Metal Hydride Systems Research Articles

Multiscale modeling of metal-hydride interphases—quantification of decoupled chemo-mechanical energies

The quantification of interphase properties between metals and their corresponding hydrides is crucial for modeling the thermodynamics and kinetics of the hydrogenation processes in solid-state hydrogen storage materials. In particular, interphase boundary energies assume a pivotal role in determining the kinetics of nucleation, growth, and coarsening of hydrides, alongside accompanying morphological evolution during hydrogenation. The total interphase energy arises from both chemical bonding and mechanical strains in these solid-state systems. Since these contributions are usually coupled, it is challenging to distinguish via conventional computational approaches. Here, a comprehensive atomistic modeling methodology is developed to decouple chemical and mechanical energy contributions using first-principles calculations, of which feasibility is demonstrated by quantifying chemical and elastic strain energies of key interfaces within the FeTi metal-hydride system. Derived materials parameters are then employed for mesoscopic micromechanical analysis, predicting crystallographic orientations in line with experimental observations. The multiscale approach outlined verifies the importance of the chemo-mechanical interplay in the morphological evolution of growing hydride phases, and can be generalized to investigate other systems. In addition, it can streamline the design of atomistic models for the quantitative evaluation of interphase properties between dissimilar phases and allow for efficient predictions of their preferred phase boundary orientations.

Modeling of a metal hydride energy storage tank dynamics using hybrid numerical, experimental, and machine learning methods

This study presents an integrated analysis combining numerical simulations, experimental investigations, and machine learning models to simulate the performance of metal hydride systems for hydrogen storage under various conditions by using a LaNi5 metal hydride cylindrical tank of 500 NL capacity, with a focus on PCM thermal enhancements and surface water heating and cooling. Numerical simulations offer insights into thermal and reaction dynamics, while experimental data are used for model validation and supplemented with additional numerical data for training a FFNN model to predict dynamic hydrogen flow, surface temperature, and surface heat flux. The obtained mean RMSEs for charging/discharging experimental data is 2.8 SOC% for the state of charge and 0.3 °C for surface temperatures. The study compares the effectiveness of water cooling and heating in metal hydride surface across different temperatures, highlighting their impact on the efficiency of hydrogen absorption and desorption processes. Energy consumption is shown to be non-linear; during charging, heat flux peaks before decreases rapidly within around 0.2 h. During discharging, heat flux rises steadily. The study also explores the impact of adding copper fins to the PCM covering metal hydride system, revealing significant improvements in charging and discharging efficiency, specifically, the integration of 16 copper fins led to a notable decrease in complete charging time from approximately 6.5 h to just over 5.2 h, and in complete discharging time from around 4.5 h to under 3.96 h. Using PCM, the highest heat flux is 5 times less during charge and 2 times less during discharge than that for water cooling mode.

Towards standalone commercial buildings in the Mediterranean climate using a hybrid metal hydride and battery energy storage system

Given the critical role of hybrid energy storage systems in the building sector for enhancing renewable energy reliability and integration, this study examines the techno-economic feasibility of adopting a dual-level energy storage system for a PV-driven commercial building in the Mediterranean climate. The proposed system encompasses both hydrogen metal hydride and battery storage units. Aimed at off-grid electrification, the optimal component sizing of the hybrid system is identified by establishing a statistical optimization framework using the response surface methodology. Dynamic simulations of the hybrid system are performed through a TRNSYS model coupled with a numerical code that simulates the metal hydride system. Regarding optimal net-zero solutions, it is shown that the share of the direct PV electricity supply to end-use fluctuates within a limited range for all scenarios, namely between 57.7 and 60.5 %, while the share of each storage system varies distinctively in each solution. The results indicate a striking difference between scenarios in terms of economic aspects; differences of $ 19,791 and $ 32,621 are observed between the minimum and maximum values of the initial investment and life cycle cost, respectively. The levelized cost of electricity varies between 0.354 and 0.403 $/kWh, in which the case having the lowest payback period (10.8 years) demonstrates the lowest levelized cost of electricity too. Furthermore, an inverse relationship between the levelized cost of hydrogen and production rate is observed; the lowest levelized cost and the highest annual production are achieved in the scenario with the lowest BESS capacity and the highest electrolyzer power and hydrogen storage volume, which are equal to 5.77 $/kg and 304.7 kg H2/yr, respectively.

Hydrogen Absorption in Palladium‐Based Nanocrystals for Electrocatalysis Investigation

AbstractHydrogen absorption in transition metals has received enormous attention for applications such as the hydrogen storage, sensing and corrosion. In particular, the Pd‐H system is a simple and classical metal hydride system that serves as a platform for a deeper understanding of hydrogen behavior. In the past few years, Pd‐H has been reported as electrocatalyst in multiple reactions, whereas the impact of hydrogen absorption/desorption in electrocatalytic applications remains unclear. Therefore, in this concept, factors influencing the hydrogen adsorption/desorption of palladium in the gas phase, such as facet engineering, ligand effects, and alloying effects, are summarized. Subsequently, in the context of electrocatalysis, factors affecting electrochemical hydrogen adsorption/desorption are outlined. Particularly, prospects for the further investigation of electrochemical hydrogen adsorption/desorption in catalysis are discussed.

Atomistic-scale insights into hydrogen diffusion barrier in nickel hydride: Complex interplay between short- and long-range hydrogen arrangement and hydrogen concentration

Metal hydrides, such as those containing Pd, Ni and Mg, are being considered as potential candidates for hydrogen storage applications. The sluggish hydrogen uptake/release in such materials at ambient conditions presents a major issue. The timescales are dictated mainly by diffusion, as it is usually the rate-controlling step. In order to identify practical strategies for improving the kinetics, one must therefore gain an atomistic-scale understanding of the hydrogen diffusion, which is generally lacking from experiments. We address this gap by analyzing the hydrogen hopping mechanism and the associated barriers in two million different hydrogen configurations in NiHx (x = 0–1) using computational techniques. A distribution of hopping barriers is observed. The barriers lie between 0.3–0.7 eV. Three factors, namely, the short- and long-range hydrogen arrangement and the hydrogen concentration influence the barrier. We also show that depending on these factors, two different H hopping mechanisms may prevail. At higher H concentration, the lattice expands by as much as 19 % by volume, making it easier for the hydrogen atom to hop. Therefore, hydrogen diffusion is sluggish in the initial α phase, which may explain the experimentally-observed induction behavior. This study highlights the complexity associated with the metal hydride systems and provides the basis for further molecular scale kinetic studies of metal hydride systems.

Understanding electronic structure tunability by metal dopants for promoting MgB2 hydrogenation

Hydrogen is a promising energy carrier, but its onboard application is limited by the need for compact, low-pressure storage solutions. Solid-state complex metal hydride systems, such as MgB2/Mg(BH4)2, offer high storage capacities but suffer from sluggish kinetics and poor reversibility. One avenue for improving reactivity is to introduce metal dopants to alter electronic and atomic properties, but the role of these chemical additives remains poorly understood, particularly for the hydrogenation reaction. In this work, we used density functional theory calculations on model MgB2 systems to rationalize the potential role of metal dopants in destabilizing B–B bonding within the MgB2 lattice. We carried out detailed electronic structure analyses for 28 different metal dopant adatoms to identify properties that contribute to a dopant’s efficacy. Based on the simulation results, we propose that an intermediate ionic and covalent character of the bonds between adatoms and B atoms is desirable for facilitating charge redistribution, disrupting the B–B bond network, and promoting H2 dissociation and H atom chemisorption on MgB2.

Thermodynamic characterisation and application of the ZrNi–H metal hydride system in the low-pressure regime

A temperature-driven Sieverts' technique allows high-accuracy thermodynamic characterisation of the AB-type metal hydride ZrNi under vacuum. The applicability of the ZrNi–H system as a thermally operated hydrogen sorption pump is investigated.

Study of a proton exchange membrane fuel cell and metal hydride system based on double spiral structure coupling

The coupling system of a Proton Exchange Membrane Fuel Cell (PEMFC) and Metal Hydride (MH) canister was investigated, employing a double spiral structure to redirect waste heat from the PEMFC to the MH.

A hybrid modeling method of metal hydride tank and dynamic characteristic analysis

To design and optimize the thermal management of metal hydride (MH) tank, high-fidelity model (HFM) composed of numerous partial differential equations, is often adopted to capture the spatial evolution of key parameters accurately. However, computational difficulties raise in dealing with such nonlinear interconnections for system-level simulation. Therefore, the model reduction of MH system has drawn much attention aiming at the trade-off between accuracy and computational cost. In this paper, a hybrid modeling method which integrates advantages of the state-space model (SSM) and HFM, is proposed and applied for the model reduction of MH tank. In particular, four data-driven matrices are introduced to improve the model accuracy. The results show that the root mean square errors of the average temperature between hybrid reduced model (HRM) and HFM are 0.0399 K and 0.1989 K respectively for the cases without and with thermal management. In addition, the HRM is able to capture dynamic characteristic under perturbed input variables with a relative error of temperature within 0.4%, indicating great potential for system-level simulation. What's more, the analysis of predominant pole derived from the state matrices of different thermal managements, reveals that the expanded graphite has superior effect on the adjustment time extension compared with fins, while the fins have distinct advantages in heat transfer enhancement at the cost of volumetric hydrogen storage density.

Thermal performance of a metal hydride reactor for hydrogen storage with cooling/heating by natural convection

Metal hydride (MH) systems can be used for storage in stationary facilities of hydrogen with a high volume density at temperatures and pressures close to ambient ones. Recently, the possibility of using passive heating/cooling systems or regenerative heat exchangers has been studied to improve the energy efficiency of MH systems for hydrogen storage without the need for forced circulation of a heating/cooling fluid. Natural convection of air may be used to passively remove/add heat as required for proper operation of a MH reactor. Under these conditions, the MH reactor can operate at a constant ambient air temperature and be driven by a difference in pressure between the source and the consumer of hydrogen. Since operation of MH systems with natural convective heating/cooling has not been systematically investigated as yet, a tubular MH reactor based on this principle is examined in this paper. Two-thirds of the internal volume of ø25.4 × 1 mm tube is occupied by a composition of LaNi5 and aluminium foam (one linear metre contains 1.1 kg of LaNi5 with a hydrogen capacity of 153 NL H2). Annular fins are used to increase heat transfer to air. Detailed and simplified mathematical models of the systems of this class are proposed and validated. It is shown that acceptable hydrogen charging/discharging rates in such systems are achieved with proper selection of fining characteristics. Charging from a hydrogen source at a pressure of 10 atm and an ambient air temperature of 10 to 30 °C takes 15 min. A reactor with a length of 1 m can desorb almost all stored hydrogen at a minimum outlet pressure of 0.45 bar to feed 30–300 W fuel cells.

Experimental investigation, development of machine learning model and optimization studies of a metal hydride reactor with embedded helical cooling tube

Metal hydride hydrogen storage systems are gaining popularity due to their advantages and suitability for various applications in variety of fields. In this study, a metal hydride reactor using LaNi5 as metal hydride and using water as heat transfer fluid flowing through embedded helical tube was fabricated and experimentally studied. The aim of this study is to experimentally investigate the effect of internal heat transfer arrangement on the absorption and desorption of hydrogen in a metal hydride system. The effect of mass flow rate and temperature of heat transfer fluid, effect of hydrogen supply pressure on the rate of hydrogen absorption and desorption was investigated. It was found that the increase in the hydrogen supply pressure, increase in mass flow rate and decrease in the temperature of heat transfer fluid, results in faster hydrogen absorption rate. Similarly, the increase in mass flow rate and the temperature of heat transfer fluid results in faster hydrogen desorption rate. It was also found out that maximum hydrogen absorbed inside metal hydride reactor was around 34.5 g which corresponds to a gravimetric capacity of 1.34 wt%. Further based on the experimental data various machine learning models were developed and tested and then these models were used for performance prediction. It was found that tree-based regression machine learning models are better compared to other models. Such models can thus be used for prediction of rate of hydrogen absorbed or desorbed and metal hydride bed temperature for different parametric values without doing detailed experimental and numerical trial. Finally, the brute force approach is used to optimize the system for three different applications. The optimization techniques help to fix the value of parameters for particular application and hence save multiple experimental run of absorption and desorption. This is a novel work in the field of using machine learning for modelling and optimizing the metal hydride-based reactor. Use of such tools can save lot of computational time, efforts and experimental resources.

A dynamic model for predicting the absorption and desorption behaviors of metal hydride systems and its implementation for screening of alloys for metal hydride hydrogen compressor

The goal of the current study is to develop a dynamic model for forecasting the absorption and desorption behavior of metal hydride hydrogen system. The accuracy of the developed dynamic model is verified with the actual model. The effect of reactor diameter (10–25 mm), hydrogen supply pressure (5–20 bar) and desorption temperature (40–70 °C) on the accuracy of the temperature profile predicted by the dynamic model as compared to the actual model is investigated. The results showed that the percentage deviation of the dynamic model with actual model increase with the reactor diameter. The dynamic model predicted the average bed temperature during absorption with a maximum deviation of 4.32% (14 K) for a reactor of 25 mm diameter compared to the actual model. A maximum deviation of only 2.11% (6.32 K) was observed for the same reactor during desorption at 323 K. Further, the percentage deviation increases with the supply pressure and desorption temperature. Overall, it is observed that the slower the absorption/desorption, the better is the prediction accuracy of the dynamic model. On the other hand, the dynamic model is over 300 times faster than the actual, which saves computational time and cost. Furthermore, the dynamic model is extended for studying the coupled reactor system of a dual-stage metal hydride hydrogen compressor. Four alloy pairs are compared in terms of compression ratio, the amount of energy lost due to hysteresis, average hydrogen discharge rate, and isentropic efficiency. The comparison results suggested that an appropriate combination of AB5-AB2 type alloy is suitable for higher delivery plateau pressure, lower energy loss due to hysteresis, and a reasonable compression ratio.

A cleaner and more efficient energy system achieving a sustainable future for road transport

A novel integrated cooling system is developed for future medium to large electric vehicles by integrating the fuel cell, battery, metal-hydride, heat pump, and liquid desiccant dehumidification system to reduce power consumption and extend vehicle's driving range. The system benefits from the reuse of the normally wasted energy in the form of pressure difference and wasted thermal energy, from the hydrogen vessel, the fuel cell stack, and the battery pack. A numerical model for the proposed system and a finite element model for the dehumidifier and regenerator are developed and validated by experimental results from published data. A comprehensive evaluation of the impacts of the ambient air temperature and humidity, fuel cell current output, battery discharging C rate, and air mass flow rate on the Coefficient of Performance (COP), outlet air temperature, and cooling capacity is conducted. Two operating modes, namely non-compressive mode and heat pump supplemental mode are investigated and a detailed comparison between these two modes is undertaken. Furthermore, the proposed system under heat pump supplemental mode has been compared to other published cooling systems and dehumidification systems. Under non-compressive mode, results indicate that the proposed system can provide sufficient cooling capacity without the need of the compressor when the supply air mass flow rate is lower than 0.03 kg/s, under the specific operating situation. Under the heat pump supplemental mode, the proposed system can operate at 36 °C with a COP greater than 4, which is 56% higher than the cited published results, although the COP of the proposed system also considers battery cooling. Heat pump supplemental mode drastically reduces the 12-s insufficient cooling period that occurs at the beginning of the charging to discharging transition between the two metal hydrides to 2 s compared to non-compressed mode. Overall, this study provides a potential solution for future zero-emission vehicles by utilizing the heat and electric co-generation characteristic of the fuel cell, the isothermal characteristic of the metal hydride, and dehumidification and cooling characteristics of the liquid desiccant dehumidification system to extend the driving range of the electric vehicles and reduce energy consumption for cooling. Moreover, the proposed system can also provide domestic cooling loads and power by integrating the system into residential buildings.

Dynamic analysis and control optimization of hydrogen supply for the proton exchange membrane fuel cell and metal hydride coupling system with a hydrogen buffer tank

Dynamic response hysteresis in the hydrogen supply process of a proton exchange membrane fuel cell (PEMFC) and metal hydride (MH) coupling system (PEMFC-MH system) is a significant challenge, especially during transient loads. Accordingly, this study proposes a PEMFC-MH system equipped with a hydrogen buffer tank, and the heat required by MH tanks is supplied by PEMFC waste heat through the circulating water. Additionally, this study develops three control methods, including proportional-integral-derivative control (PID), fuzzy PID control, and PID coupled with model predictive control (PID-MPC) to address the response hysteresis issue. Furthermore, this study analyzes and summarizes the variation regulations of key performance parameters, and evaluates the overall performance and energy-saving effects of the system under periodic variable current conditions. Results demonstrate that dynamic response of the proposed system can be significantly improved by implementing the pressure control target in the buffer tank. Additionally, the PID-MPC control method exhibits the optimal comprehensive control effect, combining the fast regulation rate and strong anti-interference advantages. Under PID-MPC control, the main performance parameters such as the output voltage, output power, and hydrogen supply flow, can be rapidly stabilized following short fluctuations and hysteresis, even during current transient changes. Under periodic variable current conditions, the waste heat can provide sufficient heating power for MH to meet the required transient response when the hydrogen state of charge (SOC) is above approximately 3.1%. However, if the SOC drops below this level, the MH desorption flow will sharply decrease, necessitating prompt supplementation of external heaters or additional hydrogen. Moreover, the MH system can recover around 32.1% of the PEMFC waste heat under overall operating conditions, demonstrating significant energy-saving potential. This study can provide a theoretical basis and novel approaches for controlling the hydrogen supply process of such systems.

Thermal Management Techniques in Metal Hydrides for Hydrogen Storage Applications: A Review

Metal hydrides are a class of materials that can absorb and release large amounts of hydrogen. They have a wide range of potential applications, including their use as a hydrogen storage medium for fuel cells or as a hydrogen release agent for chemical processing. While being a technology that can supersede existing energy storage systems in manifold ways, the use of metal hydrides also faces some challenges that currently hinder their widespread applicability. As the effectiveness of heat transfer across metal hydride systems can have a major impact on their overall efficiency, an affluent description of more efficient heat transfer systems is needed. The literature on the subject has proposed various methods that have been used to improve heat transfer in metal hydride systems over the years, such as optimization of the shape of the reactor vessel, the use of heat exchangers, phase change materials (PCM), nano oxide additives, adding cooling tubes and water jackets, and adding high thermal conductivity additives. This review article provides a comprehensive overview of the latest, state-of-the-art techniques in metal hydride reactor design and heat transfer enhancement methodologies and identifies key areas for future researchers to target. A comprehensive analysis of thermal management techniques is documented, including performance comparisons among various approaches and guidance on selecting appropriate thermal management techniques. For the comparisons, the hydrogen adsorption time relative to the reactor size and to the amount of hydrogen absorbed is studied. This review wishes to examine the various methods that have been used to improve heat transfer in metal hydride systems and thus aims to provide researchers and engineers working in the field of hydrogen storage with valuable insights and a roadmap to guide them to further explore the development of effective thermal management techniques for metal hydrides.

Metal-Hydride-Based Hydrogen Storage as Potential Heat Source for the Cold Start of PEM FC in Hydrogen-Powered Coaches: A Comparative Study of Various Materials and Thermal Management Techniques

The successful and fast start-up of proton exchange membrane fuel cells (PEMFCs) at subfreezing temperatures (cold start) is very important for the use of PEMFCs as energy sources for automotive applications. The effective thermal management of PEMFCs is of major importance. When hydrogen is stored in hydride-forming intermetallics, significant amounts of heat are released due to the exothermic nature of the reaction. This excess of heat can potentially be used for PEMFC thermal management and to accelerate the cold start. In the current work, this possibility is extensively studied. Three hydride-forming intermetallics are introduced and their hydrogenation behavior is evaluated. In addition, five thermal management scenarios of the metal hydride beds are studied in order to enhance the kinetics of the hydrogenation. The optimum combination of the intermetallic, hydrogenation behavior, weight and complexity of the thermal management system was chosen for the study of thermal coupling with the PEMFCs. A 1D GT-SUITE model was built to stimulate the thermal coupling of a 100 kW fuel cell stack with the metal hydride. The results show that the use of the heat from the metal hydride system was able to reduce the cold start by up to 8.2%.

Effects of tank heating on hydrogen release from metal hydride system in VoltaFCEV Fuel Cell Electric Vehicle

Metal hydride (MH) storage is known as a safe storage method because it does not require complex processes like high pressure or very low temperature. However, it is necessary to use a heat exchanger due to the endothermic and exothermic reactions occurring during the charging and discharging processes of the MH tanks. The performance of the MH is adversely affected by the lack of a heat exchanger or a suitable temperature range and it causes non-stable hydrogen supply to the fuel cell systems. In this study, effect of the tank surface temperature on hydrogen flow and hydrogen consumption performance were investigated for the MH hydrogen storage system of a hydrogen Fuel Cell Electric Vehicle (FCEV). Different temperature values were arranged using an external heat circulator device and a heat exchanger inside the MH tank. The fuel cell (FC) was operated at three different power levels (200 W, 400 W, and 600 W) and its performance was determined depending on the temperature and discharge flow rate of the MH tank. When the heat exchanger temperature (HET) was set to 40 °C, the discharge performance of the MH tank increased compared to lower temperatures. For example, when the FC power was set to 200 W and the HET of the system was at 40 °C, 1600 L hydrogen was supplied to the FC and 2000 Wh electrical energy was obtained. The results show that the amount of hydrogen supplied from the MH tank decreases significantly by increasing the flow rate in the system and rapid temperature changes occur in the MH tank.

Influence of element substitution on structural stability and hydrogen storage performance: A theoretical and experimental study on TiCr2-xMnx alloy

AB2-type alloys have been widely used for metal hydride hydrogen compressors and hydrogen storage systems. The crystal structure and hydrogen storage properties mostly rely on their composition and atomic distribution. Thus, revealing the relationship between structure and properties can lead to the design of alloys with optimized properties for hydrogen storage application. Here, the structure stability, bonding energy, thermodynamic and kinetic properties of TiCr2-xMnx (x = 0, 0.25, 0.5, 0.75, 1) alloy/hydride have been firstly investigated by combining density functional theory calculation and experiment. It demonstrates that Mn-doped TiCr2 alloy has a stable C14 phase, and Mn can optionally substitute for Cr sites. Additionally, with increase of Mn content, the desorption plateau increases and the ΔH value decreases. In particular, the ΔH values of TiCr2-xMnx hydrides are consistent with the heat released when H atoms occupy the interstitial interstices. Finally, the hydrogen absorption kinetics simulation shows that Mn is unfavorable to the hydrogen absorption kinetics, in which TiCrMn is 124 s longer than TiCr2 when 90% hydrogen-absorption capacity is reached. The relationship between calculations and experiments presents here can be used as a reference for subsequent screening of alloying elements with high melting point and cost for metal hydride system.

(Digital Presentation) Heat Transfer Enhancement in Room-Temperature Metal Hydride Storage Systems

Among the existing methods of short- and long-term storage of renewable energy, reversible metal hydrides (MH) are considered safe and volume efficient. They provide efficient hydrogen storage capacity for various applications, including Low Temperature PEM Fuel Cells (LT PEMFCs) [1]. The heat transfer in the MH reactor has a substantial influence on the efficiency of the storage process. In order to achieve the established goals for tank filling times, enhanced heat transfer techniques will be essential [2]. Therefore, this work investigates technical solutions for thermal conductivity enhancement in MH storage systems. Different tank designs are assessed in terms of their applicability and the effect of different solid matrices in the storage system on the internal heat transfer is studied. With the help of thermal imaging, the impact of the geometry of the solid matrices on the uniformity of gas distribution along the MH bed is analysed. The MH tanks are operated with room temperature (RT) metal hydrides that achieve a hydrogen storage capacity of up to 105 kgH2 m−3 in a wide range of temperatures (from 50 to -40°C). The tests are carried out within a limited pressure range of 1 to 0.1 MPa to reduce the reliance on additional H2 compressors when used in stationary applications.[1] M. V. Lototskyy et al., „Metal hydride systems for hydrogen storage and supply for stationary and automotive low temperature PEM fuel cell power modules“, Int. J. Hydrog. Energy, Bd. 40, Nr. 35, S. 11491–11497, Sep. 2015.[2] K. C. Smith, Y. Zheng, T. S. Fisher, T. L. Pourpoint, und I. Mudawar, „Heat Transfer in High-Pressure Metal Hydride Systems“, J. Enhanc. Heat Transf., Bd. 16, Nr. 2, S. 189–203, 2009.

Numerical investigation of energy desorption from magnesium nickel hydride based thermal energy storage system

The use of dual metal hydride system for thermal energy storage consists of high and low-temperature metal hydrides. In this study, a 3D cylindrical Magnesium Nickel hydride bed is analyzed for thermal energy discharge. The energy discharge from metal hydride bed initially at temperature of 400 K, a heat transfer fluid at 500 K temperature is supplied to extract the heat generated due to exothermic chemical reaction. In this article, variation of the number of heat transfer fluid tubes and effect of variation of aspect ratio (ratio of diameter to height) on energy desorption and heat transfer from metal hydride bed is performed. The optimal number of heat transfer fluid tubes is determined for various aspect ratios. The temperature variation of the metal hydride bed with an increase in the number of heat transfer fluid tubes is analyzed. The study of aspect ratio variation on energy desorption and heat transfer characteristics is analyzed for three aspect ratios 0.5, 1, and 2. The variation of thermal energy desorbed, net heat transfer and temperature variation of metal hydride bed are analyzed. The adequate number of heat transfer fluid tubes for AR 0.5, 1, and 2 is identified as 32, 48, and 72, respectively. The cumulative heat released from MH bed with AR 0.5, 1, and 2 is 350.94 kJ, 330.56 kJ, and 310.42 kJ, respectively. The study will be useful in designing the optimized metal hydride bed reactor for thermal energy storage applications.