Hydride Hydrogen Storage System Research Articles

An efficient uncertainty analysis of performance of hydrogen storage systems

The metal hydride hydrogen storage systems are gaining popularity due to their high volumetric capacity, safety and stability. The designing of these systems is complex due to many reasons, including input uncertainties. The performances of these systems are often evaluated in deterministic framework, ignoring uncertainties. This includes over-conservative safety factors in the design process increasing time and costs involved in designs. The uncertainty analysis could be a better alternative to assess system performance under such scenarios. This study investigates– i) the effect of input uncertainties on uncertainties of multiple and implicit system outputs, i.e., reaction fraction and bed temperature, ii) application of response surface and Borgonovo’s global sensitivity analysis for efficient analysis, and iii) a comparative assessment between different uncertainty methods. The methodology is demonstrated for a space heating system. Initially, a surrogate relationship is constructed between inputs-outputs using moving least square response surface, based on known input-output data estimated using COMSOL for random input realizations. Next, the sensitive inputs were identified using Monte-Carlo simulations based Borgonovo’s analysis. Finally, the effect of uncertainties of sensitive inputs on outputs were estimated using different uncertainty methods. Harr’s and Hong’s (2n) point estimate methods were observed to be highly accurate, mathematically simpler and efficient, as compared to other methods. The uncertainties of outputs were directly dependent on uncertainties of sensitive inputs. The probabilistic safety measure, reliability index, estimated using output statistics was of significant practical utility for industries to avoid deterministic safety factors based over-conservative and costly designs of storage systems.

Performance improvement of magnesium-based hydrogen storage tanks by using carbon nanotubes addition and finned heat exchanger: Numerical simulation and experimental verification

One of the important tasks of improving the properties of metal hydride reactors is the design of system with optimized heat and mass transfer. Many works are devoted to the selection of the optimal heat exchanger for metal hydride hydrogen storage systems. At the same time, it is necessary to consider the composition of the metal hydride bed, which affects thermal conductivity as well. Little attention has been paid to the study of heat transfer properties in hydrogen storage systems with a heat exchanger and a metal hydride bed based on magnesium hydride and carbon nanotubes. In this work we used numerical simulation to determine the effectiveness of carbon nanotubes addition and heat exchangers with different fin number and geometries on high-temperature magnesium-based hydrogen storage tanks performance. It was found, that increasing the number of fins from three to five makes a smaller contribution in the temperature increasing as compared to the addition of three fins to the heater. The three solid, radial and complex fins have a similar effect on the average Mg/MgH2 bed temperature at 60 min. The most optimal fin number and geometry is three radial fins in terms of the efficiency and the volume it occupies. The addition of carbon nanotubes increases the average temperature of the Mg/MgH2 bed by 67 K for a reactor equipped with a heater without fins. Hydrogen storage system with three radial fins and Mg/MgH2 bed enhanced with carbon nanotubes provides an increase in the average bed temperature of about 180 K as compared to system without fins and nanotubes. This leads to a reduction in the hydrogen absorption time to reach 90% saturation by almost 63% for the three radial fins reactor with carbon nanotubes addition to the metal hydride bed. It has been confirmed that the addition of carbon nanotubes to Mg/MgH2 makes a significant contribution to the heat transfer in the metal hydride bed. In addition, it is shown that both an increase in the heat transfer area and the thermal conductivity coefficient leads to a significant improvement in the efficiency of the metal hydride reactor. In the future, the obtained results can be taken into account when designing hydrogen storage systems based on these materials.

Modeling heat and mass transfer in metal hydride hydrogen storage systems: Impact of operating parameters and reactor geometry

This work introduces a transient 2D axis-symmetrical model for hydrogen absorption in a cylindrical LaNi5 reactor employing finite volume method with a fully implicit Euler's time integration scheme, coupling equations for heat, mass, and momentum transport. The validated model is used to investigate the impacts of pressure, cooling fluid temperature, and variations in reactor geometry and size on temperature and reacted fraction profiles. The findings reveal that the charging pressure affects both peak temperature and reaction kinetics, whereas cooling fluid temperature predominantly impacts the absorption kinetics. A comparative analysis of two models, one incorporating Darcy's velocity and one without, demonstrates that while Darcy's law introduces numerical instability in the coupled equations, its impact on the model outcomes is negligible. The effect of changing the non-homogeneous Neumann to Dirichlet boundary condition is also demonstrated to anticipate the utilization of phase change materials (PCM) instead of the cooling fluid.

Experimental and numerical investigations on synergistic coupling of metal hydride hydrogen storage systems with low-temperature proton exchange membrane fuel-cell

Hydrogen has emerged as a promising alternative for various energy needs, and metal hydride hydrogen systems offer significant potential due to their near-ambient working conditions and safe storage. This study presents experimental and numerical investigations on a lab-scale metal hydride fuel cell system to showcase its viability in addressing future energy demands. The experimental setup includes a 41-tube Metal Hydride (MH) reactor with an outer cooling jacket, containing 3.75 kg of La0.7Ce0.1Ca0.3Ni5. The output of the reactor is coupled to a 1 kW fuel cell, with controlled hydrogen discharge at temperatures ranging from 30 to 50 °C through numerical modelling. The study found that maintaining the reactor at 40 °C was sufficient to sustain the required bed pressure for a 1 kW fuel cell. Numerical simulations revealed that a 1 kW fuel cell operating at a current density of 0.8 A/cm2 and 50 °C rejected approximately 1.3 kW of waste heat. Moreover, 3.75 kg MH reactor could discharge hydrogen at a constant rate of 13 l/min for 36.3 min with just 125–225 W of heat input, highlighting the thermal coupling potential between these systems. The energy efficiency of the coupled MH-PEMFC system increased by 1.8 times to reach 49% at 50 °C. Additionally, the waste heat generated proved sufficient to provide the required endothermic heat to multiple MH reactors, with a single reactor utilizing only 16.3% of the total waste heat. This integrated system demonstrates promising efficiency and sustainability for future energy applications.

CFD simulation of heat and mass transfer processes in a metal hydride hydrogen storage system, taking into account changes in the bed structure

CFD modelling of heat-and-mass transfer in metal hydride (MH) beds is an important step in the development and optimisation of MH reactors for hydrogen storage, compression and separation/purification. In the existing models, the mass conservation equation includes the density of solid in the non-hydrogenated (ρs) and hydrogen-saturated (ρss) states. To provide constant porosity of the MH bed during H2 absorption/desorption, assumption ρs<ρss is typically taken. However, this assumption contradicts to well-known fact that hydrogenation of hydride-forming alloys is accompanied by the expansion of crystal lattice of the metallic matrix and, therefore, by the decrease of the solid density by 15–25%.This work presents results of the modelling which takes this effect into account. The model assumes that the density of the MH changes linearly as the starting hydride-forming alloy is saturated with hydrogen, while the volume of the MH bed remains constant. The last assumption is a limiting estimation because it provides the maximum possible reduction in the porosity during H2 absorption process.The model was validated using published experimental data on a cylindrical MH reactor filled with 422 g of LaNi5. It was shown that accounting the realistic changes in the MH density can significantly affect the simulation results.

Experimental study on charging and discharging characteristics of copper finned metal hydride reactor for stationary hydrogen storage applications

With the shift in power generation methods from conventional to renewable, the need for energy storage has increased, and hydrogen as a carrier has great potential. The storage of hydrogen is one of the main obstacles to the effective deployment of the hydrogen economy. Since metal hydride offers a higher energy density than conventional methods, it can potentially be used to store and deliver hydrogen. Also, the metal hydride hydrogen storage system is the primary element of the energy storage system that connects hydrogen production and consumption. Therefore, the present study is focused on the development and testing of a metal hydride reactor. In the present experimental study, 9 kg of La0.7Ce0.1Ca0.3Ni5 is loaded in a single tube copper finned reactor attached to an external jacket, and the charging and discharging characteristics related to hydrogen storage are analysed along with variations in its thermal performance under various operating conditions. Also, the effect of HTF temperature on the hydrogen release performance of the copper finned reactor is studied under constant discharge pressure and constant discharge flow rate. Further, a comparison has been made between the copper and aluminium finned reactors. This fabricated copper finned reactor attained volumetric and gravimetric storage densities of 21.78 kg per m3 of H2 and 0.77%, respectively. The results indicated that La0.7Ce0.1Ca0.3Ni5 filled within the copper finned reactor stores 1.45 wt.% (130.7 g) of hydrogen in 680 s, corresponding to 25 bar feed gas pressure. At the HTF temperature of 60 °C, the copper-finned reactor discharged 1.42 wt.% (127.3 g) of hydrogen in 1450 s, showing the release of 98% of the stored mass of hydrogen. Further, the developed copper finned MH reactor could supply hydrogen at a constant rate of 13 lpm with a capability of 90% discharge even at a discharge temperature of 30 °C. Beside this, the comparative results showed that adding copper fins showed a considerable improvement over aluminium fins during discharging compared to the charging process. The copper-finned reactor consumed 20.9% and 23.6% less time to release 1 wt.% of hydrogen than the aluminium-finned reactor at discharge temperatures of 40 °C and 50 °C, respectively.

Research on hydrogen fuel cell backup power for metal hydride hydrogen storage system

Abstract Hydrogen fuel cells are characterized by non-pollution, high efficiency and long power supply time, and they are increasingly used as backup power systems in substations, communication base stations and other fields. In this paper, based on the thermodynamic model of the hydride hydrogen storage system, the relationship between pressure, composition, and temperature in metal hydride hydrogen storage is quantitatively analyzed using a PCT curve. The hydrogen fuel power supply is used as the overall backup power supply of the DC system, and the hydrogen-fuel integrated backup power supply is established to realize the uninterrupted switching between the utility power and the backup power supply. Finally, the working process of the backup power supply and the reaction process of hydrogen are analyzed to test the feasibility of a hydrogen fuel cell backup power supply. The results show that the operating current climbs to the end of 80 A under the 5 kW workload demand of the communication equipment. In addition, the hydrogen absorption reaction rate was 0.29 Mpa, and the hydrogen release reaction rate was 0.21 Mpa at a temperature of 291 K. This study has developed a fuel cell backup power system that can provide uninterruptible backup power and has a wide market capacity and application prospects.

Machine learning modelling and optimization for metal hydride hydrogen storage systems

Use of machine learning models for solid state hydrogen storage reactor development.

Thermal Energy Storage technologies for the optimal management of metal hydride hydrogen storage systems

Hydrogen is an excellent energy carrier that could enable the energy transition, however, storing it in a proper and effective way is one of hydrogen key issues. Storing hydrogen via metal hydrides (MH) can be considered a potential solution to avoid problems (safety, pressurization/liquefaction costs) related to conventional storage systems. A thermal energy storage could be coupled to the MH one, to store the heat obtained from the hydrogen absorption reaction and subsequently to release it to start and support the desorption reaction. This technology allows not to use external sources of heat or of compression, guaranteeing significant energy savings. In this work a MH hydrogen storage system (coupled to a 1 MW electrolyser used in an industrial use case) is studied, focusing on its thermal management supported by a Latent Heat Thermal Energy Storage (LTES) via Phase Change Materials (PCM). The study analyses three different metal hydrides, namely LaNi5, TiFe, TiMn1.5, and phase change materials produced by Rubitherm® Technologies GmbH. A model representing a specific electrolyser case study is then built up, enabling the evaluation of the hourly behaviour of the integrated system, the sizing of the thermal energy storage and to conduct a sensitivity analysis towards the identification of most relevant geometry parameters which affect the techno-economic performances of the system, whose are reported in the concluding part of the paper.

Study of the Structural-Phase State and Heat Transfer in a Metal Hydride Hydrogen Storage System

Study of the Structural-Phase State and Heat Transfer in a Metal Hydride Hydrogen Storage System

Cogeneration system combining reversible PEM fuel cell, and metal hydride hydrogen storage enabling renewable energy storage: Thermodynamic performance assessment

The world is still largely dependent on oil and natural gas for its energy requirements which are harmful to the environment; therefore, it is high time that we look for alternative technologies for our growing energy needs. One such emerging area is fuel cell technology which produces clean energy in the form of electrical power. Integrating a Metal Hydride Hydrogen Storage (MHHS) system with a fuel cell can help increase energy efficiency. The heat dissipated during hydrogen absorption in MHHS can be used in other applications. In this paper, energy and exergy analysis of a fuel cell-based integrated system is performed. The system presents a Reversible Proton Exchange Membrane Fuel Cell capable of working in dual modes, i.e., as an Electrolyser as well as a fuel cell. The MHHS and Vapour Absorption Refrigeration System (VARS) are coupled with a reversible fuel cell for hydrogen storage and cooling applications, respectively. While working in the fuel cell mode, maximum efficiency of 47.84% is evaluated at 80 °C. The system efficiency with and without the VARS system at 80 °C was 73.29% and 47.84%, respectively. On the contrary, in the electrolyzer mode, the maximum efficiency comes out to be 85.65%. The use of the MHHS system for hydrogen storage results in excess heat release, and as a result, the overall efficiency of the electrolyzer was increased to 94.05%.

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.

Dynamic modeling and performance analysis of metal hydride hydrogen storage system

Metal hydride hydrogen storage has the advantages of high hydrogen storage volume density, high safety, and high hydrogen purity, which can meet the hydrogen storage and supply needs of fuel cells in both mobile and fixed scenarios. It has become one of the most promising hydrogen storage methods. This work studies the dynamic performance of metal hydride hydrogen storage systems under absorption and desorption process by establishing dynamic models and heat exchange models. The dynamic properties of metal hydride hydrogen storage system are analyzed in different reaction process with the experimental test. Results show that when the ambient temperature is within a certain range, low temperatures are conducive to hydrogen absorption, while high temperatures can improve hydrogen release dynamics. Besides, raising the flow rate of hydrogen and reducing the volume fraction of hydrogen storage materials can help to improve the efficiency of hydrogen absorption and desorption reaction.

State of the Art in Development of Heat Exchanger Geometry Optimization and Different Storage Bed Designs of a Metal Hydride Reactor.

The efficient operation of a metal hydride reactor depends on the hydrogen sorption and desorption reaction rate. In this regard, special attention is paid to heat management solutions when designing metal hydride hydrogen storage systems. One of the effective solutions for improving the heat and mass transfer effect in metal hydride beds is the use of heat exchangers. The design of modern cylindrical-shaped reactors makes it possible to optimize the number of heat exchange elements, design of fins and cooling tubes, filter arrangement and geometrical distribution of metal hydride bed elements. Thus, the development of a metal hydride reactor design with optimal weight and size characteristics, taking into account the efficiency of heat transfer and metal hydride bed design, is the relevant task. This paper discusses the influence of different configurations of heat exchangers and metal hydride bed for modern solid-state hydrogen storage systems. The main advantages and disadvantages of various configurations are considered in terms of heat transfer as well as weight and size characteristics. A comparative analysis of the heat exchangers, fins and other solutions efficiency has been performed, which makes it possible to summarize and facilitate the choice of the reactor configuration in the future.

Metal Hydride Hydrogen Storage (Compression) Units Operating at Near-Atmospheric Pressure of the Feed H2

Metal hydride (MH) hydrogen storage and compression systems with near-atmospheric H2 suction pressure are necessary for the utilization of the low-pressure H2 produced by solid oxide electrolyzers or released as a byproduct of chemical industries. Such systems should provide reasonably high productivity in the modes of both charge (H2 absorption at PL ≤ 1 atm) and discharge (H2 desorption at PH = 2–5 atm), which implies the provision of H2 equilibrium pressures Peq &lt; PL at the available cooling temperature (TL = 15–20 °C) and, at the same time, Peq &gt; PH when heated to TH = 90–150 °C. This work presents results of the development of such systems based on AB5-type intermetallics characterized by Peq of 0.1–0.3 atm and 3–8 atm for H2 absorption at TL = 15 °C and H2 desorption at TH = 100 °C, respectively. The MH powders mixed with 1 wt.% of Ni-doped graphene-like material or expanded natural graphite for the improvement of H2 charge dynamics were loaded in a cylindrical container equipped with internal and external heat exchangers. The developed units with a capacity of about 1 Nm3 H2 were shown to exhibit H2 flow rates above 10 NL/min during H2 charge at ≤1 atm when cooled to ≤20 °C with cold water and H2 release at a pressure above 2 and 5 atm when heated to 90 and 120 °C with hot water and steam, respectively.

Exergy analysis of reversible sofc coupled with organic Rankine cycle and hydrogen storage for renewable energy storage

Due to the ever-rising demand for energy and the need to address the critical issue of global warming, the focus on efficient energy systems driven by renewable energy has gained a lot of attention. Integrating fuel cells with renewable energy is a very attractive and promising solution to achieve this aim. In this study, a novel tri-generation system is presented and analysed for its exergetic performance. A Metal hydride hydrogen storage (MHHS) system is used in the study to supply hydrogen to the Solid oxide fuel cell (SOFC). In the ORC cycle, n-octane is selected as the working fluid due to its high critical temperature. Exergy analysis of the overall system helps in finding out the system components where the most energy is getting degraded. For the analysis, the exergy efficiency pertaining to net electrical power output, heating and cooling performance and tri-generation is considered as the basis of exergy assessment. MATLAB is used to develop a steady-state Parametric analysis is performed by varying the important parameters such as SOFC current density, SOFC temperature and pressure at the turbine inlet. As per the outcome of the present study, the maximum exergy efficiency was reported to be 46.5% at specific operating conditions. The ORC evaporator, heating application and fuel heat exchanger were the major sites for the exergy destruction with values of 258 kW, 175 kW and 91 kW respectively. Also, a maximum gain in exergy efficiency of around 17.4% was reported after incorporating a tri-generation system instead of power cycle alone.

Review of thermal management technology for metal hydride reaction beds

Metal hydride (MH) hydrogen storage systems have gained interest in the last decades. This review evaluates and compares the impact of thermal management measures on heat and mass transfer, summarizing the benefits and drawbacks of different reactor structures.

ЭКСПЕРИМЕНТАЛЬНОЕ ИССЛЕДОВАНИЕ МОДЕЛИ ТРАНСПОРТНОГО СРЕДСТВА С СИЛОВОЙ УСТАНОВКОЙ НА ВОДОРОДНЫХ ТОПЛИВНЫХ ЭЛЕМЕНТАХ

The design and principle of operation of the hydrogen generator are considered, the process efficiency is determined. The chemical composition of the metal hydride hydrogen storage system was investigated. Description of the design and operating principle of the hydrogen fuel cell is given. The results of an experimental study of a hydrogen fuel cell vehicle model with registration of electrical parameters are given.

Effects of Different Heat Transfer Conditions on the Hydrogen Desorption Performance of a Metal Hydride Hydrogen Storage Tank

To investigate the influence of thermal effects on the hydrogen desorption performance of the metal hydride hydrogen storage system, a two-dimensional numerical model was established based on a small metal hydride hydrogen storage tank, and its accuracy was verified by the temperature variations in the reaction zone of the hydrogen storage tank during hydrogen desorption. In addition, the influence of the heat transfer medium on the heat and mass transfer performance of the hydrogen desorption reaction was analyzed. An external heat transfer bath was added to simulate the thermal effect of the model during the hydrogen desorption reaction. The temperature and type of heat transfer medium in the heat transfer bath were modified, and the temperature and reaction fraction variations in each zone of the hydrogen storage model were analyzed. The results showed that under heat transfer water flow, the reaction rate in the center region of the hydrogen storage tank was gradually lower than that in the wall region. The higher the temperature of water flow, the shorter the total time required for the hydrogen desorption reaction and the shortening amplitude is reduced. The variations in the temperature and hydrogen storage capacity during hydrogen desorption were similar, with water and oil as the heat transfer medium, under the same flow rate and heat transfer temperature, however, the heat transfer time and hydrogen desorption time of water were about 10% and 5% shorter than that of oil, respectively. When the air was used as the heat transfer medium, the heat transfer rate of the air convection in the channel was lower than the heat transfer rate of the tank wall, reducing the temperature difference between the air and alloy on both sides of the wall, decreasing heat transfer efficiency, and significantly prolonging the time required for hydrogen desorption.

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.