Hydrogen Storage Beds Research Articles

Modeling of creep-fatigue features of hydrogen storage bed and its parameter optimizing based on finite element method and orthogonal experimental design with artificial neural networks

Regarding the creep-fatigue behavior of hydrogen storage bed (HSB) structures under high-temperature loading and internal pressure loading under repeated hydrogen absorption and desorption process, the heat transfer characteristics and creep-fatigue life during a complete service process in HSB were calculated using Ansys Workbench and Ncode software, and the reliability of the life results calculated by finite element method were validated using ASME code. Based on orthogonal experimental design (OED) theory, an orthogonal experimental table with 4 factors and 5 levels was compiled for the four process parameters: diameter of cooling tube, thickness of cylinder wall, spacing between inner and outer layers, and heat transfer coefficient of condensate. Moreover, an optimization method based on OED coupled with BP ANNs was proposed to find the best process parameters. And the importance of each parameter was analyzed based on range analysis and analysis of variance (ANOVA) to divide the process parameters into rough optimized parameters and precise optimized parameters in this method. In order to identify the optimal process parameter combination of HSB, the maximum life and corresponding process parameter combinations were identified based on OED and the combined method, respectively. The maximum life identified by the combined method proposed in this work is increased by 10.23 % than that identified by OED, which shows the superiority of this combined method.

Method for screening paired metal hydrides with appropriate phase change material for a thermochemical energy storage system

Thermochemical energy storage (TES) systems using coupled metal hydrides (MHs) have long been recognized as an option for sustainable energy systems such as solar power plants. The MHs-TES system consists of two linked MH beds (energy storage bed and hydrogen storage bed) that exchange hydrogen during the heat storage/release cycles. The heat reaction of the hydrogen storage bed is stored in a PCM as latent heat, which is recovered during the heat release step. One of the main issues of the MHs-TES system is selecting the best-suited combination of MHs and compatible PCM to satisfy application requirements. Herein, an approach is proposed for screening the right pairs of hydrides and the suitable PCM. To assess this procedure's effectiveness, a 2D-mathematical model is developed, and a computer code is established. In addition, using this code, the dynamic behavior of the MHs-TES system and the effect of the hydrogen storage bed temperature on the system's performance are examined. The Mg2Fe alloy as HTMH bed, and two LTMH beds as LTMH (LaNi4.25Al0.75 at medium temperature and LaNi5 at low temperature) are used. With an efficiency of 86.5%, the results show that Mg2Fe/LaNi5 is a viable MHs combination for a thermal storage system.

Research on the Creep and Fatigue Evaluation Method of the Double-Layered Annulus Metal Hydride Bed Combined with Numerical Modeling and ASME Code

Applied to a hydrogen absorption-desorption cycle, the hydrogen storage bed will experience higher exchange temperatures and variety of mechanical load. Due to the complex structure of the double-layered annulus metal hydride bed and the importance of thermal stress on the failure of a metal hydride bed, the numerical modeling of its hot spot stress was carefully carried out. Moreover, in this paper, an analysis method considering the limit failure mode condition is proposed to deal with the stress analysis in the process of hydrogen absorption and desorption. According to the proposed analysis method, the maximum stress of thermal-structural coupling in the process of hydrogen absorption occurs at about 1/3 along the diameter direction and at the geometric mutation of the connection between the cooling pipe and the main body of the hydrogen storage bed in the process of hydrogen desorption. Apart from that, the hydrogen storage bed is also subjected to thermal-mechanical fatigue by the iterative process of absorption and desorption, and its operating temperature range is in the thermal creep temperature region. Based on the distribution of the stress and temperature, evaluation hot sites were selected and the ASME-NB and ASME-NH codes were used to evaluate fatigue and fatigue creep, respectively. The evaluation showed that the fatigue damage generated during its service life is small, while the creep damage is relatively large and the total damage generated during the service life of the hydrogen storage bed is within the safe range. Aiming at the structure and complex process of a double-layer hydrogen storage bed, creep and fatigue evaluation methods are proposed, various failure modes of hydrogen storage bed are highlighted, and the relationship between process parameters and life is established.

Studies on long-term and buffer modes of operations of a thermal energy storage system using coupled metal hydrides

Metal hydride based thermal energy storage systems have attracted great attention due to their compactness and wide operational range. In long-term mode of operation, thermal energy is stored for long durations, whereas in buffer mode the heat storage is for immediate consumption, usually to cater for load fluctuations. This paper investigates a thermal energy storage system consisting of Mg2Ni-LaNi5 pair of metal hydrides in long-term and buffer modes of operation. Two inter-connected cylindrical reactors are simulated for multiple operating cycles using COMSOL Multiphysics®. The variations in porosity and density of hydride beds with hydrogen concentration during charging and discharging processes are considered. The effects of heat source temperature and the hydrogen storage bed temperature on the thermal performance of the system are investigated. The influence of hydrogen storage bed temperature is more significant in buffer operation than in long-term mode operation. With the heat source at 300 °C, the system achieved a storage density of 532.64 MJ m−3 with 67.8% and 430.28 MJ m−3 with 91.2% in long-term and buffer modes, respectively.

Numerical simulation of thermal stress and life assessment of a thin double-layer metal hydride bed under combined thermal and mechanical loads

In this work, the finite element model of the hydrogen absorption process in the thin double-layered metal hydride bed (MHB) has been established. The Johnson–Cook constitutive model, considering the temperature softening and strain rate hardening effect, was used to simulate the mechanical behavior of 316L stainless steel during the hydrogen absorption and desorption processes. The simulation results agree well with the experimental results, which verifies the effectiveness of the numerical model. The equivalent stress distribution of the stainless steel bed in the process of hydrogen absorption and desorption has been calculated by the aforementioned model. The influence of the defect depth and opening angle on tank safety has been calculated and analyzed considering the possible defects in the welding process and service life. Finally, according to the American Society of Mechanical Engineers boiler and pressure vessel code criterion, the fatigue–creep interaction condition of the MHB was predicted and analyzed. This work can provide an effective reference for the design of a hydrogen storage bed.

Hydrogen storage and heat transfer properties for large-capacity double thin-layered annulus ZrCo bed with secondary containment cavity

Fast heat and mass delivery with high cycling stability of the core component, hydrogen storage bed, in SDS are essential for the operation of the future tritium factory in ITER project. However, the aforementioned properties are still perplexing in large-capacity ZrCo bed, especially for that with secondary containment structure required by the actual tritium operation in the future. Herein, the performance including heating, cycling and cooling with two different size ZrCo beds (loading of ZrCo are 200 g and 2000 g respectively) were systematically studied. The experimental data shows that the maximum heating ability of the middle-size/full-scale storage bed are both about 10 °C/min, and the maximum hydrogen absorption capacity of these ZrCo beds are 44.6 L/405.5 L, respectively. Besides, hydrogen pressure and hydrogen retention during the following desorption can affect the cycling performance of the ZrCo bed. The use of transfer pump can reduce the pressure of the bed during the hydrogen desorption process (operated at 500 °C), which inhibits the disproportionation reaction of the ZrCo alloy. However, the degree of hydrogen pressure reduction in two the types of ZrCo bed are different. As a result, the cycling capacity of the middle-size bed (93.4%, lower hydrogen pressure) is higher than the full-scale bed (68.7%, higher hydrogen pressure) after 10 cycles. When the transfer pump was not used and operated at lower temperature (350 °C), the beds cannot release hydrogen completely, and partial hydrogen atoms are retained in the ZrCo alloy. The middle-size bed still maintains a hydrogen storage capacity of 94.5% after 10 cycles, while 75.9% of the hydrogen storage capacity remained for the full-scale bed. Therefore, the increase of hydrogen surplus in ZrCo alloy is helpful to improve its cycling stability. At last, the cooling performances of the beds under 10 different cooling methods were studied. Among the cooling methods, the best cooling rate was achieved by filling nitrogen in the secondary containment cavity and flowing water passing through the cooling circuit of the bed. This work will provide a crucial reference for the design and optimization of the subsequent operation technology of SDS in ITER. • Thin double-layered annulus ZrCo bed with secondary containment cavity is manufactured. • Real-time pumping transfer helps to improve the circulation stability of the ZrCo bed. • Keep remaining H in the ZrCo is benefits to improve its cycling stability.

System optimization of heat transfer performance of hydrogen storage bed based on backpropagation neural network-genetic algorithm

ABSTRACT Seven structural parameters that affected the heat transfer performance were proposed as optimization variables to enhance the heat transfer and thermal reaction capacity of the thin double-layered annular zirconium–cobalt (ZrCo) bed of hydrogen metal reactor and to improve the hydrogen storage performance. We used the Taguchi method to conduct numerical experimental sampling and construct a three-dimensional model of the hydrogen absorption of a hydrogen storage bed. COMSOL software was used to simulate 36 models of the hydrogen absorption process and changes in the temperature and time of the hydrogen storage bed under different conditions were identified. A new hybrid method combining a neural network and the genetic algorithm was proposed by taking the hot-spot temperature of the bed and the cooling time when it was cooled to 300 K as the optimization objectives. The algorithm was implemented, and the relationship between the process parameters and the objective function was established. A model response analysis was conducted to improve the understanding of the behavior of the backpropagation model and to analyze the sensitivity of the parameters. This hybrid method was used to optimize the parameters to obtain an excellent hydrogen storage performance. The results showed that the predicted value of the neural network model was highly consistent with the numerical simulation results. The number of cooling tubes had the greatest impact on the heat transfer performance, and the optimal combination of the input parameters was obtained. When the optimized parameters were used to reach the target temperature, the cooling time was reduced by 78s, which provided guidance for the design and operation of hydrogen storage beds.

Optimal design of a metal hydride hydrogen storage bed using a helical coil heat exchanger along with a central return tube during the absorption process

Metal-hydride (MH) reactors are one of the most promising approaches for hydrogen storage because of their low operating pressure, high storage volumetric density and high security. However, the heat transfer performance of the MH reactor for high hydrogenation rate is inferior. In this study, the heat transfer and hydrogen absorption process of metal hydride tank performance in Mg2Ni bed is analyzed numerically using commercial ANSYS-FLUENT software. The MH reactor is considered a cylindrical bed including a helical tube along with a central straight return tube for the cooling fluid. The effects of geometrical parameters including the tube diameter, the pitch size and the coil diameter as well as operational parameters on the heat exchanged and hydrogen absorption reactive time are evaluated comprehensively. The results showed that the helical heat exchanger along with central return tube could effectively improve heat exchanged between the cooling fluid and the metal alloy and reduce the temperature of the bed results in a higher rate of hydrogen absorption. For a proper configuration and geometry of the helical coil heat exchanger with a central return tube, the absorption reaction time is reduced by 24% to reach 90% of the storage capacity. After the optimization study of the geometrical parameters, a system with the heat exchanger tube diameter of 5 mm, coil diameter of 18 mm and the coil pitch value of 10 mm is recommended to have lower hydrogen absorption time and higher hydrogen storage capacity. The presented MH reactor can be applied for improvement of heat exchange and absorption process in industrial MH reactors.

Numerical simulations on the leakage and diffusion of tritium

Based on the knowledge that the surroundings of tritium leakage and diffusion in hydrogen storage vessels can be either open space or closed space, the subsonic jet flow of a slow tritium leak from a hydrogen storage bed under open and closed spatial conditions is simulated by Fluent finite element software. Furthermore, the quantitative relationship between mass flow rate and time is established by using the user defined function (UDF) to compile interface codes. The subsonic tritium jet, velocity profiles, tritium diffusion distance, and the tritium concentration along the jet trajectory are obtained in two different scenarios (open space and closed space). The results show that the closed space inhibits the vertical convection diffusion of tritium and has a favorable improving effect on the horizontal convection diffusion of tritium, whereas the open space has the opposite influence on the convection diffusion of tritium. In addition, an eddy current whirlpool develops under the closed space condition. The concentration distribution along the jet center line can be significantly influenced by the spatial boundary condition and leak aperture. An increase of leak aperture facilitates vertical diffusion of tritium and the velocity near the leakage hole. The oblique downward wind and horizontal wind lead to an enhancement of tritium cloud horizontal drifting. The oblique upward wind can be considered as a method to effectively dilute leaked tritium concentration.

Modeling, system identification and design of fuzzy PID controller for discharge dynamics of metal hydride hydrogen storage bed

This paper presents the mathematical modeling of metal hydride based hydrogen storage bed. The novelty of this research work is the identification of transfer function for the dynamic discharge process of hydrogen storage bed is carried out using system identification tool box. A Fuzzy PID controller is modeled to regulate the pressure rate of hydrogen storage bed using MATLAB Simulink toolbox. The proposed controller reduces the complexity in controlling the pressure rate of hydrogen storage bed during desorption process for an adequate use in fuel cell and in other applications. To validate the reliability of the hydrogen storage bed model, the obtained results are verified with the results of other literature. The exact system transfer function model chosen is Box-Jenkin model, based on the simulated results of different black box model structures for the parameters such as percentage of fitness, final prediction error and the cost function. Usually, for the safer discharge of hydrogen gas, the classical PID controller is employed to control the pressure by manipulating the heating temperature of the storage bed. In order to have a better control, a Fuzzy-PID controller is proposed in this study. The proposed controller produces improved time domain response and better performance compared to the conventional PID controller.

New Power Technology for Venus Aerial Missions

In-situ exploration of Venus is challenging due to its severe environment, which is benign (25oC) at an altitude of 55 km, but rapidly becoming more hostile at lower altitudes. The temperature increases at ~7oC/km to ~465°C, with the pressure reaching 90 bars at the surface.1 These challenging conditions have limited in-situ exploration missions to high altitude balloons at 55 km (above the clouds) that lasted for 48 h, or even shorter duration surface missions that survived for two hours.2,3 The high-altitude (55-65km) balloon missions are stymied by the opaqueness of the Venusian clouds, which underlines the need for more long-duration in-situ missions for a better understanding of the Venus atmosphere across the cloud layers and below, as recommended by the Venus science community, Venus Exploration Analysis Group (VEXAG).4 Long-duration variable-altitude balloons (VABs) extending below the clouds have gained particular interest. Durable VABs would allow i) long-term measurements across Venus clouds, ii) determination of chemical species and isotopes underneath the clouds, iii) transport to different longitudes on the planet and measure atmospheric flow patterns, especially with the altitude control, iv) probing the interior structure through close-range imaging, and v) investigation of the seismic activity from acoustic measurements at various altitudes. For these missions, conventional power technologies are inadequate. For example, the performance of photovoltaics (PV) is hampered by the decreasing solar flux deeper in the clouds, the selective loss of short wavelength radiation, and the performance loss from the high temperatures.5 An energy storage system tolerant to high temperatures is needed to compensate for the reduced power generation of PVs at low altitudes, and to support nighttime operations for the VABs. In this paper, we will describe a novel ‘Venus Interior Probe using in-situ Power and Propulsion (VIP-INSPR) architecture we have been developing under NASA-NIAC (Novel Innovative and Advanced Concepts) program for sustained Venus atmospheric exploration. The probe concept utilizes: i) PV as a power source to the probe at high altitudes, and to electrolyze water carried from ground using regenerative solid oxide fuel/ electrolysis cell (SOEC), ii) Solid oxide fuel cell (SOFC)6 to provide power at low altitudes, iii) hydrogen storage bed for on-demand storage or release of hydrogen,7 iv) and a balloon filled with hydrogen and with hydrogen buoyancy-based altitude control system. Both H2 and O2 would be regenerated through electrolysis of the water produced in the fuel cell (a closed–system) at high altitudes. Acknowledgments: This work presented here was carried out at the Jet Propulsion Laboratory, California Institute of Technology under a contract with National Aeronautics and Space Administration and supported NASA-NIAC.

储氢床不锈钢疲劳寿命预测及棘轮效应和应变强化竞争机理描述

储氢床不锈钢疲劳寿命预测及棘轮效应和应变强化竞争机理描述

Hydrogen storage adsorbent systems acceptability envelope

A methodology was developed to determine the range of coupled material parameters and operating conditions that allow an adsorbent based hydrogen storage system to meet performance targets. The range of acceptable parameters forms a multi-dimensional volume, or envelope. For this reason, the methodology is referred to as the Adsorbent Acceptability Envelope. The model evaluates the performance of the overall storage tank, comprised of the adsorbent material, the heat transfer system and the pressure vessel. Two cases were analyzed, both based on the flow-through cooling approach providing the cooling power required to charge hydrogen, with results presented and discussed. The first application (the forward problem) analyzed the gravimetric and volumetric performance of MOF-5® based hydrogen storage beds, under various operating conditions. Results demonstrated that the system can reach a gravimetric capacity of approximately 4 wt% and volumetric capacity of about 20 g/L within 200 s during the absorption process. The second application (the inverse problem) identified the range of selected material parameters, required to meet the U.S. Department of Energy targets for gravimetric and volumetric capacity. Results showed that the most important parameters are the maximum capacity and the density of the material. Adsorbents having a density on the order of twice that of nominal powder form MOF-5® can meet the 2020 DOE targets (i.e. system gravimetric capacity of 0.045 kgH2/kgSystem and system volumetric capacity of 0.030 kgH2/LSystem). A density of about 3–4.5 times the nominal value is required to meet the DOE 2025 targets (i.e. system gravimetric capacity of 0.055 kgH2/kgSystem and system volumetric capacity of 0.040 kgH2/LSystem). Likewise, a material with a maximum adsorption capacity approximately equal to three times that of nominal MOF-5® can meet the 2020 DOE targets, while a maximum capacity about 4.5 times the nominal value is required to meet the 2025 DOE targets.

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.

Numerical comparison of heat-fin- and metal-foam-based hydrogen storage beds during hydrogen charging process

We numerically studied the effects of additional components for internal heat transfer enhancement—that is, heat fins and metal foams—on the hydrogen charging performance. First, we applied a three-dimensional transient hydrogen absorption model developed in our previous works to two different experimental MHBs: one with heat fins and the other with metal foam. The simulation results were then compared with the experimental data measured during the hydrogen charging processes. The model predictions were found to be in good agreement with the experimental data in terms of the bed temperature evolution and hydrogen charging time. In addition, a parametric study was conducted on various MHBs with heat fins or metal foams that were designed to contain the same amount of ZrCo powder for the sake of comparison. The detailed analysis of the hydrogen absorption behavior with different MHB designs clearly demonstrated that superior MHB design should exhibit a higher effective conductivity in the metal powder region and lower overall thermal mass; these two advanced features can be achieved by using a metal foam with optimum porosity.

Metal hydride bed system model for renewable source driven Regenerative Fuel Cell

A Regenerative Fuel Cell system, driven by renewable energy sources, has the potential to overcome the intermittent nature of renewable energy and become a reliable and feasible solution for small power stationary systems, producing electricity without pollutants. The present work describes a new system model for a metal hydride hydrogen storage bed (based on an AB5-type material) integrated into a Regenerative Fuel Cell system. The model has been validated against experimental data obtained from a Savannah River National Laboratory metal hydride bed at different operating conditions and has been integrated into a Regenerative Fuel Cell system using TRNSYS® to simulate the behavior of the overall system for selected scenarios. Results show the technical feasibility of the Regenerative Fuel Cell concept with short term energy storage (i.e. hydrogen storage) and suggest useful solutions to make the system adaptable to long term storage scenarios as well.

A numerical investigation of hydrogen desorption phenomena in ZrCo based hydrogen storage beds

Abstract In this paper, a three-dimensional (3D) hydrogen desorption model is applied to the thin double layered annulus ZrCo based hydrogen storage bed to precisely study the hydrogen desorption reaction and resultant heat and mass transport phenomena inside the bed. The 3D hydrogen desorption simulations are carried out and calculated results are compared with the experimental data measured by Kang et al. [1] . The present model reasonably captures the bed temperature evolution behavior and the hydrogen discharging time for 90% desorption. In addition, the thin double layered annulus metal hydride bed (MHB) design is numerically evaluated by comparing with a simple cylindrical MHB. More uniform distributions in the bed temperature and H/M atomic ratio and resultant superior hydrogen desorption performance are achieved with the thin double layered annulus bed owing to its high external surface to volume ratio and thus more efficient heating. This numerical study indicates that efficient design of the metal hydride bed is key to achieve rapid hydrogen discharging performance and the present 3D hydrogen desorption model is a useful tool for the optimization of bed design and operating conditions.

A multiphysics numerical model of oxidation and decomposition in a uranium hydride bed

The reaction of uranium hydride and oxygen gas in a hydrogen storage bed has been studied with multiphysics finite element modeling. The model considers rates of chemical reaction, heat transport, and mass transport within a hydride bed. Three scenarios of oxygen gas injection have been considered and the model predictions are in good agreement with experimental measurements. We find that, under the conditions studied, uranium hydride and oxygen react quickly, forming U3O8 and hydrogen gas. We also find that oxidation of uranium hydride to U3O8 produces significant material swelling which, in the reactor studied, reduces the bed porosity from 0.60 to 0.39, and decreases the permeability by a factor of almost 20. A simple, yet reasonably general, description of the process is proposed which accounts for the major changes in global bed flow properties. This model may be used to better anticipate the effects of air-ingress accidents on uranium hydride storage beds and possibly also to explore design options for uranium hydride based hydrogen generation systems.

Discharge dynamics of coupled fuel cell and metal hydride hydrogen storage bed for small wind hybrid systems

In small hybrid wind systems, excess wind energy is stored for later use during the deficit power generation. Excess wind energy can be stored as hydrogen in a metal hydride storage bed and reused later to generate power using a fuel cell. This paper deals with the discharge dynamics of the coupled fuel cell and metal hydride storage bed during the power extraction. Thermal coupling of the fuel cell and metal hydride bed is also discussed. The waste heat generated in the fuel cell is removed using a water coolant. The exit fuel cell coolant stream is passed through the metal hydride storage bed to supply the necessary heat required for desorption of hydrogen from the bed. This will also lead to a reduction in the load on the radiator. The discharge dynamics and the thermal management of the coupled system are demonstrated through a system simulation model developed in Matlab/Simulink platform.

Charging dynamics of metal hydride hydrogen storage bed for small wind hybrid systems

Small hybrid wind systems are capable of storing and supplying power for residential applications. In this paper, the excess wind energy is converted into hydrogen by electrolysis and is stored in a metal hydride. Metal hydride beds are known for their high volumetric capacity compared to the compressed hydrogen storage, and offers hydrogen storage at a reasonable operating temperature and pressure. A system simulation model is developed in Matlab/Simulink platform for the dynamics of the metal hydride hydrogen storage system, which is charged by the wind energy. The thermal loads of the metal hydride storage system is met by passing water at ambient temperature for cooling the bed while hydrogen is being absorbed. The effect of the transient turbulent wind velocity profile on the storage system is analyzed. The thermal management of the storage system plays an important role in the overall design, and hence it is discussed in detail.