电解重整式甲醇燃料电池系统

为解决直接甲醇燃料电池中甲醇氧化活性低及甲醇穿透问题,提出一种新型的电解重整式甲醇燃料电池系统。在系统中,高温电解重整器重整甲醇为常温燃料电池供氢,燃料电池的部分电能供给电解重整器使用。通过对系统的物料流、焓流、有效能流的分析,确定了系统中的不可逆因素。结果表明:电解重整器电压是影响系统效率的重要参数;升高重整器温度可以显著降低其电压,但必须采用合理的压力、甲醇溶液浓度以抑制甲醇溶液的蒸发,降低热量损失。与传统的直接甲醇燃料电池系统以及高温甲醇热重整联合质子交换膜燃料电池系统相比,该系统性能较高、结构紧凑。     

Control of stationary and transportation fuel cell systems: Progress and opportunities

Fuel cell power systems have witnessed intense development in the recent years as they offer a clean and efficient alternative for power generation in stationary and transportation applications. In this paper, we present an overview of recent work on dynamic modeling and control design for stationary and transportation fuel cell systems including the research at United Technologies Corporation.The use of equation oriented modeling framework for system level dynamic modeling enabled by tools, such as Dymola and gPROMS is described. It is demonstrated that the non-linear system level models readily allow linear model derivation and the application of advanced control analysis and design techniques that provide more insight into the system level dynamic and control issues in fuel cell systems. The dynamic modeling and advanced control design research performed at UTC for a hydrogen fed PEMFC power plant for a bus and a natural gas fed PEMFC power plant for stationary power generation is described.We also identify, for future research, the challenges and opportunities in several areas relating to fuel cell systems ranging from power management and freeze startup to system level modeling, control, diagnostics and hardware-in-the-loop validation of the control system. The emphasis is on polymer electrolyte membrane fuel cell (PEMFC) systems but phosphoric acid fuel cell (PAFC) systems are also briefly discussed.     

质子交换膜燃料电池电源系统停机特性及控制策略

质子交换膜燃料电池(PEMFC)电源系统在停机后,燃料电池开路高电压被认为是造成电池性能下降和寿命缩短的重要因素。这主要是因为PEMFC电源系统停机后,燃料电池处于开路状态,阳极侧残留的氢气和阴极侧的空气发生电化学反应,电池电压为开路高电压且维持在开路电压的时间比较长,这容易引起催化剂碳载体发生氧化,使分布在载体上的铂(Pt)颗粒脱落,造成燃料电池性能衰减以及寿命缩短。以最大程度缩短停机后开路高电压的时间和加快阳极侧残留氢气的消耗速度为目标,提出了一种PEMFC电源系统的停机策略,通过实验分别研究了直接停机和停机策略停机对PEMFC输出特性的影响。以该停机控制策略为基础,通过实验验证了该停机策略的有效性,为提出保护性的PEMFC电源系统停机控制策略提供了参考性指导。     

Model‐based optimization of hydrogen generation by methane steam reforming in autothermal packed‐bed membrane reformer

An autothermal membrane reformer comprising two separated compartments, a methane oxidation catalytic bed and a methane steam reforming bed, which hosts hydrogen separation membranes, is optimized for hydrogen production by steam reforming of methane to power a polymer electrolyte membrane fuel cell (PEMFC) stack. Capitalizing on recent experimental demonstrations of hydrogen production in such a reactor, we develop here an appropriate model, validate it with experimental data and then use it for the hydrogen generation optimization in terms of the reformer efficiency and power output. The optimized reformer, with adequate hydrogen separation area, optimized exothermic‐to‐endothermic feed ratio and reduced heat losses, is shown to be capable to fuel kW‐range PEMFC stacks, with a methane‐to‐hydrogen conversion efficiency of up to 0.8. This is expected to provide an overall methane‐to‐electric power efficiency of a combined reformer‐fuel cell unit of ～0.5. Recycling of steam reforming effluent to the oxidation bed for combustion of unreacted and unseparated compounds is expected to provide an additional efficiency gain. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Chloride free Pt‐ and PtRu‐ Nanoparticles Stabilised by “Armand's Ligand” as Precursors for Fuel Cell Catalysts

Chloride residues on the surface of fuel cell catalysts are known to decrease the catalytic activity, especially for O₂ reduction. Using Armand's ligand, which contains the chloride free DCTA anion, for the colloidal stabilisation of nanoscopic Pt and PtRu catalysts precursors (< 2 nm size) leads to PEMFC and DMFC catalysts with improved activity compared to commercial E‐TEK catalysts as evidenced by both methanol oxidation and CO‐stripping voltametric studies.     

Operation Characteristic Analysis of a Direct Methanol Fuel Cell System Using the Methanol Sensor‐less Control Method

The application of methanol sensor‐less control in a direct methanol fuel cell (DMFC) system eliminates most of the problems encountered when using a methanol sensor and is one of the major solutions currently used in commercial DMFCs. This study focuses on analyzing the effect of the operating characteristics of a DMFC system on its performance under the methanol sensor‐less control as developed by Institute of Nuclear Energy Research (INER). Notably, the influence of the dispersion of the methanol injected on the behavior of the system is investigated systematically. In addition, the mechanism of the methanol sensor‐less control is investigated by varying factors such as the timing of the injection of methanol, the cathode flow rate, and the anode inlet temperature. These results not only provide insight into the mechanism of methanol sensor‐less control but can also aid in the improvement and application of DMFC systems in portable and low‐power transportation.     

A Pumpless Methanol Feeding Method for Application in Direct Methanol Fuel Cell Systems

This paper presents a simple and reliable pumpless methanol feeding (PLMF) method for application in direct methanol fuel cell (DMFC) systems. The primary feature and advantage of the PLMF is as follows: it employs an approach that allows the cathode gas pressure to be connected with a fuel container for supplying the methanol fuel into the anode fuel loop, instead of using any feeding pump or other specially designed apparatuses. The PLMF has been used in a portable 25 W DMFC system and realised feeding methanol in real time for meeting the requirements of the system. The PLMF method not only is suitable for the DMFC system, but also can be used in other liquid‐feeding fuel cell systems.     

PBI‐Based Polymer Membranes for High Temperature Fuel Cells – Preparation,Characterization and Fuel Cell Demonstration

Proton exchange membrane fuel cell (PEMFC) technology based on perfluorosulfonic acid (PFSA) polymer membranes is briefly reviewed. The newest development in alternative polymer electrolytes for operation above 100 °C is summarized and discussed. As one of the successful approaches to high operational temperatures, the development and evaluation of acid doped polybenzimidazole (PBI) membranes are reviewed, covering polymer synthesis, membrane casting, acid doping, physicochemical characterization and fuel cell testing. A high temperature PEMFC system, operational at up to 200 °C based on phosphoric acid‐doped PBI membranes, is demonstrated. It requires little or no gas humidification and has a CO tolerance of up to several percent. The direct use of reformed hydrogen from a simple methanol reformer, without the need for any further CO removal, has been demonstrated. A lifetime of continuous operation, for over 5000 h at 150 °C, and shutdown‐restart thermal cycle testing for 47 cycles has been achieved. Other issues such as cooling, heat recovery, possible integration with fuel processing units, associated problems and further development are discussed.     

直接甲醇燃料电池

介绍了直接甲醇燃料电池的原理、结构,并与发展较早的氢气燃料电池进行优劣比较。针对近期商业化便携式燃料电池的技术指标,主要讨论了直接甲醇燃料电池在性能和成本上的现状和问题,并着重阐述了阳极催化剂和电解质膜(决定其性能的两个关键因素)的研发进展。     

Fuel cell performance of polymer electrolyte membrane based on hexafluorinated sulfonated poly(ether sulfone)

The potential-current fuel cell characteristics of membrane electrode assemblies (MEAs) using hexafluorinated sulfonated poly(ether sulfone) copolymer are compared to those of Nafion^® based MEAs in the case of proton exchange membrane fuel cell (PEMFC) and direct methanol fuel cell (DMFC). The hexafluorinated copolymer with 60 mol% of monosulfonated comonomer based acid form membrane is chosen for this study due to its high proton conductivity, high thermal stability, low methanol permeability, and its insolubility in boiling water. The catalyst powder is directly coated on the membrane and the catalyst coated membrane is used to fabricate MEAs for both fuel cells. A current density of 530 mA cm^?2 at 0.6 V is obtained at 70 °C with H₂/air as the fuel and oxidant. The peak power density of 110 mW cm^?2 is obtained at 80 °C under specific DMFC operating conditions. Other electrochemical characteristics such as electrochemical impedance spectroscopy, cyclic voltammetry, and linear sweep voltammetry are also studied.     

Development of a Self‐Adaptive Direct Methanol Fuel Cell Fed with 20 M Methanol

A passive and self‐adaptive direct methanol fuel cell (DMFC) directly fed with 20 M of methanol is developed for a high energy density of the cell. By using a polypropylene based pervaporation film, methanol is supplied into the DMFC's anode in vapor form. The mass transport of methanol from the cartridge to the anodic catalyst layer can be controlled by varying the open ratio of the anodic bipolar plate and by tuning the hydrophobicity of anodic diffusion layer. An effective back diffusion of water from the cathode to the anode through Nafion film is carried out by using an additive microporous layer in the cathode that consists of 50 wt.% Teflon and KB‐600 carbon. Accordingly, the water back diffusion not only ensures the water requirement for the methanol oxidation reaction but also reduces water accumulation in the cathode and then avoids serious water flooding, thus improving the adaptability of the passive DMFC. Based on the optimized DMFC structure, a passive DMFC fed with 20 M methanol exhibits a peak power density of 42 mW cm^–2 at 25 °C, and no obvious performance degradation after over 90 h continuous operation at a constant current density of 40 mA cm^–2.     

直接甲醇燃料电池技术及应用

本文回顾了直接甲醇燃料电池（ＤＭＦＣ）的研究开发历史,系统阐述了ＤＭＦＣ系统中电催化剂选择与设计基本原则、电解质膜材料与甲醇渗透的关系。分析了电池工作温度、工作压力和甲醇进料方式对ＤＭＦＣ电化学性能的影响。     

低温燃料电池催化剂的研究进展

综述了近年来低温燃料电池,如质子交换膜燃料电池（PEMFC）和直接甲醇燃料电池（DMFC）催化剂的研究进展,着重介绍了近年来出现的几种制备高分散和高活性的燃料电池催化剂的新技术和新方法,以及关于低Pt和非Pt催化剂的研究情况,简要介绍了关于燃料电池催化剂基础研究方面的情况。     

直接甲醇燃料电池

介绍了直接甲醇燃料电池的原理、结构,并与发展较早的氢气燃料电池进行优劣比较。针对近期商业化便携式燃料电池的技术指标,主要讨论了直接甲醇燃料电池在性能和成本上的现状和问题,并着重阐述了阳极催化剂和电解质膜（决定其性能的两个关键因素）的研发进展。     

Georgetown University Fuel Cell Transit Bus Program

Georgetown University (GU) has been at the forefront in the development of transportation fuel cells for over eighteen years. GU has been involved in the development, demonstration and testing of several fuel cell power plants and vehicles, including three 30‐foot transit buses and two 40‐foot transit buses. All of these vehicles are still operational. GU rolled out a 40‐foot fuel cell powered transit bus May 1998. This electric bus is powered by a 100 kW Phosphoric Acid Fuel Cell (PAFC) manufactured by UTC Fuel Cells, LLC. A second 100 kW Proton Exchange Membrane Fuel Cell (PEMFC) power plant has been fabricated by Ballard Transportation Business Unit and has been integrated into a second 40‐foot transit bus platform. This is the world′s largest PEMFC power plant capable of operating on liquid methanol; it rolled out in December, 2001. The GU program is the only one of its kind that is addressing the commercialization of the easily refueled and longer‐range, liquid‐fueled fuel cell buses. As a hydrogen carrier, methanol greatly exceeds the vehicular weight percent storage targets for hydrogen set by the US Department of Energy (DOE). Coal, an abundant US domestic fuel, can be used to produce methanol. The potential to make domestic coal the feedstock for transportation fuel cannot be ignored. This offers a realistic approach to true energy independence. The GU Fuel Cell Powered Transit Bus Program is supported by a grant from the Federal Transit Administration (FTA).     

Comparing Anode Gas Recirculation with Hydrogen Purge and Bleed in a Novel PEMFC Laboratory Test Cell Configuration

In automotive‐type polymer electrolyte membrane fuel cell (PEMFC) systems, impurities and inert gases accumulate in the anode gas recirculation loop. Therefore, the impurity limits, dictated by the current hydrogen fuel specification (ISO 14687‐2:2012), also require quantification with representative fuel cell test systems applying anode gas recirculation, that enables high fuel utilization rates and accumulation of impurities.We report a novel PEMFC laboratory test cell configuration mimicking automotive conditions. This setup enabled comparison of two operation modes, hydrogen bleed and purge, within 84.4%–98.6% fuel utilizations. The results indicate that similar enrichment dynamics apply to both bleed and purge modes.The configuration employed a membrane dryer to circumvent the 60 °C limit of commercially available recirculation pumps. The membrane dryer allows heat and humidity extraction from the anode exit gas stream, enabling the adoption of conventional recirculation pumps, minimizing water condensation, and making sampling with on‐line gas analysis instruments easier. The results show that anode gas recirculation systems with hydrogen bleed can be implemented in conventional test stations by resorting to commercially available recirculation pumps. This enables realistic and cost‐effective determination of impurity effects for fuel cell system development and new hydrogen fuel standards.     

Forecast of Performance Parameters of Automotive Fuel Cell Systems – Delphi Study Results

Fuel cells are a promising propulsion technology option in sustainable and zero‐emission drivetrain strategies as they offer a high potential to significantly reduce well‐to‐wheel greenhouse gas emissions and the dependency on fossil energy resources. At the same time, the current technological performance of automotive fuel cell systems is not yet sufficient to meet market demands. Therefore, the technical development of fuel cells is a critical factor for a successful market introduction of fuel cell electric vehicles (FCEV). This paper describes the methodology and results of a two‐round Delphi Survey conducted by the Institut für Kraftfahrzeuge of RWTH Aachen University to assess the technological potential of polymer electrolyte membrane fuel cell (PEMFC) systems in automotive applications by 2030. The analysis of the current and future performance level of key performance indicators (KPI) of automotive fuel cell systems helps to identify critical performance parameters and to prioritize research and development demands. KPI analyzed in the Delphi Survey as forecast parameters include system efficiency, durability, power density, and specific power.     

直接甲醇燃料电池质子交换膜研究进展

直接甲醇燃料电池(DMFC)以其燃料来源丰富、储存方便、结构简单、安全等优点而日益受到广泛的关注。预计将在很多领域中能得到广泛的应用。过去,人们对DMFC做了很多研究,针对直接甲醇燃料电池中的质子交换膜(PEM)的阻甲醇性能方面的研究进展作如下评述。     

A dual functional staged hydrogen purifier for an integrated fuel processor–fuel cell power system

This paper describes the operation of a dual functional, membrane/catalytic CO_x methanator, hydrogen purifier that is well-suited for an integrated fuel processor/fuel cell power system. In combination with a pressure swing reformer (PSR) and a PEMFC, the system provides high overall efficiency and portability for distributed power or onboard vehicle use. Gas testing results illustrate the ability of the purifier to produce fuel cell purity hydrogen at peak power flux. The durability of this purifier is shown by its ability to meet target hydrogen purity even with a membrane that permeates >3000 ppm CO. Gas purge streams from both fuel cell electrodes are combined with the membrane retentate and combusted in the PSR combustion cycle to provide heat for the reforming reaction leading to high thermal efficiency. Most significantly, it is shown that staging of this purifier, enables recovery of some fraction of the purified hydrogen at pressures substantially approaching that of the feed hydrogen partial pressure. This creates an onboard source of high pressure hydrogen to be optionally fed to a storage device for use during vehicle startup, or to the fuel cell, either directly or via the storage device, under high power load conditions. The beneficial impact of this two-stage, dual functional purifier on membrane cost, dependability and fuel processor/fuel cell integration, will be discussed.     

Positioning the reference electrode in proton exchange membrane fuel cells: calculations of primary and secondary current distribution

The primary and secondary current distribution study indicates the geometry of a thin electrolyte in a proton exchange membrane (PEM) fuel cell has a direct relation to the measured electrode polarization, thus making the positioning of the reference electrode and ohmic compensation critical. The different kinetic overpotentials on the electrodes can also affect the potential distribution and therefore affect the measurement accuracy. The measurement error can be significant for the fuel cell system with different kinetic overpotentials and with electrode misalignment. The measurement error for both hydrogen and direct methanol fuel cells (DMFC) has been analyzed over the current density region with no mass transfer effects. By using two reference electrodes, the measurement error can be substantially decreased for both anode and cathode measurement in a direct methanol fuel cell, and for the cathode measurement in a hydrogen/air fuel cell.