Author: admin
-
Introduction and Overview of Systems Analysis
In contrast to the battery, a fuel cell is typically a steady-state device. As such, the fuel and oxidant are supplied continuously. In the previous chapter, we focused on the electrochemistry of the fuel cell. Now we will examine the entire fuel-cell system. Many cells are combined to form a cell stack assembly (CSA), which…
-
Solid Oxide Fuel Cells
A second major type of fuel cell is the SOFC. Here the electrolyte is a ceramic material that conducts oxygen ions. The electrode reactions for a SOFC were provided in Table 9.2. Note that in contrast to the PEMFC, although the overall reaction is the same, water is produced at the anode rather than the cathode. Additionally,…
-
Proton-Exchange Membrane (PEM) Fuel Cells
The electrolyte in PEM fuel cells is a solid polymer material with covalently bonded sulfonic acid groups. These materials are similar to ion-exchange resins. A cation is associated with each negatively charged sulfonic acid group. For fuel-cell applications, the cations are protons. In other applications, see Chapter 14 and the chlor-alkali process, sodium ions are present rather…
-
Electrode Structure
Electrode structures were introduced in Chapter 5. One of the distinguishing features of a fuel-cell electrode is that three phases are present. First, there is a solid phase that is electronically conductive to supply or remove electrons. Second, an electrolyte phase that conducts ions is needed. The electrolyte may be solid or liquid. So far, this…
-
Current–Voltage Characteristics and Polarizations
A key objective in this chapter is to gain a detailed understanding of what is known as the polarization curve. This curve represents the steady-state relationship between the potential of the cell, Vcell, and its current density, i. It is typically measured experimentally. During this measurement, the temperature and pressure are held constant, and the flow of reactants…
-
Types of Fuel Cells
There are many different kinds of fuel cells, which are distinguished primarily by the electrolyte used and also by the type of fuel that is consumed. The most common fuel is hydrogen gas; hydrocarbons are frequently reformed to produce hydrogen for consumption in the fuel cell. Fuels other than hydrogen can also be used directly,…
-
Introduction
Operation of a methanol fuel cell is illustrated in Figure 9.1. This particular fuel cell uses a proton-exchange membrane separator in which the ionic current is carried by protons. In contrast to batteries, where we were careful to use the terms negative and positive for electrodes rather than anode and cathode, the terms anode and cathode…
-
Thermal Management Systems
The spirally wound cylindrical cell is particularly convenient to manufacture. Why then are these cells typically small? To answer this question, heat removal must be considered. A number of simplifying assumptions will be made, but the basic physics will provide clear guidance for the engineer. As was discussed in the previous chapter, during operation heat…
-
Battery Management
In order to get the most out of the battery and to ensure safe operation, current flow in and out of the cells that make up that battery must be carefully monitored and controlled. A battery management system (BMS) serves this function. Generally, we have no means of looking inside a cell or module after…
-
Use of Resistance to Characterize Battery Peformance
The laboratory tests to determine the capacity and rate capability of a cell that were described in Chapter 7 can also be applied to a battery and are not repeated here. Rather, the focus in this section is on the use of resistance to provide information on the power capability and health of the battery. Health in…