Hydride Container Research Articles

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.

Thermal design of a combined hydrogen and oxygen supply system for a fuel cell in low-oxygen environments

In low-oxygen environments such as submarines or unmanned underwater vehicles, the utilization of metal hydride and hydrogen peroxide reformers has become prevalent for generating hydrogen and oxygen for fuel cell power systems. However, these systems necessitate additional thermal sources to function properly. This study presents a novel thermal management module designed to enhance the operational efficiency of fuel cell power systems in such environments. Our proposed thermal management module addresses the dual requirements of supplying heat to the metal hydride and dissipating heat from the high-temperature oxygen produced by the reformer. By strategically diverting the high-temperature wet oxygen outside the metal hydride container, heat is absorbed effectively. To accomplish this, an extensive parametric study was conducted, analyzing the phase-change heat transfer of wet oxygen, enabling us to design and manufacture a prototype of the thermal management module. The accuracy of our design was verified through experimental analysis, confirming the validity of our predictions regarding heat absorption by the metal hydride based on oxygen temperature. Notably, the implementation of our thermal management module resulted in a remarkable 2.6-fold increase in the average dehydrogenation rate of the metal hydride. In summary, this research demonstrates the excellent performance of the proposed thermal management module, offering substantial improvements to fuel cell power systems operating in low-oxygen environments.

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.

200 NL H2 hydrogen storage tank using MgH2–TiH2–C nanocomposite as H storage material

MgH2-based hydrogen storage materials are promising candidates for solid-state hydrogen storage allowing efficient thermal management in energy systems integrating metal hydride hydrogen store with a solid oxide fuel cell (SOFC) providing dissipated heat at temperatures between 400 and 600 °C. Recently, we have shown that graphite-modified composite of TiH2 and MgH2 prepared by high-energy reactive ball milling in hydrogen (HRBM), demonstrates a high reversible gravimetric H storage capacity exceeding 5 wt % H, fast hydrogenation/dehydrogenation kinetics and excellent cycle stability. In present study, 0.9 MgH2 + 0.1 TiH2 +5 wt %C nanocomposite with a maximum hydrogen storage capacity of 6.3 wt% H was prepared by HRBM preceded by a short homogenizing pre-milling in inert gas. 300 g of the composite was loaded into a storage tank accommodating an air-heated stainless steel metal hydride (MH) container equipped with transversal internal (copper) and external (aluminium) fins. Tests of the tank were carried out in a temperature range from 150 °C (H2 absorption) to 370 °C (H2 desorption) and showed its ability to deliver up to 185 NL H2 corresponding to a reversible H storage capacity of the MH material of appr. 5 wt% H. No significant deterioration of the reversible H storage capacity was observed during 20 heating/cooling H2 discharge/charge cycles. It was found that H2 desorption performance can be tailored by selecting appropriate thermal management conditions and an optimal operational regime has been proposed.

Auto-Tuning Control of Proton Exchange Membrane Water Electrolyzer With Self-Assessment and Gain Scheduling

Abstract Proton exchange membrane (PEM) electrolyzer can produce gases at the pressure suitable for direct storage into metal hydride cylinders, bypassing compressors, and other auxiliary components. For direct storage into metal hydride containers, hydrogen gas's pressure and flowrate must be well controlled. However, the PEM electrolyzer's time-variant and nonlinear dynamics call for an adaptive control to maintain its output performance. Therefore, in this paper, a model-free relay-feedback autotuning approach is proposed to tune a proportional-integral (PI) controller online. The controller determines the voltage supply to the electrolyzer to track a certain current setpoint, which corresponds to a constant hydrogen production rate. A gain scheduling approach is developed to pick up the right controller gain at different setpoints, minimizing the tuning frequency. A self-assessment algorithm is developed to determine the situations where the autotuner should activate to update the PI parameters, thus allowing the control system to be tuned autonomously. The autotuning PI control is successfully tested with a PEM electrolyzer setup. Experiment results showed that autotuner with gain scheduling could tune the controller parameters producing a desired transient behavior and is adaptive to the variations in setpoint and operating conditions.

Stress reduction in a hydride container by the addition of a glidant agent

Hydrogen absorbing materials, such as metal hydrides, present a possible solution for hydrogen storage. During the absorption process these materials swell, which can put the mechanical integrity of its container at risk. One possibility is to increase the flowability of the absorbing material, usually a fine cohesive powder, so that it can rearrange within its container during the swelling stage. In this work, we study if this rearrangement could be improved by the addition of Aerosil, a type of colloidal silica widely used as glidant agent. The walls of a stainless steel reactor are instrumented with strain gauges to measure the accumulation of stresses due to hydrogen absorption-desorption cycles. We explore the container filled with pure LaNi5 absorbing material previously activated, so as with different Aerosil-added proportions. Results show that Aerosil allows avoiding stress build-up, for all glidant concentrations used in present study.

Analysis of the fast hydrogen release from the metal hydride container applied in automotive industry

This article discusses the analysis of the hydrogen release consequences from a metal hydride container. It is focused on the hydrogen flow behaviour and temperature field change, which participates in the reduction of hydrogen desorption kinetics. Despite the thermal input of Peltier thermopiles used for heating the container, at rapid hydrogen leakage the metal hydride material cools down and this affects the self-regulation of the volume flow rate. The article describes the investigation of the container operating parameters (temperature field, pressure, flow rate, thermal input) during a rapid release of hydrogen with subsequent analysis of pressure effects on the obstacles located in the surrounding environment during an undesired hydrogen explosion. The concluding part of the article explains the mathematical relationship between the pressure of the shock wave and the distance between the obstacle and the centre of the explosion.

LaNi5 hydride powder flowability as a function of activation and hydrogen content

Volume expansion of hydrogen absorbing materials, together with inter-particle friction can cause tension accumulation in hydride containers during absorption. When hydride particles absorb hydrogen there is an important volume increase, in the order of 25%. Particles have to accommodate to the container geometry but this movement is opposed by inter-particle friction. Under certain conditions tensions can build up, compromising the mechanical integrity of the container. This phenomenon needs to be addressed at the design stage to avoid mechanical failure of the container.Flow behavior of powder materials is a relevant technological field, usually addressed by means of qualitative or quantitative flowability measuring devices. The rotating drum technique, while mainly qualitative, is well established and can be modified into a completely sealed unit. To determine the flowability of a hydride under different activation stages and hydrogen content levels we developed a rotating drum device that can be pressurized with hydrogen or depressurized. We report particle size evolution and flowability measurements of a hydrogen absorbing material (LaNi5) at different stages of activation for both absorbed and desorbed states. The results of the present study show that the flowability of LaNi5 in more dependent on the degree of activation of the sample than on hydrogen absorption state.

Novel fuel cell stack with coupled metal hydride containers

Abstract Air-cooled, self-humidifying hydrogen fuel cells are often used for backup and portable power sources, with a metal hydride used as the hydrogen storage material. To provide a stable hydrogen flow to the fuel cell stack, heat must be provided to the metal hydride. Conventionally, the heat released from the exothermic reaction of hydrogen and oxygen in the fuel cell stack to the exhaust air is used to heat a separate metal hydride container. In this case, the heat is only partially used instead of being more closely coupled because of the heat transfer resistances in the system. To achieve better heat integration, a novel scheme is proposed whereby hydrogen storage and single fuel cells are more closely coupled. Based on this idea, metal hydride containers in the form of cooling plates were assembled between each pair of cells in the stack so that the heat could be directly transferred to a metal hydride container of much larger surface-to-volume ratio than conventional separate containers. A heat coupled fuel cell portable power source with 10 cells and 11 metal hydride containers was constructed and the experimental results show that this scheme is beneficial for the heat management of fuel cell stack.

Performance of a Thermally Coupled Hydrogen Storage and Fuel Cell System Under Different Operation Conditions

The performance of a hydrogen storage prototype loaded with AB5H6 hydride, whose equilibrium pressure makes it suitable for both feeding a H2/air proton exchange membrane (PEM) fuel cell and being charged directly from a low-pressure water electrolyzer, interacting thermally with the fuel cell exhaust air, is reported. The nominal 70 L hydrogen storage capacity of the prototype suffices for hydrogen delivery at 0.5 L min−1, which allows a power supply of 50 W for 140 min from the H2/air fuel cell in the absence of thermal interaction. The storage prototype was characterized by monitoring the internal pressure and the temperatures of the external wall and at the center inside the container at different hydrogen discharge conditions. The responses of the integrated system after either immersing the metal hydride container in air or exposing it to the fuel cell hot exhaust air stream under forced convection were compared. The system shows the best performance when the heat generated at the fuel cell is used to increase the metal hydride container temperature, allowing the operation of the fuel cell at 280 W for 16 min at a high hydrogen flow rate of 4 L min−1.

Measurement of boundary conditions for numerical solution of temperature fields of metal hydride containers

The presented paper describes the measurement of boundary conditions while cooling a metal hydride (MH) container with the La0.85Ce0.15Ni5 alloy. Results are subsequently used for 3D simulation of thermal field in the container during the process of hydrogen absorption. To solve the complicated flow of cooling medium among individual pressure receptacles, ANSYS CFX simulation tool is used and the finite volume method is applied. The same simulation tool is used to describe heat conduction in the metal alloy and the container. For the given construction of the container, uniform distribution of stored hydrogen can be expected among individual receptacles. For cooling the system, cooling radiator is used which is based on Peltier elements. The radiator also enables, in case of desorption, to warm the container. By measuring flows of working substances and the relevant temperatures, it is possible to obtain, by subsequent analysis of temperature flows, the resulting value of the internal heat source. This internal heat source creates a temperature gradient in the container, which impedes exact determination of Pressure Concentration Isotherm curves that should be ideally measured at constant temperature. In addition, measuring in combination with numerical calculations offers a closer look at the absorption process directly in the hydrogen manufacturing plant where, using the alternative energy source, hydrogen is produced and subsequently stored. The results enable to optimize the cooling process in MH hydrogen storage equipment of similar construction and indicate problems with meeting the requirements of the American Department of Energy (DOE).

A case study of a hydride container performance applying non dimensional parameters

Many efforts have been done so far to understand sorption dynamics of hydride containers for hydrogen storage. Particularly, there are many articles in literature where experimental results for different hydride systems and container set-ups were successfully simulated using basically the same group of models. This fact is the base of a previous work where we defined a series of non dimensional parameters which may be used to estimate absorption time of hydride containers.In this work we compare estimated absorption times with experimental outcomes for a prototype hydride container. We performed non dimensional analysis of our finned container prototype at two scales, i.e.: overall or macroscopic container scale and pore or microscopic scale. We discuss about this simplified model approach that allows estimating, with few parameters, the reaction time of a complex-geometry prototype.The prototype container was designed according to the results of a numerical optimization that maximized the amount of hydrogen absorbed for a 3 min charging period. Experimental results indicate good agreement between estimated and experimental absorption time, making the non dimensional method a useful tool at preliminary stages of hydride container design.

Hydrogen desorption from a hydride container under different heat exchange conditions

The desorption behavior of a hydrogen storage prototype loaded with AB5H6 hydride, whose equilibrium pressure makes it suitable for both feeding a PEM fuel cell and being charged directly from a low pressure water electrolyzer without need of additional compression, was studied. The nominal 70 L hydrogen storage capacity of the container (T = 20 °C, P = 101.3 kPa) suffices for ca. 2.5 h operation of a 50 W hydrogen/oxygen fuel cell stack. The hydride container is provided with aluminum extended surfaces to enhance heat exchange with the surrounding medium. These surfaces consist of internal disk-shaped metal foils and external axial fins. The characterization of the storage prototype at different hydrogen discharge flow rates was made by monitoring the internal pressure and the temperatures of the external wall and at the center inside the container.The response of the storage device was tested at room temperature under different conditions such as natural convection in air and forced air ventilation, and at different temperatures in a thermostated water bath, representing possible real situations to feed hydrogen/oxygen fuel cells. Current results are discussed and correlated with each particular environmental condition and hydrogen flow rate. It is found that for some environmental conditions the flow rate discharge behavior improves significantly.

Guidelines for thermal management design of hydride containers

Hydrogen storage by means of hydride forming alloys has been intensely studied during last three decades. Container heat management is among the most relevant aspects of study in this field, particularly because in many cases it is the limiting factor for charge and discharge rate. However, given the complexity of the container system and the great variety of possible configurations (type of absorbing material, geometry of the container, hydrogen charge pressure, cooling temperature, etc.), according to the authors' best knowledge, yet there is no general rule for hydride containers design. In this paper we propose general design guidelines using non-dimensional parameters to assess the thermodynamic and kinetics behavior in order to predict the absorption fill up time. ► A general design criterion for hydride containers is proposed. ► Heat transfer, kinetic and reaction time are summarized in dimensionless parameters. ► Three different hydrides are studied (Ti 1.1 CrMn, LaNi 5 and Mg). ► Results are validated with analytical solution and with other authors experiments.

Experimental study and characterization of metal hydride containers

Two metal hydride containers were built at the laboratory respecting a simple and modular design for the purpose of getting useful knowledge about the similarity of elements of metal hydride containers relevant in the prediction of larger size storage unit behaviour. In this paper, we present a description of the containers and an investigation of the parameters influencing the hydrogen storage performance.

Study and characterization of a metal hydride container

Sorption performance tests were conducted on a small metal hydride hydrogen-storage prototype container. The relevant aspects considered are mainly the activation behavior, desorption capacity, desorption flow rates and heat transfer. The alloy employed to fill the container is of the AB 5 intermetallic type, its chemical composition is MmNi 4.7 Al 0.3 (Mm stands for “mischmetal,” a mixture of rare earths) and its equilibrium pressure at room temperature is about 300 kPa, which is adequate for the required operating conditions. Pressure evolution was monitored during discharge tests at constant temperature for different flow rates and initial charge pressures. A decrease in the dynamic pressure measured during the discharge was observed as a function of time, in agreement with the alloy plateau pressure slope. Also, a decrease in the dynamic discharge pressure with increasing discharge flow rates was found, associated with the hydride decomposition kinetics and heat transfer conditions.

Fuel cell power source for a cold region

Electric power generation at Maitri—the Indian Antarctic station is based on a conventional diesel generator. In spite of the high reliability and simplicity of operation, the main disadvantages of this kind of power source are its pollution potential and fuel transportation costs. In a place like Antarctica environmental protection requirements are of prime importance. Apart from gas pollution, they also suffer from various other problems such as degradation of performance due to sub-zero temperature of operation, noise pollution, solidification of lubricants and mechanical wear and tear. Fuel cells find an ideal application for alternate energy solution, and can maintain the pristine nature of Antarctica. With this objective in mind, Research & Development Establishment (Engineers), Pune, Defence Research & Development Organisation, Ministry of Defence, Government of India joined hands with Centre for Electro-Chemical & Energy Research, SPIC Science Foundation, Chennai and developed three prototype 500 W, 12 V, PEMFC fuel cell power sources for this application. PEMFC has been chosen for study and experimentation at Antarctica because the solid electrolyte Nafion-117 is used in this cell and the electro-chemical reaction is exothermic so that the fuel cell can be activated at low temperature. PEMFC was first installed and successfully demonstrated during the XVII Indian Antarctic Expedition. Further studies continued during the XVIII Indian Antarctic Expedition and a series of scientific experiments were conducted in the areas of optimisation of humidification, temperature for reactants (hydrogen and oxygen), elimination of existing humidification system, feasibility of provision of air-cooling system in lieu of water cooling system, humidifcation of gases using membrane as a medium, charging/discharging characteristics of a metal hydride container for hydrogen storage, and performance of a dc–dc converter and static inverter under sub-zero temperature of operation. Based on the results of these experiments, the design of the fuel cell power source for cold region application has been finalised. The paper deals with the design criteria and design factors to be considered for the fuel cell power source for cold region application and details of tests and test results that led to the final design concept for such an application. The paper also deals with a proposed hybrid power plant taking into account the exploitation of wind energy with a fuel cell and generation of hydrogen by an electrolyser and provision of hydrogen storage.

Feasibility study of a metal hydride hydrogen store for a self-sufficient solar hydrogen energy system

The feasibility of using metal hydride hydrogen storage in a self-sufficient solar hydrogen energy system is studied. Several potential commercial and non-commercial metal hydrides are considered to find a material having a low Δ H value, a low hysteresis effect, gentle P- C- T, plateau slopes and a high hydrogen storage capacity. A 1 N m 3 metal hydride container employing a commercial Hydralloy C15 metal hydride with the proper P- C- T curves is analysed in more detail. As the thermal behaviour of the container is crucial in our application, steady-state and time-dependent thermal properties of the container are measured and the respective models are derived. The metal hydride container is also tested under realistic conditions to get further operational experience on its technical feasibility. Based on this study, low-temperature metal hydrides seem to be technically and economically feasible for small-scale self-sufficient solar hydrogen systems in which high volumetric energy density is needed due to limited space.

The recovery, purification, storage and transport of hydrogen separated from industrial purge gas by means of mobile hydride containers

In this paper the experiment results of the recovery, purification to a high purity and transport of the hydrogen abstracted from the purge gas of a synthetic ammonia plant and the application of the hydrogen to the tin bath in a float glass factory 25 km away from the ammonia plant by means of mobile metal hydride hydrogen container are reported. Four hydride containers loaded on a truck were used to store and transport 200 Nm 3 of high-purity hydrogen on each journey. The hydrogen was abstracted from purge gas of 45–50% hydrogen content and purified to a purity of 99.999% hydrogen with a maximum recovery ratio above 70%. The influence of gas pressure and the flow rate scheme of the pretreated purge gas through the container on the hydrogen storage capacity of the container and the ratio of hydrogen recovery was reported. This process is proved to be of merit economically, environmentally and in the safety aspect. It is believed that this technology is also applicable to other industries, where high purity hydrogen in large quantities is used.

Hydrogen storage properties of Ml1−xCaxNi5 pseudobinary intermetallic compounds

The hydrogen storage properties of the pseudobinary intermetallic compounds Ml1−xCaxNi5 (where Ml is La-rich mischmetal and x varies from 0 to 0.9) were investigated over the temperature range of 25–80°C, It was found in experiment that with increasing x in Ml1−xCaxNi5 the incubation time for its first hydrogenation shortened, the first hydrogen absorption rate accelerated, the hysteresis lowered, and the dissociation pressure of the hydrides (25°C) increased when x < 0.3 but decreased in the range of x = 0.3 to 0.9. Considering the effect of the geometrical and electric factors, we deduced an equation for the dissociation pressure as a function of Ca content x. The equation agrees well with the test results.Owing to the lower cost and favourable properties of Ml0.8Ca0.2Ni5, a metal hydride container of 30 N m3 hydrogen capacity was designed and built to supply hydrogen for the hydrogen-gasoline hybrid fuel for an automobile engine.