Several disadvantages in general unipolar/bipolar plates are that cost is expensive, weight is heavy and the volume is large. The high compressing pressure is also necessary to reduce the contact resistance in making up a fuel cell stack. Therefore, it is difficult in making use general unipolar/bipolar plates to portable fuel cells. With a new heterogeneous carbon fiber bipolar plate, pumpless and air-breathing design and in cooperating with a special MEA, a portable fuel cell stacks developed in our lab have made portable applications to be possible. The structure of the DMFC stack made with the new carbon fiber bipolar plate is much more simple and weight-light than the other designs. The three portable DMFC stacks flat type, cylinder type (I), and cylinder type (II) are developed in series in our lab. The methanol solution can be stored directly in the flow channel of the anode, and does not need the extra auxiliary equipment, so it easy to apply to the portable fuel cell. The developed portable DMFC of cylinder type (II), weight is only 20g, volume is 30cm3, and the fuel stored capacity is 7.5ml. In the flat type DMFC, In anode Pt-Ru loading 3 mg/cm2, and cathode Pt loading 1 mg/cm2, methanol concentration 3 M, pumpless, air-breathing, and room temperature, the largest of output power density of the fuel cell can reach 5.27 mW/cm2, and the total power can reach 71 mW. The weight of DMFC of cylinder type (II) is far lower than DMFC of flat type in addition, so its power density 1.33mW/g is about 1.68 times of flat type 0.79 mW/g.

In this thesis the experimental method is used to study the characteristics of a DMFC when a heterogeneous carbon fiber bipolar plate is applied to it. The first main study is about the effect of the different structures of the carbon fiber bunch on the fuel cell performance. Additionally, a high temperature hot-pressing process is performed to change the inner molecular structure so that the hydrogen ion can be blocked to avoid the lateral migration between two adjacent cells. Finally, the two techniques are applied to make our new portable DMFC stack. The bipolar plates with the sawtooth or non-sawtooth carbon fiber bunches have been used in making our DMFC stack. The experimental results display that the performances of the two structures both are better than the traditional graphite bipolar plate. However, the performance of DMFC with the sawtooth bipolar plate is much better than that without sawtooth, especially in high current density. When carbon fiber bunches with sawtooth use at anode and cathode of bipolar plates, the performance can be enhanced and its power density 27.6% higher than that without sawtooth. During our study we also found that part of hydrogen ions can laterally migrate to its adjacent cathode and do not directly cross to its opposite cathode, when the banded type MEA are used to multiple cell stack. Therefore, the performance cannot be performed well due to this type ion transfer. In order to block the lateral migration, the narrow area of the membrane between two adjacent electrodes is pressed with a high temperature hot-pressing device. After a short time hot-press between two adjacent electrodes, the hydrogenion migration phenomenon reduced, and the performance had been improved about 10% higher than that without hot-press. Finally, a double layer 2x6-cell flat type DMFC is made. This 12-cell stack is composed of each electrode area 0.5x5cm2, two sheets of membrane for 6-cell using Nafion 117, the anode catalyst Pt-Ru loading 4mg/cm2, and cathode catalyst Pt loading 4mg/cm2, the methanol concentration 3M, air-breathing, and operating in room temperature. The output power of the cell can reach an average power density 8.0mW/cm2 and total power 240mW with our handmade stack. If the performance of each fuel cell is more uniform, we expect that total power can reach 480 mW. The power level should be satisfied for any kind mobile phone.

Abstract In search for new investments, innovative investment corporations need to consider many factors, including, the market side, technology side, finance side, human resources quality level and so on¡K. However, with regards to Fuel Cell and similar new heavy duty products, it is not just a normal technology and 3-5 years investment analysis; as a technological researcher, the initial research ideology is to find a norm, which can be used as a lead target at the start of the new innovative technology investment. This is one of the issues besides technological analysis, that a company investing in fuel cell need to consider at the point of investment. This also can be used as a reference for normal public investors. This research takes the point of view of the technology growth curve. It makes an attempt by representing the growth curve with accumulated patent numbers. It also investigates whether the over rated remuneration for the fuel cell industry is supported by increase in technology levels and if there were significant increases. From historical data, the results were initially unexpected as there was a positive relationship. After investigation, the main reason was that related applicable products haven¡¦t reached mature levels. Hence using fuel cell cars as the research objective, with the assistance of a realistic growth curve, initial estimates predicts the product will mature around 2008 and will be in mass production in 2010 ~ 2012. This is very similar to the prediction of future new technology schedule provided by George Washington University. Therefore the conclusion of this thesis is as below: 1. Illustrate that accumulated patent numbers represents technological advancement which can be reflected in the industry¡¦s technology capability, the growth curve. 2. According to technological capability growth curve, the over rated remuneration stock prices will raise once it reaches the applicable growth period. This is generally predicted to be after the year 2012. Even if Honda¡¦s fuel cell car is in production, the investors will still continue to invest. Otherwise, according to each company¡¦s financial analysis the investment risks will be too high.

The main aim of this study is to develop three dimensional models for micro flow-field plate of PEMFC and use numerical simulations to discuss the reliability of micro flow-field plate which works in real. A crack exists in the plate is loaded by the shear force, which is produced by the fuel H2 enter from inlet, and will propagate. The Ag, which is used to collect the electrons, will peel off and the efficiency of fuel cell will decrease. The commercial package software ANSYS was used to simulate the stress state around crack tip. Three modes of stress intensity factors K£L, K£L£L and K£L£L£L, were calculated in order to describe the stressed behavior of crack. Finally, the inlet pressure, geometry of crack and channel size is changed and Taguchi method with ANOVA is used to find the factors which influence the stressed behavior of crack most. The simulation results show that K£L and K£L£L are influenced most by geometry of crack and K£L£L£L is influenced more by geometry of crack and channel size

This research is to develop procedures on the fabrication of membrane electrode assembly (MEA), which is the heart of the Proton Exchange Membrane Fuel Cell. Sensitivity studies of the manipulated variable, such as pressure, temperature, and time, in the hot press process, which is adopted in the assembling on the performance of the MEA are also performed. The developed products on the cleaning of membrane as well as the hot press of MEA have been verified through many experiments. The tests of the MEA¡¦s thus produced reveal that temperature and pressure in hot press process have significant influence on MEA performance. Both have to be kept in a suitable range. Optimal operating conditions in the hot press process may be achieved by conducting more experiments and a detail understanding on the internal structure variation of membrane under high pressure and temperature condition.

Abstract Reformer, the most important link of fuel cell, is the main set to create the hydrogen. After the fuel passes through the catalytic reaction by reformer, will produce hydrogen and chemical substances, the hydrogen will become the energy to support fuel cell. At the present day, the technology of PEM fuel cell and traditional fuel reformer has already existed, only need to reduce the volume, cost and to promote the efficiency. Catalytic layer, with the construction of microchannel, makes the adequate impact to gas and catalyst to promote the efficiency. This research uses the Lattice Boltzmann method (LBM) to simulate the fluid field and heat-mass transfer of microchannel, to discuss the function influence to the different parameter such as velocity, temperature, channel length, and channel height. The result displays, with the same inlet speed and temperature, by the increasing of the channel length, the amount of hydrogen will raise and residual methanol will reduce. When the channel length is more than 500£gm, the produce rate of hydrogen will not be a big change. If fix the channel length at 500£gm, under the different inlet temperature, while the maximum concentration at inlet, the speed of hydrogen at inlet is not the same. The best inlet speed will increase with the higher temperature. When fix the channel length at 500£gm, raising the altitude to 500£gm, the hydrogen product will not increase, on the contrary, it¡¦ll go down. Keywords¡GFuel cell reformer¡BMicorchannel of hat and mass transfer¡BNumerical simulations

Fuel cells are expected to play an important role in future power generation. However, significant technical challenges remain and the commercial breakthrough of fuel cells is hindered by the high price of fuel cell components. As is well known, the fuel cells do not provide the robust source characteristics required to effectively follow the load during significant load steps and they have limited overload-handling capability. Further, the performance of the fuel cell is significantly degraded when the CO (Carbon Monoxide) is contained in the hydrogen fuel. In this thesis several new approaches to improve the performance of PEM based fuel cell power systems are discussed. In the first section an impedance model of the Proton Exchange Membrane Fuel Cell Stack (PEMFCS) is first proposed. This equivalent circuit model of the fuel cell stack is derived by a frequency response analysis (FRA) technique to evaluate the effects of the ripple current generated by the power-conditioning unit. Experimental results are presented to show the effects of the ripple currents. In the second section, a fuel cell powered UPS (Uninterruptible Power Supply) system is proposed. In this approach, two PEM Fuel Cell modules along with suitable DC/DC and DC/AC power electronic converter modules are employed. A Supercapacitor module is also employed to compensate for instantaneous power fluctuations including overload and to overcome the slow dynamics of the fuel processor such as reformers. A complete design example for a 1-kVA system is presented. In the third section, an advanced power converter topology is proposed to significantly improve the CO tolerance on PEM based fuel cell power systems. An additional two-stage dc-dc converter with a supercapacitor module is connected to the fuel cell to draw a low frequency (0.5Hz) pulsating current of the specific amplitude (20-30[A]) from the fuel cell stack. CO on the catalyst surface can be electro-oxidized by using this technique, and thereby the CO tolerance of the system can be significantly improved. Simulation and experimental results show the validity and feasibility of the proposed scheme.

In this thesis analysis and design of a wide input range DC-DC converter is proposed along with a robust power control scheme. The proposed converter and its control is designed to be compatible to a fuel cell power source, which exhibits 2:1 voltage variation as well as a slow transient response. The proposed approach consists of two stages: a primary three-level boost converter stage cascaded with a high frequency, isolated boost converter topology, which provides a higher voltage gain and isolation from the input source. The function of the first boost converter stage is to maintain a constant voltage at the input of the cascaded DC-DC converter to ensure optimal performance characteristics with high efficiency. At the output of the first boost converter a battery or ultracapacitor energy storage is connected to take care of the fuel cell slow transient response (200 watts/min). The robust features of the proposed control system ensure a constant output DC voltage for a variety of load fluctuations, thus limiting the power being delivered by the fuel cell during a load transient. Moreover, the proposed configuration simplifies the power control management and can interact with the fuel cell controller. The simulation results and the experimental results confirm the feasibility of the proposed system.

The rapid emergence of distributed fuel cell powered generations (DFPGs) operating in parallel with utility has brought a number of technical concerns as more DFPGs are connected to utility grid. One of the most challenging problems is known as islanding phenomenon. This situation occurs when a network is disconnected from utility grid and is energized by local DFPGs. It can possibly result in injury to utility personnel arriving to service isolated feeders, equipment damage, and system malfunction. In response to the concern, this dissertation aims to develop a robust anti-islanding algorithm for utility interconnection of DFPGs. In the first part, digital signal processor (DSP) controlled power electronic converters for utility interconnection of DFPGs are developed. Current control in a direct-quadrature (dq) synchronous frame is proposed. The real and reactive power is controlled by regulating inverter currents. The proposed digital current control in a synchronous frame significantly enhances the performance of DFPGs. In the second part, the robust anti-islanding algorithm for utility interconnection of a DFPG is developed. The power control algorithm is proposed based on analysis of a real and reactive power mismatch. It continuously perturbs (±5%) the reactive power supplied by the DFPG while monitoring the voltage and frequency. If islanding were to occur, a measurable frequency deviation would take place, upon which the real power of the DFPG is further reduced to 80%; a drop in voltage positively confirms islanding. This method is shown to be robust and reliable. In the third part, an improved anti-islanding algorithm for utility interconnection of multiple DFPGs is presented. The cross correlation method is proposed and implemented in conjunction with the power control algorithm. It calculates the cross correlation index of a rate of change of the frequency deviation and (±5%) the reactive power. If this index increases above 50%, the chance of islanding is high. The algorithm initiates (±10%) the reactive power and continues to calculate the correlation index. If the index exceeds 80%, islanding is now confirmed. The proposed method is robust and capable of detecting islanding in the presence of several DFPGs independently operating. Analysis, simulation and experimental results are presented and discussed.

Before studying to increase the catalyst utilization is one way to improve the performance of a fuel cell. But because it wastes a lot of time on making the hydrophobic pillared micro structures (HMPS) process. So this study aims to develop a fast and effective manufacturing method in order to increase the reaction surface area and catalyst utilization. The experiment has used the metal mesh stamping method to make the specific structure so as to increase the reaction surface area. The size of the metal mesh was the line path 35£gm, and the net square 70£gm*70£gm. The pressure was 300kg/cm2 and 500kg/cm2 that made the stamping structure in order to increase the reaction surface area. When the reaction surface area nearly increased 27 %, the performance also nearly increased 27 %; And when the reaction surface area nearly increased 36 %, the performance also nearly increased 36 %. So the increment of its performance nearly accorded with the increment of the reaction surface area. This method has saved a lot of time in the production process. Furthermore, the catalyst loading of cathode is halved in this experiment, the performance of fuel cell have no obviously decreased or reduced by half. As a result, the utilization of catalyst is raised.