Metal Hydride Materials Research Articles

Parametric Analysis of a Novel Array-Type Hydrogen Storage Reactor with External Water-Cooled Jacket Heat Exchange

Hydrogen energy is a green and environmentally friendly energy source, as well as an excellent energy carrier. Hydrogen storage technology is a key factor in its commercial development. Solid hydrogen storage methods represented by using metal hydride (MH) materials have good application prospects, but there are still problems of higher heat transfer resistance and slower hydrogen absorption and release rate as the material is applied to reactors. This study innovatively proposed an array-type MH hydrogen storage reactor based on external water-cooled jacket heat exchange, aiming to improve the heat transfer efficiency and absorption reaction performance, and optimize the absorption kinetics encountered in practical applications of LaNi5 hydrogen storage material in reactors. A mathematical model was built to compare the hydrogen absorption processes of the novel array-type and traditional reactors. The results showed that, with the same water-cooled jacket, the hydrogen absorption rate of the array-type reactor can be accelerated by 2.78 times compared to the traditional reactor. Because of the existence of heat transfer enhancement limits, the increase in the number of array elements and the flow rate of heat transfer fluid (HTF) has a limited impact on the absorption rate improvement of the array-type reactor. To break the limits, the hydrogen absorption pressure, as a direct driving force, can be increased. In addition, the increased pressure also increases the heat transfer temperature difference, thereby further improving heat transfer and absorption rate. For instance, at 3 MPa, the hydrogen absorption time can be shortened to 147 s.

Modeling and design for metal hydride-based hydrogen storage systems in underwater PEMFC applications

Utilizing metal hydride materials presents a promising avenue for establishing a highly concentrated hydrogen medium suitable for onboard vehicle applications, including underwater contexts. This paper introduces a design solution devised to estimate the characteristics of a metal hydride-based hydrogen storage system tailored for underwater vehicle deployment. The solution facilitates sensitivity analysis across various parameters by offering system mass and volume estimations. The findings highlight the significance of thermodynamic properties and operational conditions in determining the suitability of metal hydrides for compact and efficient hydrogen storage. The study underscores the importance of refueling time, L/D ratio, cooling fluid temperature and velocity, and hydrogen storage capacity in influencing system mass, volume, and thermal management. The model provides insights into the design and optimization of metal hydride-based hydrogen storage systems, offering a comprehensive approach to enhancing performance and reliability for underwater applications.

Development of a high-pressure 700 bar metal hydride hydrogen compressor

HySA Systems and TF Design have recently developed a single-stage prototype high-pressure metal hydride hydrogen compressor (MHHC) which is able to compress hydrogen from 100 to >700 bar at the working temperatures from 20 to 150 °C, with estimated productivity about 1 Nm3/h. The MHHC comprises of two 2 m-long fibre-wound high-pressure MH containers developed by the authors earlier and assembled in two modules operating in a mode of a cyclic lower-pressure H2 absorption (on cooling) and high-pressure H2 desorption (on heating). The containers operate using a self-developed multicomponent C14 Laves type Ti–based AB2 intermetallic alloy. The article considers phase-structural and hydrogen sorption properties of the utilized metal hydride material, hydrogen compression performances of the metal hydride container, as well as layout and the expected performance characteristics of the compressor assembly.

MXenes and MXene-Based Metal Hydrides for Solid-State Hydrogen Storage: A Review.

Hydrogen-driven energy is fascinating among the everlasting energy sources, particularly for stationary and onboard transportation applications. Efficient hydrogen storage presents a key challenge to accomplishing the sustainability goals of hydrogen economy. In this regard, solid-state hydrogen storage in nanomaterials, either physically or chemically adsorbed, has been considered a safe path to establishing sustainability goals. Though metal hydrides have been extensively explored, they fail to comply with the set targets for practical utilization. Recently, MXenes, both in bare form and hybrid state with metal hydrides, have proven their flair in ascertaining the hydrides' theoretical and experimental hydrogen storage capabilities far beyond the fancy materials and current state-of-the-art technologies. This review encompasses the significant accomplishments achieved by MXenes (primarily in 2019-2024) for enhancing the hydrogen storage performance of various metal hydride materials such as MgH2, AlH3, Mg(BH4)2, LiBH4, alanates, and composite hydrides. It also discusses the bottlenecks of metal hydrides for hydrogen storage, the potential use of MXenes hybrids, and their challenges, such as reversibility, H2 losses, slow kinetics, and thermodynamic barriers. Finally, it concludes with a detailed roadmap and recommendations for mechanistic-driven future studies propelling toward a breakthrough in solid material-driven hydrogen storage using cost-effective, efficient, and long-lasting solutions.

The effect of powder and pellet forms of added metal hydride materials on reaction kinetics and storage

In the present research, metal hydride pellets were synthesized to enhance the kinetics of hydrogen charge/discharge processes. By incorporating ENG (expanded natural graphite) and copper additives, we observed improvements in the heat transfer coefficients and storage capacities of the hydrogen storage materials. The reactor is designed to contain 1000 g of storage material in the form of powder or 25 pellets each weighing 40 g. The influence of storage materials with enhanced thermal conductivity on the hydrogen charge/discharge process was experimentally studied in a metal hydride reactor under a pressure of 10 bar. The reactor was heated under vacuum (10−4 mmHg) to approximately 200 °C for 2 h in order to complete the activation process. Following the heating process, the reactor was allowed to cool to ambient temperature, after which the hydrogen was introduced to the reactor at 10 bar pressure for 50 min. The absorption and desorption procedure was reiterated up to 20 cycles, and recordings of data were taken at intervals of 5 cycles to monitor the variations between the cycles. After 10 charge/discharge cycles under pressure of 10 bar, the hydrogen stored in the reactor amounted to approximately 9.93 g in pellet form and 7.20 g in powder form.

Simulation study on a novel solid–gas coupling hydrogen storage method for photovoltaic hydrogen production systems

Compressed hydrogen storage in photovoltaic hydrogen production systems faces several challenges, including limitations in storage volume, compression energy consumption and safety concerns. To improve the comprehensive hydrogen storage performance, this study develops a novel solid–gas coupling hydrogen storage method that combines metal hydride and phase change material (MH-PCM). Firstly, a vertical MH-PCM solid storage model considering the natural convection effect is proposed and investigated. Building upon this model, the solid–gas coupling hydrogen storage is constructed and integrated into the photovoltaic hydrogen production system to evaluate its comprehensive storage performance. Results reveal that considering natural convection leads to an approximately 12.7 % increase in the average storage rate, but is also accompanied by an uneven storage process. To address this unevenness and further enhance the storage rate, it's advisable to focus on structural optimization at the bottom of the tank. Additionally, improving the PCM thermal conductivity and hydrogen inlet pressure (to approximately 1 MPa) are also proven effective strategies. The proposed solid–gas coupling hydrogen storage demonstrates comprehensive advantages, particularly compact size and reduced energy consumption. Furthermore, appropriately increasing the coupling ratio between solid and gaseous capacities can achieve the even smaller storage volume. These findings can provide valuable theoretical and engineering guidance for implementing such hydrogen production and storage systems.

New insights into the impurity transport and separation behaviours during metal hydride dehydrogenation for ultra-pure hydrogen

The hydrogen separation and purification method based on metal hydride (MH) is viewed as one of the ideal methods for recycling industrial by-product hydrogen. Usually, self-produce hydrogen purging is conducted to remove the impurity. However, the mechanism of impurity transport and separation under the MH dehydrogenation process is still not clear so that the purity of produced hydrogen or the hydrogen recovery ratio is low. In this paper, a novel poisoning dehydrogenation kinetics considering the effect of passivation layer is proposed to accurately describe the dehydrogenation properties under the impurity poisoning conditions. The poisoning factor is introduced to describe the poisoning effect of impurities on MH materials. More active impurity or higher impurity concentration result in the larger poisoning factor. Based on the poisoning dehydrogenation kinetics, the MH dehydrogenation reaction model for self-produce hydrogen purging process is developed to describe the impurity transport and separation behaviours. The effects of operating parameters on the impurity transport and separation are further investigated for ultra-pure hydrogen. It is found that the low temperature and low outlet flow rate results in the low hydrogen loss for ultra-pure hydrogen. After the optimization, an efficient hydrogen separation and purification with both a hydrogen purity of 99.9999% and a hydrogen recovery ratio of more than 80% is achieved, which shows the potential in the hydrogen separation and purification of industrial by-product hydrogen.

An overview of TiFe alloys for hydrogen storage: Structure, processes, properties, and applications

Hydrogen-based energy systems offer potential solutions for replacing fossil fuels in the future. However, the practical utilization of hydrogen energy depends partly on safe and efficient hydrogen storage techniques. The development of hydrogen storage materials has attracted extensive interest for decades. Solid-state hydrogen storage systems based on metal hydride materials provide great promises for many applications. Recently, interest has been revived in TiFe alloys as a prime candidate for stationary hydrogen storage material. The advantages of TiFe alloys over some of the other solid metal hydrides include that it can hydrogenate and dehydrogenate at near room temperature under near atmospheric pressures and that it is a low-cost material because there are abundant supplies of Fe and Ti on the earth's crust. However, the TiFe alloy must be activated at relatively high temperatures (400–450 °C) and high pressure of hydrogen (65 bar) before it can be hydrogenated, which is a hindrance to the industrial-scale application of TiFe alloys. The materials science community on hydrogen storage materials has conducted and reported considerable amounts of studies on TiFe-based alloys. In this work, we provided a comprehensive review of TiFe-based alloys. The fundamentals and synthesis approaches of TiFe-based alloys were summarized. The activation properties of TiFe-based alloys including the understanding of the activation mechanisms and the methods for improving the activation kinetics were reviewed. Moreover, the cycle stability and anti-poisoning ability were discussed. Finally, the potential applications and the perspective of TiFe-based alloys were introduced.

Advancements in Metal Hydride Materials for Hydrogen Storage

Hydrogen energy is attracting the attention of scientists because of its high energy density and low environmental pollution in the world trend of clean energy use. In addition, the basis for the use of hydrogen energy is its secure, cost-effective, and efficient storage. After decades of devotions by experts, many high-performance hydrogen storage materials have been created. The poor hydrogen storage capacity, challenging hydrogen storage circumstances, slow hydrogen storage speed, and potential safety concerns remain, nonetheless, with the present hydrogen storage materials. Metal hydride materials, which have a high hydrogen storage density and safe reactions, have so steadily been a research focus in recent years. In this paper, magnesium-based materials and titanium-based materials are selected as the representatives of metal hydride materials, and their hydrogen storage mechanisms, common modification methods, and the advanced research progress of these methods are reviewed. Through the analysis of data, the hydrogen storage properties and the respective characteristics of each modified hydrogen storage material are rigorously presented. The key technical limitations and possible improvement directions of these materials are summarized, and the future application prospects and development trends of hydrogen storage materials are predicted at the end.

Core-Shell, Critical-Temperature-Suppressed V Alloy-Pd Alloy Hydrides for Hydrogen Storage—A Technical Evaluation

Hydrogen storage for energy applications is of significant interest to researchers seeking to enable a transition to lower-pollution energy systems. Two of the key drawbacks of using hydrogen for energy storage are the low gas-phase storage density and the high energy cost of the gas-phase compression. Metal hydride materials have the potential to increase hydrogen storage density and decrease the energy cost of compression by storing the hydrogen as a solid solution. In this article, the technical viability of core-shell V90Al10-Pd80Ag20 as a hydrogen storage material is discussed. LaNi5, LaNi5/acrylonitrile-butadiene-styrene copolymer mixtures, core-shell V-Pd, and core-shell V90Al10-Pd80Ag20 are directly compared in terms of reversible hydrogen-storage content by weight and volume. The kinetic information for each of the materials is also compared; however, this work highlights missing information that would enable computational dynamics modelling. Results of this technical evaluation show that V90Al10-Pd80Ag20 has the potential to increase gravimetric and volumetric hydrogen capacity by 1.4 times compared to LaNi5/acrylonitrile-butadiene-styrene copolymer mixtures. In addition, the literature shows that Pd80Ag20 and V90Al10 both have similarly good hydrogen permeabilities, thermal conductivities, and specific heats. In summary, this evaluation demonstrates that core-shell V90Al10-Pd80Ag20 could be an excellent, less-expensive hydrogen storage material with the advantages of improved storage capacity, handleability, and safety compared to current AB5-polymer mixtures.

Numerical study on hydrogen and thermal storage performance of a sandwich reaction bed filled with metal hydride and thermochemical material

Hydrogen storage and release process of metal hydride (MH) accompany with large amount of reaction heat. The thermal management is very important to improve the comprehensive performance of hydrogen storage unit. In present paper, thermochemical material (TCM) is used to storage and release the reaction heat, and a new sandwich configuration reaction bed of MH-TCM system was proposed and its superior hydrogen and thermal storage performance were numerically validated. Firstly, the optimum TCM distribution with a volume ratio (TCM in inner layer to total) of 0.4 was derived for the sandwich bed. Then, comparisons between the sandwich reaction bed and the traditional reaction bed were performed. The results show that the sandwich MH-TCM system has faster heat transfer and reaction rate due to its larger heat transfer area and smaller thermal resistance, which results in the hydrogen storage time is shortened by 61.1%. The heat transfer in the reaction beds have significant effects on performance of MH-TCM systems. Increasing the thermal conductivity of the reaction beds can further reduce the hydrogen storage time. Moreover, improving the hydrogen inflation pressure can result in higher equilibrium temperature, which is beneficial for the enhancing heat transfer and hydrogen absorption rates.

Performance evaluation of a novel concentric metal hydride reactor assisted with phase change material

Hydrogen storage is a promising technique that could handle the challenges of intermittent renewable production on the electric grid. Metal Hydride (MH) is a promising hydrogen storage technique owing to its safety, availability, and high volumetric storage density. However, MH requires an efficient heat management system. Therefore, this paper proposes a multi-layer cylindrical reactor where layers of MH and phase change material (PCM) are alternatively arranged. A numerical model is developed utilizing COMSOL Multiphysics software and is validated to predict the performance of the proposed reactor at various design parameters. As PCM thermal conductivity changes from 0.2 to 3 W/m.K, absorption time, based on 90 % absorption, reduces from 3555 s to 675 s (∼5.33 times reduction). Compared to a reference case, four layers system reduces absorption time by 78 %. Lithium nitrate trihydrate as PCM material exhibits the best performance, allowing four layers to greatly reduce reactor volume with a slight absorption time delay. The analysis introduces two novel parameters expressing the absorption rate per system mass and volume. From the intensive analysis, the specific capacity rate (SCR) of the proposed reactor is 1.51 gH2/min/kgsys, while the volumetric capacity rate (VCR) of the proposed reactor is 3016 gH2/min/m3sys. SCR and VCR are 3.4 and 3.12 times higher than the corresponding values in literature.

Modelling Nickel Metal Hydride Batteries for System Integrated Applications

The NiMH battery is resilient against mistreatment and can be charged in a large temperature window. It also has a high power-capability, which has made it popular in for instance power tools. Today, the battery is often found in large scale stationary energy storage, as well as applications which require high power capability.In large scale energy storage, small differences in run cycles can have large total effects on power efficiency and safety. It is therefore desirable to develop better methods of battery management. In recent years, development in system hardware has made it possible to implement on-line models in battery management systems. Such an implementation requires a model capable of working in dynamic conditions simulating voltage, temperature, and pressure. In this study, a model for this purpose is developed and verified.There are two major features that present a challenge when modelling a NiMH-system dynamically: Open Circuit Voltage (OCV) hysteresis and pressure build-up. Handling the hysteresis effect is important to accurately predict voltage and OCV.[1] OCV is especially important, as OCV is used to estimate the battery state of charge (SOC). Pressure build-up can be an important tool for charge termination, as it is the build-up of oxygen pressure and subsequent temperature increase that signal end of charge, Figure 1. In addition, the hydrogen pressure behavior changes with battery age and can be used to estimate end-of-life.OCV hysteresis is when the open circuit voltage at a certain SOC depends on the path taken to reach that charge state. This mean that a battery that has been charged to 50% will have a drastically different OCV than when the same battery has been discharged to 50%. This effect is believed to arise primarily from structural changes in the positive electrode, where the potential of the electrode surface is dependent on the material structure of the surface. An example of open circuit voltage hysteresis in a NiMH cell is found in Figure 1.The gas phase in the battery consists of four gases: nitrogen, hydrogen, oxygen and water. Nitrogen is an inert remnant from the battery manufacture.[2] Water is in equilibrium with the aqueous electrolyte. Hydrogen is in equilibrium with intercalated hydrogen in the negative metal hydride (MH) electrode. Finally, oxygen is the product of a side reaction that occurs at high potentials on the positive electrode. The production of oxygen at the positive electrode and ensuing oxygen recombination on the negative electrode produces a great deal of heat, which heats the battery and produces the temperature response that can be used to set a temperature derivative determined end of charge criteria. However, the presence of oxygen and high temperatures also drives the major aging mechanism: oxidation of the negative electrode. As the negative electrode is consumed, the capacity decreases. This leads to a difference in the hydrogen equilibrium pressure, as reaching a higher intercalation fraction increases the equilibrium pressure. [3]An implementation of a model for system battery management could help improve the following functions for a NiMH system: SOC estimation, SOH estimation, charge termination, fault detection and aging prevention. Therefore, development of a fully dynamic NiMH model has great value in improving over all system function for large scale energy storage applications. This study presents a fully dynamic and experimentally verified model for the NiMH battery that takes both pressure and OCV hysteresis into consideration. References Axén, J. B.; Ekström, H.; Zetterström, E. W.; Lindbergh, G. Evaluation of Hysteresis Expressions in a Lumped Voltage Prediction Model of a NiMH Battery System in Stationary Storage Applications. J. Energy Storage 2022, 48 (January). https://doi.org/10.1016/j.est.2022.103985.Mank, A. J. G.; Belfadhel-Ayeb, A.; Krüsemann, P. V. E.; Notten, P. H. L. In Situ Raman Analysis of Gas Formation in NiMH Batteries. Appl. Spectrosc. 2005, 59 (1), 109–114. https://doi.org/10.1366/0003702052940503.Tserolas, V.; Katagiri, M.; Onodera, H.; Ogawa, H. Thermodynamical Modeling of P-C Isotherms for Metal Hydride Materials. Trans. Mater. Res. Soc. Japan 2010, 35 (2), 221–226. https://doi.org/10.14723/tmrsj.35.221. Figure 1 Left: Open Circuit Voltage of a NiMH cell with exhibited hysteresis behavior. Right: Pressure and Temperature behavior of a NiMH module during a charge discharge cycle. Figure 1

Absorption of poisoned hydrogen from metal hydride under CO+H2 mixture gas for the production of clean, high purity hydrogen

The properties of metal hydride materials will be significantly degenerated by the poisoning effect of impurity gases such as CO, O 2 , H 2 S, etc. However, there are few reports on the poisoning kinetic model of metal hydride, which is important for the high-purity hydrogen purification and production from industry H 2 -contained waste gas. Hence, in this work, a novel poisoning hydrogen absorption kinetic model for metal hydride running in the CO + H 2 mixture gas is developed, which considers the effect of poisoning on the volume growth rate of the product phase based on classical Johnson-Mehl-Avrami model. The novel model is also validated by comparison with experimental data of hydrogen absorption of LaNi 4.3 Al 0.7 in a hydrogen atmosphere containing CO (∼0.1% v/v). The comparison results showed good agreement between model and experiment in the temperature range of 323–403 K. Based on experimental data and model, the reaction mechanism and rate-controlling steps of LaNi 4.3 Al 0.7 hydrogenation process with 0.1%v/v CO were further uncovered. • A novel poisoning hydrogen absorption kinetic model is developed and validated. • The poisoning factor related to the temperature is introduced into the kinetic model. • The effect of impurities becomes weakened with the rise of temperature. • Hydrogenation rate-controlling step under CO + H 2 depends on surface CO absorption/desorption.

Dehydrogenation performance of metal hydride container utilising MgH2-based composite

Mg-based hydrides have gained formidable interest for hydrogen storage applications due to their high intrinsic hydrogen capacity up to 7.6 wt%. However, their ability to absorb/desorb hydrogen is limited by their slow inherent kinetics and the heat and mass transfer within the storage container. The dehydrogenation of the metal hydride material in the container becomes important when coupling with a fuel cell, since the fuel cell requires a constant H2 flow rate to provide constant power output. In this study, we investigate numerically the dehydrogenation performance of a cylindrical container filled with 300 g of ball milled Mg90Ti10 + 5 wt% C with the objective to identify the operating conditions at which the H2 flow rate is higher or equal to the threshold for a proper functioning of a fuel cell. The heat exchange in the container is improved by a combination of internal basin-like and external annular fins. The heat transfer characteristics used in the numerical model are determined from the experimental work conducted in our laboratory. The results show that during the dehydrogenation process, at low convective heat transfer coefficient of 5–35 W/m2 K, the hydride container can supply H2 to a fuel cell with different power rating from 100 to 250 W for a long period of time with nearly constant flow rate.

Potassium hydride-intercalated graphite as an efficient heterogeneous catalyst for ammonia synthesis

Due to the high energy needed to break the N ≡ N bond (945 kJ mol−1), a key step in ammonia production is the activation of dinitrogen, which in industry requires the use of transition metal catalysts such as iron (Fe) or ruthenium (Ru), in combination with high temperatures and pressures. Here we demonstrate a transition-metal-free catalyst—potassium hydride-intercalated graphite (KH0.19C24)—that can activate dinitrogen at very moderate temperatures and pressures. The catalyst catalyses NH3 synthesis at atmospheric pressure and achieves NH3 productivity (µmolNH3 gcat−1 h−1) comparable to the classical noble metal catalyst Ru/MgO at temperatures of 250–400 °C and 1 MPa. Both experimental and computational calculation results demonstrate that nanoconfinement of potassium hydride between the graphene layers is crucial for the activation and conversion of dinitrogen. Hydride in the catalyst participates in the hydrogenation step to form NH3. This work shows the promise of light metal hydride materials in the catalysis of ammonia synthesis. Ammonia is industrially synthesized through an established process based on iron or ruthenium transition metal catalysts, although the quest for alternative and more sustainable processes is still ongoing. Here, the authors show that potassium hydride confined between graphene layers can reduce dinitrogen and catalyse ammonia synthesis under mild conditions.

Reactive Hydride Composite Confined in a Polymer Matrix: New Insights into the Desorption and Absorption of Hydrogen in a Storage Material with High Cycling Stability

AbstractHydrogen is key to the transformation of today's energy technology toward a sustainable future without carbon dioxide emissions. Hydrogen can be produced from water using renewable or sustainable energy sources such as solar or wind power. It can buffer fluctuations between energy generation and use in all energy sectors, stationary heat, and power, as well as mobility. Safe, fast, and easy to handle solutions for storing and releasing hydrogen are essential for the implementation of hydrogen technology. Among the storage alternatives, metal hydride materials represent a safe and efficient option. For the first time, detailed investigations of the local chemical changes in a confined hydrogen storage material before and after 21 hydrogen‐unloading and loading cycles are reported. The system is based on micrometer‐sized reactive hydride composite (RHC) particles, namely 6Mg(NH2)2 + 9LiH + 1LiBH4, dispersed in a matrix of poly(4‐methyl‐1‐pentene) (TPXTM). The morphological stability of the confined RHC particles during the reversible and almost complete reaction with hydrogen is visualized in detail, explaining the excellent long‐term cycling stability.

Nimh Gas Model for Dynamic Behaviour Study

The NiMH battery is an intercalation battery with a positive NiOH electrode and a negative metal hydride electrode. The electrolyte used is a highly alkaline aqueous solution, typically 6:1 KOH:LiOH. As a consequence of this and the reaction potentials of the electrodes, splitting of water into its constituting elements is a part of normal battery operation. When charging at high SOC, as well as when overcharging, oxygen is formed as a side-reaction. It then diffuses through the separator and recombines at the negative electrode. This recombination cycle causes the temperature in the battery to rise, something that is commonly used to terminate battery charging, either through ΔT or -ΔV criteria. In addition to oxygen production at high state of charge, overdischarging of the battery can produce hydrogen at the positive electrode, with a pressure increase at end of discharge indicating a harmful overdischarge of the battery [1]. Hydrogen is also present in the battery gas composition as a consequence of the negative hydrogen intercalation electrode material which is in equilibrium with gaseous hydrogen, an equilibrium which shifts with electrode hydrogen content [2]. Figure Left: A schematic showing the main gas reactions in the metal NiMH battery. Right: An example cycle of a NiMH battery, showing cell voltage (blue), cell gas pressure (green) and cell surface temperature (teal).The internal gas reactions of the NiMH battery have a great impact on battery function, both in regard to energy efficiency and battery aging. While measurements of battery internal total gas pressure occur in some battery systems, measurements of individual constituents would be impractical in the field, as such measurements require laboratory equipment. Therefore, a gas model that can estimate the internal pressure distribution under dynamic conditions would be a valuable tool to study the effects of different application drive cycles, as well as a possibility to further enhance BMS function for battery stability and longevity.There have been many attempts at modeling the gaseous side reactions in the NiMH battery. Some of these models are part of comprehensive battery models, which combines a voltage response model with added side reactions [3,4]. Other models look only at specific gas related processes [5]. However, a limitation with these models is that they are not able to model the battery during dynamic current conditions. The main reason for this is the presence of a strong open circuit voltage hysteresis, something that these models do not capture well.This study presents a model of the gas reactions and heat generation in the NiMH battery. The model is not coupled to a voltage model, instead it simulates internal temperature and pressure when supplied with experimental current, voltage and surface temperature data. This removes the complication of the open circuit voltage hysteresis effect and lets us model dynamic battery behavior. The model is in zero dimensions and based on physical principles. There are several parameters that are optimized by fitting to experimental data. The model is then validated by simulating pressure for a second set of data, based on the fitted values of the parameters. The simplicity of the model not only allows for it to be used in battery monitoring hardware, it can also be coupled to voltage and multidimensional models to build a more comprehensive predictive model.References Notten, P. H. L.; Latroche, M. Nickel-Metal Hydride: Metal Hydrides. In Encyclopedia of Electrochemical Power Sources; Garche, J., Dyer, C., Moseley, P., Ogumi, Z., Rand, D., Scrosati, B., Eds.; Elsevier B.V., 2009; Vol. 50, pp 502–521.Tserolas, V.; Katagiri, M.; Onodera, H.; Ogawa, H. Thermodynamical Modeling of P-C Isotherms for Metal Hydride Materials. Trans. Mater. Res. Soc. Japan 2010, 35 (2), 221–226. https://doi.org/10.14723/tmrsj.35.221.Albertus, P.; Christensen, J.; Newman, J. Modeling Side Reactions and Nonisothermal Effects in Nickel Metal-Hydride Batteries. J. Electrochem. Soc. 2008, 155 (1), A48. https://doi.org/10.1149/1.2801381.Ledovskikh, A.; Verbitskiy, E.; Ayeb, A.; Notten, P. H. L. Modelling of Rechargeable NiMH Batteries. J. Alloys Compd. 2003, 356–357, 742–745. https://doi.org/10.1016/S0925-8388(03)00082-3.Notten, P. H. L.; Ouwerkerk, M.; Ledovskikh, A.; Senoh, H.; Iwakura, C. Hydride-Forming Electrode Materials Seen from a Kinetic Perspective. J. Alloys Compd. 2003, 356–357, 759–763. https://doi.org/10.1016/S0925-8388(03)00085-9. Figure 1

Enhanced hydrogen storage of a LaNi5 based reactor by using phase change materials

Safe and efficient hydrogen storage technology is of great significance for large-scale hydrogen energy utilization. Using metal hydride (MH) materials such as LaNi5 for hydrogen storage is an effective way. In application, the heat and mass transfer characteristics in the reactor are one of the important factors and key problems affecting the hydrogen storage performance of MH. This paper proposes a novel hydrogen storage reactor installing a concentric finned tube heat exchanger and using phase change materials (PCM) by surrounding the reactor to improve heat transfer and hydrogen storage performance. A numerical model is built to describe transportation and reaction of two reactors with or without PCM. By comparison, the reactor surrounded by PCM has faster heat discharge and hydrogen absorption rate, and the absorption time is shortened by 50%. For the reactor with PCM, the optimal amount of PCM and the inlet velocity of heat transfer fluid (HTF) are investigated. The results show that the effective thermal conductivity of MH play a key role to improve heat transfer and reaction rate rather than that of PCM. Furthermore, increasing hydrogen supply pressure can effectively accelerate heat discharge and hydrogen absorption rate owning to larger temperature differences and improved reaction kinetics.

Studying the properties of polymeric composites of metal hydrides and carbon particles for hydrogen storage

Metal hydrides are promising hydrogen storage materials widely studied and accepted by many authorities, but still, it has not reached the set goal. In this work, polymer-based carbon particles along with metal hydride materials are proposed as a storage medium for hydrogen. Metal hydride particles were integrated into a polymeric matrix with carbon particles to improve the thermal stability and hydrogen storage capacity. Some physical properties, morphological effects, and thermal conductivity values of the polymeric composite were investigated using X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), and scanning electron microscopy (SEM). The test results indicated that metal hydrides and carbon particles were well integrated into the polymeric structure, which could drastically affect the hydrogen storage capacity of the polymeric composites for applications in the transportation industry.