Hydrogen Pump Research Articles

Characterization of a NEG cartridge under high pressure conditions

The development of advanced sintered pumping elements based on the ZAO® alloy, characterized by a high affinity towards hydrogen and its isotopes, make Non Evaporable Getter (NEG) pumps particularly appealing for applications in fusion research, which typically deal with large fluxes of these gaseous species. NEG getters show high pumping speeds and capacity, excellent reliability with ability to withstand a high number of loading and unloading cycles without showing any type of failure, ease of integration within a complex system (such as a fusion reactor) because of their high specific properties and the simplicity of the mechanism that regulates its operation. These properties make NEG technology particularly suitable for the development of compact, efficient and easily scalable solutions, which are also very safe, since the release of absorbed hydrogen is prevented in the case of power outage or subsystem failures, as it can occur only by providing an adequate amount of heat to the getter material. This paper reports the results of an experimental campaign conducted on a new type of NEG pump, aimed to obtaining an accurate characterization in response to different operating conditions. Hydrogen pumping speed was investigated in a range of pressures of particular interest for the activities of the Divertor Tokamak Test facility (between 0.1 and 10 Pa). The influence of nitrogen absorption and getter material operating temperature on the pumping performances of the NEG pump were also examined. Finally, numerical simulations have been performed to estimate the nominal pumping speed of the NEG pump, that is, the one acting at the absorbing surface, stripped of the effects of the conductance of the paths from the pump NEG to the pressure gauges.

Rapid activation of proton exchange membrane fuel cell stack and underlying mechanisms involved

Activation is a crucial procedure to improve the performance of newly fabricated fuel cell stacks to meet the power requirements in actual application scenarios. However, traditional activation procedures generally last for several hours or even days, which greatly increases the cost and limits the production efficiency. In response to this problem, this paper proposes a rapid activation procedure composed of hydrogen pumping (HP) and limiting-current activation with limited air (LCA). The influence of current density for HP and air supply for LCA on activation effect is studied and the best operating conditions are determined. The importance of water supply to the cathode is highlighted during HP. The influence of air supply for LCA on activation effect is limited, which contributes to gas saving. According to the experiments conducted on a single cell and a 10-cell stack, only 40 min are needed with this combined procedure, which is much shorter than that of the traditional step-current activation. Furthermore, nearly 75% of hydrogen is saved due to the short activation time and the control of gas supply, thus significantly reducing the cost during activation. Furthermore, to reveal the underlying mechanisms, membrane electrode assembly parameters before and after activation are obtained by micro-current excitation. A decrease in ohmic resistance and an increase in roughness factor of catalyst are observed, which contribute to performance improvement. According to the characterizations in the microstructure of membrane electrode assembly and platinum catalyst valence state, the electrolyte hydration and oxide reduction are determined as key factors and principles during activation.

Effect of in-situ formation of CeH2.73/CeO2-x and V2O3 on hydrogen storage performance of MgH2

MgH2, one of the most promising lightweight hydrogen storage mediums, has aroused intensive attention due to its outstanding reversible hydrogen storage capacity. However, it suffers from the intrinsic high operating temperature and sluggish kinetics from de-/hydrogenation, hindering its further industrial application. Herein, we successfully synthesized a novel rare earth Ce co-doping with V element forming bimetallic oxide additive, CeVO4 nanoparticles, which exhibits an excellent catalytic effect for enhancing the hydrogen storage performance in MgH2. With an optimization addition of 10 wt% CeVO4, the initial dehydrogenation temperature of the composite decreased from 286 °C to 212 °C. The composite can desorb 6.03 wt% H2 within 6 min at 300 °C and absorb 1.9 wt% H2 within 20 min even at a low temperature of 50 °C. The apparent dehydrogenated activation energy of the composite was obtained as 61.38 ± 3.9 kJ mol−1. The catalyst mechanism analysis revealed that the “hydrogen pumping” effect of the in-situ formed CeH2·73/CeO2-x and V2O3 play a crucial role in boosting the de-/hydrogenation properties of CeVO4-catalyzed MgH2. This work is helpful for further rational designs of novel catalysts in promoting the commercialization of MgH2.

A recirculation system for concentrating CO2 electrolyzer products

Ethylene concentrations from electrochemical carbon dioxide reduction are increased 20-fold by using a recirculation system with a hydrogen pump.

Hydrogen refueling station synergistically driven by liquid hydrogen pump and thermal compression

The energy consumption of conventional 70-MPa hydrogen refueling stations (HRS) with liquid hydrogen (LH2) pumps remains at a high level due to the low efficiency of LH2 pumps working at extremely high pressures, up to nearly 90 MPa. This paper presents a novel HRS with significantly lower energy consumption, based on a step-by-step compression strategy enabled by a highly-efficient 50-MPa LH2 pump for low-pressure compression and a subsequent thermal compression module for high-pressure compression driven by thermal energy. The performance of the cryogenic pressure vessels in the HRS process is analyzed via a numerical model, and then several improvements to the HRS process are proposed for large-scale refueling requirements. Finally, the techno-economic performance of the HRS is compared with the conventional HRSs and the HRS with pure thermal compression. Compared to the conventional HRSs with 90-MPa LH2 pumps, the capital cost of the proposed 400-kg/day HRS is reduced to $1.52M from $1.80M, while its energy consumption is reduced to 0.3 kWh/kgH2 from 1.3 kWh/kgH2. This work provides a new solution for low-energy-consumption hydrogen refueling which would be beneficial for reducing the overall cost of the hydrogen supply chain.

Investigation of the Distribution of the Mass Transport and Reaction Rates in a Fuel Cell By the Integrated Fuel Cell System Simulator Including the Dynamics of Air, H2, and Cooling Systems

:A model to estimate the distribution of the current density, pressure, flowrate, temperature, and gas composition in the through-plane and along-channel (1+1D) directions of a fuel cell (FC) was developed. The developed model was integrated to the FC system model of the 2nd-Generation MIRAI, state-of-the-art fuel cell electric vehicle (FCEV), and the controllers of the system components. The impacts of the dynamic operating conditions of the FC system components on the 1+1D distribution in a fuel cell were investigated with the developed model. Modeling method: The modeling method of the distribution in a fuel cell is depicted in Fig. 1. In this study, the distribution in the through-plane and along-channel (1+1D) directions is considered and the distribution in the across-channel direction (2D) is assumed to be uniform to ensure acceptable computational time. The anode and cathode channels are divided into 20 nodes in the along-the-channel direction, respectively. The mass, momentum, and energy balance between the adjacent nodes of the channels were expressed by the similar methods as the model developed in the authors’ past research [1]. The models of the mass transport and reactions in the through-plane direction of MEA developed in the authors’ past research [2] were connected to each node of the cathode and anode channels. The in-house numerical solvers which calculate the distribution of current density, flowrate, total pressure, partial pressure of each gas component, and temperature in 1+1D direction were implemented. This model was integrated to the FC system models of the 2nd-Generation MIRAI [1], state-of-the-art fuel cell electric vehicle (FCEV) [3], and controllers for H2, air, and cooling systems developed in the authors’ past research [4] as shown in Fig. 2 to investigate the interactions among the dynamics behaviors of the system components, controller specification, and distribution in a fuel cell. Results and discussion: The impacts of operating conditions of the fuel cell system components on the distribution in a fuel cell were investigated as shown in Table 1. In case 2 in Table 1, rotational speed of the hydrogen pump (HP) is increased and other variables changed accordingly. The dynamic target power shown in Fig. 3 was given to the system model as the input and simulation was done for 700 s. Figs. 4(a)–4(e) show the simulation results at 480 s. In case1, current density was lower due to the high cell resistance in the region of the nodes 1–12 as shown in Figs. 4(a) and 4(b). In this region, the PEM was intensively dried and the H2O activity in PEM was below 0.2 as shown in Fig. 4(c) due to the no-humidifier configuration in air system. The H2O flowrate in through-plane and along-channel direction at the anode channel became almost 0 as shown in Figs. 4(d) and 4(e), suggesting that H2O cannot be delivered on both the cathode and anode sides on this region. In case 2, where the gas flowrate of anode inlet was increased by accelerating hydrogen circulation pump, the current density was higher and the resistance was lower in the region of the nodes 4-12 as shown in Figs. 4(a) and 4(b). The H2O activity at PEM in this region excesses 0.2 following the increased H2O flowrate in along-channel direction at the anode channel as shown in Figs. 4(c)ｰ4(e). The mechanism of the interactions between the system operating condition and the distribution in a fuel cell was depicted in Fig. 5. The increase in HP rotational speed enlarged the humidity difference between anode and cathode, thus, the through-plane H2O transported from the cathode to the anode side around the cathode outlet region. It also enlarged the H2O transport in along-channel direction from the anode inlet to outlet by increasing the volumetric flowrate in the anode channel. Despite of the improvement of the distribution, HP power consumption increased from 125.9 W to 806.5 W following the acceleration of HP speed from 3009 rpm to 7200 rpm as shown in Table 1. It was demonstrated that the complicated relationships among the distribution of reaction and mass transport, the specifications of the system components, and controllers can be investigated with the proposed model. References : [1] S. Hasegawa, et al., ECS Trans., 109(15), 15–70 (2022).[2] S. Hasegawa, et al., ECS Trans., 104(8), 3–26 (2021).[3] T. Takahashi and Y. Kakeno, EVTEC 2021 Proceeding, No. B1.1 (2021).[4] S. Hasegawa, et al., Comput. Aided Chem. Eng, 49, 1123–1128 (2022). Figure 1

CO2 Separation Using Electrochemical Hydrogen Pumping

IntroductionCarbon dioxide (CO2) separation and capture technologies are necessary for a decarbonized society. The chemical absorption method using an amine solvent has been demonstrated in steel and power industry. However, the separation process has some drawbacks such as material corrosion. In this study, we examined CO2 separation by electrochemical approach using hydrogen pumping.ExperimentalThe JARI fuel standard cell was employed and modified. It was divided in anode and cathode compartment by a cation exchange membrane. KHCO3 solution and KCl solution were circulated in the anode and cathode compartment, respectively. H2 gas was supplied to the anode at a constant flow rate by mass flow controller. Electrolysis was carried out at various cell voltages using a DC power supply unit. The gas from the anode was introduced into a quadrupole mass spectrometer (QMS). The volume rate of CO2 gas was measured by a mass flow meter.Results and discussionFigure 1 shows the current-voltage curve when H2 gas was supplied, and constant voltage electrolysis was carried out. The current was detected below the theoretical decomposition voltage of water (1.23 V). This supported that the reversible reaction of hydrogen pumping (H2 ⇆ 2H+ + 2e-) was occurred as expected. The Pt catalyst was contributed to the small overvoltage.During electrolysis, gas was generated in the anode solution. It was separated by a gas-liquid separator, and then introduced to QMS. Figure 2 shows the relationship between the ratio of CO2 gas and cell voltage. In our experiment, the CO2 purity was over 90% at all voltages. This suggested that water electrolysis with O2 evolution did not occur. That is, by controlling the cell voltage, the hydrogen pumping reaction take place preferentially, and H+ is effectively supplied to the anode compartment. This archive high CO2 gas separation. In poster session, results on energy consumption will also be presented. Figure 1

Deconvolution of Charge-Transfer, Mass Transfer, and Ohmic Resistances of Phosphonic Acid-Sulfonic Acid Ionomer Binders in Electrochemical Hydrogen Pumps

Ion-pair high-temperature polymer electrolyte membranes (HT-PEMs) paired with phosphonic acid ionomer electrode binders have substantially improved the performance of HT-PEM electrochemical hydrogen pumps (EHPs)1, 2 and fuel cells3. Recently, blending poly(pentafluorstyrene-co-tetrafluorostyrene phosphonic acid) (PTFSPA) with NafionTM improved ionomer conductivity under anhydrous conditions in the temperature range of 100 °C to 250 °C. Using the said polymer blend as an electrode binder resulted in a 2 W.cm-2 peak power density of fuel cells4 at 240 °C (a HT-PEM fuel cell record). However, much is still unknown about how phosphonic acid ionomers blended with perfluorosulfonic acid (PFSA) materials affect electrode kinetics and gas transport in porous electrodes. In this work, we studied the ionic conductivity, electrode kinetics, and gas transport resistance of 3 types of phosphonic acid ionomers, poly(vinyl phosphonic acid), poly(vinyl benzyl phosphonic acid) by themselves and when blended with Aquivion®. These studies were performed in the context of an EHP platform – both membrane electrode assemblies (MEAs) and interdigitated electrode arrays (IDAs) decorated with nanoscale platinum electrocatalysts with thin film ionomer electrolytes. For all phosphoric acid ionomer types, the addition of Aquivion® promoted ionic conductivity, hydrogen oxidation/evolution reaction kinetics (HOR/HER), and hydrogen gas permeability. Solid-state 31P NMR revealed that the addition of Aquivion® significantly reduced phosphate ester formation in phosphoric acid ionomers and this played a vital role in enhancing ionomer blend conductivity. Using the best blend variant, PTFSPA-Aquivion®, a remarkable EHP performance of 5.1 A.cm-2 at 0.4 V at T = 200 °C was attained. Density functional theory (DFT) simulations identified that phosphonic acids with electron-withdrawing moieties reduced the propensity of the phosphonic acid to adsorb to platinum electrocatalyst surfaces. All phosphonic acid ionomers are anticipated to have a greater affinity for adsorption on platinum when compared to sulphonic acid ionomers (PFSAs). The relative adsorption affiliation of the various phosphoric acid ionomers from DFT is consistent with an explanation that stronger anion-specific adsorption has a detrimental impact and is commensurate with experimentally obtained MEA charge-transfer kinetics. A machine learning-aided compositional model5 revealed that the addition of Aquivion® reduced activation and concentration overpotentials in EHP MEAs and improved exchange current density and diffusivity in EHP IDAs. Future work involves employing the EHPs in a real-world application for separating and compressing hydrogen from the natural gas mixture.References Venugopalan, G.; Bhattacharya, D.; Andrews, E.; Briceno-Mena, L.; Romagnoli, J.; Flake, J.; Arges, C. G., Electrochemical Pumping for Challenging Hydrogen Separations. ACS Energy Letters 2022, 7 (4), 1322-1329.Venugopalan, G.; Bhattacharya, D.; Kole, S.; Ysidron, C.; Angelopoulou, P. P.; Sakellariou, G.; Arges, C. G., Correlating high temperature thin film ionomer electrode binder properties to hydrogen pump polarization. Materials Advances 2021, 2 (13), 4228-4234.Atanasov, V.; Lee, A. S.; Park, E. J.; Maurya, S.; Baca, E. D.; Fujimoto, C.; Hibbs, M.; Matanovic, I.; Kerres, J.; Kim, Y. S., Synergistically integrated phosphonated poly(pentafluorostyrene) for fuel cells. Nat Mater 2021, 20 (3), 370-377.Lim, K. H.; Lee, A. S.; Atanasov, V.; Kerres, J.; Park, E. J.; Adhikari, S.; Maurya, S.; Manriquez, L. D.; Jung, J.; Fujimoto, C.; Matanovic, I.; Jankovic, J.; Hu, Z.; Jia, H.; Kim, Y. S., Protonated phosphonic acid electrodes for high power heavy-duty vehicle fuel cells. Nature Energy 2022, 7 (3), 248-259.Briceno-Mena, L. A.; Venugopalan, G.; Romagnoli, J. A.; Arges, C. G., Machine learning for guiding high-temperature PEM fuel cells with greater power density. Patterns 2021, 2 (2), 100187. Figure 1

Understanding the Break-in of PEM Fuel Cells: A Comprehensive Study of Break-in Methods and Underlying Mechanisms

The break-in process of Proton Exchange Membrane (PEM) fuel cells is critical for their performance and durability. While there is a rising number of publications on break-in procedures, a comprehensive comparison of break-in procedures is missing. In this study, we investigate the impact of several break-in procedures, including potentiostatic holds, potential cycling, air starvation, and hydrogen pumping, on the performance of PEM fuel cells using electrochemical impedance spectroscopy and polarization curves. The measurements provide valuable insights into the underlying break-in mechanisms that contribute to the activation of the catalyst layers, the membrane and the interface of both. The results can guide the optimization of break-in protocols and reduce the break-in time and, therefore, the production costs of PEM fuel cells.

Enhanced methanol reforming gas fuel cell system with electrochemical hydrogen pump: Conceptual design, system analysis, and multi-objective optimization

In this work, two methanol-reforming gas fuel cell systems coupled with an electrochemical hydrogen pump (EHP), namely, EHP pre-coupling and post-coupling fuel cell systems were proposed to achieve performance enhancement. A back propagation neural network surrogate model was established for the two systems to accurately describe system behavior, and a second-generation multi-objective non-dominated genetic algorithm was utilized for addressing the multi-objective optimization problem encompassing net output power, carbon mass-specific emission and the levelized cost of electricity. The linear non-weighted multi-attribute preference and technique for order preference by similarity to ideal solution multi-attribute decision-making methods were employed to select the optimal solutions. The optimized EHP pre-coupling fuel cell system exhibited lower carbon emissions (0.69 kgCO2/(kW·h)) and higher net output power (126.02 kW) compared to previous studies. While the EHP post-coupling system achieves a lower levelized cost of electricity (0.36 USD/(kW·h)), and stronger system stability (total efficiency reduction less 1 %). Both EHP-coupling systems offer viable process enhancements for fuel cell systems.

Microstructure and hydrogen storage properties of Ti1-xCexV0.45Mn1.5 (x = 0, 0.05, 0.10, 0.15, and 0.20) alloys

In this work, the microstructure and hydrogen storage properties of Ti1-xCexV0.45Mn1.5 (x = 0, 0.05, 0.10, 0.15, and 0.20) alloys have been studied. It shows that the x = 0 alloy consists of a C14 Laves single phase. Moreover, alloys containing Ce can exhibit the CeO2 phase, whose content rises as Ce content does. Furthermore, CeO2 phase aggregation causes the alloy to fracture and the hydrogen diffusion channel to enlarge. According to the PCT curves (25 °C), the plateau pressure increases with increasing Ce content, and the hydrogen storage capacity decreases with increasing Ce content due to increase in Ce content which does not absorb hydrogen. And it is also found that increase in Ce substitution for Ti results in better dynamic properties for the alloys. And the dehydrogenation kinetics curves show that hydrogen desorption rate substantially increases with x getting larger. This is because CeO2 phase acts as the "hydrogen pump" to increase the rate of hydrogen discharge in the alloy, The fastest hydrogenation kinetics are shown, the best hydrogen storage performance is achieved, and the maximum hydrogenation is reached in less than 100 s.

Magnesium based multi-metallic hybrids with soot for hydrogen storage

Magnesium hydride is one of the most sought-after materials for solid state hydrogen storage due to its low cost and high gravimetric capacity (7.6 wt% hydrogen). However, high temperature of desorption (>350 °C) and slow kinetics limit its use for commercial on-board applications. In this work, accumulative roll bonding (ARB) technique has been utilized to synthesise Mg–LaNi5–Mg2Ni-soot hybrid with enhanced hydrogen storage properties. It is seen that the hybrid absorbs ∼6.2 wt% hydrogen at a plateau pressure of ∼2 bar at 300 °C and exhibits fast kinetics with ∼6.6 wt% hydrogen absorption within ∼30 min at 300 °C and 20 bar hydrogen pressure. The role of Mg2Ni as a catalyst as well as hydrogen absorbing medium provides an effect akin to ‘hydrogen pump’, thus enhancing the rate of hydrogen absorption. Presence of carbon in various forms such as aciniform, carbonaceous microgel and cenospheres (derived from soot) plays a vital role by providing channels for diffusion of hydrogen through the hybrid. The ARB technique provides an inexpensive and scalable method of synthesis of Mg based hybrids with large number of interfaces and high amount of strain leading to enhanced hydrogen storage properties.

Preparation of Mg-Mg2Ni/C composite and its excellent hydrogen storage properties

Magnesium hydride (MgH2) is a promising hydrogen storage material with high weight and volume hydrogen capacity. However, higher operating temperature and reversible hydrogen capacity decay inhibit its wide application. To address these issues, Mg-Mg2Ni/C was obtained by ball milling magnesium and nickel-Metal Organic Framework (Ni-MOF), and following calcinations. Initial dehydrogenation temperature of the composite is 530 K, 70 K lower than that of MgH2, and the apparent activation energy of the composite is 77.6 ± 2.1 kJ/mol, which is only 50% of MgH2. At 423 K, the hydrogen capacity of the composite is about 6 wt% within 3600 s, and keeps unchanged after ten cycles. The carbon material introduced by Ni-MOF inhibits the agglomeration of Mg, and Mg2Ni/Mg2NiH4 acts as a “hydrogen pump” in de/hydrogenation process. The carbon coating and “hydrogen pump” lead to the improvement of the ab/desorption kinetics and cycling stability. This attempt paves a potential way to achieve high performance Mg-based composite hydrogen storage materials.

A new design method for the vortex hydrogen circulating pump system

Against the backdrop of “carbon peak and carbon neutrality,” the hydrogen and fuel cell vehicle industry are rapidly developing. Within the on-board hydrogen supply system, the hydrogen circulation pump serves as an essential component of the hydrogen fuel cell system. The spiral disk, as a core part of the hydrogen fuel cell system’s vortex hydrogen circulation pump (VHCP), plays a crucial role in determining the performance of the hydrogen circulation system in hydrogen fuel cell vehicles. To meet the requirements for high-performance and high-reliability development of the hydrogen circulation pump, the VHCP scheme is adopted as the choice for the hydrogen pump solution. Through the magnetic suspension and no connection shaft structural design, the feasibility of applying the high speed and high flow hydrogen turbine was initially validated. Utilizing Fluent analysis software and high precision performance test bench, a comprehensive three-dimensional numerical simulation of the turbine design under various operating conditions was conducted and performance test verification, demonstrating that the performance meets the required specifications. By conducting research in both strength optimization design and performance requirement, two major technical challenges in turbine pump application were overcome. Combined with the experimental results of the turbine medium, it is concluded that the vortex pump can meet the flow and pressure rise under the premise of low power consumption in the hydrogen circulation system so as to perfectly increase the hydrogen return amount. Based on these findings, recommendations are proposed for the future development direction of hydrogen supply systems in hydrogen fuel cell vehicles.

Features of Electrochemical Hydrogen Pump Based on Irradiated Proton Exchange Membrane.

An electrochemical hydrogen pump (EHP) with a proton exchange membrane (PEM) used as part of fusion cycle systems successfully combines the processes of hydrogen extraction, purification and compression in a single device. This work comprises a novel study of the effect of ionizing radiation on the properties of the PEM as part of the EHP. Radiation exposure leads to nonspecific degradation of membranes, changes in their structure, and destruction of side and matrix chains. The findings from this work reveal that the replacement of sulfate groups in the membrane structure with carboxyl and hydrophilic groups leads to a decrease in conductivity from 0.115 to 0.103 S cm-1, which is reflected in halving the device performance at a temperature of 30 °C. The shift of the ionomer peak of small-angle X-ray scattering curves from 3.1 to 4.4 nm and the absence of changes in the water uptake suggested structural changes in the PEM after the irradiation. Increasing the EHP operating temperature minimized the effect of membrane irradiation on the pump performance, but enhanced membrane drying at low pressure and 50 °C, which caused a current density drop from 0.52 to 0.32 A·cm-2 at 0.5 V.

The race between hydrogen and heat pumps for space and water heating: A model-based scenario analysis

This paper analyses different levels and means of the electrification of space and hot water heating using an explorative modelling approach. The analysis provides guidance to the ongoing discussion on favourable pathways for heating buildings and the role of secondary energy carriers such as hydrogen or synthetic fuels. In total, 12 different scenarios were modelled with decarbonisation pathways until 2050, which cover all 27 member states of the European Union. Two highly detailed optimisation models were combined to cover the building stock and the upstream energy supply sector. The analysis shows that decarbonisation pathways for space and water heating based on large shares of heat pumps have at least 11% lower system costs in 2050 than pathways with large shares of hydrogen or synthetic fuels. This translates into system cost savings of around €70 bn. Heat pumps are cost-efficient in decentralised systems and in centralised district heating systems. Hence, heat pumps should be the favoured option to achieve a cost-optimal solution for heating buildings. Accordingly, the paper makes a novel and significant contribution to understanding suitable and cost-efficient decarbonisation pathways for space and hot water heating via electrification. The results of the paper can provide robust guidance for policymakers.

The effect of concentration polarization and chemical interactions on electrochemical hydrogen pump

Electrochemical hydrogen pump is expected to play an important role in, e.g., H2 extraction from natural gas pipelines, by-product hydrogen purification. The influence of typical concomitant CH4 and CO2 on electrochemical hydrogen pump is systematically investigated in this study over a wide range of gas content (CH4 or CO2: 10-80 %) and temperature (26-60 °C), with the focus on two main inhibition effects, i.e., concentration polarization and chemical interaction. An Faradaic efficiency of 86–96 %, i.e., below 100 %, is obtained as to the H2/CH4 mixture separation due to concentration polarization effect, which is even lower in case of H2/CO2, due to additional chemical interactions between CO2 and Pt anode catalysts. The inhibition of concentration polarization is more significant than that of chemical interactions, and the former can be suppressed by increasing the operating temperature and pressure due to enhance catalytic activity and proton conductivity. As to these two gas mixtures, the energy consumption ranged from 0.2 to 2.0 kWh/m3 with the increase of applied current from 125 to 1250 mA. The electrochemical pump exhibits limited H2 purity of 98.6 %–99.7 % due to the existence of nafion membrane defects, which requires to be further improved.

Design of Fire Risk Estimation Method Based on Facility Data for Thermal Power Plants.

In this paper, we propose a data classification and analysis method to estimate fire risk using facility data of thermal power plants. To estimate fire risk based on facility data, we divided facilities into three states-Steady, Transient, and Anomaly-categorized by their purposes and operational conditions. This method is designed to satisfy three requirements of fire protection systems for thermal power plants. For example, areas with fire risk must be identified, and fire risks should be classified and integrated into existing systems. We classified thermal power plants into turbine, boiler, and indoor coal shed zones. Each zone was subdivided into small pieces of equipment. The turbine, generator, oil-related equipment, hydrogen (H2), and boiler feed pump (BFP) were selected for the turbine zone, while the pulverizer and ignition oil were chosen for the boiler zone. We selected fire-related tags from Supervisory Control and Data Acquisition (SCADA) data and acquired sample data during a specific period for two thermal power plants based on inspection of fire and explosion scenarios in thermal power plants over many years. We focused on crucial fire cases such as pool fires, 3D fires, and jet fires and organized three fire hazard levels for each zone. Experimental analysis was conducted with these data set by the proposed method for 500 MW and 100 MW thermal power plants. The data classification and analysis methods presented in this paper can provide indirect experience for data analysts who do not have domain knowledge about power plant fires and can also offer good inspiration for data analysts who need to understand power plant facilities.

Experimental study of the electrochemical hydrogen pump based on proton exchange membrane for the application in fusion fuel cycle

An electrochemical hydrogen pump (EHP) can be used in the fuel cycle of fusion devices for purifying (separating) and compressing fuel (a mixture of hydrogen isotopes). One of the distinguishing features of the fuel cycle of fusion devices is a relatively narrow range of operating pressures of the fuel mixture from high vacuum (∼1–10 Pa) to several atmospheres (2–3·105 Pa), and in most of the fuel cycle systems, especially in transmission systems (like gas lines), the pressure shall not exceed atmospheric. In this study, the possibility of using EHP with a proton exchange membrane (PEM) in the fuel cycle of fusion devices in the pressure range of 0.01 – 0.30 MPa and temperatures of 20 – 70 °C was considered, and i-V curves were obtained. A regression analysis of the i-V curves was carried out. The temperature dependence of limiting current and resistance of EHP cell was obtained as follows: lnilim=−1140±1001T+(3.0±0.3) and lnρ=1780±2801T+(6.5±1.1). It is shown that there is no dependence of these parameters on pressure. The EHP cell productive capacity was determined in the studied ranges of pressure and temperature as follows: lni2F=−0.0119×T−4.2×Ecell0.05+Ecell+20.4. The results obtained allow one to predict the performance of the EHP device under conditions of subatmospheric hydrogen pressure at the anode and to select the most effective operating parameters of the EHP.

Synergetic catalysis of Ni@C@CeO2 for driving ab/desorption of MgH2 at moderate temperature

Multiple catalysts have exhibited high activity on improving the hydrogen storage performance of MgH2. Herein, the hydrogen ab/desorption kinetics of MgH2 is significantly improved by using Ni@C@CeO2 as the catalyst. The results show that 10 wt%-Ni@C@CeO2 doped MgH2 can absorb 4.51 wt% hydrogen within 60 min under low temperature 75 °C. Furthermore, the MgH2-Ni@C@CeO2 composites release approximately 4.88 wt% H2 within 10 min at 325 °C. Moreover, the composites show excellent cycling performance, with negligible decrease in hydrogen storage capacity, hydrogen uptake rate and hydrogen release rate after ten cycles at 350 °C. The Rietveld refinement of X-ray diffraction and transmittance electron microscopy measurements reveal that Mg2NiH4/Mg2Ni and CeH2.73 phases are in-situ formed. The mutual conversion of “Mg2Ni/Mg2NiH4” during hydrogen ab/desorption is a well-known “hydrogen pump” effect, which improvs the hydrogen storage performance of MgH2. The presence of CeH2.73 accelerate the conversion of Mg2Ni/Mg2NiH4, which we call ‘facilitated hydrogen pump’ effect. This attempt paves a potential way to achieve high performance Mg-based composites hydrogen storage materials via collaborative action between Ni and Ce species.