storage, particularly for utility vehicles, due to their relatively high reversible H2 storage capacity (1.6 wt%) and low plateau pressure at room temperature (<5 bar). The addition of oxygen improved hydrogen absorption kinetics in the AB2 alloy allowing it to immediately absorb H2 without activation while for the non-modified sample an incubation period (30 min) was observed at the same conditions.

Study on an actuation system development using temperature control of metal hydrides.

BACKGROUND: Hydrogen storage using metal hydride (MH) offers various advantages so the global research and development using MH alloys keeps growing.OBJECTIVE: In this paper, we developed a new actuation system using temperature control of the MH module.METHODS: The actuation system consisted of an MH module, fan, mass flow controller (MFC), solenoid valve, actuator, and a temperature and pressure sensor. The MH module, two fans and temperature sensors were set for heating and cooling the MH power by electricity. Two MFCs and four pneumatic solenoid valves were used for controlling the direction and measuring hydrogen flow. Two actuators were used to evaluate performance of the MH alloy, and all the results were measured by LabVIEW software. Hydrogen was absorbed by the MH alloy by pressurizing at 1 MPa, and the absorbed hydrogen was desorbed using a vacuum pump.RESULTS: The temperature condition of the driving test was 20–50C. As the module was heated, it was confirmed that the actuator connected to the system was driven by the pressure of desorbed hydrogen.CONCLUSION: It is confirmed that the actuation system is suitable for the evaluation of characteristics of MH alloy. Future studies are planned to develop MH alloys and test the actual driving performance using this system.

High-capacity Zr-based AB2-type alloys as metal hydride battery anodes

This work focused on the structural and electrochemical properties of AB2-type Zr/Ti-based metal hydride anode alloys. The as-cast and annealed Ti0·24Zr0·76Ni1·1Mn0·7V0.2 alloys were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and electrochemical characterization (EC). X-ray diffraction (XRD) results indicated the presence of homogenous C14 Laves phase in the annealed alloy, and the major C15 and C14 phases coexisted with the TiNi and Zr9Ni11 secondary phases in the as-cast alloy. SEM images showed the phase compositions in these alloys and confirmed the significant decrease in the secondary phases of the annealed alloy. During EC, the as-cast alloy showed better activation performance than the annealed alloy. This result was related to the catalytic effect of the Ti-/Zr-related secondary phases during electrochemical reactions. Annealing increased the maximum discharge capacity from ∼350 mAh/g for the as-cast alloy to ∼400 mAh/g for the annealed alloy during activation. The annealed alloy also showed considerable cycling stability and a slightly high discharge rate. We developed a C14-Laves phase metal hydride alloy showing a discharge capacity ∼400 mAh/g at a 100 mA/g rate (C/4) suitable for electric vehicle (EV) application.