Metal Hydride Bed Research Articles

Hydrogen discharging and thermal behaviors of ZrCo based hydrogen storage beds equipped with heat-fins or metal-foam

A numerical study is conducted to investigate the influence of additional components – a heat-fin and metal-foam – on the hydrogen discharging performance of metal hydride beds. First, a three-dimensional, transient hydrogen desorption model developed in our previous works is applied to two different experimental metal hydride beds (MHBs): one with a heat-fin and the other with metal-foam. Then, the simulation results are compared with the experimental data measured during the heat-up and hydrogen discharging processes. The prediction based on the proposed model was found to be in good agreement with the experimental data in terms of the beds temperature evolution and the hydrogen discharging time. In addition, a parametric study is conducted on various MHBs with heat-fins or metal-foams that were designed to contain the same amount of ZrCo powder for comparison purposes. Our results clearly demonstrate that a superior MHB design should exhibit higher effective conductivity in the metal powder region and a lower overall thermal mass, which can be achieved by using metal-foam with optimum porosity.

Simulation of Effective Thermal Conductivity of Metal Hydride Packed Beds

Several mathematical models are available for estimation of effective thermal conductivity of nonreactive packed beds. Keeping in view the salient differences between metal hydride beds in which chemisorption of hydrogen takes place and conventional nonreactive packed beds, modified models are proposed here to predict the effective thermal conductivity. Variation in properties such as solid thermal conductivity and porosity during hydrogen absorption and desorption processes are incorporated. These extended models have been applied to simulate the effective thermal conductivity of the MmNi4.5Al0.5 hydride bed and are compared with the experimental results. Applicability of the extended models for estimation of the effective thermal conductivity at different operating conditions such as pressure, temperature, and hydrogen concentration is discussed.

Measurement and Simulation of Transient Phenomena in Metal Hydride Bed

The article analyses the measurement with increased absorption kinetics of hydrogen into the La0.85Ce0.15Ni5alloy. Within a time interval of 180 s an amount of 0.142 kg (1.58 m3) of hydrogen was absorbed into 56 kg of alloy. The process of absorption was accompanied by an increased temperature of the bed. Therefore it was simultaneously cooled by a cooler using Peltier elements. The numerical calculation of non-stationary heat transfer within the bed was performed with a known amount of heat generated in the bed, known temperatures and flow rates. Simulation results allow us to determine temperature time paths at key points of the bed and give insight on the transient phenomena which occurs in the extreme load of the metal hydride (MH) bed. This allows establishing safe limits for the absorption of hydrogen into a particular alloy.

Measurement of Temperature Fields in Methal Hydride Storage Container

The article analyses the measurement with increased absorption kinetics of hydrogen into the La0.85Ce0.15Ni5 alloy. Within a time interval of 180 s an amount of 0.142 kg (1.58 m3) of hydrogen was absorbed into 56 kg of alloy. The process of absorption was accompanied by an increased temperature of the bed. Therefore it was simultaneously cooled by a cooler using Peltier elements. The numerical calculation of non-stationary heat transfer within the bed was performed with a known amount of heat generated in the bed, known temperatures and flow rates. Simulation results allow us to determine temperature time paths at key points of the bed and give insight on the transient phenomena which occurs in the extreme load of the metal hydride (MH) bed. The temperature field is analyzed for different values of thermal conductivity, view of its change during the lifetime of metal hydride. This allows establishing safe limits for the absorption of hydrogen into a particular alloy.

Direct Delivery of Hydrogen Isotopes from a DU Hydride Bed

A tritium plant for nuclear fusion power plants consists of an SDS (Storage and Delivery System), an ISS (Hydrogen Isotope Separation System), a TEP (Tokamak Exhaust Processing system), and an ANS (tritium plant Analytical System). Korea has been developing an SDS. The main purpose of this tritium storage and delivery system is to store and supply the D-T gas needed for DT plasma operation and to provide the necessary infrastructure for short- and long-term storage of large amounts of tritium. We have been developing tritium storage beds for the SDS.The primary role of the metal hydride beds in the SDS is to store and supply D-T fuel during DT plasma operation. ZrCo and depleted uranium (DU) have been extensively studied. Compared to the use of ZrCo, which is disproportionate at temperatures of higher than 350°C, DU hydride can be heated up to very high temperatures sufficient to pump hydrogen isotopes without using gas compressors. Our experimental apparatus used to test the experimental DU bed consists of a tank that stores and measures the hydrogen, and a DU bed used for the hydriding/dehydriding of hydrogen. Our DU bed is a horizontal double-cylinder type with sintered metal filters. The bed is composed of primary and secondary vessels. The primary vessel contains a DU, and a vacuum layer is formed between the primary and secondary vessels. In this study, we present our recent experimental results on the direct delivery of hydrogen isotopes from a DU hydride bed. We also present the effect of the initial bed temperature and impurity gas on the hydriding rates.

CFD investigation on performance enhancement of metal hydride hydrogen storage vessels using heat pipes

To predict the hydrogen storage performance, this study presents a mathematical model for simulating the thermal-fluid behaviours in the metal hydride beds embedding heat pipes. Computational fluid dynamics (CFD) simulations were conducted using a commercial code (ANSYS Fluent) using LaNi5 as the storage media. The model was validated by comparison with previous experimental data in literature that proves the effectiveness of heat pipes to increase the heat transfer rate between the metal hydride bed and outside the storage tank. The results showed that heat pipes profoundly changed the distribution of temperature, hydrogen content and equilibrium pressures over the metal bed. The dry-out limits of the heat pipe exerted considerable effects on the tank performance. By contrast, changing the thermal conductivity of the heat pipe made little difference because the effective thermal conductivity of the metal beds was typically much smaller than that of the heat pipe. The model was then applied to compare tank designs, with and without heat pipes and internal fins, to demonstrate the effects of using heat pipes to improve the heat and mass transfer in a hydrogen storage tank.

Fabrication and experimental validation of a full-scale depleted uranium bed with thin double-layered annulus configuration for hydrogen isotopes recovery and delivery

Metal hydride beds play an important role in the application of hydrogen-related energy. In the present work, a full-scale DU (depleted uranium) bed with the newly proposed bed design of thin double-layered annulus configuration was fabricated for hydrogen isotopes recovery and delivery. The hydrogen recovery/delivery properties and the thermal effect of the fabricated bed were experimentally investigated. It was found that the fabricated bed was able to achieve the hydrogen storage target of 17.5 mol H2 with a fast hydrogen recovery rate. Not only hydrogen delivery amount as high as 16.5 mol (∼94% of recovery amount) but also an average delivery rate of 20 Pa m3/s could be obtained at 450 °C, even though the hydrogen delivery time of the bed reached as long as 30.9 min. The fabricated DU bed also exhibited outstanding cyclic hydrogen recovery/delivery performances. Deterioration in both hydrogen recovery/delivery amount and rate was not observed even up to 10 cycles. Besides, it was shown that utilization of the water cooling loops drilled in the DU bed was beneficial to enhance the heat transfer and promote the hydrogen recovery process of the bed. Meanwhile, the internal structure of the fabricated bed was observed by ICT (industrial computed tomography). And the ICT results demonstrated that DU expanded seriously after hydrogen recovery/delivery cycles, resulting in the deformation of the filters in the bed. The experimental results suggested that the fabricated DU bed was technically feasible to be applied for hydrogen isotopes recovery and delivery in the International Thermonuclear Experimental Reactor.

Comparative study of full-scale thin double-layered annulus beds loaded with ZrCo, Zr0.8Hf0.2Co and Zr0.8Ti0.2Co for recovery and delivery of hydrogen isotopes

Metal hydride bed is a necessary component for deuterium–tritium fusion energy under development in International Thermonuclear Experimental Reactor (ITER), which is used for rapid and safe recovery/delivery of hydrogen isotopes. In the present work, full-scale thin double-layered annulus beds loaded with ZrCo, Zr0.8Hf0.2Co and Zr0.8Ti0.2Co were fabricated. The corresponding hydrogen storage behaviors including hydrogen recovery/delivery and cycling properties of the three beds were systematically investigated and compared. It was found that all the three fabricated beds could reach the hydrogen storage target of 17.5 mol. Compared with ZrCo bed and Zr0.8Hf0.2Co bed, Zr0.8Ti0.2Co bed exhibited superior hydrogen delivery properties in terms of higher hydrogen delivery amount, faster delivery rate and better cyclic delivery performance, which could deliver 17.06 mol H2 (∼94.7% of total capacity) at 450 °C within 31.8 min holding at the critical delivery rate of 20 Pa m3/s. Although the hydrogen delivery amount gradually decreased during the recovery/delivery cycles, which was revealed to be caused by the characteristic disproportionation of ZrCo based alloy, significant improvement had been gained for Zr0.8Ti0.2Co bed relative to ZrCo bed and Zr0.8Hf0.2Co bed. In addition, the industrial computed tomography (ICT) results showed that the thin double-layered annulus bed owned good structural stability during the hydrogen recovery/delivery cycles. In view of its beneficial hydrogen recovery and delivery performances, the Zr0.8Ti0.2Co bed with thin double-layered annulus configuration appeared to be a potential option for hydrogen isotopes recovery and delivery in ITER if the anti-disproportionation property could be further enhanced.

Numerical heat and mass transfer investigation of hydrogen absorption in an annulus-disc reactor

This work presents a numerical investigation of two-dimensional coupled heat and mass transfer process in a LaNi5-based annulus-disc reactor, during hydrogen absorption using the commercial software ANSYS-FLUENT 14.5. Temperature and amount of hydrogen absorbed and their averages inside the metal hydride bed are presented for different reactor design configurations and different cooling tube radii, respectively. Numerical simulations revealed that the pressure drop in the bed caused by fluid inertia may be considerable in this flow type, and the hydriding process time for the LaNi5 alloy depends on the configuration and geometrical dimensions of the tubular heat exchange device. Thus, the hydriding time minimization relates to the accommodation of the amount of heat removed from the bed reactor. A good agreement was found between the present computational results and the experimental data reported in the literature.

Effect of Delivery Condition on Desorption Rate of ZrCo Metal Hydride Bed for Fusion Fuel Cycle

For the safety of fusion fuel cycle, hydrogen isotope gases including tritium are stored as metal hydride form. To satisfy fueling requirement of fusion machine, rapid delivery from metal hydride bed is one of major factors for the development of tritium storage and delivery system. Desorption from metal hydride depends on the operation scenario by pressure and temperature control of the bed. The effect of operation scenario and pump performance on desorption rate of metal hydride bed was experimentally investigated using ZrCo bed. The results showed that the condition of pre-heating scenario before actual delivery of gas affected the delivery performance. Different pumps were connected to desorption line from bed and the effect of pump capacity on desorption rate were also found to be significant.

Numerical Comparison of Hydrogen Desorption Behaviors of Metal Hydride Beds Based on Uranium and on Zirconium-Cobalt

In this paper, the hydrogen delivery capabilities of uranium (U) and zirconium-cobalt (ZrCo) are compared quantitatively in order to find the optimum getter materials for tritium storage. A three-dimensional hydrogen desorption model is applied to two identically designed cylindrical beds with the different materials, and hydrogen desorption simulations are then conducted. The simulation results show superior hydrogen delivery performance and easier thermal management capability for the U bed. This detailed analysis of the hydrogen desorption behaviors of beds with U and ZrCo will help to identify the optimal bed material, bed design, and operating conditions for the storage and delivery system in ITER.

Experimental study on full-scale ZrCo and depleted uranium beds applied for fast recovery and delivery of hydrogen isotopes

Abstract Metal hydride bed is an important component for the deuterium–tritium fusion energy under development in International Thermonuclear Experimental Reactor (ITER), in which the hydrogen recovery and delivery properties are influenced by the bed configuration, operation conditions and the hydrogen storage materials contained in the bed. In this work, a thin double-layered annulus bed configuration was adopted and full-scale beds loaded with ZrCo and depleted uranium (DU) for fast recovery and delivery of hydrogen isotopes were fabricated. The properties of hydrogen recovery/delivery together with the inner structure variation in the fabricated beds were systematically studied. The effects of operation conditions on the performances of the bed were also investigated. It was found that both of the fabricated ZrCo and DU beds were able to achieve the hydrogen storage target of 17.5 mol with fast recovery rate. In addition, experimental results showed that operation of employing extra buffer vessel and scroll pump could not only promote the hydrogen delivery process but also reduce the possibility about disproportionation of ZrCo. Compared with ZrCo bed, DU bed exhibited superior hydrogen delivery performances in terms of fast delivery rate and high hydrogen delivery amount, which could deliver over 16.4 mol H2 (93.7% of recovery amount) within 30 min at the average delivery rate of 20 Pa m3/s. Good reversibility as high as 10 cycles without obvious degradation tendency in both of hydrogen delivery amount and delivery rate for DU bed was also achieved in our study. It was suggested that the fabricated thin double-layered annulus DU bed was a good candidate to rapidly deliver and recover massive hydrogen isotopes for fusion energy application.

Niche applications of metal hydrides and related thermal management issues

This short review highlights and discusses the recent developments and thermal management issues related to metal hydride (MH) systems for hydrogen storage, hydrogen compression and heat management (refrigeration, pump and upgrade, etc.). Special attention is paid to aligning the system features with the requirements of the specific application. The considered system features include the MH material, the MH bed on the basis of its corresponding MH container, as well as the layout of the integrated system.

Performance analysis of cylindrical metal hydride beds with various heat exchange options

A 3D numerical heat-and-mass transfer model was used for the comparison of H2 uptake performances of powdered cylindrical MH beds comprising MmNi4.6Al0.4 hydrogen storage material. The considered options of heat exchange between the MH and a heat transfer fluid included internal cooling using straight (I) or helically coiled (II) tubing, as well as external cooling of the MH bed without (III) and with (IV) transversal fins. The dynamic performances of these layouts were compared based on the numerical simulation. The effect of heat transfer coefficient was also analysed.

Influence of dynamic operating conditions on the performance of metal hydride based solid sorption cooling systems

The performance of metal hydride based solid sorption cooling systems depends on the driving pressure differential, and the rate of hydrogen transfer between coupled metal hydride beds during cooling and regeneration processes. Conventionally, the mid-plateau pressure difference obtained from ‘static’ equilibrium PCT data are used for the thermodynamic analysis. It is well known that the processes are ‘dynamic’ because the pressure and temperature, and hence the concentration of the hydride beds, are continuously changing. Keeping this in mind, the pair of La0.9Ce0.1Ni5 – LaNi4.7Al0.3 metal hydrides suitable for solid sorption cooling systems were characterised using both static and dynamic methods. It was found that the PCT characteristics, and the resulting enthalpy (ΔH) and entropy (ΔS) values, were significantly different for static and dynamic modes of measurements. In the present study, the solid sorption metal hydride cooling system is analysed taking in to account the actual variation in the pressure difference (ΔP) and the dynamic enthalpy values. Compared to ‘static’ property based analysis, significant decrease in the driving potentials and transferrable amounts of hydrogen, leading to decrease in cooling capacity by 57.8% and coefficient of performance by 31.9% are observed when dynamic PCT data at the flow rate of 80 ml/min are considered.

Numerical study of the dynamic behavior of a metal hydride pump

Metal hydride pump (MHP) is one of the unconventional pumping systems. This type of pump converts thermal energy into mechanical energy using hydrogen as a working fluid to pump liquid for low head and high discharge by Solovey AI and Frovol VP (2001).[1]. The MHP has been worked out in order to solve problems of availability of electricity or fossil energies in certain freestanding regions.In the present paper a numerical study of the dynamic behavior of MHP has been carried out with Mg2Ni alloy at various operating parameters (Desorption temperature, absorption temperature, gear ratio, pump head and surfaces of piston). This study shows that, with MHP, it is possible to pump as much as 1375 l of water in 10,000 s at a desorption temperature of 623 K and for pumping head of 5 m using one kg of Mg2Ni. Also a simulation was performed to optimize the pumping time by the integration of a heat exchanger in the metal hydride bed. In addition, a comparison between results obtained with steady and unsteady models is done.

Studies on La based intermetallic hydrides to determine their suitability in metal hydride based cooling systems

The La0.9Ce0.1Ni5, La0.8Ce0.2Ni5, LaNi4.7Al0.3 and LaNi4.6Al0.4 intermetallic hydrides were characterised to determine their suitability in metal hydride based cooling system (MHCS). The performance of the MHCS depends on the driving potential, and rate and amount of hydrogen transfer between coupled metal hydride (MH) beds. Therefore, the effect of compositional changes on the variation of these parameters due to the variation in pressure – concentration isotherm (PCI) properties (storage capacity, plateau slope, hysteresis effect, etc.) of metal hydrides employed was studied. Compared to other possible MH pairs, La0.9Ce0.1Ni5 – LaNi4.7Al0.3 hydride pair exhibited high driving potential and transferrable amount of hydrogen, during cooling and regeneration processes, thereby better MHCS performance. In addition, the effect of change in hydrogen concentration (due to hydrogen transfer between coupled MH beds) on reaction enthalpy (ΔH) consequently on MHCS performance was found significant.

Using metal hydride H2 storage in mobile fuel cell equipment: Design and predicted performance of a metal hydride fuel cell mobile light

This study examines the practical prospects and benefits for using interstitial metal hydride hydrogen storage in “unsupported” fuel cell mobile construction equipment and aviation GSE applications. An engineering design and performance study is reported of a fuel cell mobile light tower that incorporates a 5 kW Altergy Systems fuel cell, Grote Trilliant LED lighting and storage of hydrogen in the Ovonic interstitial metal hydride alloy OV679. The metal hydride hydrogen light tower (mhH2LT) system is compared directly to its analog employing high-pressure hydrogen storage (H2LT) and to a comparable diesel-fueled light tower with regard to size, performance, delivered energy density and emissions. Our analysis indicates that the 5 kW proton-exchange-membrane (PEM) fuel cell provides sufficient waste heat to supply the desorption enthalpy needed for the hydride material to release the required hydrogen. Hydrogen refueling of the mhH2LT is possible even without external sources of cooling water by making use of thermal management hardware already installed on the PEM fuel cell. In such “unsupported” cases, refueling times of ∼3–8 h can be achieved, depending on the temperature of the ambient air. Shorter refueling times (∼20 min) are possible if an external source of chilled water is available for metal hydride bed cooling during rapid hydrogen refueling. Overall, the analysis shows that it is technically feasible and in some aspects beneficial to use metal hydride hydrogen storage in portable fuel cell mobile lighting equipment deployed in remote areas. The cost of the metal hydride storage technology needs to be reduced if it is to be commercially viable in the replacement of common construction equipment or mobile generators with fuel cells.

Experimental investigations and a simple balance model of a metal hydride reactor

The metal hydride reactor filled with 5 kg of the AB5-type (LaFe0.5Mn0.3Ni4.8) alloy was investigated with respect to the hydrogen discharge rates classified using C-rate value, which is discharge of the maximum hydrogen capacity 750 st L within 1 h. The reactor cannot be fully discharged with a constant flow rate, for each temperature of hot water and flow rate there exists a moment of crisis at which the hydrogen flow drops under the constant value. The nominal capacity of the reactor reaches 80% of maximum capacity if sufficient heat transfer is provided. The simple balance model of a metal hydride reactor is developed based on the assumption of uniform temperature and pressure inside a metal hydride bed. The model permits to predict behavior of the metal hydride reactor in different operation regimes, quantitative agreement is obtained for low C-rates (less than 4) and sub-critical modes.

Risk-based multi-criteria design concept of the ITER SDS getter bed

The main objective of ITER tritium Storage and Delivery System (SDS) is contracted to develop an optimal metal hydride bed that can be reveal the unprecedented fueling performance for the Tokamak. One function of the hydride bed is to keep safety requirements in terms of confinement of tritium. The hydride material for storing the deuterium and tritium fuelling gases is being made narrow with depleted uranium (DU) by its good performance. DU also has its own uncertainties, however, in applying it to realize the getter bed system having an all-round capability, especially in aspect of safety. This paper deals with from bed design target to the design variables in terms of comparison of risk-based multi-criteria using HAZOP (risk matrix) analysis. In analysis of the risks, important variables that denotes safety-effective, or cost-effective, or maintainability-effective, or manufacturability-effective are sometimes mutually interrelated with each other. As a conclusion the authors could recommend the way to concentrate and minimize the bed design variables with most meaningful risk-containing components that can be applied to increase the performance of hydride bed. It needs, however, that further study of comparison of risk analyses should be proceeded to complete the hydride bed design.