Feasibility investigations on a novel micro-manufacturing process for fabrication of fuel cell bipolar plates: Internal pressure-assisted embossing of micro-channels with in-die mechanical bonding

In this paper, we present the results of our studies on conceptual design and feasibility experiments towards development of a novel hybrid manufacturing process to fabricate fuel cell bipolar plates that consists of multi-array micro-channels on a large surface area. The premises of this hybrid micro-manufacturing process stem from the use of an internal pressure-assisted embossing process (cold or warm) combined with mechanical bonding of double bipolar plates in a single-die and single-step operation. Such combined use of hydraulic and mechanical forming forces and in-process bonding will (a) enable integrated forming of micro-channels on both surfaces (as anode and cathode flow fields) and at the middle (as cooling channels), (b) reduce the process steps, (c) reduce variation in dimensional tolerances and surface finish, (d) increase the product quality, (e) increase the performance of fuel cell by optimizing flow-field designs and ensuring consistent contact resistance, and (f) reduce the overall stack cost. This paper explains two experimental investigations that were performed to characterize and evaluate the feasibility of the conceptualized manufacturing process. The first investigation involved hydroforming of micro-channels using thin sheet metals of SS304 with a thickness of 51 μm. The width of the channels ranged from 0.46 to 1.33 mm and the height range was between 0.15 and 0.98 mm. Our feasibility experiments resulted in that different aspect ratios of micro-channels could be fabricated using internal pressure in a controllable manner although there is a limit to very sharp channel shapes (i.e., high aspect ratios with narrow channels). The second investigation was on the feasibility of mechanical bonding of thin sheet metal blanks. The effects of different process and material variables on the bond quality were studied. Successful bonding of various metal blanks (Ni201, Al3003, and SS304) was obtained. The experimental results from both investigations demonstrated the feasibility of the proposed manufacturing technique for making of the fuel cell bipolar plates.     

A well-dispersed catalyst on porous silicon micro-reformer for enhancing adhesion in the catalyst-coating process

A Cu/Mn/ZnO catalyst slurry was modified with polyvinyl alcohol (PVA) as a dispersant and organic binder. The slurry, which forms a crack-free coating, was injected directly into an open microchannel before anodic bonding with Pyrex glass. To improve adherence, porous silicon (pore size <1 μm) was fabricated in the microchannel. Ultrasonic vibration test (180 W, 20 min) showed good adhesion with only 6 wt.% loss. The thicker catalyst layer, with lower thermal diffusivity (0.98 mm²/s), reduced heat loss during reaction on cratered design and performed better than two other geometric designs (blank, straight). The microchannel with cratered design can be deposited with a catalyst up to 24.4 mg, and has a hydrogen production rate of 0.85 mmol h⁻¹ and 86% methanol conversion at 200 °C under a feed rate of 2SCCM.     

Numerical modeling of microchannel reactors with gradient porous surfaces for hydrogen production based on fractal geometry

A microchannel reactor with a porous surface catalyst support has been applied to methanol steam reforming (MSR) for hydrogen production. The fluid flow, heat transfer, and hydrogen production efficiency of the microchannel reactor are significantly affected by the fabricated porous surface support, such as the pore sizes and their distributions. This paper presents a novel microchannel reactor with a gradient porous surface as the reaction substrate to enhance the performance of the microreactor for hydrogen production. Numerical modeling of the gradient porous surface is developed based on fractal geometry, and three different types of porous surfaces as the catalyst supports (two gradient porous surfaces and one uniform pore-size surface) are investigated. The fluid flow and heat transfer characteristics of these three types of microchannel reactors are studied numerically, and the results showed that the microreactor with a positive gradient pore sized surface exhibited relatively better overall performance. Experimental setups and tests were performed and the results validate that the microchannel reactor with a positive gradient porous surface can increase the heat transfer performance by up to 18% and can decrease the pressure drop by up to 8% when compared to a microreactor with a uniform pore sized surface. Hydrogen production experiments demonstrated that the microreactor with positive gradient pore sizes has the highest methanol conversion rate of 56.3%, and this rate is determined to be 6% and 9% higher than that of microreactors with reverse gradient porous surfaces and uniform pore sized surface, respectively.     

The sol-gel route: A versatile process for up-scaling the fabrication of gas-tight thin electrolyte layers

Sol-gel routes are often investigated and adapted to prepare, by suitable chemical modifications, submicronic powders and derived materials with controlled morphology, which cannot be obtained by conventional solid state chemistry paths. Wet chemistry methods provide attractive alternative routes because mixing of species occurs at the atomic scale. In this paper, ultrafine powders were prepared by a novel synthesis method based on the sol-gel process and were dispersed into suspensions before processing. This paper presents new developments for the preparation of functional materials like yttria-stabilized-zirconia (YSZ, 8% Y₂O₃) used as electrolyte for solid oxide fuel cells. YSZ thick films were coated onto porous Ni-YSZ substrates using a suspension with an optimized formulation deposited by either a dip-coating or a spin-coating process. The suspension composition is based on YSZ particles encapsulated by a zirconium alkoxide which was added with an alkoxide derived colloidal sol. The in situ growth of these colloids increases significantly the layer density after an appropriated heat treatment. The derived films were continuous, homogeneous and around 20 μm thick. The possible up-scaling of this process has been also considered and the suitable processing parameters were defined in order to obtain, at an industrial scale, homogeneous, crack-free, thick and adherent films after heat treatment at 1400 °C.     

A novel method for producing hydrogen based on the Ca–Br cycle

The Ca–Br cycle is a promising method for efficiently producing hydrogen from water; however, it suffers from limitations inherent to gas–solid reactions. The cycle depends on the repeatable transformation of calcium bromide to calcium oxide and back to calcium bromide. The use of pure solids for these reactions would lead to rapid particle degradation and slow reaction kinetics. To circumvent these problems, a new reactor concept based on molten calcium bromide with dissolved calcium oxide has been proposed and developed. Preliminary experimental results indicate that the solubility of calcium oxide in calcium bromide at 800 °C is at least 1.2 wt%, a level that is expected to be high enough to make the proposed process work as designed. Early attempts to hydrolyze molten calcium bromide indicated that solid calcium oxide formation may inhibit reactivity, and thus injection of the moisture into the salt must be optimized.     

A novel practical state of charge estimation method: an adaptive improved ampere-hour method based on composite correction factor

The research of the real-time state of charge (SOC) estimation method for lithium-ion battery is developing towards the trend of model diversification and algorithm complexity. However, due to the limitation of computing ability in the actual battery management system, the traditional ampere-hour (Ah) method is still widely used. First, temperature, charge-discharge current, and battery aging are considered as the main factors, which affect the estimation accuracy of the Ah method under the condition that detection accuracy of the current sensor is determined. Second, the relationship between the SOC and battery open-circuit voltage at different temperatures is analyzed, which is used to modify the initial SOC. Third, the influence mechanism of main factors on the effect of the Ah method is analyzed, and proposes a capacity composite correction factor to reflect the influence of charge-discharge efficiency, coulomb efficiency, and battery aging comprehensively, and then update its value in real-time. Lastly, the adaptive improved Ah formula and the complete SOC estimation model is designed, and the estimation effect of this model is verified by comparing with other SOC estimation methods in the experiment of dynamic cycle test. The results show that the estimation error of the adaptive improved method is less than 2% under two comprehensive working conditions, while the error of the traditional method is 5% to 10%, and compared with an extended kalman filter algorithm, it also gets a better SOC estimation performance, which proves that this method is scientific and effective.     

A CFD study on H2-permeable membrane reactor for methane CO2 reforming: Effect of catalyst bed volume

A 2D axisymmetric model is developed for a H₂-permeable membrane reactor for methane CO₂ reforming. The effect of catalyst bed volume on CH₄ conversion and H₂ permeation rate is investigated. The simulation results indicate that catalyst bed volume with a shell radius of 9 mm is optimal for a tubular Vycor glass membrane with a diameter of 10 mm and H₂ permeance of 2x10⁻⁶ mol/m²/Pa/s. The concentration polarization at the retentate side and the accumulation of H₂ at permeate side make it hard to extract the H₂ production at the zone far from the membrane surface. Though increasing pressure at the retentate side enhances H₂ permeation, CH₄ conversion is even decreased due to unfavorable thermodynamics. And increasing sweep gas flow rate at permeate side benefits to both CH₄ conversion and H₂ permeation. This work highlights the importance of determining the optimal catalyst bed volume to match the membrane in the design of membrane reactors.     

A novel beam-down,gravity-fed,solar thermochemical receiver/reactor for direct solid particle decomposition: Design,modeling, and experimentation

A novel solar-thermochemical reactor for the reduction of ZnO powder using concentrated sunlight has been designed, constructed and tested. The purpose of the reactor is to accomplish the first step in a two-step water-splitting process to generate hydrogen renewably from sunlight using the ZnO redox cycle. Abbreviated as GRAFSTRR (Gravity-Fed Solar-Thermochemical Receiver/Reactor), the reactor is closed to the atmosphere, and features an inverted conical-shaped reaction surface along which reactant powder descends continuously as a moving bed, undergoing a thermochemical reaction at high temperature upon exposure to highly concentrated sunlight within the reaction cavity. Heat transfer and Zn production within the cavity have been modeled, as well as the influence of effective reactant particle size on reactive surface area. Initial experiments using a high-flux solar simulator successfully demonstrated the mechanical stability of the reactor and primary systems, namely particle entrainment in the vortex flow, moving bed adhesion to the reaction surface, and the solid particle delivery and exit mechanism. This paper presents the GRAFSTRR concept, select design choices, and a summary of pertinent findings from experimental and numerical investigations.     

A novel approach to improve the mathematical modelling of the internal reforming process for solid oxide fuel cells using the orthogonal least squares method

This paper presents a novel approach to experimental and numerical investigations of the methane/steam reforming reaction process over a nickel/yttria-stabilized zirconia fine powder catalyst. Methane/steam reforming is primarily considered as a hydrogen production process for Solid Oxide Fuel Cells, and therefore its reaction kinetic was investigated experimentally and numerically. The present paper describes the innovative implementation of an orthogonal least squares (generalized least squares: GLS) algorithm for the calculation of the reaction kinetics involving precise information and the uncertainties of the obtained results. The GLS method was applied to evaluate the reaction rate and therefore fractional conversion of methane. An analysis of the mathematical model points out that the experimental inaccuracy could be reduced and allowed for the calculation of the most probable values of kinetic parameters and their uncertainties. The GLS method secures a higher accuracy of measured data and estimates the most probable value of all model parameters.     

Bio-hydrogen production based on catalytic reforming of volatiles generated by cellulose pyrolysis: An integrated process for ZnO reduction and zinc nanostructures fabrication

The paper presents a process of cellulose thermal degradation with bio-hydrogen generation and zinc nanostructures synthesis. Production of zinc nanowires and zinc nanoflowers was performed by a novel processes based on cellulose pyrolysis, volatiles reforming and direct reduction of ZnO. The bio-hydrogen generated in situ promoted the ZnO reduction with Zn nanostructures formation by vapor-solid (VS) route. The cellulose and cellulose/ZnO samples were characterized by thermal analyses (TG/DTG/DTA) and the gases evolved were analyzed by FTIR spectroscopy (TG/FTIR). The hydrogen was detected by TPR (Temperature Programmed Reaction) tests. The results showed that in the presence of ZnO the cellulose thermal degradation produced larger amounts of H₂ when compared to pure cellulose. The process was also carried out in a tubular furnace with N₂ atmosphere, at temperatures up to 900 °C, and different heating rates. The nanostructures growth was catalyst-free, without pressure reduction, at temperatures lower than those required in the carbothermal reduction of ZnO with fossil carbon. The nanostructures were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and transmission electron microscopy (TEM). The optical properties were investigated by photoluminescence (PL). One mechanism was presented in an attempt to explain the synthesis of zinc nanostructures that are crystalline, were obtained without significant re-oxidation and whose morphologies are dependent on the heating rates of the process. This route presents a potential use as an industrial process taking into account the simple operational conditions, the low costs of cellulose and the importance of bio-hydrogen and nanostructured zinc.     

A novel method for determination of a time period for stabilization of power generation of microbial fuel cell with effect of microorganisms

Microbial fuel cells (MFCs) are quickly gaining traction in the mainstream industry due to their capabilities in simultaneous power generation and wastewater purification. They use bacteria like Shewanella and Geobacter as primary units for the same. However, their power generation capabilities are limited by a lack of stability in certain configurations. For the development of appropriate power storage and management systems, this instability must be investigated. Therefore, the present study proposes the artificial intelligence (AI) methodology of artificial neural search (ANS) networks to predict the period for stabilization of power generation of microbial fuel cell in the presence of microorganisms. An output voltage has been measured as a function of time (approximately 1600 h). A stabilization period of power generation has been predicted from the slope obtained from the graph of voltage vs time. The analysis of the ANS model indicated that the power generation stabilization has occurred between 12th and 16th weeks. Experiments were then performed to validate the findings from the ANS model. This may serve as an indication for the development of energy management and storage systems that can account for the trends observed during this study     

A process for decision-making on natural gas : Fiscal competitiveness in reservoir development

This paper refers to the principal realities, although disguised for obvious reasons, which the oil companies have to face if they intend to promote gas initiatives. The key factors in selling natural gas are mainly the market and the fiscal terms. They are both conditions of competitiveness. The following analysis considers the latter form of competitiveness and makes an attempt to quantify it. Although the scenario considered in this paper does not contemplate the steep fall in oil prices in 1986, it is still valid for its principal purpose. The aim of the study is a methodological procedure which enables one to select the variables and define the interrelationship in the hydrocarbons sector. The structure of the paper follows the decision-making process of analysing a resource allocation problem by seeking to identify the variables involved. The variables are expressed by a number to which an absolute value is not attributed, but rather a relative one in the definition of the problem terms. The final proposal of a model with different rules does not appear to be too utopian if the rules of the game are followed in order to seek both stability and flexibility in the response which each operator seeks to obtain in this sector.     

A novel co-precipitation method for preparation of Pt-CeO2 composites on multi-walled carbon nanotubes for direct methanol fuel cells

Ceria (CeO₂) as co-catalytic material with Pt on multi-walled carbon nanotubes (Pt-CeO₂/MWCNT) is synthesized by a co-precipitation method. The physicochemical characterizations of the catalysts are carried out by using transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) techniques. Electrocatalytic activities of the catalysts for methanol oxidation is examined by cyclic voltammetry and chronoamperometry techniques and it is found that Pt-CeO₂/MWCNT catalysts exhibited a better activity and stability than did the unmodified Pt/MWCNT catalyst. CO-stripping results indicate the facile removal of intermediate poisoning species CO in the presence of CeO₂, which is helpful for CO and methanol electro-oxidation.     

A novel decentralized method based on the system engineering concept for reliability‐security constraint unit commitment in restructured power environment

In the deregulated power environment, including Central operator (CO) and Micro Grids (MGs), different parts of the network are dedicated to the private sector, and each of them seeks to increase their profits independently. The CO and MGs should cooperate and collaborate in terms of operating, security and reliability in the whole power system. This article proposes a new method based on a System of System (SoS) concept for the secure and economic hourly generation scheduling to find optimal operational point. The main methodology includes three steps. In the first step, the power system is divided into several subsystems by using a spectral clustering partitioning technique to reduce converge time by decentralizes methods. And also load forecasting based on a Gaussian probability distribution function to avoid conventional calculation and considering uncertainty of the loads has been presented. To find a similar scenario, and reduction scenario with low probability, the probabilistic method has been addressed. The main contribution of this method is removing scenarios with low value of probabilities and scenarios which are similar to each other. In fact, the reduced set must include scenarios which are scattered appropriately in the uncertain space while holding high probabilities. In order to estimate the similarity (distance) between two scenarios the Kantorovich distance is implemented. In the second step, the hierarchical Bi‐level optimization approach is used to execute the decentralized decision making to solve the Security Constraints Unit Commitment (SCUC) problem between CO and MGs. Regarding all physical relations and shared data among CO and MGs, the SoS concept and Bi‐level optimization are presented to find the optimal operating point of autonomous systems. In the third step, a random number of generators will be select. Hence, the initial iteration number is set. In this step, sampling from state space to classifying reliability object achieved (The expected energy not supplied and loss of load probability are the reliability criterion). The presented method is evaluated using a 6‐bus, the RTS 24‐bus, 118‐bus, and 4672‐bus as an IEEE test systems. The suggested structure has been implemented by GAMS, and the results illustrate the usefulness of the presented methodology. To comparing proposed approach with the centralized method, the results illustrate improving total operational costs and security (in RTS‐24($603,209), 118 bus ($2 562 154) and 4672‐bus ($9 185 168)) in scenario 3 near to 9%, 10% and 8% respectively. Similarly, by comparison (in three test systems) with genetic algorithm these improvements are near to 23%, 22% and 13% respectively.     

Photo-generation of ultra-small Pt nanoparticles on carbon-titanium dioxide nanotube composites: A novel strategy for efficient ORR activity with low Pt content

Despite extensive work on Pt/C based catalyst materials for fuel cells towards oxygen reduction reaction, the high cost of catalyst is still a major problem for efficient use of fuel cells in daily life. This demands at designing a new electrocatalyst with high catalytic activity for oxygen reduction reaction. In this regard, we present a novel composite material consisting of functionalized acetylene black and TiO₂ nanotube (FAB/TNT) as the substrate for Pt as catalyst. Using this novel composite, Pt was decorated using photo-reduction process. Due to the presence of photo-electrons all over the conducting part of the material, H₂PtCl₆ was photo-reduced to Pt nanoparticles with extremely small size ∼1.6 nm. The material demonstrated that even with as less as 3.5 wt% of Pt, mass activity was found to be 37.5 A/g and specific actitvity was found to be 0.75 A/m² which is higher than commercial catalyst, Pt-Vulcan XC-72 (mass activity and specific activity was found to be 10.7 A/g and 0.81 A/m², respectively) at 0.85 V vs RHE.     

A novel real‐time energy management strategy for plug‐in hybrid electric vehicles based on equivalence factor dynamic optimization method

The universal adaptive equivalent consumption minimization strategy (A‐ECMS) has the potential of being implemented in real‐time for plug‐in hybrid electric vehicles (PHEVs). However, the imprecise prediction of a long‐term future driving cycle and biggish computation burdens remain the barriers for further real vehicle application. Thus, it is of great significance to develop a real‐time optimal energy management strategy for PHEVs by weakening the influence of future driving cycle to the control accuracy and improving its computation efficiency. In this paper, a novel real‐time energy management strategy for PHEVs based on equivalence factor (EF) dynamic optimization method is proposed. Firstly, a novel proportional plus integral adaption law for calculating the dynamic optimal EF is established for A‐ECMS using only instantaneous information of current vehicle speed and battery state of charge. Second, three key coefficients are obtained and converted into a three‐dimensional look up tables, so as to determine the dynamic optimal EF. Finally, the method of fast searching the optimal engine torque is proposed, which significantly enhances the computational efficiency. Compared with A‐ECMS, the computational time of A‐ECMS2 is decreased near 94.8% and the deviation of fuel consumption is controlled within 4.4%. Both the numerical results and hardware‐in‐loop results prove that the proposed novel energy management strategy A‐ECMS2 has better real‐time performance and less computing burden than the general A‐ECMS.     

A novel Swiss-roll micro-combustor with double combustion chambers: A numerical investigation on effect of solid material on premixed CH4/air flame blow-off limit

A novel Swiss-roll micro-combustor with double combustion chambers is proposed to improve flame stability and extend blow-off limits. This study is aimed to numerically investigate the effect of solid material (i.e., SiC, stainless steel and copper) on premixed CH₄/air flame blow-off limit and reveal the flame stability mechanism. The simulated results show that this developed novel Swiss-roll micro-combustor not only can significantly anchor the flame owing to the flow recirculation behind the flame holders and the backward-facing steps, but also can further extend CH₄ blow-off limits owing to heat recirculation in the long Swiss-roll preheating channels. The three solid material micro-combustors present the relatively slight difference in the recirculation-zone size but the remarkably difference in heat recirculation and heat loss. Good heat recirculation and low heat loss rate are the dominant reason that is responsible for the differences of the blow-off limits in this micro-combustor. The stainless steel micro-combustor achieves the highest blow-off limits while the copper micro-combustor achieves the lowest blow-off limit. These deep insights can give some useful information to design a similar Swiss-roll micro-combustor.     

A novel forecasting method based on the economic and demand response for FC/WT/PV unit and a 3 in 1 TES energy storage

Due to the lack of distribution resources and increasing demand in the daily market, the use of renewable resources is increasing. But renewable sources and market prices are uncertain behavior and cause economic problems. This paper introduces a novel market participation model include wind turbine, photovoltaic, fuel cell integrated with a novel hybrid TES energy storage system (3 in 1 concept) to minimize cost and improve load demand reliability. Also, to solve he mentioned problem a novel forecasting method are proposed. This model is a new multi artificial neural network based on the complete ensemble empirical mode decomposition which is coupled with Tanh function and using RMSE, MAPE and NMAE method the error rate of the proposed method is calculated. By using this method, the forecasting accuracy is improved and also with a novel energy storage the economic issue and market reliability are improved. Also, using the stochastic model the uncertainty system's behavior are modeled to obtain an accurate results of market participation and increase demand supply. Finally, a testing system includes wind turbine/photovoltaic/fuel cell/storage system and demand response are used to prove the superiority of the proposed model in comparison to other models.     

Electrospun core-shell nanofibers based on polyethylene oxide reinforced by multiwalled carbon nanotube and silicon dioxide nanofillers: A novel and effective solvent-free electrolyte for lithium ion batteries

Insertion of conductive fillers into solvent-free polymer electrolytes enhances electrochemical behavior of the electrolyte membranes leading to higher ionic conductivity, lower capacity fading, and so on. Although, the presence of the conductive fillers in the polymer matrixes increases the risk of electrical shorting, herein, polyethylene oxide (PEO)-based core-shell nanofibers were prepared via a simple electrospinning method. In the core-shell electrospun fibers, ethylene carbonate (EC) and lithium perchlorate (LiClO₄) were used as a plasticizer and as a lithium salt, respectively. The core component was enwrapped by the PEO/EC/LiClO₄ shell part incorporated with SiO₂ nanoparticles. Various properties of the fabricated membranes were evaluated by changing the ratio of multiwall carbon nanotubes (MWCNTs) in the core part of the nanofibers. The morphology and core-shell structure of the electrospun fibers were studied by FESEM and TEM images. According to FTIR and XRD results, addition of the EC plasticizer and the fillers into the as-spun fibers increased the fraction of free ions and the amorphous regions. From electrochemical impedance spectroscopy studies, the ionic conductivity enhanced by insertion of the plasticizer molecules and the filler particles into the core-shell structures. The highest ionic conductivities of 0.09 and 0.21 mS.cm⁻¹ were obtained for the free-filler and the filler-loaded nanofibrous membranes, respectively. The prepared mats obeyed the Arrhenius behavior ( R²~1 ). Dielectric studies confirmed the obtained data from the ionic conductivities. Furthermore, the capacity residual was enhanced from 69% to 85% by incorporation of the MWCNTs filler into the core component of the electrospun nanofibers. The presented results may facilitate development of versatile nanofibrous membranes embedded with the conductive fillers as solvent-free electrolytes applicable in lithium-ion batteries.