Fuel cell basic operating principles

BP) acts, on the one hand, as a positive cathode for one cell and, on the other, as a negative anode for the next cell. A schematic diagram of the fuel cell configuration and basic operating principles of a hydrogen-fed PEMFC and a DMFC are shown in Figure 5.1. 

At the heart of a PEM fuel cell is a polymer membrane that has some unique capabilities. It is impermeable to gases but it conducts protons (hence the name, proton exchange membrane). The membrane that acts as the electrol5q e is squeezed between the two porous, electrically conductive electrodes. These electrodes are typically made out of carbon doth or carbon fiber paper. At the interface between the porous electrode and the polymer membrane there is a layer with catalyst particles, typically platinum supported on carbon [1]. A schematic diagram of cell configuration and basic operating principles is shown in the Figure in.l. 

Aside from the original assumption of a lumped analysis, thus far there have been no other assumptions or approximations to the model. The model relies completely on basic thermodynamic principles, a known cell performance R(I), and rigorous mathematical operations. To solve the model, we need to know the bulk mass and heat capacity of the cell, M and C, respectively the reactant supply flow rate (m = fuel flow + air flow) the inlet temperature and pressure and the change in stream composition due to the electrochemical reaction, AX, so that the change in enthalpy can be calculated the electrical load current, / and the inlet and exit temperatures, Tm and rout. 

Basic Principle of Operation of Polymer Electrolyte Membrane Fuel Cells.760... 

Equation (3) and (4) mean that the supply of the energetic e is needed to split water. This is the basic principle of water-electrolysis. The PEMFC is just the reverse operation of the SPE. Hydrogen fuel is decomposed into 2e and 2H+ by the catalytic cathode. The protons pass through the solid polymer (electrolyte) and arrive at the anode (A) to react with the electrons and the supplied oxygen. Then, water is produced. The electrons come to A via the external resistance. This fuel cell generates, ideally, about 1 V-direct current power. A stack of the cells is constructed to give the output power with, for example, 25 kW, which is set together to drive the vehicles. 

While there are many different fuel cell designs, the basic principle is similar (Figure 1.1). The proton exchange membrane (PEM) fuel cell currently is preferred for use in vehicles because of its low operating... 

To understand the basic principles of operation of an energy conversion or storage device it is important to know what an electrochemical cell is. Basically, it is a device in which a chemical reaction either generates or is caused by an electric current. A galvanic cell is an electrochemical cell in which a spontaneous chemical reaction is used to generate an electric current. An electrolytic cell, in turn, is an electrochemical cell in which a reaction is driven in its nonspontaneous direction by an externally applied electric current. There are three types of galvanic cell the primary, the secondary, and the fuel cell [5,6]. 

The basic components of a general fuel cell are two porous electrodes, i.e. anode and cathode, which are separated by a solid or liquid electrolyte. The electrolyte is impervious to gases. Fuel is supplied to the anode side and air is supplied to the cathode side. The oxidation reaction is made possible by conduction of ions through the electrolyte. Although the basic principle behind the operation of a fuel cell is quite simple, many challenges have to be overcome before its successful implementation. 

Basic Principles of Single-Chamber Fuel Cell Operation... 

Figure IILl. The basic principle of operation of a PEM fuel cell...

Chapter 2 summarizes the operating principles of the fuel cells in order to provide an understanding of the basic operations. 

Fuel Cells Principles, Design, and Analysis considers the latest advances in fuel cell system development and deployment and was written with engineering and science students in mind. This book provides readers with the fundamentals of fuel cell operation and design and incorporates techniques and methods designed to analyze different fuel cell systems. It builds on three main themes basic principles, analysis, and design. 

Direct methanol fuel cells are a class of polymer electrolyte membrane (PEM) fuel cells that typically employ a cation exchange membrane to separate the anode and cathode compartments. To illustrate the basic principles of DMFC operations, we shall take a typical, liquid-feed cell with a cation exchange membrane (alkaline exchange membranes are an alternative, and these are discussed later in this chapter). This is depicted in Figure 5.1. 

---