A comparison of temperature distribution in PEMFC with single-phase water cooling and two-phase HFE-7100 cooling methods by numerical study

Thermal management has been considered as one of the critical issues in proton exchange membrane fuel cell (PEMFC). Key roles of thermal management system are maintaining optimal operating temperature of PEMFC and diminishing temperature difference over a single fuel cell and stack. Severe temperature difference causes degradation of performance and deterioration of durability, so understanding temperature distribution inside a single fuel cell and stack is crucial. In this paper, two-phase HFE-7100 cooling method is suggested for PEMFC thermal management and investigated regarding temperature change inside a fuel cell. Also, the results are compared to single-phase water cooling method. Numerical study of temperature distribution inside a single PEMFC is conducted under various conditions for the two different cooling methods. Fuel cell model considering mass transfer, electrochemical reaction and heat transfer is developed.The result indicates that two-phase HFE-7100 cooling method has an advantage in temperature maintenance and temperature uniformity than single-phase water cooling method, especially in high current density region. It is also revealed that the cell temperature is less dependent on system load change with two-phase cooling method. It indicates that the fuel cell system with two-phase cooling method has high thermal stability. In addition, the effect of coolant flow rate and coolant inlet pressure in two-phase HFE-7100 cooling method are discussed. As a result, two-phase cooling method showed reliable cooling performance even with low coolant flow rate and the system temperature increased as coolant pressure rose.     

Water transport characteristics of polymer electrolyte membrane fuel cell

This paper describes the performance of a polymer electrolyte membrane fuel cell (PEMFC) system without humidification of the reactants which consumes a lot of parasitic power, increases the weight of the PEMFC system and thus adds complexity. Such PEMFC systems are preferable for portable applications. The results indicate that dry gas operation depends on various factors like reactant flow field design, area of the electrode and equilibration time for the product water. The performance of the fuel cell can be improved by giving some equilibration time for the product water, produced by the electrochemical reactions, to get transported across the membrane to the anode side, thus increasing the conductivity of the membrane. The water transported through the membrane across the cell was investigated by measuring the amount of product water at the anode side which allows humidification for the anode gas and less condensed water in the fluid flow channels of the cathode.     

Performance enhancement in a H2/O2 PEMFC with dual-ejector recirculation

Water management in various components of the proton exchange membrane fuel cell (PEMFC) is a significant and challenging issue affecting output performance. PEMFC utilizing dual ejector-based recirculation has been developed to evaluate and improve the performance and water transport properties. A detailed investigation into the effects of ejector operating conditions, such as primary flow pressure and secondary flow relative humidity, on the performance of PEMFC is conducted. The results show that significant performance improvement of PEMFC can be achieved by increasing the operating pressure. The power density can be increased by 37.8% and 86.5% with ejector primary flow pressures of 300 and 400 kPa, respectively. Furthermore, an optimization strategy integrating PEMFC operating condition is proposed to ensure the stability and lifespan of performance. The water management and integration optimization strategy obtained in this paper can provide valuable insight into options for improving the performance of PEMFC with dead-ended anode and cathode.     

Gas diffusion layers for PEM fuel cells: Materials,properties and manufacturing – A review

The complexity in proton exchange membrane fuel cell (PEMFC) stack stems from the fact that numerous physio-chemical processes as well as multi-functional components are involved in its operation. Among the various components a Gas Diffusion Layer (GDL) being an integral component that plays a significant role in determining the performance, durability, and the dynamic characteristics, when air is used as oxidant. In addition, it serves as an armour to safeguard the membrane (Nafion), which is a delicate as well as one of the most expensive components of the PEMFC stack. A comprehensive insight on the GDL can help us to assess the fuel cell stack performance and durability. Apparently, the gas (hydrogen and air/oxygen) being converted to the energy in a PEM fuel cell needs to be diffused uniformly for which surface attributes and porosity must also be well interpreted. This review is a comprehensive assessment made on the fundamental mechanism of the diffusion process along with the various materials involved and evaluating their pros and cons. Eventually, the various manufacturing techniques involved in the GDL fabrication process are also reviewed holistically. It is envisaged that the additive manufacturing process can be a potential option to fabricate a GDL in a cost-effective and simple manufacturing approach.     

Intensifying vehicular proton exchange membrane fuel cells for safer and durable,design and operation

The explosion in a proton exchange membrane fuel cell (PEMFC) powered forklift in Louisiana, USA in May 2018 and the resulting fatality highlights the need for the improved safety of this technology. Apart from the safety concerns, PEMFC durability has been an important issue towards its further commercialization. Both the safety and durability concerns associated with this technology can be attributed to the temporal degradation of its components. In this study, we have developed a mathematical model that relates the microscale PEMFC degradation to the probability of a macroscale explosion in a Fuel Cell Electric Vehicle (FCEV). Using the model and the inherent safety principle of intensification, it was observed that increasing the operating temperature of the PEMFC system can significantly improve both its safety and durability while intensifying membrane design parameters i.e. membrane thickness and membrane conductivity do not provide any significant improvements. A key inference from this study is that the durability (expressed in voltage loss) and safety (expressed in explosion probability) of a PEMFC system are not perfectly correlated.     

质子交换膜燃料电池的多尺度传热传质

介绍了目前质子交换膜燃料电池(PEMFC)在膜、电极、单电池、电堆或系统等四个结构尺度上的传热传质过程研究;主要讨论了PEMFC内的多组分传输、膜内水管理和多孔电极内的传热、传质过程;认为建立在孔尺度水平的研究方法是深入探讨电池内多孔材料微结构传热传质的有效途径;多维、多尺度模型的建立及其模拟计算能准确反映PEMFC内部的传递过程机理,为进一步优化电池结构和操作条件提供有价值的参考。     

Design and control of a PEMFC powered electric wheelchair

This paper proposes the design and control of a fuel-cell powered wheelchair. Electric wheelchairs can improve moving ability for people with walking problems. However, their traveling distances are limited by the capacity of their batteries. We designed a fuel-cell powered electric wheelchair that can be continuously operated, thereby extending the moving range. The system consisted of three subsystems: a commercial electric wheelchair, a proton exchange membrane fuel cell (PEMFC), and two secondary battery sets. The study was carried out in three parts, investigating the fuel-cell control, power management, and system integration. First, we designed multivariable robust controllers for a 500 W PEMFC system to charge the battery sets by constant voltage/current. Second, we designed a serial power management system, where the wheelchair motors were directly driven by the secondary battery sets, which in turn were charged by the PEMFC when their capacities dropped below a certain level. Lastly, we integrated the three subsystems and verified the system performance by experiments. The results confirmed the effectiveness of the PEMFC system as a way to extend the traveling distance of a motorized wheelchair.     

Review of hydrogen crossover through the polymer electrolyte membrane

Proton exchange membrane fuel cell (PEMFC) is considered to be a promising, clean, and efficient energy conversion device. At present, the main challenges faced by the application of PEMFC in the automotive are cost and durability. Hydrogen from anode to the cathode through polymer electrolyte membrane (i.e. crossover hydrogen) affects the durability of fuel cells. In this paper, the existing literature on hydrogen crossover is reviewed and summarized from consequences, causes, mitigation measures, and detection methods. The influences of hydrogen crossover on the components and performance are discussed. The causes are analyzed from structural permeation and membrane degradation. The methods of alleviating the degradation of the membrane are summarized. The electrochemical and non-electrochemical monitoring methods are described, and the segmented current method is explained separately. The existing problems and research prospects are put forward, which lays a foundation for further research on hydrogen crossover and improvement fuel cell durability.     

Water transport in polymer electrolyte membrane fuel cells

Polymer electrolyte membrane fuel cell (PEMFC) has been recognized as a promising zero-emission power source for portable, mobile and stationary applications. To simultaneously ensure high membrane proton conductivity and sufficient reactant delivery to reaction sites, water management has become one of the most important issues for PEMFC commercialization, and proper water management requires good understanding of water transport in different components of PEMFC. In this paper, previous researches related to water transport in PEMFC are comprehensively reviewed. The state and transport mechanism of water in different components are elaborated in detail. Based on the literature review, it is found that experimental techniques have been developed to predict distributions of water, gas species, temperature and other parameters in PEMFC. However, difficulties still remain for simultaneous measurements of multiple parameters, and the cell and system design modifications required by measurements need to be minimized. Previous modeling work on water transport in PEMFC involves developing rule-based and first-principle-based models, and first-principle-based models involve multi-scale methods from atomistic to full cell levels. Different models have been adopted for different purposes and they all together can provide a comprehensive view of water transport in PEMFC. With the development of computational power, application of lower length scale methods to higher length scales for more accurate and comprehensive results is feasible in the future. Researches related to cold start (startup from subzero temperatures) and high temperature PEMFC (HT-PEMFC) (operating at the temperatures higher than 100 °C) are also reviewed. Ice formation that hinders reactant delivery and damages cell materials is the major issue for PEMFC cold start, and enhancing water absorption by membrane electrolyte and external heating have been identified as the most effective ways to reduce ice formation and accelerate temperature increment. HT-PEMFC that can operate without liquid water formation and membrane hydration greatly simplifies water management strategy, and promising performance of HT-PEMFC has been demonstrated.     

A review on water balance in the membrane electrode assembly of proton exchange membrane fuel cells

Water balance has been proven to be critical not only for the performance but also for the durability of proton exchange membrane fuel cells (PEMFCs). This paper reviews experimental investigations and modeling works on water transport and balance in different constituents of the membrane electrode assembly (MEA), which is the most important component determining the performance and durability of a PEMFC. Major water transport mechanisms in the membrane and porous layers of MEA are summarized and the strategies to balance water in these components are also discussed. However, the experimental water transport data for different components under varied operating conditions are still insufficient and the understanding of transport mechanisms is still limited. To obtain better water management in PEMFCs, the design of the key components requires refinements. For future investigations more attention should be paid to the fundamental understanding and systematic data of water transport in each component of the MEA under varied operating conditions.     

Numerical investigation of innovative 3D cathode flow channel in proton exchange membrane fuel cell

Two kinds of innovative 3‐dimensional (3D) proton exchange membrane fuel cell (PEMFC) cathode flow channel designs were proposed to improve the water removal on the surface of gas diffusion layer and enhance mass transfer between flow channel and gas diffusion layer. A validated 2‐phase volume of fluid model was used to investigate different water removal behaviors in flow channel. The optimal length of water baffle and other parameters of the proposed designs were determined. A validated 3D PEMFC performance model was adopted to assess the new designs. The results suggest that these 2 designs can improve PEMFC performance as to 9% when operating at the high current density because of the significant enhancement of mass transfer induced by air baffles.     

A data-driven digital-twin prognostics method for proton exchange membrane fuel cell remaining useful life prediction

Prognostics and health management of proton exchange membrane fuel cell (PEMFC) systems have driven increasing research attention in recent years as the durability of PEMFC stack remains as a technical barrier for its large-scale commercialization. To monitor the health state during PEMFC operation, digital twin (DT), as a smart manufacturing technique, is applied in this paper to establish an ensemble remaining useful life prediction system. A data-driven DT is constructed to integrate the physical knowledge of the system and a deep transfer learning model based on stacked denoising autoencoder is used to update the DT with online measurement. A case study with experimental PEMFC degradation data is presented where the proposed data-driven DT prognostics method has applied and reached a high prediction accuracy. Furthermore, the predicted results are proved to be less affected even with limited measurement data.     

Corrosion resistance of functionally graded TiN/Ti coatings for proton exchange membrane fuel cells

Bipolar Plates (BPP) are important components of proton exchange membrane fuel cell (PEMFC) stacks. In the development of innovative fuel cell designs, it is advantageous to use aluminum for these applications, however, this material lacks the necessary corrosion resistance. Since the performance of PEMFC stacks depends on BPP properties, in particular, corrosion resistance, depositing titanium nitride (TiN) thin films onto aluminum substrates may improve their efficiency and durability. The present work focuses on improving corrosion resistance and hydrophobicity of TiN/Ti by using N graded films deposited onto aluminum substrates (AA-1100) by grid-assisted magnetron sputtering (GAMS). Electrochemical impedance spectroscopy (EIS) and potentiodynamic and potentiostatic polarization are used to investigate the performance of the substrate/film system at room temperature and 70 °C, thus simulating a prototypic PEMFC electrolyte environment. Electrochemical test results showed that graded TiN films improved corrosion resistance when compared with both the homogeneous films and the AA1100 uncoated substrate. Furthermore, contact angle results reveal improved hydrophobicity for both homogeneous and graded TiN coatings when compared with the AA1100 substrate.     

Exergy analysis of an ethanol fuelled proton exchange membrane (PEM) fuel cell system for automobile applications

An integrated ethanol fuelled proton exchange membrane fuel cell (PEMFC) power system was investigated following a second law exergy analysis. The system was assumed to have the typical design for automobile applications and was comprised of a vaporizer/mixer, a steam reformer, a CO-shift reactor, a CO-remover (PROX) reactor, a PEMFC and a burner. The exergy analysis was applied for different PEMFC power and voltage outputs assuming the ethanol steam reforming at about 600 K and the CO-shift reaction at about 400 K. A detailed parametric analysis of the plant is presented and operation guidelines are suggested for effective performance. In every case, the exergy analysis method is proved to allow an accurate allocation of the deficiencies of the subsystems of the plant and serves as a unique tool for essential technical improvements.     

Effects of water induced pore blockage and mitigation strategies in low temperature PEM fuel cells – A simulation study

Ineffective water management in proton exchange membrane fuel cells (PEMFCs) can cause performance degradation. A simple mathematical model capturing the effect of water on the overall performance of the fuel cell system is of immense use in developing tools for water management. In this work, a computationally efficient first principles dynamic model for PEMFC system simulations and concomitant water management studies are developed. The steady-state version of this model is validated with experimental data. The effect of various operating conditions and design parameters on the performance of the fuel cell is studied using this model. Various control strategies for improving fuel cell performance in the presence of flooding are evaluated using the model. The simplicity and adequate predictive capability of the model make it amenable to be used in a model-based feedback control framework for online water management.     

基于仿射热模型的质子交换膜燃料电池电堆的热管理控制

质子交换膜燃料电池（PEMFC）电堆工作温度对电堆的性能和运行寿命有很大影响.为了实现质子交换膜燃料电池电堆温度的有效控制,根据电堆能量守恒原理建立了电堆动态热管理模型.由于该模型是具有参数不确定和易受外界干扰的非线性模型,为此,采用了线性二次型优化控制和李亚普诺夫函数的递推设计方法设计了具有强鲁棒性的自适应控制器两种控制算法对电堆温度进行控制,数字测试验证了该算法的有效性.图1参11     

Optimization of blocked flow field performance of proton exchange membrane fuel cell with auxiliary channels

The flow field optimization design is one of the important methods to improve the performance of proton exchange membrane fuel cell (PEMFC). In this study, a new structure with staggered blocks on the parallel flow channels of PEMFC and auxiliary flow channels under the ribs is proposed. Through numerical calculation method, the effect of blocks auxiliary flow field (BAFF) on pressure drop, reactant distribution and liquid water removal in the fuel cells are investigated. The results show that when the operating voltage is 0.5 V, the current density of BAFF is 21.74% higher than that of the straight parallel flow field (SPFF), and the power density reaches 0.65 W cm^?2. BAFF improves performance by equalizing the pressure drop across sub-channels, promoting the uniform distribution of reactant, and enhancing transport across the ribs. In addition, through parameter analysis, it is found that BAFF can discharge liquid water in time at the conditions of high humidification, high current density and low temperature, which ensures the output performance of the fuel cell and improves the durability of the fuel cell. This paper provides new ideas for the improvement of PEMFC flow field design, which is beneficial to the development of PEMFC with high current density.     

Thermal management issues in a PEMFC stack – A brief review of current status

Understanding the thermal effects is critical in optimizing the performance and durability of proton exchange membrane fuel cells (PEMFCs). A PEMFC produces a similar amount of waste heat to its electric power output and tolerates only a small deviation in temperature from its design point. The balance between the heat production and its removal determines the operating temperature of a PEMFC. These stringent thermal requirements present a significant heat transfer challenge. In this work, the fundamental heat transfer mechanisms at PEMFC component level (including polymer electrolyte, catalyst layers, gas diffusion media and bipolar plates) are briefly reviewed. The current status of PEMFC cooling technology is also reviewed and research needs are identified.     

Numerical investigation on the characteristics of mass transport and performance of PEMFC with baffle plates installed in the flow channel

A 3D numerical model of proton exchange membrane fuel cell (PEMFC) with the installation of baffle plates is developed. The majority of the conservation equations and physical parameters are implemented through the user defined functions (UDFs) in the FLUENT software. The characteristics of mass transport and performance of PEMFC are investigated. The results reveal that the baffle plate can enhance the mass transport efficiency and the performance of PEMFC. The baffle plate installed in the PEMFC flow channel increases the local gas velocity, which can promote the reactant gas transport and the liquid water removal in the porous electrode. As a result, the reactant gas concentration is larger in the porous electrode, which enhances the fuel cell performance for decreasing the over-potential of concentration. The fuel cell output power increases with the blockage ratio of the baffle plate. Considering the extra pumping power resulted from pressure loss caused by the baffle plate, the fuel cell with the blockage ratio of 0.8 is found to perform best in terms of the fuel cell net power generation. The fuel cell performance increases first with the baffle plate number, due to the better reactant distribution and water management, but decreases when the baffle plate number is too large, due to the excessive blockage for the reactant gas transport to the channel downstream. The PEMFC investigated with 5 baffle plates in the channel is found to be optimal. A channel design to achieve gradually increasing blockage ratios is also proposed, which exhibits better cell performance than the design with even blockage ratios.