甲醇质子交换膜燃料电池的水和热管理

甲醇质了换燃料电是未来最有希望获得工程应用的燃料电池，文章简述了燃料电的发电原理及其分类。对多孔电极，直接甲醇质子交换膜燃料电及甲醇改质质子交换膜燃料电作了分析和讨论，指出了对质子交换膜燃料电池系统进行水管理和热管理的重要性和必要性。     

氢能知识系列讲座(9)微型燃料电池

一微型燃料电池电源微型燃料电池定义为功率为几瓦到十几瓦的燃料电池,用于日常微电器(图1)。它可以是直接甲醇燃料电池,也可以是改型的质子交换膜燃料电池。     

燃料电池发电与电解镁结合的探索研究

文提出了一种新型的用于电解镁生产的燃料电池发电系统,研究了燃料流量和燃料利用率对系统性能的影响,同时在设计工况下对系统的能量平衡和火用平衡进行了分析。研究表明：在设计工况下,系统的热效率为69.24%,质子交换膜燃料电池(Proton Exchange Membrane Fuel Cell, PEMFC)电堆的发电效率和系统发电效率分别为39.34%和33.42%;当燃料流量从1.0 mol/s提高到1.3 mol/s时,电堆的发电功率从95.14 kW增加到119.95 kW,电堆的发电效率从39.34%提高到43.05%。当燃料利用率从0.65提高到0.95时,电堆发电功率从67.93 kW增加到95.14 kW;电堆发电效率从28.09%提高到39.34%。     

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     

质子交换膜燃料电池的稳态分析

通过建立质子交换膜燃料电池稳态模型,考察了电堆温度和反应压力对电堆性能的影响。仿真结果表明,升高电堆温度使得氢气分压和氧气分压下降,但氢气分压下降的更快;在电堆工作温度范围内,电堆温度升高,热动力电势、欧姆极化电势和活化极化电势均下降,但电堆总输出电压上升;提高阴极侧压力有利于提高热动力电势,同时使得活化极化电势降低,有利于电堆整体性能的改善;提高阳极侧压力对电堆性能改善影响不大。     

基于模糊PID控制的家用燃料电池热电联供系统建模与仿真

家用燃料电池热电联供技术,是燃料电池应用领域的一个具有广阔发展前景的研究方向.质子交换膜燃料电池在运行时消耗燃料中的化学能,同时除了将一部分化学能转化为电能外,其余部分的化学能则以热量的形式散失.如果对这部分热量不能进行合理有效地利用,那么将会导致系统的能源利用率降低,同时还会影响燃料电池的安全运行.因此在正常发电的前提下,为了对质子交换膜燃料电池在运行过程中产生的热量进行回收利用,本文提供了一种水冷型质子交换膜燃料电池热电联供方案.通过冷却液将电堆产生的热量带出,并在换热器中将吸热后的高温冷却液与常温自来水进行热量交换,同时使用水箱储存热水,实现热量回收利用.基于MATLAB/Simulink软件平台建立了燃料电池热电联供系统仿真模型,主要包括电堆模型、散热器模型、储热水箱模型等.同时设计了系统在不同工作模式下的控制策略和用于电堆温度控制的模糊PID控制器.结果表明,通过采用模糊PID控制器对系统进行控制仿真,系统可获得良好的动态响应和抗干扰性能.同时通过仿真得到系统在功率负载范围内最大热电联供效率约为83％,满足了家庭的日常供热和用电需求,提高了能源的利用率.     

燃料电池发展现状与应用前景

介绍了各种类型燃料电池（碱性燃料电池,熔融碳酸盐燃料电池,固体氧化物燃料电池,磷酸燃料电池及质子交换膜燃料电池）的技术进展,电池性能及其特点。其中着重介绍了当今国际上应用较广泛,技术较为成熟的磷酸燃料电池和质子交换膜燃料电池。对燃料电池的应用前景进行探讨,并对我国的燃料电池研究提出了一些建议。     

我国燃料电池汽车用质子交换膜产业发展分析

氢燃料电池汽车是未来新能源清洁动力汽车的主要发展方向之一,质子交换膜作为氢燃料电池的核心原材料,其性能的好坏直接决定着燃料电池的性能和使用寿命,因而也成为近年来研究的热点。按照含氟量对质子交换膜进行分类,主要包括全氟磺酸质子交换膜、部分氟化聚合物质子交换膜、复合质子交换膜和新型非氟化聚合物质子交换膜,其中全氟磺酸质子交换膜由于其优异的性能成为当前最为商业化的电解质膜。未来几年,随着氢燃料电池汽车规模化应用,质子交换膜也必将迎来新的高峰,蕴藏着巨大的市场潜力。我国质子交换膜产业整体正处于加速发展阶段,市场开始活跃,企业正在加速布局,但目前产能利用率较低。国内质子交换膜整体供给仍然不足,大部分需求方仍使用进口膜。国内生产企业正在加速发展,部分代表性企业已经实现批量供货,并正在扩大产能,其他企业也在加快布局。全氟磺酸质子交换膜仍然是当前商业化应用的最优选择,如何在提升性能的同时降低成本是重点研究方向。从长远看,在发展全氟磺酸质子交换膜的同时,仍需布局发展部分氟化、无氟型以及复合质子交换膜。     

燃料电池水下应用可行性研究

[目的]为了进一步提升水中装备的续航作战能力,高比能量电能源系统是解决问题的关键,通过对比不同燃料种类对系统比能量的影响,探究燃料电池在水下应用的可行性。[方法]通过对目前广泛研究的质子交换膜燃料电池和固体氧化物燃料电池的特点进行对比分析,依据指标要求对比不同储氢和储氧的方式,确定燃料系统阴极侧采用液氧方式供给可以满足设计要求,不同燃料电池类型其阳极侧可采用的供给方式不同,液氢、有机液体、甲醇重整、直接甲醇和直接丙烷具有应用潜力。[结果]结合不同燃料电池的特点,分析尾气处理装置参数,综合比较水下应用燃料电池能源系统的可行方案,以液氧、液化丙烷或有机液体为燃料的固体氧化物燃料电池能源系统和以液氧、有机液体为燃料的质子交换膜燃料电池可以满足设计需求。[结论]燃料电池能源系统可以显著提升能源系统的比能量,燃料的供给形式是影响电能源系统比能量的主要因素。     

均匀磁场对质子交换膜燃料电池工作性能影响研究

通过在质子交换膜燃料电池加载不同方向、不同强度的均匀磁场,研究均匀磁场对质子交换膜燃料电池工作性能的影响。研究发现,在燃料电池两侧加载不同方向、不同强度的均匀磁场,可以不同程度提升质子交换膜燃料电池的工作性能。文章对比了磁场方向与质子交换膜燃料电池双极板两侧平行及垂直时的工作性能,垂直磁场下的电池输出功率和工作电流提升幅度最大。当质子交换膜燃料电池分别置于不同强度(270,440,530 m T)的均匀磁场时,磁场下的电池输出功率与不加载磁场时有所增大,并且随着外加均匀磁场的增大,电池的输出功率也随之提高。     

Operational characteristics of the direct methanol fuel cell stack on fuel and energy efficiency with performance and stability

This paper is presented to investigate operational characteristics of a direct methanol fuel cell (DMFC) stack with regard to fuel and energy efficiency, including its performance and stability under various operating conditions. Fuel efficiency of the DMFC stack is strongly dependent on fuel concentration, working temperature, current density, and anode channel configuration in the bipolar plates and noticeably increases due to the reduced methanol crossover through the membrane, as the current density increases and the methanol concentration, anode channel depth, and temperature decreases. It is, however, revealed that the energy efficiency of the DMFC stack is not always improved with increased fuel efficiency, since the reduced methanol crossover does not always indicate an increase in the power of the DMFC stack. Further, a lower methanol concentration and temperature sacrifice the power and operational stability of the stack with the large difference of cell voltages, even though the stack shows more than 90% of fuel efficiency in this operating condition. The energy efficiency is therefore a more important characteristic to find optimal operating conditions in the DMFC stack than fuel efficiency based on the methanol utilization and crossover, since it considers both fuel efficiency and cell electrical power. These efforts may contribute to commercialization of the highly efficient DMFC system, through reduction of the loss of energy and fuel.     

A small mono-polar direct methanol fuel cell stack with passive operation

A passive direct methanol fuel cell (DMFC) stack that consists of six unit cells was designed, fabricated, and tested. The stack was tested with different methanol concentrations under ambient conditions. It was found that the stack performance increased when the methanol concentration inside the fuel tank was increased from 2.0 to 6.0 M. The improved performance is primarily due to the increased cell temperature as a result of the exothermic reaction between the permeated methanol and oxygen on the cathode. Moreover, the increased cell temperature enhanced the water evaporation rate on the air-breathing cathode, which significantly reduced water flooding on the cathode and further improved the stack performance. This passive DMFC stack, providing 350 mW at 1.8 V, was successfully applied to power a seagull display kit. The seagull display kit can continuously run for about 4 h on a single charge of 25 cm³ 4.0-M methanol solution.     

A high-performance chitosan-based double layer proton exchange membrane with reduced methanol crossover

A novel double layer proton exchange membrane (PEM) comprising a layer of structurally modified chitosan, as a methanol barrier layer, coated on Nafion^®112 was prepared and assessed for direct methanol fuel cell (DMFC) applications. Scanning electron microscope (SEM) micrographs of the designed membrane revealed a tight adherence between layers, which indicate the high affinity of opposite charged polyelectrolyte layers. Proton conductivity and methanol permeability measurements showed improved transport properties of the designed membrane compared to Nafion^®117. Moreover, DMFC performance tests revealed a higher open circuit voltage and power density, as well as overall fuel cell efficiency for the double layer membrane in comparison with Nafion^®117, especially at elevated methanol solution feed. The obtained results indicate the designed double layer membrane as a promising PEM for high-performance DMFC applications.     

A review of polymer electrolyte membranes for direct methanol fuel cells

This review describes the polymer electrolyte membranes (PEM) that are both under development and commercialized for direct methanol fuel cells (DMFC). Unlike the membranes for hydrogen fuelled PEM fuel cells, among which perfluorosulfonic acid based membranes show complete domination, the membranes for DMFC have numerous variations, each has its advantages and disadvantages. No single membrane is emerging as absolutely superior to others. This review outlines the prospects of the currently known membranes for DMFC. The membranes are evaluated according to various properties, including: methanol crossover, proton conductivity, durability, thermal stability and maximum power density. Hydrocarbon and composite fluorinated membranes currently show the most potential for low cost membranes with low methanol permeability and high durability. Some of these membranes are already beginning to impact the portable fuel cell market.     

Lightweight current collector based on printed-circuit-board technology and its structural effects on the passive air-breathing direct methanol fuel cell

To realize lightweight design of the fuel cell system is a critical issue before it is put into practical use. The printed-circuit-board (PCB) technology can be potentially used for production of current collectors or flow distributors. This study develops prototypes of a single passive air-breathing direct methanol fuel cell (DMFC) and also an 8-cell mono-polar DMFC stack based on PCB current collectors. The effects of diverse structural and operational factors on the cell performance are explored. Results show that the methanol concentration of 6 M promotes a higher cell performance with a peak power density of 18.3 mW cm⁻². The combination of current collectors using a relatively higher anode open ratio and inversely a lower cathode open ratio helps enhance the cell performance. Dynamic tests are also conducted to reveal transient behaviors and its dependence on the operating conditions. To validate the real working status of the DMFC stack, it is coupled with an LED lightening system. The performance of this hybrid system is also reported in this study.     

Development of an air-breathing direct methanol fuel cell with the cathode shutter current collectors

An air-breathing direct methanol fuel cell with a novel cathode shutter current collector is fabricated to develop the power sources for consumer electronic devices. Compared with the conventional circular cathode current collector, the shutter one improves the oxygen consumption and mass transport. The anode and cathode current collectors are made of stainless steel using thermal stamping die process. Moreover, an encapsulation method using the tailor-made clamps is designed to assemble the current collectors and MEA for distributing the stress of the edges and inside uniformly. It is observed that the maximum power density of the air-breathing DMFC operating with 1 M methanol solution achieves 19.7 mW/cm² at room temperature. Based on the individual DMFCs, the air-breathing stack consisting of 36 DMFC units is achieved and applied to power a notebook computer.     

Study of sintered stainless steel fiber felt as gas diffusion backing in air-breathing DMFC

Adoption of a sintered stainless steel fiber felt was evaluated as gas diffusion backing in air-breathing direct methanol fuel cell (DMFC). By using a sintered stainless steel fiber felt as an anodic gas diffusion backing, the peak power density of an air-breathing DMFC is 24 mW cm⁻², which is better than that of common carbon paper. A 30-h-life test indicates that the degraded performance of the air-breathing DMFC is primarily due to the water flooding of the cathode. Twelve unit cells with each has 6 cm² of active area are connected in series to supply the power to a mobile phone assisted by a constant voltage diode. The maximum power density of 26 mW cm⁻² was achieved in the stack, which is higher than that in single cell. The results show that the sintered stainless steel felt is a promising solution to gas diffusion backing in the air-breathing DMFC, especially in the anodic side because of its high electronical conductivity and hydrophilicity.     

A silicon‐based micro direct methanol fuel cell stack with a serial flow path design

A 6‐cell silicon‐based micro direct methanol fuel cell (μDMFC) stack utilized the serial flow path design was developed. The effect of the structure of flow path on the performance of the stack was investigated using polarization characterization and electrochemical impedance analysis. Further, the voltage distribution for individual cells under different current density was discussed. The results indicated that the μDMFC stack with the serial flow path design exhibited better performance than that utilized the parallel flow path due to uniform mass transfer of methanol as a result of the use of the serial flow path. Such a μDMFC stack generates a peak output power of ca. 187 mW, corresponding to an average power density of ca. 21.7 mWcm^‐2, and exhibits a steady‐state power output for more than 100 h. Copyright © 2011 John Wiley & Sons, Ltd.     

Power management of a direct methanol fuel cell system

The effect of discharge rate of direct methanol fuel cell (DMFC) on fuel efficiency was comparatively investigated using a DMFC single cell and a DMFC system. The results obtained from the single cell were used to model the DMFC system. Several semi-empirical equations were derived that relate discharge current, voltage, power output, energy density and fuel consumption for a nominal 25 W DMFC system. The decrease in fuel efficiency with decreased power output that is observed for the DMFC system is attributable to the increase of methanol crossover that can be observed for an individual cell. A DMFC system can achieve maximum energy density and fuel efficiency at an appropriately high level of power output.     

Behavioral pattern of a monopolar passive direct methanol fuel cell stack

A passive, air-breathing, monopolar, liquid feed direct methanol fuel cell (DMFC) stack consisting of six unit cells with no external pump, fan or auxiliary devices to feed the reactants has been designed and fabricated for its possible employment as a portable power source. The configurations of the stack of monopolar passive feed DMFCs are different from those of bipolar active feed DMFCs and therefore its operational characteristics completely vary from the active ones. Our present investigation primarily focuses on understanding the unique behavioral patterns of monopolar stack under the influence of certain operating conditions, such as temperature, methanol concentration and reactants feeding methods. With passive reactants supply, the temperature of the stack and open circuit voltage (OCV) undergo changes over time due to a decrease in concentration of methanol in the reservoir as the reaction proceeds. Variations in performance and temperature of the stack are mainly influenced by the concentration of methanol. Continuous operation of the passive stack is influenced by the supply of methanol rather than air supply or water accumulation at the cathode. The monopolar stack made up of six unit cells exhibits a total power of 1000 mW (37 mW cm⁻²) with 4 M methanol under ambient conditions.