Hydrogen Tank Research Articles

Design of Fe36.29Cr28.9Ni26.15Cu4.17Ti1.67V2.48C0.46 HEA using a new criterion based on VEC: Microstructural study and multiscale mechanical response

The present work updated empirical parameter ranges with a high adjustment to the experimental results as obtained by the means of the exploratory data analysis (EDA) method. A new high entropy alloy with FCC structure reinforced by precipitation of intermetallic phases fabricated by vacuum-argon induction melting was designed and modeled. The main results showed that the valence electron concentration (VEC) is the predominant empirical phase prediction parameter in high entropy alloys and that the lattice packing factor is necessary to determine the presence of intermetallic phases effectively. Phase stability ranges based on VEC associated with the base crystal structures and the presence of intermetallics corroborated computationally by CALPHAD and experimentally were reported. The interdendritic zone proved to be a preferential precipitation zone with precipitates of σ, TiC, and γ' phases. The γ' phase showed a size difference between the dendritic and interdendritic zone associated with diffusive Ti mechanisms. The nanoscale mechanical response determined that dislocation creep and reinforcement in the interdendritic zone are predominant creep mechanisms that obtained an effective entanglement of the dislocations increasing the strain hardening coefficient. The mechanical response of the alloy obtained is superior to the average of the alloys with FCC structure. It maintains a high ductility that allows reaching an energy absorption and damage tolerance of 43.56 GPa% showing severe plastic slip lines being in the range of use for aerospace applications and hydrogen tanks.

Research on energy utilization of wind-hydrogen coupled energy storage power generation system

The world is rich in renewable energy, and wind power generation accounts for a large proportion of renewable energy generation. The coupling of hydrogen energy and wind power generation will effectively solve the problem of energy surplus. In this study, a simulation model of a wind-hydrogen coupled energy storage power generation system (WHPG) is established. The effects of different operating temperatures on the hydrogen production and electricity consumption of alkaline electrolyzer, and on the electricity generation and hydrogen consumption of the fuel cell are studied. The suitable operating temperatures of the electrolyzer and fuel cell are determined. The energy management strategy of the coupled system is proposed considering the operating characteristics of the electrolyzer, fuel cell and hydrogen storage tank. Finally the economics of hydrogen energy storage systems are analyzed. The study shows that: (1) At the various operating temperatures, the maximum difference the electrolyzer is at 40 °C and 100 °C electrolyzer reduces electricity consumption by 0.26% and increases hydrogen production by 3.7%. (2) At different operating temperatures, the maximum difference the electrolyzer is at 30 °C and 100 °C. Fuel cell increases electricity production by 30.2% and reduces hydrogen consumption by 14.4%. (3) When the users’ demand for electricity is the same, the uncoupled system 1-hour surplus electricity is about 19.5 times the coupled system 1-hour surplus electricity, the uncoupled system 1-hour deficit electricity is about 1.54 times the coupled system 1-hour deficit electricity. (4) The hydrogen storage system has a net present value of 2347,681 ¥, a dynamic payback period of 15.3 a and an internal rate of return of 11%, the coupled system has a better economics. The WHPG improves wind power utilization and power supply stability.

Optimal economic programming of an energy hub in the power system while taking into account the uncertainty of renewable resources, risk-taking and electric vehicles using a developed routing method

Energy distribution network operation will be a major problem in the systems shortly because most changes will emerge in this domain. The presence of energy hubs, natural gas grids and dispersed generation resources at the distribution network's moderate- and low-voltage levels is the first challenge facing the energy distribution network operator. When PHEV vehicles are included in the energy hub, batteries can act as a general storage system and increase the possible integration of RES within power system networks. For the optimal operation of an energy hub that involves RES, PHEV, electrolyzer, fuel cell vehicles, boiler, hydrogen tank, rectifier, a heat storage system and inverter, a new model has been proposed in this paper. A new model has been developed for estimating consumption-related uncertainty of PHEVs during trips using information gap decision-making theory IGDT under risk aversion and risk-taking strategies. Additionally, a model for the uncertainty of RES is put out based on scenario development and reduction. A unique solution based on routing is presented since tackling the problem mentioned above might be error-prone mathematically. In this model, the possibility of entrapment in local optimum is reduced by increasing local and global searches. Finally, the proposed method is evaluated on a sample system and in different scenarios. Consequently, the proposed method maximizes target operation under risk-free and risk-averse strategies while minimizing target performance under risk-taking strategies.

A combined cooling, heating and power system with energy storage of waste heat to hydrogen

To improve the recovery of waste heat, a natural-gas based combined cooling, heating and power (CCHP) system with waste-heat to hydrogen as energy storage is proposed. In the novel system, the steam reforming of methanol (SRM) is applied in between the internal combustion engine (ICE) and absorption chiller, and integrated with a hydrogen tank and proton exchange membrane fuel cell (PEMFC) for energy storage. The mathematical model is developed to identify the thermodynamic performances of the system in three operation modes (normal, storage, supplemental) under design and off-design conditions, and multi-objective optimization is conducted to explore the optimal system performances. The results show that the overall exergy efficiencies of the three modes and reference system are 41.71 %, 46.34 %, 43.63 % and 40.51 % with given conditions, respectively. Except for ICE, the reactor accounts for 10.2% and 11.1 % exergy destruction ratio in M1 and M2 modes, while PEMFC accounts for 15% in M3 mode due to the chemical reactions. The parametric analysis demonstrates that increasing reaction temperature of SRM, methanol flow rate or working pressure of PEMFC can enhance the system exergy efficiencies for all modes. The optimal points determined by two decision methods are coincident and the energy and exergy efficiencies are 80.50 % and 43.00 %, which have increased by 0.36 % and 3.09 % than that under design conditions. The study constructs a promising scheme for realizing hydrogen storage by recovering the waste heat, and the results have verified the feasibility of the system and provided thermodynamic basis for further system configurations.

Experimental investigation on sorption performance of new high–efficiency, inexpensive H2 getters in high–vacuum, variable density–multilayer insulated hydrogen storage equipment

Hydrogen (H2) is released by the manufactured materials, which results in the deterioration of the insulation performance of liquid hydrogen (LH2) storage tanks. The getter is found in the vacuum annular space of equipment and helps maintain the high vacuum of LH2 tanks. Palladium oxide (PdO), an effective H2 getter, is expensive, resource–constrained and unsuitable for the LH2 equipment. Therefore, suitable and inexpensive alternatives were examined using LH2 storage tanks, to maintain the insulation property of the high–vacuum variable–density multilayer insulation (VDMLI) equipment better. Eight types of H2 getters were designed using in the LH2 tanks, and classified into three categories, namely, chemical, physical and physico–chemical getters (PCNHG). The sorption performance of new H2 getters was compared with that of PdO. PdO could be replaced by in the 7:1, 5:1 and 4:1 ratio by PCNHG1, PCNHG2 and CNHG in the LH2 tanks, respectively. The results demonstrated that the sorption capacity of PCNHG1 and PCNHG2 were 1.70 and 2.14 times that of the same type of getters in the market (16.35% and 20.62% higher than that of PdO, respectively). Their average H2 sorption efficiency was 1.17 times and 1.05 times of that of PdO, respectively. The minimum thermal conductivity exhibited by CNHG was only 6.34% of that of PdO, and the sorption capacity of CNHG was 1.82 and 1.44 times that of PCNHG1 and PCNHG2, respectively. However, the sorption capacities of PCNHG1, PCNHG2 and CNHG were belows that of PdO. These results help facilitate reduction in the expense of H2 getters and provide an important reference to enhance the sorption performance of getters.

Model predictive control of an on-site green hydrogen production and refuelling station

The expected increase of hydrogen fuel cell vehicles has motivated the emergence of a significant number of studies on Hydrogen Refuelling Stations (HRS). Some of the main HRS topics are sizing, location, design optimization, and optimal operation. On-site green HRS, where hydrogen is produced locally from green renewable energy sources, have received special attention due to their contribution to decarbonization. This kind of HRS are complex systems whose hydraulic and electric linked topologies include renewable energy sources, electrolyzers, buffer hydrogen tanks, compressors and batteries, among other components. This paper develops a linear model of a real on-site green HRS that is set to be built in Zaragoza, Spain. This plant can produce hydrogen either from solar energy or from the utility grid and is designed for three different types of services: light-duty and heavy-duty fuel cell vehicles and gas containers. In the literature, there is a lack of online control solutions developed for HRS, even more in the form of optimal online control. Hence, for the HRS operation, a Model Predictive Controller (MPC) is designed to solve a weighted multi-objective online optimization problem taking into account the plant dynamics and constraints as well as the disturbances prediction. Performance is analysed throughout 210 individual month-long simulations and the effect of the multi-objective weighting, prediction horizon, and hydrogen selling price is discussed. With the simulation results, this work shows the suitability of MPC for HRS control and its significant economic advantage compared to the rule-based control solution. In all simulations, the MPC operation fulfils all required services. Moreover, results show that a seven-day prediction horizon can improve profits by 57% relative to a one-day prediction horizon; that the battery is under-sized; or that the MPC operation strategy is more resolutive for low hydrogen selling prices.

Thermal management of metal hydride hydrogen storage tank coupled with proton exchange membrane fuel cells

Metal hydride (MH), considered a promising hydrogen storage material, has received wide attention. As an efficient device for hydrogen energy utilization, a proton exchange membrane fuel cell (PEMFC) generates power and releases waste heat. MH tank can supply hydrogen for PEMFC, and the waste heat produced by PEMFC can be applied to heat the MH bed for dehydriding reaction. Thermal management between MH tank and PEMFC has been studied in this work. A lumped parameter model for the PEMFC-MH system has been developed and validated. The performance of the PEMFC-MH system has been predicted, the results show that it is feasible to use waste heat produced by PEMFC for heating the MH bed. The effect of the valve's opening degree on system performance has been investigated. The performance of the PEMFC-MH system with various output powers has been studied. The hydrogen supply rate from the MH bed to PEMFC can be adjusted based on different power requirements. The valve's opening degree can be considered an effective control measure in thermal management to improve the energy efficiency of the PEMFC-MH system.

Numerical Study on Thermodynamic Coupling Characteristics of Fluid Sloshing in a Liquid Hydrogen Tank for Heavy-Duty Trucks

The large-amplitude sloshing behavior of liquid hydrogen in a tank for heavy-duty trucks may have adverse effects on the safety and stability of driving. With successful application of liquid hydrogen in the field of new energy vehicles, the coupled thermodynamic performance during liquid hydrogen large-amplitude sloshing becomes more attractive. In this paper, a three-dimensional numerical model is established to simulate the thermodynamic coupling characteristics during liquid hydrogen sloshing in a horizontal tank for heavy-duty trucks. The calculation results obtained by the developed model are in good agreement with experimental data for liquid hydrogen. Based on the established 3D model, the large-amplitude sloshing behavior of liquid hydrogen under extreme acceleration, as well as the effects of acceleration magnitude and duration on liquid hydrogen sloshing, is numerically determined. The simulation results show that under the influence of liquid hydrogen large-amplitude sloshing, the convective heat transfer of fluid in the tank is greatly strengthened, resulting in a decrease in the vapor temperature and an increase in the liquid temperature. In particular, the vapor condensation caused by the sloshing promotes a rapid reduction of pressure in the tank. When the acceleration magnitude is 5 g with a duration of 200 ms, the maximum reduction of ullage pressure is 1550 Pa, and the maximum growth of the force on the right wall is 3.89 kN. Moreover, the acceleration magnitude and duration have a remarkable influence on liquid hydrogen sloshing. With the increase in acceleration magnitude or duration, there is a larger sloshing amplitude for the liquid hydrogen. When the duration of acceleration is 200 ms, compared with the situation at the acceleration magnitude of 5 g, the maximum reductions of ullage pressure decrease by 9.46% and 55.02%, and the maximum growth of forces on the right wall decrease by 80.57% and 99.53%, respectively, at 2 g and 0.5 g. Additionally, when the acceleration magnitude is 5 g, in contrast with the situation at a duration of acceleration of 200 ms, the maximum-ullage-pressure drops decrease by 8.17% and 21.62%, and the maximum increase in forces on the right wall decrease by 71.80% and 88.63%, at 100 ms and 50 ms, respectively. These results can provide a reference to the safety design of horizontal liquid hydrogen tanks for heavy-duty trucks.

Design and fabrication of composite current collector used in 2-cell stacks for portable power generator

This study designed a planar carbon fiber composite collector plate with excellent conductivity and mechanical strength for use in the proton exchange membrane fuel cell (PEMFC). The collector plate is made of phenolic resin mixed with conductive particles such as graphite powder, and coated onto carbon fiber cloth. After the solvent is allowed to evaporate, the prepreg is cut and stacked layer by layer into a mold for the heat pressing process at 150 °C. The resin in the carbon fiber prepreg cloth is cured into a carbon fiber composite board. A computer numerical control (CNC) engraving machine was used to engrave the carbon fiber composite board into the current collector shape. The carbon fiber composite current collectors were placed into a high temperature furnace for the carbonization process. The resin between the carbon fibers is removed by the high temperature to increase conductivity. The carbon fiber composite collectors were assessed for conductivity, mechanical strength, and performance. Afterwards, a planar two cell fuel cell stack was assembled for testing performance and stability. A printed circuit board (PCB) was used to design the circuit and the planar two cell fuel cell module made using the heat pressing process. The planar two cell module was combined with a small hydrogen storage tank to form a portable power generation device.

Modeling of Liquid Hydrogen Tank Cooled with Para-Orthohydrogen Conversion

With the accelerating development of liquid-hydrogen storage facilities, the problem of boil-off hydrogen losses becomes very important. A promising method to reduce these losses is to utilize the endothermic para-orthohydrogen conversion of vented hydrogen, which can effectively decrease heat loads on a hydrogen tank. To model such a process, a hybrid computational model has been developed, based on the application of computational fluid dynamics for an ullage space, where knowledge of thermal stratification is important, and reduced-order models for other system elements. The simulation results for a spheroidal tank in selected conditions indicated a 10–25% reduction of boil-off losses due to cooling produced by vented hydrogen undergoing para-ortho-conversion.

Theoretical investigation on heat leakage distribution between vapor and liquid in liquid hydrogen tanks

As a key factor affecting thermal behaviors of liquid hydrogen (LH2) tanks, heat leakage plays an important role in accurate prediction of pressure build-up for safe storage and transportation of LH2. Uniform heat flux between vapor and liquid in LH2 tanks is widely adopted as thermal boundary condition in predicting pressure build-up process. However, a distribution of heat flux between vapor and liquid was observed during the self-pressurization process in the experimental test. In light of this, an analytically theoretical model of revealing the energy exchange process among the vapor, liquid and inner wall is proposed to investigate the heat leakage distribution ratio (HDR) between vapor and liquid in LH2 tanks. The feasibility of the model is validated by the experimental results from NASA. In the whole self-pressurization process of 25,000 s, HDR reduces from 0.803 to 0.235 under a liquid fill ratio of 90% and a total heat leakage of 71.3 W. The results show that the existence of inner wall and different thermal properties between the vapor and liquid make the heat leakage flux non-uniformly distributed into the vapor and liquid. And the geometric structure of tank, thermal properties and initial states of the vapor and liquid have a significant effect on HDR. When coupling the model with thermal multi-zone model, the relative error in pressure prediction is reduced by 61.8% against experimental results. Benefiting from the coupled model, the relative error in pressure prediction caused by the uniform heat flux boundary condition reduces from 90.16% to 8.15%. The present work establishes theoretical foundation on analyzing heat leakage distribution between the vapor and liquid for LH2 tanks, and provides useful guidance on modifying boundary conditions in accurately predicting thermal behaviors of LH2 tanks.

Economic and resilient operation of hydrogen-based microgrids: An improved MPC-based optimal scheduling scheme considering security constraints of hydrogen facilities

Optimally scheduling alkaline electrolyzers (AELs) in a hydrogen-based microgrid (HBM) can greatly unleash the operational flexibility of the HBM. However, existing scheduling strategies of AELs mostly utilize a simplified AEL model, which ignores the nonlinear coupling of electric-hydrogen-thermal sectors, violating the AEL’s security constraints thereby making the scheduling scheme infeasible. This paper proposes an improved model predictive control (MPC) based optimal scheduling framework which incorporates a scheduling correction algorithm into the basic MPC structure. This framework is utilized for implementing economic and resilient scheduling of an HBM under normal and emergency conditions, respectively. With the scheduling correction algorithm, this framework can be formulated into a computationally efficient mixed-integer linear programming, meanwhile guaranteeing the solutions strictly satisfy the security constraints of hydrogen facilities (i.e. AEL and hydrogen tank). Case studies are conducted based on real operating data of a Danish energy island Bornholm. The results demonstrate that the proposed scheduling scheme under normal conditions can contribute to significant comprehensive benefits from the daily operation cost saving of 68%, computational time saving of 98%, and satisfying the security constraints of hydrogen facilities, compared to previous scheduling strategies. Besides, it sharply reduces load shedding under emergency conditions by proactively allocating distributed energy sources in the HBM.

Numerical Modeling for Rapid Charging of Hydrogen Gas Vessel in Fuel Cell Vehicle

As a fuel for power generation, high-pressure hydrogen gas is widely used for transportation, and its efficient storage promotes the development of fuel cell vehicles (FCVs). However, as the filling process takes such a short time, the maximum temperature in the storage tank usually undergoes a rapid increase, which has become a thorny problem and poses great technical challenges to the steady operation of hydrogen FCVs. For security reasons, SAE J2601/ISO 15869 regulates a maximum temperature limit of 85 °C in the specifications for refillable hydrogen tanks. In this paper, a two-dimensional axisymmetric and a three-dimensional numerical model for fast charging of Type III, 35 MPa, and 70 MPa hydrogen vehicle cylinders are proposed in order to effectively evaluate the temperature rise within vehicle tanks. A modified standard k-ε turbulence model is utilized to simulate hydrogen gas charging. The equation of state for hydrogen gas is adopted with the thermodynamic properties taken from the National Institute of Standards and Technology (NIST) database, taking into account the impact of hydrogen gas’ compressibility. To validate the numerical model, three groups of hydrogen rapid refueling experimental data are chosen. After a detailed comparison, it is found that the simulated results calculated by the developed numerical model are in good agreement with the experimental results, with average temperature differences at the end time of 2.56 K, 4.08 K, and 4.3 K. The present study provides a foundation for in-depth investigations on the structural mechanics analysis of hydrogen gas vessels during fast refueling and may supply some technical guidance on the design of charging experiments.

The Adsorption of Hydrogen in an Activated Carbon Tank Based on Modified Dubinin-Astakhov Model

Abstract: During adsorption cycles, the simulations of thermal effects play a significant role in designing adsorption-based systems such as gas separation, gas storage and heat pumps. This paper presents the two-dimensional axisymmetric model of a hydrogen storage tank on activated carbon at a particular temperature and pressure range using User Defined Functions in Fluent (UDF). The adsorption model used for CFD analysis is based on mass, momentum and energy equations and the modified form of Dubinin-Astakhov model. The simulation is implemented through Ansys Fluent. The Linear Driving Force is applied to study the cryo-adsorption kinetics. The results are varied from pipe inlet to the tank wall based on mass flux at different flow times. The pressure and temperature profile inside the system for different inlet conditions is studied in detail. The profiles of pressure and temperature are plotted at different time intervals. The velocity distribution at various time intervals is presented for charging and discharging of hydrogen adsorption Moreover, the results are compared with the model parameters of carbon and steel by varying the thermal conductivities and specific heat capacities. The results obtained for the pressure and temperature profile shows a good agreement with the other results available in the literature.

Supplying the energy of islands with geopolitical positions using distributed generations to increase energy security

The islands usually face challenges in their energy supply due to their specific location. On islands that are distant from the land, power is typically provided by diesel generators. Therefore, oil tankers must regularly refuel the island in order to supply the necessary fuel for diesel generators. As a result, if the fueling procedure is not completed for whatever reason, the island will not receive the necessary energy, which will result in an unavoidable loss of load. Due to their strategic location, some of these islands are used as military islands to protect the nations and waterways. Given the vital role that these military islands play for nations, a delay in supplying the island with energy can seriously harm security, the economy, and other factors. Transferring fuel to these islands is typically difficult, and in some cases impossible, under certain circumstances, such as war. Therefore, reducing the island's reliance on fossil fuels as much as feasible is vital to ensure the energy security of these specific islands. Diesel generators provide electricity to Larak Island, which is situated in the Strait of Hormuz. Larak Island serves as a military island due to its geopolitical location, hence it is crucial to consistently provide Larak with electricity. Therefore, in this paper, a combination of distributed generations and system storage is used to supply the Larak island. The photovoltaic, wind and tidal plants are considered the main power plants, and fuel cells with electrolyzers and hydrogen tanks have also been used as storage systems. In addition, the diesel generator is considered the system backup. The considered objective functions to design and manage Larak island's power supply system are reducing diesel generators fuel consumption, reducing electricity cost, and reducing electricity outages and lost power generation of renewable resources.

Cooling effect analysis on para-ortho hydrogen conversion coupled in vapor-cooled shield

The conversion process from parahydrogen to orthohydrogen accompanies an endothermic effect. Embedment of a para-ortho hydrogen converter into the thermal insulation could enhance the thermal protection of a liquid hydrogen storage tank. A physical model was proposed to simulate the heat transfer behavior of the insulation structure that integrates a polyurethane foam, a blanket of multilayer insulation, a vapor-cooled shield, and a para-ortho hydrogen converter. The effect of the para-ortho conversion process was considered. The model was validated by experimental data and then used to investigate how the para-ortho hydrogen conversion influences the temperature distribution inside the composite insulation. It was found that a single converter improves the cooling performance most effectively if it is placed at the middle length of the venting pipe mounted on the vapor-cooled shield. Either incorporating more converters or extending the length of the vapor-cooled shield pipes brings limited further improvement. The optimum position of the vapor-cooled shield inside the multilayer insulation moves towards the cold boundary in the presence of para-ortho conversion, compared to conventional vapor-cooled shield and multilayer insulation structures. A net heat flux reduction of over 10% could be achieved when the para-ortho conversion is located at the optimal position inside the vapor-cooled shield.

Numerical simulation on pressure evolution process of liquid hydrogen storage tank with active cryogenic cooling

Inevitable evaporation process occurring in liquid hydrogen storage may bring about safety risks associated with over-pressure and hydrogen discharge. Using a cryogenic refrigerator to compensate for the heat leakage is expected to eliminate the risk of hydrogen vent, realizing long-term lossless storage. Presently, active lossless storage technology applied on civil fields has rarely been studied. This paper presents a numerical study on the dynamic evolution process within an active cooling system of a liquid hydrogen tank. The accuracy of the model is validated with an average deviation of 0.47%. During the self-pressurized process, the maximum temperature difference is more than 26 K in the ullage zone. After cooling capacity being introduced, a three-stage depressurization process appears. Minor cooling capacity that is less than heat leakage can still realize pressure management. Further analyses show two operating modes similar to gravity heat pipes and thermal redistributors occurring in the ullage and the liquid zone, respectively. This work suggests the effectiveness of active cooling on controlling the ullage pressure, which may be applicable to future hydrogen refueling stations and intercity hydrogen transportation.

Synergistic planning of an integrated energy system containing hydrogen storage with the coupled use of electric-thermal energy

Regional integrated energy systems (RIES) can economically and efficiently use regional renewable energy resources, of which energy storage is an important means to solve the uncertainty of renewable energy output, but traditional electrochemical energy storage is only single electrical energy storage, and the energy efficiency level is low. Hydrogen energy storage has the advantages of large energy storage capacity, long storage time, clean and pollution-free, and can realize the synergistic and efficient utilization of electricity and thermal power. Based on this, this paper proposes a synergistic planning method for an integrated energy system with hydrogen storage taking into account the coupled use of electric-thermal energy, which effectively reduces the system carbon emission and improves the comprehensive energy efficiency level. Firstly, this paper constructs an electric-thermal coupling model of the hydrogen energy storage unit and proposes an optimization strategy for the integrated energy system containing hydrogen storage taking into account the utilization of electricity and thermal power. Secondly, a planning optimization model with the lowest economy and carbon emission and the highest comprehensive energy efficiency was constructed. Third, the CSPO-GE optimization algorithm is proposed for solving the problem, which significantly improves the solution efficiency. Finally, a planning optimization simulation of RIES for a residential community W in northern China verifies the effectiveness of the model and method proposed in this paper. The comparative analysis of the three schemes shows that compared with the integrated energy system with conventional electrochemical energy storage and heat storage tank as the main form of energy storage and the integrated energy system with only hydrogen storage, the integrated energy system with hydrogen storage and heat storage tank can reduce carbon emissions by 43.8% and 7.61%, respectively, and improve the integrated energy efficiency level by 337.14% and 14.44%.

Hydrogen physisorption on the (BeO)n, B2H4(Be,Ti), and B6Ti3 metal clusters: a computational study of energies and atomic charges.

The equilibrium structures of BeO clusters and Be,Ti-decorated boranes were computed with the ωB97X-D method and the 6-31G + (2d,2p) and aug-cc-pVTZ basis sets to study their intermolecular interactions with hydrogen molecules. Thermochemical and molecular properties such as the harmonic vibrational frequency, dipole and quadrupole moments, and atomic charges are employed to understand the attractive interactions that control the adsorption process. Comparison of molecular properties and atomic charges of the studied compounds before and after H2 molecule adsorption shows that most of the interactions among the BeO clusters and boranes with H2 molecules constitute a combination of dispersion, electrostatic, and weak charge transfer interactions. Calculated values of Hirschfeld atomic charges and ΔEe (in parenthesis) (BeO)4.8H2 (0.028 e and -2.0kcal.mol-1), (BeO)2.12H2 (0.030 e and -2.8kcal.mol-1), B6Ti3.10H2 (0.045 e and -15.4kcal.mol-1), and B6Ti3+.10H2 (0.058 e and -15.3kcal.mol-1) show qualitative correlation between hydrogen atomic charges and electronic energy of hydrogen interaction. The ωB97X-D/6-31 + G(2d,2p) values of Gibbs free energy at 298.15K for (BeO)4.8H2 B2H4Ti.4H2 and B6Ti3.10H2 clusters are equal to -5.0, -4.9, and -5.1kcal.mol-1, respectively, which are within the range of energy parameters of materials that could be employed in hydrogen storage tanks for light vehicles.

Numerical investigation on performance enhancement of metal-hydride hydrogen tank using electromagnetic induction heating

Due to their large volumetric storage capacity for hydrogen at safe, moderate temperatures and pressures, metal hydrides have received much attention by researchers. Since one of the major controlling factors of the storage process is heat transfer from/to the metal hydride bed, several methods to improving heat transfer have been published. In the present work, electromagnetic induction is investigated numerically as a new heating method to enhance the performance of metal-hydride hydrogen tanks. A two-dimensional mathematical model that describes the dynamic behavior of a LaNi5 hydrogen tank encircled by a copper coil crossed by an alternating current was developped and successfully validated with experimental data. Numerous numerical simulations are performed using this model, and the results reveal that electromagnetic induction can shorten the hydrogen tank's discharging time by 87 % when compared to the heat transfer fluid approach. Furthermore, by raising the desorption temperature from 303 K to 353 K, the discharging time may be reduced by 73 %. The rapidity of the discharging process is unaffected significantly by raising the desorption temperature above 353 K, though. For desorption pressures lower than 0.1 bar, the same effect was observed. Studying the impact of the coil's number of turns per unit length revealed that by increasing this parameter from 640 to 3200, the discharging time is considerably reduced. Nevertheless, increasing this number above 3200 has a negligible impact on the metal-hydride hydrogen tank's dynamic behavior.