燃料电池及应用.ppt

Chapter 1 Topics: Introduction, Basic Principles Efficiency and Open Circuit Voltage, Electrochemistry of Fuel Cells Operational Fuel Cell Voltages – Real Cell Voltages Proton Exchange Membrane Fuel Cells (PEMFC) Alkaline Electrolyte Fuel Cells (AFC) Medium and High Temperature Fuel Cells (PAFC, MCFC, and SOFC) Fueling Systems Engineering Components of Systems Fuel Cell Units (Cells) The voltage of a fuel cell is quite small, about 0.7 volts when drawing a useful current. So many fuel cells (called cells) have to be connected in series called “stack”. Simple edge connection: connecting the edge of each anode to the cathode of the next cell. The problem with this method is that the electrons have to flow across the face of the electrode to the current collection point at the top edge. A small voltage drop along the passage of the electrons will induce a substantial loss in total voltage output. Simple edge connection (continue) (continue) Bipolar Plate Connection: This makes connections all over one cathode and the anode of the next cell (hence called “bipolar”), at the same time the bipolar plate serves as a means of feeding oxygen to the cathode and fuel gas to the anode. Although a good electrical connection must be made between the two electrodes, the two gas supplies must be strictly separated. Bipolar plate connection (continue) Fuel Cell Stack (continue) (continue) (continue) (continue) Types of Fuel Cells The two fundamental technical problems with fuel cells are: the slow reaction rate, leading to low currents and power, That hydrogen is not a readily available fuel. To solve these problems many different fuel cell types have been tried. The different fuel cell types are usually distinguished by the electrolyte that is used. * Fuel Cells and Applications S. K. Wang Dept. of Mechanical and Automation Engineering I – Shou University Spring, 2005 Why fuel cells? What is a fuel cell? How does a fuel cell work? What are concepts of “fuel”