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The efficient production and sustainable operation of water electrolysis hydrogen production equipment within renewable energy systems, characterized by intermittency and volatility, necessitates dynamic simulation for the development of optimized control systems. This paper proposes the application and modification of a data-driven deep-learning model to simultaneously simulate the thermal and electrochemical responses of an alkaline water electrolyzer (AWE), yielding exceptional performance and versatility. By utilizing 4840 h of comprehensive experimental data, the causal relationships among electrolyzer operating parameters are resolved, classifying them into set values and response values for the proposed dynamic model. The model architecture is based on an attention mechanism and designed with hybrid input. Notable enhancements include embedding flow-leveraged polarization function, creating set-value cross-attention, and adopting probability-sparse attention, all of which are validated through both the validation and simulation results. Extensive exploration of various structural and training parameters leads to the selection of the best-performing model. When applied to simulation across all experimental data, the median mean percentage absolute error of the optimal model in cell voltage is a mere 1.3%, while the error in temperature is only 3.5%. Moreover, under typical operating conditions, the simulation error for both voltage and temperature remain below 2%, highlighting the outstanding dynamic modeling and simulation capabilities. These results demonstrate the potential of the proposed model for future hydrogen energy applications in dynamic control and operational optimization within renewable energy system for higher performance and better conversion efficiency. • Deep-learning model for dynamic thermoelectric simulation of water electrolyzers. • Flow-leveraged polarization function and set-value cross-attention mechanism. • Excellent accuracy, thermoelectric error of 3.5% and 1.3%, respectively. • Insights for optimizing control strategies of electrolyzer for higher efficiency. [ABSTRACT FROM AUTHOR]

The catalyst is crucial in enhancing productivity within the Fischer-Tropsch synthesis (FTS). The metal support interaction (MSI) plays a pivotal role in the FTS catalyst performance, impacting activity, stability, and selectivity. he configuration and composition of the catalyst dramatically impact MSI, with a strong MSI (SMSI) specified for the core-shell structure. In this study, two methods consisting of chemical treatment of etching and adding a promoter (Ru) for tuning the SMSI of the FTS catalyst are presented, and their footprints on the catalysts' performance are screened by utilizing various characterization tests, molecular dynamic simulation, and catalytic tests. It is recognized that the silica interfacial perimeter acts as a barrier that restricts the charge transfer and boosts the SMSI in the silica-coated catalyst. Conversely, the etched catalyst exhibits a moderate MSI, contributing to increased reducibility, stability, and activity. Furthermore, the Ru-doped etched catalyst represents the optimum MSI, resulting in the highest overall performance. [Display omitted] • The catalyst's structure, configuration, and composition significantly affect the metal support interaction (MSI). • Chemical etching and a promoter (Ru) are used to tune the SMSI of the FTS catalyst and intensify its performance. • The etched catalyst exhibits a moderate MSI, increasing ease of reduction, stability, and activity. • The etched catalyst undergoing doping with Ru with the outer shell of ceria promotes the formation of oxygen vacancies. • Ru NPs have a significant effect on the electron charge surface density of the catalyst. [ABSTRACT FROM AUTHOR]

Polymer electrolyte membrane fuel cells (PEMFCs) offer a clean and efficient energy generation technology. However, optimizing their performance in terms of water transport through the electrolyte membrane remains a challenge. In this study, we employ molecular dynamics simulation and nuclear magnetic resonance (NMR) experiments to investigate the influence of carbon materials and membrane thickness on water diffusion within the triple phase boundary of a PEMFC. Our theoretical investigation highlights the significant impact of Nafion content on water morphology within the system. The structural analysis reveals the intricate interplay between material properties and water behavior in confined environments. The formation of water channels facilitated by the ionomer enhances water mobility, while excessive ionomer content leads to reduced diffusion coefficients. Experimental measurements using NMR diffusion validate the correlation between our simulation results and real-world observations. Furthermore, our Molecular Dynamic (MD) and NMR studies identify the optimal performance range for ionomer content, with systems containing 12 to 24 oligomers (20–30 % w/w) exhibiting superior water diffusion within Vulcan Carbon (VC) structures. By shedding light on water transport phenomena in PEMFCs, our findings contribute to a better understanding of fuel cell performance and provide valuable insights for the design and optimization of fuel cell systems. [Display omitted] • The formation of water channels facilitated by the ionomer greatly enhances water mobility in fuel cell membranes. • 20-30% ionomer content exhibit the best performance in terms of water diffusion. • This work provide insights into water behavior in PEMFC triple phase boundary. [ABSTRACT FROM AUTHOR]

It is great significant to explore the changes of compressor performance for hydrogen transportation. We found that a Gray-RBF neural network prediction model improved prediction accuracy. The prediction error of the model is 2.34 % by data verification. It was found that the hydrogen blending ratio was increased from 0 % to 30 %, the pipeline transmission power was reduced by 9.3 %. Simultaneously injecting hydrogen to natural gas causes the performance curve of the compressor to shift downwards. The pressure ratio decreases by 18.9 % and shaft power decreases by 28.6 % when the hydrogen blending ratio increases from 0 % to 30 %. The injection of hydrogen to natural gas causes the surge range of the compressor to increase, so the stable range to narrow. In general, this research may provide reference and guidance for the transportation research of hydrogen blended natural gas and compressor operation about gas industry. [Display omitted] • Creating a combination model improved the accuracy of performance prediction. • Injecting hydrogen into natural gas reduced the power of pipeline gas transmission. • Enlarging initial pressure caused the gas transmission power increase. • Injecting hydrogen into natural gas caused decreases of compressor performance curves. • Injecting hydrogen into natural gas increased the surge range of the compressor. [ABSTRACT FROM AUTHOR]

Catalysts with dual functions in hydrogen production and storage are desired for the low-cost technology. In the preceding view, we used reactive force molecular dynamics to demonstrate how effective the Fe–Al core-shell structure is at breaking up water molecules and storing hydrogen free radicals via thermochemical water splitting. The results show that at T ∼600 K, water molecules begin to dissociate in the presence of a Fe–Al catalyst, releasing OH and H free radicals. It is worth noting that the produced OH free radicals are bonded to the Al-shell, whereas the H free radicals move to the Fe-core and stores via chemical bond. Interestingly, at T < 1200 K, there is no Fe–O bond. This could be due to Al having a higher oxidation potential than Fe, causing OH free radicals to preferentially associate with the Al-shell. Furthermore, at 2000K < T > 3000 K, the number of Fe–H bonds decreases while the number of H–H bonds increases, indicating that the stored H atom desorbs and forms an H 2 molecule. Temperature can thus be used to monitor the ability of Fe–Al catalysts to dissociate water, store hydrogen, and produce hydrogen. This research shows that developing core-shell type catalysts can provide an effective solution for hydrogen generation, storage, and transportation. • Fe–Al core-shell catalysts are efficient for dissociation of water molecules at T∼600 K. • Water dissociates into OH and H free radicals. • OH radical bonded to the Al-shell (Al–OH), whereas H radical bonded to Fe-core (Fe–H). • At temperature 2000K < T > 3000 K, Fe–H bonds dissociate and H 2 molecule generates. [ABSTRACT FROM AUTHOR]

Hydrogen fuel cells have become one of the most viable power sources for electric aircraft. Models representing the electrical behavior of the fuel cell stack over the full dynamic operation region are essential for the development of power electronic energy systems powered by fuel cell stacks. This work presents an electrical equivalent circuit model for PEM fuel cell stacks representing the static and dynamic electrical behavior of the fuel cell stack under pulsed loads up to frequencies of 10 kHz. Dynamic phenomena on time scales slower than the considered timescale of power-electronic switching, such as reactant flow, membrane hydration, and temperature effects, are considered stationary. The parameterization method proposed is developed on measured data from a 110 W PEM fuel cell stack and validated with a set of measured data from a 2 kW stack. The time-domain simulated behavior of the parameterized model shows an accurate representation of the measured behavior: the parameterized model reproduces both the static polarization behavior and the behavior under high-frequency pulsed loading with errors of less than 1% with respect to the nominal stack voltage. The model is suitable for dynamic simulation of power electronic systems directly connected to fuel cell stacks and can be parameterized without special electrochemical impedance spectroscopy measurements. • A novel equivalent circuit model for PEM fuel cells is proposed. • The equivalent circuit model is valid in time domain for large-signal perturbations. • The model represents the dynamic electrical behavior under pulsed loads up to 10 kHz. • The proposed model is parameterized using a novel pulsed load measurement method. • The model is aimed for highly dynamic simulations of fuel cells in pHiL environments. [ABSTRACT FROM AUTHOR]

Green hydrogen is currently eye-catching in terms of its production, storage and delivery to facilitate energy transition. In the present research, it is tried to demonstrate the capability of green hydrogen in blending with syngas (produced by biomass gasification) to feed an SOFC system in order to supply electrical power and heating for an existing educational building. Dynamic simulation has been performed in TRNSYS Software to calculate the hydrogen production annually at different scenarios. Effects of hydrogen concentration in the fuel mixture on the performance of the proposed CHP system are assessed. Results indicated that utilizing a reasonable roof area can offer approximately 10,000 kg H 2 and 70,000 kg H 2 per year in cases of grid-zero connected and grid 85% connected, respectively. It is revealed that increasing the hydrogen share in fuel mixture from 5% to 30% increases noticeably the hydrogen gas percentage at the SOFC anode inlet and outlet while it has a reverse effect on the H 2 O amount. In addition, the studied increment in hydrogen share could increase 18% of the net output power from the system. Finally, related to the CO 2 emission from the system, it is found that 58% reduction could be achieved by increasing the hydrogen share in the fuel blended. • A new CHP unit by utilisation of green hydrogen and syngas for an educational building is proposed. • Dynamic simulation results prove that grid-zero connected mode can provide 10T hydrogen annually. • Quality of syngas is enhanced by hydrogen injection revealing a positive effect on SOFC performance. • Increasing the share of green hydrogen in the final fuel would increase 18% of total power of the system. • 30% hydrogen injection to syngas can cut the total CO 2 emission from the system by up to 58%. [ABSTRACT FROM AUTHOR]

In this study, we examine a liquid hydrogen (LH 2)-fueled hybrid ship propulsion system (HSPS) consisting of an LH 2 fuel gas supply system (FGSS), a polymer electrolyte membrane fuel cell (PEMFC), and battery systems. The LH 2 -HSPS is analyzed through three dynamic simulations, representing different PEMFC outputs, for a 2-MW-class tugboat. During transient states of LH 2 FGSS, hydrogen temperature changes from 11 to 41 °C at the LH 2 vaporizer outlet. Dynamic simulations considering hydrogen temperature tolerance in the PEMFC system show interruptions of power generation during 1–5 s. In Case 3, where the PEMFC system provides all propulsive power, an energy capacity of 310–1860 kWh is calculated with maximum C-rates of 1C–6C. The average power consumption of the balance of plant in the PEMFC system is 43.64, 27.51, and 44.06 kW for Cases 1–3, respectively. Finally, the battery system's thermal management is well performed for all cases. • The LH 2 -HSPS is designed and modeled for a target ship of a 2-MW-class tugboat. • Dynamic characteristics of the LH 2 FGSS and HSPS are analyzed. • Capacity of the battery system is dependent on the operating mode of the LH2-HSPS. • Relationship between power interruption and H 2 supply temperature is examined. [ABSTRACT FROM AUTHOR]

The hydrogen fuel cell electric vehicle is fueled by the pressure difference in the fueling tank with high-pressure hydrogen compressed at the hydrogen fueling station, and the fueling delay occurs when the pressure difference becomes small. To resolve this, most hydrogen fueling stations minimize fueling time by cascade fueling method by installing two or three banks. Although there are protocols for hydrogen fueling, there are no guidelines for 3-bank operation, so each hydrogen fueling station has different ways to fuel. This study proposes a dynamic simulation model and open-source implementation in Python that can check the temperature and pressure changes of the fueling tank. To implement the n-bank model, we add factors that can be used as operating guidelines for fueling stations, such as supply pressure of the banks and switch moment. Through optimization studies on these factors using simulation models, we propose optimal operation guidelines for fueling stations. [Display omitted] • Development of dynamic simulation model for hydrogen fueling process with n-bank cascade system. • Python open-source simulator that allows users to analyze the simulation results under desired conditions. • Validated model using experimental data for actual fueling process. • Optimizing the fueling process to shorten the fueling time and minimize the fueling energy. • Fueling guidelines for station operators with safety and fast fueling. [ABSTRACT FROM AUTHOR]

Ammonia is a kind of carbonless alternative fuel with great research foresight. Improving the burning velocity of NH 3 and studying the reduce of nitrogen oxides have far-reaching significance for the effective utilization of ammonia. This paper mainly studies the characteristics of three different mixtures (NH 3 :H 2 = 1:1, NH 3 :H 2 :CO = 2:1:1, NH 3 :CO = 1:1) in closed tubes under different equivalent ratios of Ф (0.7–1.4), and use chemkin software to simulate the laminar burning velocity under different experimental conditions and at high temperature (298–650 K) and high pressure (1–10 at m), which carry out kinetic analysis and the related exploration of its nitrogen oxide emissions. The results show as follows: (1) In the closed pipe, the flame propagation speed of NH 3 /H 2 /air is the largest, when the equivalent ratio is 1.1, the flame propagation speed of three different mixtures is the highest, the overpressure phenomenon is the most obvious. and the overpressure and temperature are the highest in the pipe. (2) The symmetrical shape of the pipe changes the direction of the flame flow, creating an interesting turbulent flow that resembles a halberd. (3) Replacing half NH 3 fuel of NH 3 /air mixture with H 2 is mainly due to the chemical effect of H 2 leading to the increase of LBV, while replacing half NH 3 fuel of NH 3 /air mixture with CO is mainly due to the thermal effect leading to the increase of LBV. The promotion effect of elevated temperature is mainly due to the contribution thermal effect and chemical effect. For NH 3 /H 2 /air, chemical effect is the main component of promotion effect of elevated temperature. For NH 3 /CO/air mixture, the promotion effect of elevated temperature, which is more the influence of thermal effect. The inhibitory effect of initial pressure is the contribution of chemical effect. (4) High temperature promoted the formation of NO, while high pressure inhibited it. • The combustion characteristics of NH 3 /H 2 /air, NH 3 /CO/air, NH 3 /H 2 /CO/air in a closed pipe are discussed. • The shape of the pipe changes the direction of flame flow and forms an interesting phenomenon. • The different temperature compensation methods are used. • The kinetic analysis of elevated temperature and pressure. [ABSTRACT FROM AUTHOR]

A density functional study of the electronic structures of C 6 O 6 M 6 (M = Li, Na) clusters, as well as their potentials for dihydrogen storage, have been performed by two methods. Molecular dynamic simulations confirm that both clusters are thermodynamically stable. Calculations reveal that C 6 O 6 Li 6 /C 6 O 6 Na 6 can adsorb up to 36/38H 2 molecules with a gravimetric uptake capacity of 26.10/19.90 wt%, exceeding the goal (5.5 wt%) set by the US Department of Energy (DOE). The adsorption energies of H 2 on C 6 O 6 Li 6 and C 6 O 6 Na 6 are in the range of 0.093–0.119 eV and 0.112–0.228 eV, respectively. The interactions of C 6 O 6 M 6 (M = Li, Na) with H 2 molecules are analyzed by a variety of electronic structure methods. Thermo-chemistry calculations indicate two H 2 in C 6 O 6 Li 6 (H 2) 36 and fourteen H 2 in C 6 O 6 Na 6 (H 2) 38 can be readily adsorbed at 77 K and desorbed at 298.15 K under atmospheric pressure, corresponding to the maximal reversible hydrogen storage densities are 2.11 wt% and 8.38 wt%, respectively. Higher pressure can improve the maximal reversible hydrogen storage abilities. Atom density matrix propagation (ADMP) molecular dynamic simulations indicate that H 2 molecules are substantially and strongly bound at 77 K and get efficiently released at elevated temperature (300 K). The (C 6 O 6 M 6) 2 (M = Li, Na) dimers can also efficiently adsorb multiple H 2 molecules with high gravimetric density and reversible average adsorption energy. [Display omitted] • The cluster C 6 O 6 Li 6 /C 6 O 6 Na 6 can adsorb 36/38 hydrogen molecules. • The H 2 gravimetric density of C 6 O 6 Li 6 /C 6 O 6 Na 6 is 26.10/19.90 wt%. • The average adsorption energies of H 2 on C 6 O 6 Li 6 /C 6 O 6 Na 6 is in the range of 0.093/0.112–0.119/0.228 eV/H 2. • H 2 molecules are strongly bound at 77 K and get efficiently released at elevated temperature (300 K). • The (C 6 O 6 Li 6) 2 /(C 6 O 6 Na 6) 2 dimer can adsorb 47/50 hydrogen molecules with the gravimetric density of 19.67/14.04 wt%. [ABSTRACT FROM AUTHOR]

Thermal Cycling Absorption Process (TCAP) is an important method to separate hydrogen isotopes for the production and engineering application of tritium. There are so many influencing factors that it is difficult to fully understand the influence mechanisms only through experiments. A new simulation model of TCAP was developed. Using the simulation model, the influencing trend and optimized value of parameters of initial feeding process and total reflux mode in TCAP are obtained as follows. (1) The temperatures of initial feeding and the cold cycle are not the lower the better as commonly assumed but exists an optimal value of 30 °C in initial feeding and -20 °C in the cold cycle. (2) The heating rate and cooling rate also exist optimal values of 45 °C/min and 55 °C/min (3) Lower feeding rate is conducive to a better separation effect of hydrogen isotopes. (4) Increasing the reflux ratio benefits the enrichment of heavy hydrogen isotope at the product side but not the light hydrogen isotope at the tail side. (5) It needs more cycles to achieve the same isotope abundance in D/T separation than H/D separation and the separation degree of hydrogen isotopes exists a maximum value after multiple cycles. The findings can provide references for the process optimization and the device design of TCAP, and also can shed new light on the understanding of the basic physical and chemical process of TCAP. A new simulation model of TCAP was developed. Compared with commercial simulation softwares, device parameters and process conditions of TCAP can be flexibly considered in the numerical model. [Display omitted] • A new simulation model of TCAP was developed. • Device parameters and process conditions of TCAP can be flexibly assessed. • Optimized parameters in initial feeding process and total reflux mode was obtained. • Temperatures of cold cycles exist optimum values, not as commonly assumed. [ABSTRACT FROM AUTHOR]

The hydrogen storage material Lithium hydride (LiH) has received wide attention due to its high hydrogen density. However, the reaction process of LiH with H 2 O is complex, and the microscopic mechanism has not been reported. This paper reveals the microscopic mechanism by the ReaxFF reaction force field module of the Amsterdam Modeling Suite (AMS). Combined with Gaussian09 software, the rate constants and energy changes are determined in the reaction course. As a result, LiH reacts with H 2 O preferentially, forming Li--O bonds and shedding H from Li--H, which collides randomly to generate H 2 and H 2 LiO. As the reaction proceeds, there are by-products H 4 LiO 2 , HLiO, HLi 2 O, and H 2 Li 2 O generated. The reaction course of H 4 LiO 2 is a spontaneous exothermic reaction, and the strong chemical bonding force of Li to H prompts the formation of HLiO, HLi 2 O, and H 2 Li 2 O. 100% of H 2 comes from the H removed by LiH. Thus, LiH being fully involved in the reaction, the number of H 2 produced remains the same. • The microscopic mechanism of the products H 2 LiO, H 4 LiO 2 , HLiO, HLi 2 O, and H 2 Li 2 O were revealed. • The formation energy barrier of H 2 LiO is 0.78 kJ mol−1, accounting for 79% of the products. • The products H 4 LiO 2 , HLiO, H 2 Li 2 O, and HLi 2 O are further reactions of H 2 LiO with H 2 O and LiH, which have higher energy barriers. • 100% of the product H 2 comes from the H removed by LiH, while the H of H 2 O is difficult to cleave. • The number of H 2 production is constant after reaching the maximum as the temperature of the reaction simulation increases. [ABSTRACT FROM AUTHOR]

Knowledge about factors affecting the dynamic response process is crucial for development of mixed-potential gas sensor for various applications such as hydrogen detection. Based on a double layer capacitor model and the Butler-Volmer equation, the present work studied the dynamic hydrogen sensing process by numerical simulation in combination with experimental assessment. Simulation shows that both response and recovery times are jointly determined by the decrease rate of the net reaction current and the magnitude of response. Increase of standard reaction rate constants, transfer coefficients, standard equilibrium potential, or gas concentrations accelerates both the response and recovery processes, while double layer capacitance has a reverse effect. A power-law concentration dependence of the response/recovery time is obtained under Tafel kinetics. The simulated response curves and behavior agree quite well with the experimental results. These findings shed lights on the sensing kinetics of the mixed-potential hydrogen sensor, and may help guide the sensor design. • Theoretical and experimental study of dynamic mixed-potential gas sensing process. • Factors function via tuning decrease rate of net reaction current and response value. • Materials of high electrochemical activities favor the sensing dynamics. • Power-law concentration dependence of response time under Tafel kinetics. [ABSTRACT FROM AUTHOR]

This work reports the hydrogen storage, and delivery capacities of Sc and Y functionalized [1,1]paracyclophane using dispersion corrected density functional theory calculations. The Sc and Y atoms are bind strongly with benzene rings of [1,1]paracyclophane. Each Sc and Y atom functionalized over [1,1]paracyclophane adsorb up to 6H 2 molecules via Kubas interaction achieving maximum gravimetric density up to 8.22 wt% and 6.33 wt%, respectively. The calculated average hydrogen adsorption energy (0.36 eV) is lower than the chemisorption but higher than the physisorption process. The kinetic stabilities are verified through the HOMO-LUMO gap and different global reactive descriptors. ADMP molecular dynamics simulations reveal the reversibility of adsorbed H 2 molecules at sufficiently above the room temperature and the solidity of host material at 500 K. Average Van't Hoff desorption temperature for Sc and Y decorated system was calculated to be 439 K and 412 K respectively at 1 atm of pressure. Hence, we believe that Sc and Y functionalized [1,1]paracyclophane can be considered as a thermodynamically viable, and potential reversible hydrogen storage materials at ambient environment. [Display omitted] • H 2 adsorption mechanism in Sc and Y functionalized [1,1]Paracyclophane is reported. • On saturation each Sc and Y adsorb 6H 2 leading 8.22 wt% and 6.33 wt% respectively. • Molecular dynamic simulations ensure the solidity of host and reversibility of H 2. • Thermodynamic usable hydrogen capacity meet the US-DOE targets. •. Each Sc atom adsorb H 2 molecules via Kubas interaction with average BE of 0.36 eV. [ABSTRACT FROM AUTHOR]

Hydrogen-blended electricity-gas integrated energy system (EG-IES) utilizes surplus renewable energy power generation to blends hydrogen into the natural gas pipeline network for achieve efficient and economical large-scale hydrogen consumption and long-distance transportation. While enhancing the coupling between the power grid and gas grid, the scheduling control of such a complex system becomes increasingly important. The paper presents a dynamic model of a hydrogen blended EG-IES with high renewable energy permeability, and a modeling method that considers distribution parameters of the natural gas pipeline is obtained by using the cell segmentation and calculating the blended gas composition in real-time to avoid the assumption of constant composition. After the validation against available operational data, a case study of the certain area of Central China is simulated. The coordinate control law is reasonably designed according to the dynamic characteristics of EG-IES and the objective of realizing the load increase within the hydrogen concentration constraint, and the PID is utilized as the benchmark to compare dynamic performance. The results demonstrate that the coordinated control based on the alternate adjustment control law has no overshoot and shorter adjustment time of p l and ε about 33% and 42% than benchmark on the large delay system. • Establish a dynamic hydrogen blended electricity-gas integrated system model. • Solve the distribution parameter characteristics of the natural gas pipeline network. • Dynamic simulation and verification of a real EG-IES in Central China was carried. • Analysis of the different coordinate control performance during the load up process. [ABSTRACT FROM AUTHOR]

In this research study, a real model of a hydrogen fuel cell vehicle is simulated using Simcenter Amesim software. The software used for vehicle simulation enabled dynamic simulation, resulting in more precise simulation. Furthermore, considering that fuel cell degradation is one of the significant challenges confronting fuel cell vehicle manufacturers, we examined the impact of fuel cell degradation on the performance of hydrogen vehicles. According to the findings, a hydrogen vehicle with a degraded fuel cell consumes 14.3% more fuel than a fresh fuel cell hydrogen vehicle. A comprehensive life cycle assessment (LCA) is also performed for the designed hydrogen vehicle. The results of the hydrogen vehicle life cycle assessment are compared with a gasoline vehicle to fully understand the effect of hydrogen vehicles in reducing air emissions. The methods considered for hydrogen production included natural gas reforming, electrolysis, and thermochemical water splitting method. Furthermore, because the source of electricity used for electrolysis has a significant impact on the life cycle emission of a hydrogen vehicle, three different power sources were considered in this assessment. Finally, while a hydrogen vehicle with a degraded fuel cell emits lower carbon dioxide (CO 2) than a gasoline vehicle, the emitted CO 2 from this vehicle using hydrogen from electrolysis is approximately 25% higher than that of a new hydrogen vehicle. • Devloping a dynamic model of PEM fuel cell vehicle. • Assessing the effect of degradation on the fuel economy vehicle performance. • Comparative life cycle assessment of different hydrogen production methods. • Comparison of life cycle emission of non-degraded and degraded FCV with ICEV. [ABSTRACT FROM AUTHOR]

In this study, some locations with different climates, off-grid zero energy buildings with hydrogen energy storage systems are designed, and transient analysis is conducted. These considered buildings supply their electricity consumption without using the electrical grid and PV panels or wind turbines. Also, they supply thermal comfort to occupants by using a vapor compression chiller and humidifier. Domestic hot water of occupants is supplied using solar collectors. For analyzing building's performance and objectives achievement, TRNSYS software is used. Also, for evaluating occupant thermal comfort, the Fanger model is used. The considered building is a one-story building with a 150 m2 area. Four occupants are considered. Both of them are seated at rest, and another is seated with light working such as typing. Using the Fanger model equation and MATLAB software, the thermal comfort of occupants is determined. For domestic hot water consumption, verified profiles that vary during 24 h of the day are considered. Achieved results show that for humid and cold cities, PV panels with an area of 73 and 76 m2 can be supplied the required electricity of considered building with four occupants and battery state of charge is higher than 50% and 10%, respectively. Moreover, with a suitable air conditioner system, the predicted percentage of dissatisfied (PPD) can be lower than 12% and 8% for humid and cold cities. Therefore, the building can be converted to a zero-energy building using its rooftop area. • Analyzing wind and PV panels as renewable energy suppliers for supplying energy. • Storing hydrogen energy system as for off-grid zero energy buildings. • Transient analysis and design of off-grid zero energy buildings. • Evaluating thermal comfort of occupant in zero energy buildings. • Using Fanger model and PPD and PMV parameters. [ABSTRACT FROM AUTHOR]

In this article, the solar hydrogen storage is modeled and hourly investigated with TRNSYS software. The Photovoltaic (PV) panel is employed for green power generation that is consumed in the electrolyzer subsystem and produced hydrogen. Additionally, the required electricity at the lack of enough solar irradiation is supplied from the grid. The performance of the system is comparatively analyzed for three main cities. Results show that the maximum power generation by PV panel is about 1670 kW in June which approximately is the same for two cities. The energy and Faraday efficiency of electrolyzer changes between 0.85-0.89 and 0.89–0.92 respectively. The amount of hydrogen production reaches 1235 m3/h for one of them in May. The total amount of hydrogen production is 13,181 m3/year in Yazd, 13,143 m3/year in hot city, and 13,141 m3/year in most populated city. • Transient simulation of power to hydrogen system using TRNSYS. • Influence of various places on hydrogen production rate. • Designing a hydrogen storage system with a solar energy source. • Analyzing the performance of the electrolyzer from an energy viewpoint. [ABSTRACT FROM AUTHOR]

In this study, a practical fuel cell vehicle considering the Heating, Ventilation, and Air conditioning system is considered to analyze hydrogen consumption under different working conditions. As a prevalent hydrogen-fueled vehicle, Toyota Mirai has been meticulously modeled in Simecenter Amesim software. The simulated model covers all of the vehicle's components with a concentration on Heating, Ventilation, and Air conditioning system. Since the air temperature and 'weather conditions can significantly impact the vehicle's overall performance, various environmental conditions, including temperature variations, humidity, and varied solar fluxes, are taken into account. Furthermore, New York City is chosen as a densely populated megacity to simulate the dynamic behavior of the fuel cell vehicle under actual driving circumstances. The results illustrate that the Heating, Ventilation, and Air conditioning system can notably alter hydrogen consumption under real driving conditions. In this regard, turning on the Heating, Ventilation, and Air Conditioning system results in a 19% increase in fuel consumption. Moreover, the degradation phenomenon, which is a typical result of using fuel cell vehicles under urban driving conditions, impacts the vehicle's mileage and hydrogen consumption. The simulation results indicate that a fresh fuel cell stack consumes 80 g of hydrogen, while for 2500 and 5500 working hours fuel cells, the stack consumes 89.6 and 107 g of hydrogen, respectively. Based on the obtained results, a 33.75% increase in fuel consumption occurs by implementing a degraded fuel cell stack under real driving conditions. • Toyota Mirai hydrogen-fueled vehicle is modeled precisely in Simcenter Amesim software considering Heating, Ventilation, and Air conditioning system. • Various climate conditions, including temperature changes, humidity differences, different solar powers, and four different vehicle's colors are considered. • Vehicle performance under real driving conditions in New York City is analyzed to model the overall vehicle's performance dynamically. • Hydrogen consumption under different climate conditions is recorded, and the results have been discussed. [ABSTRACT FROM AUTHOR]

Solar energy systems are an effective way to meet the needs of zone heating, cooling, electricity, and domestic hot water. However, to reach sustainability, and energy storage unit should be considered for installation. In this study, two combined cooling, heating and power (CCHP) systems are simulated and studied using TRNSYS software; both using natural gas engine generators and photovoltaics as prime movers and a hydrogen fuel cell/electrolyzer storage unit, one with absorption chiller and another with compression chiller cooling. For the study, a residential building is modeled for three major populated climate zones of the United States of America, namely, Hot-humid, mixed-humid and cold using DesignBuilder and EnergyPlus software. The energy demand for its HVAC operation and domestic electricity is obtained and used for system simulation in TRNSYS software. Due to choosing actual equipment for the CCHP arrangement, precise economic and environmental models are designed to further evaluate the possibility of execution of the system. The results show that absorption chiller-equipped CCHP has better performance both environmentally and economically. In addition, the outcome shows that the suggested systems show less favorability to be utilized in hot humid climate zones. • Design a multi objective optimization system with TRNSYS simulator. • Various geographical location is considered for study the proposed system. • Designed system with chiller in colder climates has less Carbon-dioxide emission. • Hot climate leads to a higher energy consumption in the designed unit. [ABSTRACT FROM AUTHOR]

The bubble covering phenomenon has been considered one of the most critical factors affecting Proton Exchange Membrane Electrolysis Cell (PEMEC) at high current densities. However, the relationship between bubble dynamics and electrochemistry has not been clearly defined. This study analyzes the bubble coverage and PEMEC performance under different input conditions and develops a mathematical model of PEMEC incorporating bubble dynamics. The model successfully predicted the polarization curves and coincided with the experimental data. The results show that bubble coverage increases with increasing current density, bubble detachment radius, and temperature. It decreases with increasing pressure and water inlet velocity. Bubble coverage is influenced by temperature, pressure, wettability, current density, and water inlet velocity. Meanwhile, bubbles covering the electrode deteriorate the performance of the PEMEC, leading to higher overpotentials and lower efficiencies, which becomes more apparent with increasing current density. This paper elucidates the relationship between bubble growth/detachment, bubble coverage, and electrochemistry for the first time, and the results can provide a reference for the development and optimization of high-performance PEMEC. • A bubble dynamic model of a PEMEC was developed and verified by experiments. • Considering Bubble dynamics, bubble coverage and overpotential effects in this model. • Assessing the effects of temperature, pressure and water velocity on bubble coverage. • Bubble coverage results in higher overpotential and lower efficiency. [ABSTRACT FROM AUTHOR]

In this study, a nuclear hybrid energy system (NHES) with large-scale hydrogen storage integrated with a gas turbine cycle is proposed as a flexible system for load following. The proposed system consists of a nuclear reactor, a steam Rankine cycle, a hydrogen electrolyzer, a storage system for hydrogen in an underground salt cavern, and a Brayton cycle that uses hydrogen as fuel to generate additional electricity to meet peak demand. A dynamic mathematical model is developed for each subsystem of the NHES. To evaluate the potential benefits of the system, a one-year study is conducted, using scaled grid demand data from ISO New England. The dynamic simulation results show that the system is capable of meeting the demand of the grid without additional electricity from outside sources for 93% of the year, while decreasing the number of ramping cycles of the nuclear reactor by 92.7%. There is also potential for economic benefits as the system only had to ramp up and down 7.4% of the year, which increased the nuclear capacity factor from 86.3% to 98.3%. The simulation results show that the proposed hybrid system improves the flexibility of nuclear power plants, provides more electricity, and reduces greenhouse gas emissions. • A novel Nuclear Hybrid Energy System with large-scale hydrogen storage is proposed. • A one-year dynamic simulation was conducted to evaluate the benefits of the system. • The simulation results show that the system increased flexibility of nuclear energy. • The system decreases nuclear ramping cycles by 92.7%, increases the capacity by 12%. • Increased the demand met by almost 20%, from 73.4% of the year to 93% of the year. [ABSTRACT FROM AUTHOR]

The objective of this study was to simulate a proton-electrolyte membrane fuel cell (PEMFC) system, namely a PEMFC stack, an anode gas supply subsystem, an anode gas-recovery subsystem, a cathode gas supply subsystem, and a tail gas exhaustion subsystem. In addition, this paper presents an analysis of the efficiency of combined heat and power (CHP) systems. MATLAB and Simulink were employed for dynamic simulation and statistical analysis. The rates of active and the passive anode hydrogen recirculation were considered to elucidate the mechanism of hydrogen circulation. When recovery involved diverse recovery mechanisms, the recirculation rate was affected by the pressure at the hydrogen outlet of the PEMFC system. The greater the pressure was at that outlet, the higher the recovery rate was. In the hydrogen recovery system, when the temperature of the hydrogen supply end remained the same, increasing the temperature of the gas supply end increased the efficiency of the fuel cells; fixing the flow of the hydrogen supply end and increasing the temperature of the hydrogen supply end increased the efficiency of the PEMFC system. A calculation of the efficiency of the recovery system indicated that the thermal efficiency of the fuel cells exceeded 35%, the power generation efficiency exceeded 45%, and the efficiency of the CHP system exceeded 80%. • Active pumps are used to recover the surplus gas. • Thermal efficiency of the fuel cells, and the CHP efficiency exceeded 80%. • Hydrogen supply end could enhance the efficiency of the fuel cell system. [ABSTRACT FROM AUTHOR]

High temperature proton exchange membrane fuel cell (HT-PEMFC) with phosphoric acid doped polybenzimidazole (PBI) electrolyte shows multiple advantages over conventional PEMFC working at below 373 K, such as faster electrochemical kinetics, simpler water management, higher carbon monoxide tolerance. However, starting HT-PEMFC from room temperature to the optimal operating temperature range (433.15 K–453.15 K) is still a serious challenge. In present work, the start-up strategy is proposed and evaluated and a three-dimensional non-isothermal dynamic model is developed to investigate start-up time and temperature distribution during the start-up process. The HT-PEMFC is preheated by gas to 393.15 K, followed by discharging a current from the cell for electrochemical heat generation. Firstly, different current loads are applied when the average temperature of membrane reaches 393.15 K. Then, the start-up time and temperature distribution of co-flow and counter-flow are compared at different current loads. Finally, the effect of inlet velocity and temperature on the start-up process are explored in the case of counter-flow. Numerical results clearly show that applied current load is necessary to reduce start-up time and just 0.1 A/cm2 current load can reduce startup time by 45%. It is also found that co-flow takes 18.8% less time than counter-flow to heat membrane temperature to 393.15 K, but the maximum temperature difference of membrane is 39% higher than the counter-flow. Increasing the inlet gas flow velocity and temperature can shorten the start-up time but increases the temperature difference of the membrane. • Applying a current load can significantly shorten start-up time. • Start-up time and temperature distribution are compared for co-flow and counter-flow. • Counter-flow needs more time to start, but temperature distribution is more evenly. • The effect of inlet gas temperature and velocity on start-up process are investigated. [ABSTRACT FROM AUTHOR]

Titanium tetra hydride is considered for hydrogen storage purposes. Firstly, formation energy, hydrogen desorption temperature and gravimetric hydrogen density of TiH 4 is computed. Secondly, an ab initio constant pressure molecular dynamic simulation under pressure is performed to reveal behaviour of TiH 4 for the first time. The result exhibits two phase transitions successively. C2/m phase of TiH 4 transforms into C2/c phase at 40 GPa simulation pressure. Then, elastic constants of phases are determined to examine mechanical stability of phases. Based on the evolution of elastic constants, it is found that C2/m phase fulfils Born stability criteria for a monoclinic structure, indicating that C2/m phase is mechanically stable whereas C2/c phase is not mechanically stable. Additionally, several critical parameters which are important for hydrogen storage such as brittleness and ductility, Young and Shear modulus are obtained and analysed. In addition, electronic structures of phases are calculated and evaluated. Finally, dynamic stability from phonon dispersion curves is examined. C2/m phase is also found to be dynamically stable. Image 1 [ABSTRACT FROM AUTHOR]

Solar biomass steam gasification using concentrated sunlight offers an efficient means of storing intermittent solar energy into renewable solar fuels while upgrading the carbonaceous feedstock. Such solar-driven (allothermal) processes have demonstrated the ability and the effectiveness for the production of high quality hydrogen-rich syngas, but they suffer from inherent barriers related to the variability of solar energy caused by cloud passages and shut off at night. The concept of hybrid solar/autothermal gasification appears promising to meet the requirement for stable and continuous operation under fluctuating or intermittent solar irradiation. To date, dynamic modelling to simulate coupled solar/combustion heating and steam gasification using real solar irradiation data has never been proposed and could be used to predict the annual performance of large-scale solar gasification plants. In this study, a dynamic mathematical model of a scaled-up solar gasification reactor was developed. The model was composed of a system of differential equations that were derived from unsteady mass and energy conservation equations. After an experimental validation step with the results from a lab-scale solar reactor, the dynamic model was applied at large scale to determine the reactor temperature and syngas production evolution during continuous day and night operation in both solar-only (allothermal) and hybrid solar/autothermal modes. Different reactants feeding management strategies were proposed and compared with the aim of achieving enhanced syngas productivity and optimized use of solar energy during solar-aided steam gasification. It was shown that the hybrid mode with partial oxy-combustion of the feedstock and dynamic feeding control results in the most stable process operation upon fluctuating solar power input, while ensuring continuous production of H 2 and CO at night and during cloudy periods. • A dynamic model is proposed to study the dynamic response of MW-scale solar gasifier. • The model is validated against experimental data for a lab-scale solar reactor. • The temperature and syngas production evolutions are determined using representative solar data. • Three feeding management strategies are proposed for controlled and optimized biomass conversion. • The hybrid control mode results in the highest syngas yield and continuous day and night production. [ABSTRACT FROM AUTHOR]

A novel configuration of hybrid wind-solar PV based cascaded ammonia synthesis is proposed in this article. A comprehensive dynamic analysis is conducted in this study which is substantial to explore the system functionality under different atmospheric conditions as the power achieved by the wind farm source is dependent on the wind speed and power extracted from the solar PV source depends upon solar radiation intensities. The system is designed to supply the electrical output extracted from the wind-solar PV sources to the proton exchange membrane electrolyser after meeting the system work requirements for hydrogen production. The produced hydrogen reacts with nitrogen separated from pressure swing adsorption to synthesize ammonia. A cascaded ammonia synthesis system is employed in this study to achieve high fractional conversion and simulated using Aspen Plus V11. Toronto is chosen as the geographical location for the dynamic simulation. The minimum exergetic efficiency is found to be 19.21% during the month of December and maximum exergetic efficiency is determined as 26.06% during the month of April. Similarly, the minimum energetic efficiency is found to be 18% during December and maximum energetic efficiency was determined as 24.42% during the month of April. In addition, the results obtained from comprehensive dynamic analyses are presented and discussed. • A novel hybrid wind-solar PV based cascaded ammonia synthesis is proposed. • A comprehensive dynamic analysis is conducted to explore the system functionality. • Toronto is chosen as the geographical location for dynamic simulations. • The maximum efficiency is determined for the month of April. [ABSTRACT FROM AUTHOR]

This study concerns MC Formula and the table-based protocol hydrogen fueling methods described in SAE J2601 2016 edition fueling protocols for light duty gaseous hydrogen surface vehicles. It considers the overall efficiency and performance of the two methods. This is achieved by dynamic simulations, using the Dymola hydrogen fueling station library. The MC formula and table-based methods are implemented in the library and different simulations are performed, to evaluate the performance of the two different fueling methods under various conditions. The efficiency is evaluated according to; fueling time, State of Charge levels and total energy consumption. The MC formula is up to 26% faster. The state of charge levels are similar between the table-based and MC formula. The energy consumption for the MC formula is up to 6.9% higher than for the table-based method. Comparing consecutive fuelings without recharging the station, the table-based method is able to fill 7 vehicles and the MC formula 5 vehicles. • Comparison between the average pressure ramp rate and MC hydrogen fueling methods. • Different fueling conditions are compared with respect to time end energy consumption. • Description of the methodology and equations used to implement the MC method. • The effect on consecutive fuelings depending on the fueling method. [ABSTRACT FROM AUTHOR]

This study explains the fundamental mathematical equations used for the main component models that are implemented in freely available library for hydrogen fueling station. The paper provides a background to the model formulation and theory, useful for the further investigations of hydrogen fueling stations. The model was verified against a specific manufacturer model, and it was validated by using test data from an actual fueling station. The study works as documentation and validation of the model formulation. The simulation library is used to make a model for investigating how the pressure loss in the vehicle affects the fueling process. Keeping the temperature out of the station constant and fueling to 80 MPa in the compressed hydrogen storage system, the pressure loss in the compressed hydrogen storage system directly correlates to the final temperature. The final temperature increases with increasing pressure losses. It is also shown that with no pressure loss in the vehicle the fueling has no limit in fueling speed as the heat of compression depends on the mass filled and the enthalpy of the mass, and not the filling time. • Validated and verified dynamic model description of cascade hydrogen fueling. • Influence of vehicle storage system pressure loss on the fueling performance. • Thermodynamic development depending on pressure losses. • Thermodynamic development depending on average pressure ramp rate. [ABSTRACT FROM AUTHOR]

This article describes the thermodynamical analysis of a hydrogen ( H 2 ) fueling station (HFS) with cryopump technology. A dynamic, object-oriented computer model of the HFS is developed in Matlab-Simulink. This model calculates, amongst other thermodynamic properties, the temporal and spatial variation of the H 2 temperature and the component temperatures within the HFS. The validation of the computer model with data from a series of measurements at a testing facility confirms a good accuracy of the model. The most important model object is the high pressure pipe through which the H 2 flows. The pipe is modeled and validated in different configurations. The thick-walled pipe material is discretized in radial and axial direction. In comparison to measurements the simulations show acceptable accuracy with an radial discretization length of s < 0.0026 m. In axial direction a discretization length of l < 1.18 m is found to deliver acceptable accuracy of the simulations compared to measurements. Based on the simulation results a new method of controlling the H 2 temperature by mixing two H 2 mass flows with different temperatures is assessed as practicable. The electrical power requirement of the electric heat exchanger in this HFS design is determined. Depending on the load cases it varies between 0.13 kWh el / (kg H 2 ) and 0.40 kWh el / (kg H 2 ). [ABSTRACT FROM AUTHOR]

Abstract Solid oxide electrolyzer cells pose a promising technology for the production of hydrogen gained from renewables, such as wind and PV. Due to the fluctuating nature of these sources, the transient behavior of SOECs under various load cases plays a crucial role in terms of their long-time stability, degradation behavior, conversion efficiency and application. This study presents a dynamic, 2D-FEM model of a single tubular SOEC. The transient operational behavior of the cell under fast load variations and different flow configurations is assessed based on the conducted simulations. Highlights • Development of a transient 2D model of a tubular SOEC. • Examination of the cell behavior for different load variation speeds. • The use of different load switching speeds is proven insufficient for advanced cell control. • Counter-current flow configurations lead to moderate temperature gradients inside tubular cells. [ABSTRACT FROM AUTHOR]

Abstract A bioethanol reforming system, capable of converting a diluted water-ethanol mixture into hydrogen, is sized and set up to produce 5 kW of electric power via a polymer electrolyte membrane fuel cells (PEMFC). A part of the produced hydrogen supplies heat for the reforming reaction without impairing the power generation, then no additional fuel is required. According to the different configurations of the control variables, the heat released from the system is distributed between two different temperature ranges and coupled to a standard house-scale combined heat and power (CHP) cogeneration apparatus. Hot water can be produced continuously at a high enough temperature to cover the need of a F-class home in the moderately cold Northern Italy winter climate. With a micro-accumulation solution and a careful choice of the set-points, also the sanitary hot water demand (DHW) of a 4-members family might be fulfilled with 2–3 daily cycles of the same system. Highlights • Description of an integrated system for heat and power cogeneration based on fuel cells. • Dynamic simulation of hot water supply under different power output. • Design of a microaccumulation system for hot water supply. • Description and comparison of different operating cases referred to a class F flat in Northern Italy. [ABSTRACT FROM AUTHOR]

Abstract Three alternative transport options for hydrogen generated from excess renewable power to a refinery of different scales are compared to the reference case by means of hydrogen production cost, overall efficiency, and CO 2 emissions. The hydrogen is transported by a) the natural gas grid and reclaimed by the existing steam reformer, b) an own pipeline and c) hydrogen trailers. The analysis is applied to the city of Hamburg, Germany, for two scenarios of installed renewable energy capacities. The annual course of excess renewable power is modeled in a coupled system approach and the replaceable hydrogen mass flow rate is determined using measurement data from an existing refinery. Dynamic simulations are performed using an open-source Modelica® library. It is found that in all three alternative hydrogen supply chains CO 2 emissions can be reduced and costs are increased compared to the reference case. Transporting hydrogen via the natural gas grid is the least efficient but achieves the highest emission reduction and is the most economical alternative for small to medium amounts of hydrogen. Using a hydrogen pipeline is the most efficient option and slightly cheaper for large amounts than employing the natural gas grid. Transporting hydrogen by trailers is not economical for single consumers and realizes the lowest CO 2 reductions. Highlights • The potential to supply a real crude-oil refinery with renewable H 2 is identified. • Three transport ways for different RE capacities and refinery scales are analyzed. • CO 2 reduction is always highest for injecting H 2 into the natural gas grid. • Cost is lowest for H 2 injection at small and for a H 2 pipeline at large scales. • H 2 trailers cannot compete at short distances and for a single consumer. [ABSTRACT FROM AUTHOR]

Abstract A hydrogen supply system of 70 MPa hydrogen storage cylinder on vehicles is designed, in which a compressor is proposed to use the new type of ion compressor. The system is simulated statically by Aspen Plus. Meanwhile, during the process of hydrogen charged from the third-stage high-pressure hydrogen storage tank to the hydrogen storage cylinder on vehicles, the dynamic variety of the third-stage high-pressure hydrogen storage tank is simulated dynamically by Aspen HYSYS Through the simulation, obtaining the results that there are difference between theoretical calculation and simulation for the volume of third-stage high-pressure hydrogen storage tank and the average volume flow of hydrogen in a third-stage high-pressure hydrogen storage tank varies with its pressure and volume. By comparing the results of Aspen Plus simulation and Aspen HYSYS simulation, there are some differences. The designed system can be applied to hydrogen stations and any operating conditions involving the supply hydrogen. Highlights • Designing a complete hydrogen supply system with the ionic liquid compressors. • Introducing a method for determining the parameters of the hydrogen supply system. • Obtaining the trend of pressure and volume flow during the pressure relief. • Acquiring the changes of pressure and volume with average volume flow. • Comparing steady state simulation with dynamic simulation. [ABSTRACT FROM AUTHOR]

Low-temperature polymer electrolyte membrane fuel cell (PEMFC) acts as a promising energy source due to the non-pollution and high-energy density. However, as hydrogen supply is a major constraint limiting the wide spread of fuel cell vehicles, a dimethyl ether (DME)-steam on-board reformer (SR) based on catalytic reforming via a catalytic membrane reactor with a channel structure is a possible solution to a direct hydrogen supply. The DME-SR reaction scheme and kinetics in the presence of a catalyst of CuO/ZnO/Al 2 O 3 +ZSM-5 are functions of the temperature and hydrocarbon ratio in the hydrogen-reforming reaction. An electric heater is provided to keep the temperature at a demanded value to produce hydrogen. As there is no available analysis tool for the fuel cell battery hybrid vehicle with on-board DME reformer, it is necessary to develop the tool to study the dynamic characteristics of the whole system. Matlab/Simulink is utilized as a dynamic simulation tool for obtaining the hydrogen production and the power distribution to the fuel cell. The model includes the effects of the fuel flow rate, the catalyst porosity, and the thermal conductivity of different subsystems. A fuel cell model with a battery as a secondary energy storage is built to validate the possible utilization of on-board reformer/fuel cell hybrid vehicle. In consideration of time-delay characteristic of the chemical reactions, the time constant obtained from the experiment is utilized for obtaining dynamic characteristics. The hydrogen supplied by the reformer and the hydrogen consumed in the PEMFC prove that DME reformer can supply the adequate hydrogen to the fuel cell hybrid vehicle to cope with the required power demands. [ABSTRACT FROM AUTHOR]

A dynamic simulation approach to investigate an optimal hydrogen refueling method is proposed. The proposed approach simulates a transient temperature, pressure and mass flow rate of hydrogen flowing inside filling equipment in an actual station during the refueling process to an Fuel Cell Vehicle (FCV) tank. The simulation model is the same as in an actual hydrogen refueling station (HRS), and consists of a Break-Away, a hose, a nozzle, pipes and an FCV tank. Therefore, we can set actual configurations and thermal properties to the simulation model, and then simulate the temperature, pressure and mass flow rate of hydrogen passing through each position based on the supply conditions (temperature and pressure) at the Break-Away. In this study, the simulated temperature, pressure and mass flow rate are compared with the corresponding experimental data. Therefore, we show that the dynamic simulation approach can accurately obtain those values at each position during the refueling process and is an effective step in proposing the optimal refueling method. [ABSTRACT FROM AUTHOR]

Hydrogen gas cycling test can provides stress factors associated with rapid and simultaneous interior pressure and temperature swings and infusion of hydrogen into materials; therefore, it is considered as an effective method to detect the safety of the compressed hydrogen storage system. However, the energy consumption of gas cycling test is high. In order to reduce energy consumption, an optimization gas cycling test system was designed based on multi-stage storage and self-pressurized method in this paper. A dynamic simulation model which considers the process of refueling, pressure control, pre-cooling and discharging was also established to calculate the energy consumption. Using the model, the energy consumption of different system with different storage stages, different pressure, and different volumes was calculated. The results show that with the increase of gas storage stages, total energy consumption of the system decreases, but taking into account the complexity of the system, the stages should be less than three; In the range of 20–50 MPa and 1–4 m 3 , lower pressure and smaller volume of low pressure tank can not only reduce the gas the construction cost, but also reduce the energy consumption; In the range of 45–60 MPa and 1–3 m 3 , the effect of medium pressure tank on the energy consumption is not significant. This study provides a new optimization design method for compressed hydrogen cycling test system, has an important significance in development of high pressure hydrogen gas cycling test. [ABSTRACT FROM AUTHOR]

Cryogenic distillation is a very widely applied technique for separating the components of a mixture of hydrogen isotopes, which may contain up to six isotopic species. This work presents a simple dynamic model for evaluating the major performance characteristics of a cryogenic distillation column for hydrogen isotope separation. Liquid hold up, pressure drop and flooding point have been predicted for the tower using known packing characteristics and fluid properties. The column has been modelled as an equivalent tray tower using a known value of the height equivalent to theoretical plate (HETP) and its dynamic behaviour and separation performance under various conditions have been predicted. The effect of parameters like temperature, reflux ratio, feed point location and feed composition on the final isotopic contents of top and bottom products at steady state has also been studied. Consequences of neglecting the decay heat of tritium in distillation calculations have also been evaluated. This model is intended for preliminary column design work using data from literature, without the need for prior experimental activity. [ABSTRACT FROM AUTHOR]

In this study, the effect of environmental conditions on plant operation was investigated for hydrogen refuelling stations with an external storage facility. Hydrogen storage pressure with respect to tank surface temperatures have been measured and used to create empirical equations for each tank showing the effect of surface temperature on the tank pressure. A physical model of the hydrogen storage tanks has been created in DesignBuilder (EnergyPlus) to simulate the surface temperature of tanks throughout the course of a year with respect to location, site orientation, tank size and surface colour, shading and operating pressure. Finally, the effect that environmental conditions may have on a plant operation is assessed through the prediction of pressure dependent events, namely the frequency of alarms and pressure relief occurrences and hours of plant downtime over the course of a year. The modelling results indicate that location, tank size, surface colour and sunshade can have substantial impacts on the plant operation, whereas the influence of site orientation is less significant. Frequency of pressure dependant events increase as the tank size decreases due to more significant heat gain observed with higher surface-to-volume ratios. Simulation results also prove that the provision of a sunshade or white paint colour could avoid/minimise the interference of ambient conditions in plant operation in cold and mild climates. However, they are not sufficient enough to mitigate against solar gain effect in warmer climates. Although reducing the maximum operating pressure would also help reduce the number of solar gain pressure events, it would also result in increased cushion level and hence reduced plant performance. The optimum design and operating strategy should be chosen for each individual station considering the daily and annual temperature profiles of the location. [ABSTRACT FROM AUTHOR]

Alternative designs of planar solid oxide fuel cell stack have been developed over the last decade. Depending on the application, different geometries, materials and flow configurations were adopted. This study investigates a generic solid oxide fuel cell stack with nominal power output above 1.3 kWel. The fuel cell stack is a key component of a highly integrated micro-cogenerator for domestic application. As daily, weekly and monthly variations in the electrical power load are expected, there is a need to develop numerical tools to predict the unit's performance with high accuracy. Hence, a fully physical dynamic model of a SOFC stack was developed and implemented in Aspen HYSYS 7.2 modeling software to enable predictive analysis of the off-design operation. The presented model exhibits high accuracy and accounts for thermal and electrochemical processes and parameters. The authors present the methodology used in the study to analyze the sensitivity of key parameters to load changes in cross-, co- and counter current flow configuration in the stack. Further functionality of the model, which was validated using manufacturer's data is discussed. [ABSTRACT FROM AUTHOR]

Experimental and computational study on the operating characteristics of the fuel cell with changing back pressure at the cathode and anode outlets was performed for both steady and transient operations. In the experiments, the back pressure was controlled by a pressure regulator in the fuel cell outlet, and the effects of the operating pressure under various load conditions were observed in steady-state operations. The transient responses of the fuel cell to the load changes in different operating pressures were also examined. Additionally, in order to fully understand the effects of the major parameters in various operating pressures on the fuel cell performance, a dynamic simulation model of the cell stack was developed. The performance analysis revealed that a higher voltage was produced by the cell when a high pressure was maintained because the high pressure facilitated high concentration of the reactant gas near the membrane. The mass flow rate of the liquid water also increased with increasing pressure in a given humidity, which helped to maintain higher voltage than otherwise. However, the overshoot and undershoot of the output voltage during load transition also increased with increasing back pressure, primarily because of the difference between the rates of gas supply to the membrane and gas consumption near the membrane. Whereas the consumption of the gas near the membrane was rapid, the fresh reactant gas required some time to reach the membrane. The inherent time lag resulted in undershoot and overshoot with changing load. It was observed that the remaining liquid water was also an important factor which affected the level of undershoot or overshoot during the load change. Finally, an operating strategy using a back-pressure regulator was suggested and applied in a transient operation of irregular multi-step load variation. The back pressure should be decreased before the load change and restored back to the pre-set level for the steady-operation. The former was shown to reduce the size of undershoot or overshoot during transition, and the latter could lead to the efficient operation by reducing parasitic losses in the fuel cell system. [ABSTRACT FROM AUTHOR]

This work develops a one-dimensional model of an alkaline anion-exchange membrane direct glycerol fuel cell (AEM-DGFC) for cogeneration of tartronate and electricity. The model is validated against steady state and dynamic experiments, and shows good agreement. Steady state modeling includes anode and cathode losses and predicts the single cell polarization and power density curves. Coupled mass transport, charge transport, and electrochemical kinetics predict the effects of varying reactant concentration and diffusion layer porosity on single cell performance. The results show that anode overpotential is the major source of loss at middle to high current density regions, due to limited glycerol diffusion at the catalyst layer. Furthermore, the dynamic response of AEM-DGFC to step changes in current density is simulated by considering time-dependent species transport and double-layer capacitance charging. Analysis of dynamic simulation reveals that the liquid-phase reactant diffusion is a key factor influencing the transient AEM-DGFC behavior and is very sensitive to diffusion layer design. This new numerical analysis of a glycerol-fed fuel cell demonstrates that a simple, single oxidation product model can successfully predict the steady state and dynamic losses. [ABSTRACT FROM AUTHOR]

This paper presents the conceptual design for a two-step thermochemical cycle producing hydrogen continuously, even off-sun, with the concentrated solar energy as the heat source. For a case study, the two-step iron oxide cycle (Fe3O4/FeO) is selected to illustrate the design concept. Two reactors, one storage tank and the solar collector comprise the system. Molten wustite (FeO) is accumulated in the storage tank on-sun. The FeO is not only involved in the reactions but also acts as the heat transfer medium, obtaining the energy from the solar insolation and delivering energy to support the thermal decomposition of magnetite (Fe3O4). In this way, the temperature limitation (<800 K) of molten salt is solved, and the intermittency problem of variable insolation is circumvented. A simple feedback scheme is used to control the flow rate between the storage tank and the reactors in order to minimize the temperature fluctuations. For the wustite hydrolysis reaction, the volumetric flow rate of water is regulated to control the temperature in the reactor. We derived the kinetics of the two-step iron oxide cycle from previous experimental reports. We simulated the dynamics of the system over 50 days with mass and energy balances. The simulation results show that the storage tank temperature will be stationary at 2250 K. After five days, the decomposition temperature at 2100 K, and the hydrogen production stabilized at 7 kg/min. Admitting the difficulty of high temperature operation, this design is still promising due to the high efficiency of two-step cycle itself, the process intensification of the FeO acting as the reactant/product/heat transfer medium (no need of heat exchangers), and the continuous operation/production of hydrogen. [ABSTRACT FROM AUTHOR]