Different Types of Fuel Cells

Various types of fuel cells have been developed to generate power according to the applications and load requirements (Chaurasia, 2000). There are several types of electrolyte, which plays a key role in the different types of fuel cells. It must permit only the appropriate ions to pass between the anode and cathode. The main electrolyte types are alkali, molten carbonate, phosphoric acid, proton exchange membrane (PEM), and solid oxide. The first three are liquid electrolytes, the last two are solids. 

There are several types of fuel cells with different characteristics and uses. Fuel cells are usually classified according to the electrolyte that is used. Table 7.1 shows some common fuel cell types and their uses. 

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There are six different types of fuel cells (Table 1.6) (1) alkaline fuel cell (AFC), (2) direct methanol fuel cell (DMFC), (3) molten carbonate fuel cell (MCFC), (4) phosphoric acid fuel cell (PAFC), (5) proton exchange membrane fuel cell (PEMFC), and (6) the solid oxide fuel cell (SOFC). They all differ in applications, operating temperatures, cost, and efficiency. 

Most fuel cells being developed consume either hydrogen or fuels that have been preprocessed into a suitable hydrogen-rich form. Some fuel cells can directly consume sufficiently reactive fuels such as methane, methanol, carbon monoxide, or ammonia, or can process such fuels internally. Different types of fuel cells are most appropriately characterized by the electrolyte that they use to transport the electric charge and by the temperature at which they operate. This classification is presented in Table 7.4. 

This section aims to give a brief review of the different types of fuel cell and their most important properties. With regard to hydrogen production, the focus is on the fuel gases used and the requirements made of their purity. Within the scope of this publication, it is not possible to describe the different fuel cell systems in any detail. References are made to the relevant specialist literature (see also, the Further reading section at the end of this chapter). 

There is no such thing as the fuel cell , but many different types of fuel cell, which differ mainly with regard to the electrolyte, the chemical reaction and the working... 

Figure 13.5. Different types of fuel cell (Jorissen and Garche, 2000).

The key question for mobilising further market potential is whether a steady decrease in fuel-cell costs and an increase in lifetime can be achieved. Many energy technologists believe the future of the different types of fuel cell to be very bright because of anticipated efficiency improvements and the low emissions associated... 

The so-called microbial fuel cells (MFC) are a completely different type of fuel cell. Here, bacteria are used to convert a bio-usable substrate directly into electricity. In the future, it might be possible to run an MFC for medical purposes by using glucose directly from the patient s bloodstream (Logan et al., 2006). 

In low-temperature fuel cells (PEFC, AFC, PAFC), protons or hydroxyl ions are the major charge carriers in the electrolyte, whereas in the high-temperature fuel cells, MCFC, ITSOFC, and TSOFC, carbonate ions and oxygen ions are the charge carriers, respectively. A detailed discussion of these different types of fuel cells is presented in Sections 3 through 8. Major differences between the various cells are shown in Table 1-1. 

In this paper, we will discuss the thermodynamic principles involved in fuel cells as well as the kinetic aspects of their half cell reactions. In the kinetic considerations, we will also touch, briefly, on the fundamental problem of electrocatalysis. We will then proceed to describe different types of fuel cells and finally present the status of this new electrical generation device. 

Different types of fuel cells have been developed and are classified mainly according to (i) the type of fuel, (ii) the operating temperature range and/or electrolyte or (iii) the direct or indirect utilization of fuel [19]. The state-of-the-art and the different applications of fuel cells are summarized in Table 1.1. 

Many different types of fuel cell are possible. The fuel in the cell described above is pure hydrogen, although of course an oxidizing agent, in this case oxygen, is also needed. Other fuels can be used, although the reactions are more complicated. Various electrolytes are also possible. 

Many different types of fuel cells are currently under development. Many of these are named after the electrolyte or fuel used in the cell. The polymer electrolyte membrane or proton exchange membrane cell (pern) also uses hydrogen and oxygen. The... 

Anodic hydrogen oxidation and cathodic oxygen reduction in different types of fuel cells... 

The material used for the electrolyte determines many of the fuel cell s properties, including its operating temperature, and thus is used to distinguish the different types of fuel cells. All the leading fuel cells are discussed in the sections that follow. 

In the last few decades the development of different types of fuel cells has greatly stimulated research into basic processes occurring in these cells. It is the aim of this monograph to describe and discuss the progress made in our understanding of these electrochemical processes. 

The fuel cell electrode reactions are catalyzed by different materials in different temperature ranges. A classification of the fuel cells can be made on the basis of the electrolyte, which in turn determines the operating temperature and, with it, the catalysts to be applied in the electrodes. The electrode reactions that take place in the different types of fuel cells are summarized in Table 3, which also lists the electrolytes and operating temperatures [56]. 

Table 3. Different types of fuel cells, electrode reactions and operating temperatures. 

The other parameters such as reagents, temperature, pressure, and application of the fuel cell system depend on the electrolyte in the cell. Table 2 lists these parameters for different types of fuel cells. 

Fuel cells are usually classified by the electrolyte employed in the system, which determines the operating temperature and, hence, the fuel that could be utilized. Table 1 summarizes the characteristics of different types of fuel cells. ° ... 

A variety of cogeneration processes has been recently described in the literature. A brief list is shown in Table 10.2, where representative examples involving porous materials and different types of fuel cells are included. In most cases, electrocogeneration allows for a simultaneous removal of organic pollutants and flue gas emissions. Examples of this possibility will be treated in Chapter 12. 

Table 3.2 reports the classification of the different types of fuel cells with some technical characteristics [6]. In this table the different electrolytes are specified together with the type of ions exchanged through them, while the catalysts indicated are those used on both anode and cathode to accelerate the semi-reactions (not necessary for SOFC thanks to their high operative temperature). 

Figure 6.4 Electrochemical reactions occurring in different types of fuel cell/...

The tremendous progress with respect to improving performance and longterm stability and reducing costs of different types of fuel cell, however, has essentially been achieved by sophisticated engineering efforts, making use of the few existing materials, such as Nafion and Pt-based electrocatalysts. 

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