Effects of baffle position in serpentine flow channel on the performance of proton exchange membrane fuel cells

This study used a three-dimensional numerical model of a proton exchange membrane fuel cell with five types of channels:a smooth channel(Case 1);eight rectangular baffles were arranged in the upstream(Case 2),midstream(Case 3),downstream(Case 4),and the entire cathode flow channel(Case 5)to study the effects of baffle position on mass transport,power density,net power,etc.Moreover,the effects of back pressure and humidity on the voltage were investigated.Results showed that compared to smooth channels,the oxygen and water transport facilitation at the diffusion layer-channel interface were added 11.53%-20.60%and 7.81%-9.80%at 1.68 A·cm^(-2)by adding baffles.The closer the baffles were to upstream,the higher the total oxygen flux,but the lower the flux uniformity the worse the water removal.The oxygen flux of upstream baffles was 8.14%higher than that of downstream baffles,but oxygen flux uniformity decreased by 18.96%at 1.68 A·cm^(-2).The order of water removal and voltage improvement was Case 4>Case 5>Case 3>Case 2>Case 1.Net power of Case 4 was 9.87%higher than that of the smooth channel.To the Case 4,when the cell worked under low back pressure or high humidity,the voltage increments were higher.The potential increment for the back pressure of 0 atm was 0.9%higher than that of 2 atm(1 atm=101.325 kPa).The potential increment for the humidity of 100%was 7.89%higher than that of 50%.

CFD Analysis of Spiral Flow Fields in Proton Exchange Membrane Fuel Cells

Proton exchange membrane fuel cells(PEMFCs)are largely used in various applications because of their pollution-free products and high energy conversion efficiency.In order to improve the related design,in the present work a new spiral flow field with a bypass is proposed.The reaction gas enters the flow field in the central path and diffuses in two directions through the flow channel and the bypass.The bypasses are arranged incrementally.The number of bypasses and the cross-section size of the bypasses are varied parametrically while a single-cell model of the PEMFC is used.The influence of the concentration of liquid water and oxygen in the cell on the performance of different flow fields is determined by means of Computational fluid dynamics(COMSOL Multiphysics software).Results show that when the bypass number is 48 and its cross-sectional area is 0.5 mm^(2),the cell exhibits the best performances.

Particle Swarm Optimization based predictive control of Proton Exchange Membrane Fuel Cell (PEMFC)

Proton Exchange Membrane Fuel Cells (PEMFCs) are the main focus of their current development as power sources because they are capable of higher power density and faster start-up than other fuel cells. The humidification system and output performance of PEMFC stack are briefly analyzed. Predictive control of PEMFC based on Support Vector Regression Machine (SVRM) is presented and the SVRM is constructed. The processing plant is modelled on SVRM and the predictive control law is obtained by using Particle Swarm Optimization (PSO). The simulation and the results showed that the SVRM and the PSO re-ceding optimization applied to the PEMFC predictive control yielded good performance.

A 10kW-scale Distributed Power Plant of Natural Gas-Proton Exchange Membrane Fuel Cell

A 10 kW-scale natural gas fueled proton exchange membrane fuel cell(PEMFC) distributed power plant is presented in this paper,which is designed for cogeneration of power and heat. With homemade catalysts for CO removal in a two-stage methanation process and integrated reactor in the fuel processing system,the reformed fuel with CO molar fraction less than 10-5 is obtained for the fuel cell stack. Based on Matlab/Simulink/Stateflow and xPC Target platform,a rapid control prototype(RCP) is developed for real-time condition management,signal tracking and parameter tuning,data storing,and man-machine interaction. In a typical running with 4.3 kW stack power,the hydrogen production efficiency,gross power generation efficiency and heat recovery efficiency approach to 76%,41% and 50%,respectively. The peak stack power reaches 7.3 kW. Though there is still considerable dis-tance to long-term operation at 10 kW-scale net power generation,it is a milestone for the PEMFC-based stationary application in China.

Recent insights on iron based nanostructured electrocatalyst and current status of proton exchange membrane fuel cell for sustainable transport

Bridging the performance gap of the electrocatalyst between the rotating disk electrode(RDE) and membrane electrode assembly(MEA) level testing is the key to reducing the total cost of proton exchange membrane fuel cell(PEMFC) vehicles. Presently, platinum metal accounts for ~42% of the total cost of the PEMFC vehicles for usage in the cathode catalyst layer, where the sluggish oxygen reduction reaction(ORR) occurs. An alternative to the platinum catalyst, the Fe-N-C catalyst has attracted considerable interest for PEMFC due to its cost-effectiveness and high catalytic activity towards ORR. However, the excellent ORR activity of Fe-N-C obtained from RDE studies rarely translates the same performance into MEA operating conditions. Such a performance gap is mainly attributed to the lack of atomic-level understanding of Fe-N-C active sites and their ORR mechanism. Besides, unless the cost of expensive electrocatalyst is reduced, the total operation cost of the PEMFC vehicles remains constant. Therefore,developing highly efficient Fe-N-C catalysts from academic and industrial perspectives is critical for commercializing PEMFC vehicles. Here, the scope of the review is three-fold. First, we discussed the atomiclevel insights of Fe-N-C active sites and ORR mechanism, followed by unraveling the different iron-based nanostructured ORR electrocatalysts, including oxide, carbide, nitride, phosphide, sulfide, and singleatom catalysts. And then we bridged their ORR catalytic performance gap between the RDE and MEA tests for real operating conditions of PEMFC vehicles. Second, we focused on bridging the cost barriers of PEMFC vehicles between capital, operation, and end-user. Finally, we provided the path to achieve sustainable development goals by commercializing PEMFC vehicles for a better world.

Recent Advances in Electrode Design Based on One-Dimensional Nanostructure Arrays for Proton Exchange Membrane Fuel Cell Applications

One-dimensional(1D)Pt-based electrocatalysts demonstrate outstanding catalytic activities and stability toward the oxygen reduction reaction(ORR).Advances in three-dimensional(3D)ordered electrodes based on 1D Pt-based nanostructure arrays have revealed great potential for developing highperformance proton exchange membrane fuel cells(PEMFCs),in particular for addressing the mass transfer and durability challenges of Pt/C nanoparticle electrodes.This paper reviews recent progress in the field,with a focus on the 3D ordered electrodes based on self-standing Pt nanowire arrays.Nanostructured thin-film(NSTF)catalysts are discussed along with electrodes made from Pt-based nanoparticles deposited on arrays of polymer nanowires,and carbon and TiO2 nanotubes.Achievements on electrodes from Pt-based nanotube arrays are also reviewed.The importance of size,surface properties,and the distribution control of 1D catalyst nanostructures is indicated.Finally,challenges and future development opportunities are addressed regarding increasing electrochemical surface area(ECSA)and quantifying oxygen mass transport resistance for 1D nanostructure array electrodes.

Adaptive inverse control of air supply flow for proton exchange membrane fuel cell systems

To prevent the oxygen starvation and improve the system output performance, an adaptive inverse control （AIC） strategy is developed to regulate the air supply flow of a proton exchange membrane fuel cell （PEMFC） system in this paper. The PEMFC stack and the air supply system including a compressor and a supply manifold are modeled for the purpose of performance analysis and controller design. A recurrent fuzzy neural network （RFNN） is utilized to identify the inverse model of the controlled system and generates a suitable control input during the abrupt step change of external disturbances. Compared with the PI controller, numerical simulations are performed to validate the effectiveness and advantages of the proposed AIC strategy.

Dynamic Control of Electric Output Characteristics of Proton Exchange Membrane Fuel Cell System

This paper discusses dynamic characteristics of proton exchange membrane fuel cell (PEMFC) under rapid fluctuation of power demand. Wavelet neural network is adopted in the identification of the characteristic curve to predict the voltage. The system control scheme of the voltage and power is introduced. The corresponding schemes for voltage and power control are studied. MATLAB is used to simulate the control system. The results reveal that the adopted control schemes can produce expected effects. Corresponding anti-disturbance and robustness simulation are also carried out. The simulation results show that the implemented control schemes have better robustness and adaptability.

New hybrid model of proton exchange membrane fuel cell

Model and simulation are good tools for design optimization of fuel cell systems. This paper proposes a new hybrid model of proton exchange membrane fuel cell (PEMFC). The hybrid model includes physical component and black-box com-ponent. The physical component represents the well-known part of PEMFC, while artificial neural network (ANN) component estimates the poorly known part of PEMFC. The ANN model can compensate the performance of the physical model. This hybrid model is implemented on Matlab/Simulink software. The hybrid model shows better accuracy than that of the physical model and ANN model. Simulation results suggest that the hybrid model can be used as a suitable and accurate model for PEMFC.

Ultrasonic Spray Coating for Proton Exchange Membrane Fuel Cell

Ultrasound is now a widely used method for catalyst synthesis, catalyst support treatment, catalyst layer fabrication, membrane electrode assembly (MEA) fabrication, and humidifier etc. for fuel cell applications. Among the abovementioned uses, ultrasonic technology has been utilised mainly for MEA fabrication—especially since it has demonstrated the capability to produce ultralow platinum loadings. This paper reports the power density and cathode mass power density at peak power and 500 mA/cm2 conditions for ultrasonically spray coated MEAs. These MEAs were also produced with various Nafion content ratios and platinum loadings. The results indicate varying optimum values for different conditions.

Performance decay prediction model of proton exchange membrane fuel cell based on particle swarm optimization and gate recurrent unit

The durability of proton exchange membrane fuel cells (PEMFC) is an important issue that restricts their large-scale application. To improve their reliability during use, this paper proposes a short-term performance degradation prediction model using particle swarm optimization (PSO) to optimize the gate recurrent unit (GRU). After training using only the data from the first 300 h, good prediction accuracy can be achieved. Compared with the traditional GRU algorithm, the proposed prediction method reduces the root mean square error (RMSE) and mean absolute error (MAE) of the prediction results by 44.8 % and 35.1 %, respectively. It avoids the problem of low accuracy in predicting performance during the temporary recovery phase in traditional GRU models, which is of great significance for the health management of PEMFC.

Data-driven prediction of temperature variations in an open cathode proton exchange membrane fuel cell stack using Koopman operator

In this study,a novel application of the Koopman operator for control-oriented modeling of proton exchange membrane fuel cell(PEMFC)stacks is proposed.The primary contributions of this paper are:(1)the design of Koopman-based models for a fuel cell stack,incorporating K-fold cross-validation,varying lifted dimensions,radial basis functions(RBFs),and prediction horizons;and(2)comparison of the performance of Koopman-based approach with a more traditional physics-based model.The results demonstrate the high accuracy of the Koopman-based model in predicting fuel cell stack behavior,with an error of less than 3%.The proposed approach offers several advantages,including enhanced computational efficiency,reduced computational burden,and improved interpretability.This study demonstrates the suitability of the Koopman operator for the modeling and control of PEMFCs and provides valuable insights into a novel control-oriented modeling approach that enables accurate and efficient predictions for fuel cell stacks.

Modeling of Packed Bed Methanol Steam Reformer Integrated with Tubular High Temperature Proton Exchange Membrane Fuel Cell

This work proposes a novel tubular structure of high-temperature proton exchange membrane fuel cell(PEMFC)integrated with a built-in packed-bed methanol steam reformer to provide hydrogen for power output.A two-dimensional axisymmetric non-isothermal model was developed in COMSOL Multiphysics 5.4 to simulate the performance of a tubular high temperature proton membrane fuel cell and a packed bed methanol reformer.The model considers the coupling multi-physical processes,including methanol reforming reaction,water gas shift reaction,methanol cracking reaction as well as the heat,mass and momentum transport processes.The sub-model of the tubular packed-bed methanol reformer is validated between 433 K and 493 K with the experimental data reported in the literature.The sub-model of the high temperature proton exchange fuel cell is validated between 393 K and 433 K with the published literature.Our results show that power output and temperature distribution of the integrated unit depend on methanol flow rates and working voltages.It was suggested that stable power generation performance of 0.14 W/cm_(2)and temperature drop in methanol steam reformer of≤10 K could be achieved by controlling the methanol space-time ratio of≥250 kg·s/mol with working voltage at 0.6 V,even in the absence of an external heat source.

Exploration of the oxygen transport behavior in non-precious metal catalyst-based cathode catalyst layer for proton exchange membrane fuel cells

High cost has undoubtedly become the biggest obstacle to the commercialization of proton exchange membrane fuel cells(PEMFCs),in which Pt-based catalysts employed in the cathodic catalyst layer(CCL)account for the major portion of the cost.Although nonprecious metal catalysts(NPMCs)show appreciable activity and stability in the oxygen reduction reaction(ORR),the performance of fuel cells based on NPMCs remains unsatisfactory compared to those using Pt-based CCL.Therefore,most studies on NPMC-based fuel cells focus on developing highly active catalysts rather than facilitating oxygen transport.In this work,the oxygen transport behavior in CCLs based on highly active Fe-N-C catalysts is comprehensively explored through the elaborate design of two types of membrane electrode structures,one containing low-Pt-based CCL and NPMCbased dummy catalyst layer(DCL)and the other containing only the NPMC-based CCL.Using Zn-N-C based DCLs of different thickness,the bulk oxygen transport resistance at the unit thickness in NPMC-based CCL was quantified via the limiting current method combined with linear fitting analysis.Then,the local and bulk resistances in NPMC-based CCLs were quantified via the limiting current method and scanning electron microscopy,respectively.Results show that the ratios of local and bulk oxygen transport resistances in NPMCbased CCL are 80%and 20%,respectively,and that an enhancement of local oxygen transport is critical to greatly improve the performance of NPMC-based PEMFCs.Furthermore,the activity of active sites per unit in NPMCbased CCLs was determined to be lower than that in the Pt-based CCL,thus explaining worse cell performance of NPMC-based membrane electrode assemblys(MEAs).It is believed that the development of NPMC-based PEMFCs should proceed not only through the design of catalysts with higher activity but also through the improvement of oxygen transport in the CCL.

PEMFC船形堵块阴极流场的性能

建立流体体积(VOF)两相流模型,研究船形堵块流道的排水性能。建立不同开孔率的船形堵块流道三维模型,研究船形堵块及开孔率对质子交换膜燃料电池(PEMFC)性能的影响。船形堵块流道峰值净功率密度相较于传统直流道可提升9.4%,相较于同堵塞率下的梯形堵块流道可提高2.9%,具有较好的强化传质作用。通过提高船形堵块流道的开孔率,PEMFC可以获得更好的性能。在相同开孔率下,船形堵块流道的氧气摩尔浓度较直流道和梯形堵块流道分别提高28.6%和14.0%。结果表明,相较于传统直流道,船形堵块流道可降低排水周期和流道内平均水含量,具有更好的排水性能。

兆瓦级PEMFC系统的设计和应用

质子交换膜燃料电池(PEMFC)可实现电力和热力的联合供应,是支持零碳能源战略的重要技术路径。对兆瓦级PEMFC系统进行介绍与分析,对工程化应用中的实践提供逆变器、变压器、板式换热器和能量管理系统等部件的选型依据与建议,并指出在系统运行中自耗电占比最高的部件为空压机和散热风扇,分别占自耗电总功率的82.0%和10.7%。兆瓦级PEMFC系统在氯碱工厂中的商业化应用,可将原本排空的氢气发电,提高厂区能量利用效率,创造经济效益。

加长加宽的PEMFC电堆应力分布一致性仿真与优化

质子交换膜燃料电池可以通过扩大电堆的活性区域反应面积来获得更高的功率,但电堆反应面积扩大后,容易导致膜电极应力分布的不均匀性增加,从而引起燃料电池电化学性能的下降.为此,本研究设计了4种不同结构尺寸的燃料电池电堆,结合等效刚度模型法和有限元软件,分析了扩大反应面积的电堆结构对膜电极应力分布均匀性的影响,并进一步优化电堆内钢带的安装位置,以提升电堆内部接触压力分布均匀性.研究结果表明,膜电极接触压力分布的均匀性对反应区域宽度的变化较为敏感,当活性区域尺寸加宽,电堆内部活性区域的平均应力标准差增加了23.2%.而当活性区域加长,或同时加长和加宽时,相应增加一根捆扎钢带使电堆内部活性区域的平均应力标准差分别减小了8.6%和8.7%,表明适当增加捆扎钢带的数量可以提高电堆内部接触压力分布的均匀性.此外,钢带位置优化结果显示,电堆外侧钢带越靠近端板侧面时,电堆内部活性区域的应力分布越均匀.

PEMFC压差流道构型特征参数对电池性能的影响

针对质子交换膜燃料电池PEMFC(proton exchange membrane fuel cell)压差流道构型尺寸对电池电化学性能影响机理不明的问题,研究流道高度和脊背宽度对压差流道和直流道在氧气浓度、水浓度分布特征和电流密度、功率密度、压降等方面影响规律,并对两者进行了对比分析,结果表明流道高度对压差流道和直流道性能影响较小,压差流道在脊背宽度为1.25 mm和1.50 mm时具有明显优势;进一步研究压差流道变压区对流道性能的影响,结果表明变压区高度为0.05 mm和长度为1.50 mm时,压差流道峰值功率密度最高。综合考虑功率密度和压降的影响,选择压差流道高0.40 mm、宽1.25 mm、脊背宽1.25 mm、变压区长1.50 mm、高0.05 mm,此时压差流道峰值功率密度为0.3661 W/cm^(2),相较于直流道峰值功率密度提升6.3%。

基于多场协同的PEMFC双梯形渐缩流道结构性能分析和评价

流道结构的优化设计是提高质子交换膜燃料电池(proton exchange membrane fuel cells,PEMFC)综合性能的有效路径。该文针对PEMFC的流道结构,提出一种新的双梯形渐缩流道,构建并验证其三维数值仿真模型;基于场协同理论提出PEMFC中的多场协同性能分析评价方法。通过对比平行梯形流道和渐缩梯形流道,发现渐缩流道电池的输出功率、氢气利用率以及膜排水能力均得到有效提升,同时可降低最大温度梯度。基于提出的多物理场协同性评价指标,发现渐缩流道PEMFC与平行梯形流道PEMFC相比,在阴极/阳极流道内浓度场、温度场与速度场的协同性能均提高,在两催化层内传热传质与传递电动势协同性能平均提高约10.4%,膜内的水分浓度场、温度场与速度场的协同性提高25.3%。结果可为改善PEMFC的性能提供一定理论基础。

基于最大净功率输出的PEMFC阴极供气系统优化控制研究

通过建立质子交换膜燃料电池(PEMFC)阴极供气系统数学模型,分析空气压缩机电压和背压阀开度对系统净功率输出的影响;针对负载电流变化,研究PEMFC系统对应的最优过氧比和最优阴极压力,建立最大输出净功率-过氧比-阴极压力寻优表;考虑过氧比和阴极压力之间的耦合关系,基于辨识出的传递函数矩阵,设计针对空气压缩机电压和背压阀开度的前馈解耦控制器,优化氧气供给和压力控制,并进行相应的仿真验证。结果表明,所提解耦控制器能有效减小过氧比和阴极压力之间的耦合影响,在实现最大净功率闭环控制的同时,具有更快的响应速度和更小的超调量。