Hydrogen Flow Research Articles

Vapor-phase hydrodeoxygenation of guaiacol for phenol production using bifunctional Ni/Cu-Beta zeolite catalysts

A series of bifunctional catalysts based on beta zeolite were prepared though co-impregnation and tested for vapor-phase hydrodeoxygenation (VHDO) reaction to form phenol. Among the catalysts tested, 10Ni/Cu-Beta exhibited the highest stability, catalytic activity, and selectivity for phenol. Under the optimal conditions of a contact time (W/F) of 1.5 h, a molar flow of hydrogen to guaiacol (H/G) of 24, a time of stream (TOS) of 40min. A temperature of 450 °C, and a molar flow of stream to guaiacol (S/G) of 3, complete conversion was achieved, with a phenol yield of 63.95% and a sum yield of phenolic compounds of 96.89%. The beta zeolite support provided an adequate specific surface area and initial acid sites for the VHDO process. In the absence of water, the addition of Cu metal improved catalytic performance of the catalyst. However, the increase in temperature could result in more severe deactivation. The addition of water had little effect on the catalyst activity and helped to improve its stability to a certain extent. The loading of Ni metal contributed to an increased selectivity for phenol. The characterization results from X-ray diffraction (XRD) and hydrogen temperature-programed reduction (H2-TPR) showed that reduced and oxidized metals are finely dispersed on the catalyst surface. NH3 temperature-programed desorption and pyridine infrared resonance (Py-IR) characterizations revealed that the addition of Cu and Ni metal adjusts the type and amount of acid sites. A small part of Cu2+ and Ni2+ could be bound simultaneously to the surface of beta support, of which Cu2+ forms new metal-induced L-sites while Ni2+ does not, resulting in a lower concentration of L-sites on Ni/Cu-based catalysts compared to that on Cu-based catalysts and weakening the transmethylation reaction of phenolic compounds. The combination of metal sites and acid sites enabled the VHDO reaction of guaiacol to produce more phenol in the products.

Amorphous cobalt iron oxide nanoparticles with high magnetization intensity for spin conversion of hydrogen at 77K

Conversion of ortho-hydrogen (o-H2) to para-hydrogen (p-H2) is a necessary process in hydrogen liquefaction, and investigating the catalysts that accelerate conversion is significant. Herein we report the effect of Co/Fe ratio in cobalt iron oxide catalysts on conversion of o-H2 to p-H2 at 77 K, and use XRD, BET, and VSM to explore the influence of different Co/Fe ratios on internal crystal structure, pore size, and magnetization strength. It is concluded that the synergistic effect of crystal structure disorder (increase in active sites), small pores (decrease in distance between o-H2 and active sites), and high magnetization strength (larger torque upon) resulted in the optimal catalytic performance for CFO-3 [n(Co):n(Fe) = 3:10]. When the hydrogen flow is 100 mL min−1, the content of p-H2 in the converted hydrogen is 47.61%.

Metal hydride cylindrical tank for energy hydrogen storage: Experimental and computational modeling investigations

In this paper, experimental and numerical studies of hydrogen solid storage are investigated. An experimental test bench was implemented to investigate the hydride metal tank thermal behavior upon various cooling/heating modes. The metal hydride tank (La0.9Ce0.1Ni5), a 300 W proton exchange membrane fuel cell stack, and the auxiliary equipment to measure and regulate the physical parameters were used. Absorption and desorption processes were investigated under different operating conditions in order to address the performance of metal hydride. The metal has been thermally managed to minimize the charging time and to extend the operating time of the fuel cell. Different hydrogen charge pressures (4, 5, 6, 7, 9, 10 bar) were analyzed to define their effects on the metal hydride temperature, heat flux, flow rate and charging time. All these parameters were performed during charge and discharge processes for various inlet cooling temperature of 5 °C, 10 °C, 15 °C, 20 °C, 25 °C and 30 °C. The metal hydride could be charged quickly by hydrogen under high inlet pressure and using an efficient cooling mode with high heat transfer coefficient and cold temperature. The results show that more cooling temperature is low, much faster hydrogen is absorbed. Decreasing the cooling temperature increases the difference between the equilibrium pressure and the charging pressure and a higher absorbed hydrogen flow rate will obtain. The state of charge is increased by 1.6% by decreasing cooling temperature by 1 °C. However, the state of discharge increases with the heating temperature (2.5% per 1 °C).

Hydrogen tightness evaluation in bedded salt rock cavern: A case study of Jintan, China

Hydrogen is regarded as one of the most important energy sources for the future. Safe, large-scale storage of hydrogen contributes to the commercial development of the hydrogen industry. Use of bedded salt caverns for natural gas storage in China provides a new option for underground hydrogen storage (UHS). In this study, the physical properties of multicomponent gases in UHS and salt rock are reviewed and discussed, along with the flow of hydrogen in the surrounding salt rock. Mathematical models of the two-phase multicomponent flow of the gas–brine system in the UHS were established. A numerical model of a simplified elliptical salt cavern was built to simulate the migration of the gas–brine system in the UHS. The hydrogen tightness of the UHS was evaluated through simulation with different storage strategies, salt rock and interlayer permeabilities, and gas components. The results indicate that: (1) Cyclic injection and withdrawal facilitate hydrogen leakage, which is accelerated by increasing the frequency. (2) The huff-n-puff of hydrogen gas in the injection and withdrawal cycles forces the gas into pore space and enhances the relative permeability of the gas phase. The migration of hydrogen and brine weakens the hydrogen tightness. Brine saturation is an important index for evaluating the hydrogen tightness of UHS. (3) The leakage rate of UHS increases with an increase in the permeability of the salt rock and interlayer and the total thickness of the interlayers. The average permeability Kwa weighted by the thickness of layers for the bedded salt formation is proposed to integrate three variables to facilitate field application of the simulation results. The critical Kwa is less than 3.02 × 10−17 m2 if the recommended annual hydrogen leakage rate is less than 1%. (4) The difference between hydrogen and other gas species is another important factor in the leakage rate and should be considered. This study provides theoretical guidance for evaluating the feasibility of UHS in salt caverns and site selection in China.

The Co-development of Offshore Wind and Hydrogen in the UK – A Case Study of Milford Haven South Wales

Green hydrogen produced from renewable energy resources can not only contribute to the decarbonisation of different energy sectors, but also serve as a carrier for long-distance delivery of renewable generation, offering a cost-effective way to exploit the renewables far from electrical grids. To facilitate the co-development of offshore wind and hydrogen, the paper develops a modelling framework to dispatch power and hydrogen flows across dedicated offshore wind hydrogen production systems to meet onshore hydrogen demands while keeping similar state of charge levels between multiple systems. Then the hydrogen supply to shore and the system investments and ongoing costs are discounted to their present values to calculate the levelised cost of hydrogen, which is minimised by the particle swarm optimsiation algorithm to suggest the best capacities of hydrogen system components including converters, desalination devices, electrolysers, compressors and storage assets. The proposed modelling framework is tested based on a case study at Milford Haven South Wales which is evaluated to have massive offshore wind resources in the Celtic Sea and comparable demands for hydrogen by 2040. The optimisation results are presented based on the techno-economic input parameters projected for 2030 and 2050 scenarios and discussed alongside the influences of technology advances on the system optimisation and resulting metrics including the levelised costs of hydrogen, net present values and potential levels of green hydrogen supply to Milford Haven.

Математическое моделирование натекания водорода в гермзоне реакторного здания АЭС с ВВЭР-1200

Introduction. The patterns of hydrogen-air mixtures formation during the flow of hydrogen into the upper part of a large volume room in the initial moments of time are insufficiently studied. Therefore, the determination of regularities of formation of local explosive and fire-hazardous hydrogen-air mixtures when hydrogen flows into the lower part of the dome space of the reactor building is important. Goals and objectives. The purpose of the article is a theoretical study of occurrence of local fire and explosive zones of the hydrogen-air mixture generated during hydrogen leakage in the containment area of the reactor building in order to substantiate parameters of concentration sensors of the hydrogen concentration control system. To achieve it, a zone mathematical model of hydrogen concentration calculation in a pressurized room has been developed. Numerical experiments on regularities of hydrogen-air mixtures formation have been carried out. Theoretical basis. The generalized three-dimensional non-stationary differential equation of the laws of conservation of mass, momentum and energy is used to calculate local hydrogen concentration fields. The developed zone model makes it possible to determine hydrogen concentrations in the convective column and in the ceiling layer. Results and discussion. The characteristic fields of hydrogen mass concentrations in the volume of the dome space are obtained. It has been shown that at the initial stage of hydrogen leakage, a zone of the ceiling layer is formed under the ceiling of the dome space, which confirms the validity of the usage of the zone model. The hydrogen concentrations obtained by the field and zone models are compared. The distributions of hydrogen mass concentration along the convective column height at different Reynolds numbers in the hydrogen leakage hole have been obtained. It has been shown that hydrogen concentration sensors can detect a hydrogen leakage mode in the dome space only in a narrow area of Reynolds Re = 900–5,000. There is a leakage mode (Re = 3,358), in which the maximum hydrogen volume concentration is generated at the location of the concentration sensors at the maximum size of the fire and explosive hydrogen-air mixture zones in the room. Conclusions. The hydrogen concentration sensors used in the dome space of the NPP reactor building with water-­water reactors may not detect hydrogen at the top point of the dome at a sensitivity threshold of 2 % vol. In this case, in terms of the height of the convective column, hydrogen-air mixtures are formed within the fire and explosive concentration limits.

Effect of hydrogen enrichment and TiO2 nanoparticles on waste cooking palm biodiesel run CRDI engine

In this study, we deal with the production and utilization of waste-cooking palm biodiesel (WCB) and.evaluated the influence of the addition of titanium dioxide (TiO2) nanoparticles in hydrogen-enriched single-cylinder CRDI diesel engine. XRD, SEM, and EDX decide the structure and morphology of TiO2 nanoparticles. The TiO2 nanoparticles were dispersed in the tested fuels at a dosage of 50–75 ppm with the aid of ultra-sonication. Based on the oxidation stability study, the B20 + 75 ppm (TiO2) fuel blend is the pilot fuel for the engine test. Further, the engine is enriched with a hydrogen (H2) flow of 10 lpm. Results revealed that the performance parameters were improved with the addition of H2 enrichment and TiO2 nanoparticles compared to D. The brake thermal efficiency of the engine was improved by 8.21%. In comparison, brake-specific fuel consumption decreased by 42.86%. Furthermore, adding nanoparticles also reduced CO and HC emissions by 74% and 27.27%, respectively, whereas the NOx emission was slightly increased. Thus, the findings demonstrated that hydrogen-enriched nanoparticles added to biodiesel might be considered a substitute for fossil fuels and report a positive impact on diesel engine performance without requiring significant modifications.

Low-Order Autoignition Modeling for Hydrogen Transverse Jets

This paper presents a method for evaluating the risk of autoignition for the canonical problem of an enclosed hydrogen jet in crossflow (JICF), which is highly relevant to the design of mixing ducts. The proposed method is based on the separation of the underlying mixing pattern from the evolution of the chemical reactions, whereas the effect of mixing is maintained on the latter with the purpose of creating a reliable yet computationally efficient design tool for hydrogen gas turbines. Two variants of the incompletely stirred reactor network (ISRN) approach are proposed that provide the evolution of preignition radicals and autoignition kernel location, leveraging a nonreacting computational fluid dynamics solution or an analytical mixing pattern. The ISRN governing equations include all the salient features of hydrogen transport and lead to a conservative estimate of autoignition risk. Application to a few model problems with varied operating conditions suggests that radical buildup in the JICF can lead to autoignition in the vicinity of a most reactive mixture fraction, which is consistent with other laminar or turbulent hydrogen flows. However, the radical formation and autoignition kernel location strongly depend on the prediction of the underlying mixing field and the amount of differential diffusion within the JICF, which here primarily favors lower values of the composite mixture fraction and the transport of hydrogen and radicals away from the jet trajectory.

Experimental analysis on the effect of pipe and orifice diameter in inter tank hydrogen transfer

Hydrogen is an energy carrier which can be utilized in many sectors like stationary and transportation energy with nearly zero emission. Hydrogen energy is more efficient when compared to other energy sources. Hydrogen can be a replacement for fossil fuels in future as it emits only water when it is burned. In this work a mathematical model of transfer of hydrogen between two tanks has been developed using MATLAB simulink software version 21. Flow of hydrogen inside the pipe is controlled by orifice and diameter of this orifice and pipe diameter itself has some impact on outcome parameters such as inlet temperature of pipe, outlet temperature of pipe, heat transfer from one tank to other tank and hydrogen gas flow rate. The influence of orifice diameter as well as initial pressures on outcome parameters of hydrogen gas transfer model has analyzed in this work. From the simulation results it is inferred that when one initial pressure kept constant and other initial pressure keep on varying, no change in inlet temperature, decrease in outlet temperature, increase in heat transfer and increase in gas flow rate were observed when orifice diameter increase in size from 2 cm then 4 cm and then 6 cm. The research work has significant guidance for safety and efficient way of transporting hydrogen through pipeline from one tank to other tank.

Data acquisition and monitoring system framed in Industrial Internet of Things for PEM hydrogen generators

Hydrogen is an energy carrier with increasing relevance in the current energy scenario since it contributes to reduce fossil fuels dependence and carbon emissions for a sustainable development. For its generation, Polymer Electrolyte Membrane (PEM) technology uses water and electricity to produce hydrogen and oxygen, avoiding pollutants. In this paper, a novel data acquisition and monitoring system for PEM hydrogen generators is presented. The main magnitudes of the PEM electrolyzer (PEMEL) such as current, voltage, pressure, hydrogen flow, etc., are sensed and acquired by an industrial controller. A middleware layer gathers the measurements through a communication network and stores them in a database. The user accesses online to this information in real time through a web-based interface. All components and functions are orchestrated according to an Industrial Internet of Things (IIoT) architecture, integrating industrial equipment, IoT software and sensing devices, which constitutes a novelty in literature. Experimental data of a PEMEL under real operating conditions are reported to prove the feasibility and successful performance of the developed system.

Novel dual-mixed refrigerant precooling process for high capacity hydrogen liquefaction plants with superior performance

Liquid hydrogen is a superior alternative for the current energy storage methods and energy carriers as it has higher energy density and cleanliness. However, hydrogen liquefaction is an energy-intensive process. In particular, the precooling process of hydrogen consumes a tremendous portion of about 30 % of the total compression power of the plant. Several previous studies introduced various pure-refrigerant and single mixed refrigerant (SMR) precooling processes, however, their specific energy consumption (SEC) still very high especially at large-scale capacities. Therefore, this study presents a novel, efficient, and large-scale dual-mixed refrigerant (DMR) process to precool the hydrogen from 25 °C to -192 °C at a pressure of 21 bar. New heavyweight-based mixed refrigerant MR1 and lightweight-based mixed refrigerant MR2 are developed for the DMR process using a new-proposed systematic approach. The proposed DMR process is capable of handling a wide range of hydrogen flow from 100 TPD to 1000 TPD with SEC of 0.862 kWh/kgH2Feed, which is 20.33 % lower than the most competitive SMR process available in the literature. Based on the sensitivity analysis, further optimization of the DMR operating parameters reduced the SEC to 0.833 kWh/kgH2Feed at an optimal capacity of 500 TPD. Furthermore, the COP of the new process is improved by 14.47 % and the total annualized cost is reduced by 12.24 %. Compared to five other technologies that use the pure-refrigerant and other SMR precooling processes, the DMR reduces the SEC by 39.0 % to 63.0 %. The novel precooling process presented herein has the potential to drive the development of large-scale hydrogen liquefaction processes.

Analysis of CRDI diesel engine characteristics operated on dual fuel mode fueled with biodiesel-hydrogen enriched producer gas under the single and multi-injection scheme

The present work aims to investigate the consequences of pilot fuel (PF) multiple injections and hydrogen manifold injection (HMI) on the combustion and tailpipe gas characteristics of a common rail direct injection (CRDI) compression ignition (CI) engine operated on dual fuel (DF) mode. The CI engine can perform on a wide variety of fuels and under high pilot fuel (PF) pressure. Pilot fuel injection (PFI) is achieved at TDC, 5, 10, and 15ºCA before the top dead center (bTDC), and divided injection consists of injecting fuel in three different magnitudes on a time basis and PF is injected into the engine cylinder at a pressure of 600 bar. In this work, the hydrogen flow rate (HFR) was fixed at 8 lpm constant and producer gas was inducted without any restriction. The investigational engine setup has the ability to deliver a PF and hydrogen (H2) precisely in all operating circumstances using a separate electronic control unit (ECU). Results showed that diesel-hydrogen enriched producer gas (HPG) operation at maximum operating conditions provided amplified thermal efficiency by 4.01% with reduced emissions, except NOx levels, compared to biodiesel-HPG operation. Further, DiSOME with the multi-injection strategy of 60 + 20+20 and 50 + 25+25, lowered thermal efficiency by 4.8% and 9.12%, respectively compared to identical fuel combinations under a single injection scheme. However, reductions in NOx levels, cylinder pressure, and HRR were observed with a multi-injection scheme. It is concluded that multi-injection results in lower BTE, changes carbon-based emissions marginally, and decreases cylinder pressure and heat release rate than the traditional fuel injection method.

Groundwater denitrification using a continuous flow mode hybrid system combining a hydrogenotrophic biofilter and an electrooxidation cell

An attached-growth continuous flow hydrogenotrophic denitrification system was investigated for groundwater treatment. Two bench-scale packed-bed reactors were used in series, without external pH adjustment or carbon source addition, while inorganic carbonate salts already contained in the groundwater were the sole carbon source used by the denitrifying bacteria. The hydrogen was produced by water electrolysis using renewable energy sources thus minimizing resource-draining factors of the treatment process. The biofilter was subjected to a combination of three groundwater retention times (13.5, 27 and 54 min, corresponding to 20, 10 and 5 mL min−1 inlet water flow rates) and two hydrogen flow values (10 and 20 mL min−1) to evaluate its efficiency under different operating parameters. In all cases, significant nitrate percentage removals were achieved, ranged between 64.1% and 100%. The treatment process appears to slow down with lower retention times and H2 flow rate values, although residual nitrate concentrations were always in the range of 0–5.1 mg L−1, values below the maximum permitted limit of 11.3 mg L−1. In cases where nitrite accumulation was detected, a continuous flow electrochemical oxidation process with three different current density values (5.0, 7.5 and 10.0 mA cm−2) was examined as a post-treatment step aiming to completely remove the toxic nitrite anions. Finally, an advanced mathematical model of the attached growth hydrogenotrophic denitrification process was developed to predict concentrations of all the substrates examined in the bio-filter (nitrate, nitrite, inorganic carbon and hydrogen).

High-Performance Thin-Film Transistors with ZnO:H/ZnO Double Active Layers Fabricated at Room Temperature.

H doping can enhance the performance of ZnO thin-film transistors (TFTs) to a certain extent, and the design of double active layers is an effective way to further improve a device's performance. However, there are few studies on the combination of these two strategies. We fabricated TFTs with ZnO:H (4 nm)/ZnO (20 nm) double active layers by magnetron sputtering at room temperature, and studied the effect of the hydrogen flow ratio on the devices' performance. ZnO:H/ZnO-TFT has the best overall performance when H2/(Ar + H2) = 0.13% with a mobility of 12.10 cm2/Vs, an on/off current ratio of 2.32 × 107, a subthreshold swing of 0.67 V/Dec, and a threshold voltage of 1.68 V, which is significantly better than the performance of single active layer ZnO:H-TFTs. This exhibits that the transport mechanism of carriers in double active layer devices is more complicated. On one hand, increasing the hydrogen flow ratio can more effectively suppress the oxygen-related defect states, thus reducing the carrier scattering and increasing the carrier concentration. On the other hand, the energy band analysis shows that electrons accumulate at the interface of the ZnO layer close to the ZnO:H layer, providing an additional path for carrier transport. Our research exhibits that the combination of a simple hydrogen doping process and double active layer construction can achieve the fabrication of high-performance ZnO-based TFTs, and that the whole room temperature process also provides important reference value for the subsequent development of flexible devices.

Kinetic hydrogen isotope effects and flow compensation strategy of the ZrCo-based chemical beds in full-scale SDS demo-system

ZrCo-based bed, commonly exploited to efficiently process large quantities of mixed hydrogen isotope gases, is one of crucial component in the storage and delivery system (SDS) of the tritium plant in fusion reactor. However, the hydrogen isotope effect on the desorption and adsorption processes of the ZrCo based assemblies has not yet clearly addressed, especially for a full-scale (100 g of Tritium) bed assembly. Herein, the kinetic hydrogen isotope effect of the full-scale ZrCo-based chemical beds, including ZrCo, Zr0.8Ti0.2Co, Zr0.8Hf0.2Co, with different hydrogen isotope ratios in SDS demo-system are investigated in detail. This work shows that the kinetic adsorption isotope effect of all ZrCo based beds are independent of pressure, temperature, and hydrogen isotope ratio. Conversely, the kinetic hydrogen isotope fluctuation is prominent during hydrogen desorption, where the proportion of protium is relatively high at the initial stage. After that, deuterium is easier to release. Finally, the protium gradually increases. The fluctuating degree is in the sequence of Zr0.8Ti0.2Co > ZrCo > Zr0.8Hf0.2Co for types of chemical beds, and 50%D + 50%H > 90%D + 10%H > 10%D + 90%H for isotope components. Based on experimental details, a flow compensation approach to ensure a stable ratio of hydrogen isotope gas is proposed. This work is of crucial significance for practical-scale SDS system operation, which is the prerequisite for the steady-state running of the fusion reactor.

Parametric analysis on throttling elements of conical throttling valve for hydrogen decompression in hydrogen fuel cell vehicles

As the most common component of the pressure management system in hydrogen fuel cell vehicle (HFCV), the structure of conical throttling valve affects the hydrogen decompression performance significantly, which plays an important role in the safe and stable application of hydrogen. In this paper, parametric analysis on throttling elements of conical throttling valve for hydrogen decompression is presented. The hydrogen decompression and flow model is built based on the real gas model. The velocity, pressure, temperature and turbulent kinetic energy are monitored for reflecting the hydrogen flow characteristics. The influence of the cone angle and the pressure difference between inlet and outlet on the hydrogen decompression performance is studied. The results are shown that cone angle and pressure difference significantly affect flow patterns and flow characteristics in the flow region near the cone surface of valve core. There is stronger turbulent flow along the cone surface under the smaller cone angle and higher pressure difference. When the cone angle is below 45°, the flow pattern flowing out along the cone surface transforms from free jet to parallel flow along the cylindrical surface. The multiple high-velocity regions are generated behind the narrow throttling gap under large pressure difference. With the decrease of pressure difference, the position of maximum velocity gradually moves closer to the flow region of narrow throttling gap. The optimizing structure with a convex cylinder has a positive effect on improving the flow patterns and hydrogen decompression performance. The stability of decompression can be achieved within a short distance by the optimization structure of the convex cylinder. This study can provide a reference for the design of conical throttling valves for hydrogen decompression in hydrogen fuel cell vehicles.

An Approximate Analytical Model of a Jet Flow with Mach Reflection and Pulsed Energy Supply at the Main Shock

The supersonic flow of a reactive gas mixture with Mach reflection of oblique shocks and pulsed energy supply at the Mach stem is considered within the framework of the Chapman–Jouguet theory. An approximate analytical model is proposed that quickly determines the shape and size of the shock-wave structure as well as the flow parameters in various flow regions. As an example of the application of the proposed analytical model, the “first barrel” of a highly overexpanded jet flow of an air-methane mixture with a high supersonic velocity, is studied. Flows of hydrogen–air and hydrogen–oxygen mixtures were also considered for comparison with preceding numerical results. The height of the triple point of the Mach reflection is determined in the presence of a change in the chemical composition of the mixture and an isobaric pulsed energy supply at the main shock.

Power-to-X processes based on PEM water electrolyzers: A review of process integration and flexible operation

Hydrogen produced with renewable electricity may be used to synthesize valuable chemical products, thus aiding the decarbonization of the chemical industry. Thanks to their fast dynamics, Polymer Electrolyte Membrane Water Electrolyzers (PEM-WEs) appear promising for coupling with fluctuating power inputs, e.g., from a grid balancing request or standalone renewable power supply. However, the flexibility of downstream synthesis processes under time-variable hydrogen flow rates is still unclear, and expensive hydrogen storage could be needed as buffer. We review the state of the technology with a focus on the potential for flexible operation of the key components of the main Power-to-X processes: hydrogen production via PEM-WEs, carbon capture, nitrogen production, and the synthesis of methane, methanol, syngas, and ammonia. Flexibility concepts of the units are described and the characteristic times for start-up and load variations, ramp rate limits, and operating ranges are collected. Opportunities for heat and mass integration are discussed.

The effects of flow field design on PEMFC

The flow field design plays a crucial role in the performance of proton exchange membrane fuel cells (PEMFCs). An efficient flow field design enhances electrochemical reactions in catalyst layers and facilitates the water removal process at the cathode. This study evaluates two PEMFC designs, rectangular and semicircle baffle flow fields, using computational fluid dynamics modeling. The models incorporate mass, heat and energy transport, electrode kinetics, and potential fields in PEMFCs. The research analyzes the hydrogen and oxygen mass flow rates and water distributions in PEMFCs at operating voltages of 0.3–1 V to determine the effect of the flow field design on performance. According to the results it is clear that flow field design has an important influence on PEMFC power density and performance. The calculated power density at 0.3 V and at 80°C for semicircle and rectangular baffle flow field PEMFCs respectively are 0.37 and 0.23 W cm−2, which indicates that PEMFC with semicircle baffle flow field has better performance in this study.

Global Hydrogen and Synfuel Exchanges in an Emission-Free Energy System

This study investigates the global allocation of hydrogen and synfuels in order to achieve the well below 2 °C, preferably 1.5 °C target set in the Paris Agreement. For this purpose, TIMES Integrated Assessment Model (TIAM), a global energy system model is used. In order to investigate global hydrogen and synfuel flows, cost potential curves are aggregated and implemented into TIAM, as well as demand technologies for the end use sectors. Furthermore, hydrogen and synfuel trades are established using liquid hydrogen transport (LH2), and both new and existing technologies for synfuels are implemented. To represent a wide range of possible future events, four different scenarios are considered with different characteristics of climate and security of supply policies. The results show that in the case of climate policy, the renewable energies need tremendous expansion. The final energy consumption is shifting towards the direct use of electricity, while certain demand technologies (e.g., aviation and international shipping) require hydrogen and synfuels for full decarbonization. Due to different security of supply policies, the global allocation of hydrogen and synfuel production and exports is shifting, while the 1.5 °C target remains feasible in the different climate policy scenarios. Considering climate policy, Middle East Asia is the preferred region for hydrogen export. For synfuel production, several regions are competitive, including Middle East Asia, Mexico, Africa, South America and Australia. In the case of security of supply policies, Middle East Asia is sharing the export volume with Africa, while only minor changes can be seen in the synfuel supply.