Solid oxide fuel cell different types

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. 

Several types of fuel cells have been developed and are classified according to the electrolytes used alkaline fuel cells, molten carbonate fuel cells, phosphoric acid fuel cells (PAFCs), PEMFCs, and solid oxide fuel cells (SOFCs). As shown in Figure 1.3, the optimum operation temperatures of these fuel cells are different, and each type has different advantages and disadvantages. 

All these cells differ in various respects like the type of electrolyte, fuel used, operating temperature etc. The work presented in this thesis focuses on solid oxide fuel cells and is explained in more detail in the following sections. 

There exist a variety of fuel cells. For practical reasons, fuel cells are classified by the type of electrolyte employed. The following names and abbreviations are frequently used in publications alkaline fuel cells (AFC), molten carbonate fuel cells (MCFC), phosphoric acid fuel cells (PAFC), solid oxide fuel cells (SOFC), and proton exchange membrane fuel cells (PEMFC). Among different types of fuel cells under development today, the PEMFC, also called polymer electrolyte membrane fuel cells (PEFC), is considered as a potential future power source due to its unique characteristics [1-3]. The PEMFC consists of an anode where hydrogen oxidation takes place, a cathode where oxygen reduction occurs, and an electrolyte membrane that permits the transfer of protons from anode to cathode. PEMFC operates at low temperature that allows rapid start-up. Furthermore, with the absence of corrosive cell constituents, the use of the exotic materials required in other fuel cell types is not required [4]. 

The efficiencies of the different energy conversion systems are compared in Fig. 3 as a function of the size of power plants. Figure 3 shows that the efficiencies of two types of fuel cell systems (phosphoric add fuel cell, PAFC, see Sect. 8.1.3.1.3 and solid oxide fuel cell, SOFC, see Sect. 8.1.3.2.2) are higher than those of engines and conventional power plants of comparable size. 

Carbonate Fuel Cell), and SOFC (Solid Oxide Fuel Cell). An exception to this classification is the DMFC (Direct Methanol Fuel Cell) which is a fuel cell in which methanol is directly fed to the anode. The electrolyte of this cell is not determining for the class. Table 1.1 compares the different types of fuel cell systems [2, 5-8]. A schematic representation of a fuel cell with reactant and product, and ions flow directions for these types of fuel cells are shown in Figure 1.2 [6]. 

Most engineering materials are polycrystalline in nature. The sohd electrolytes (SEs) [1-3] used in solid oxide fuel cells (SOFCs) are made of crystallites with a size of typically few micrometers. The SEs conduct ions exclusively by definition, and there are several different types of oxide... 

Solid Oxide Fuel Cells, Direct Hydrocarbon Type, Fig. 8 Temperature-programmed oxidation curves in 20 vol % O2 -I- He with samples of porous YSZ/Ce02 exposed to butane at 973 K for different times (From Ref. [62])... 

Many different types of fuel-cell membranes are currently in use in, e.g., solid-oxide fuel cells (SOFCs), molten-carbonate fuel cells (MCFCs), alkaline fuel eells (AFCs), phosphoric-acid fuel cells (PAFCs), and polymer-electrolyte membrane fuel cells (PEMFCs). One of the most widely used polymers in PEMFCs is Nalion, which is basically a fluorinated teflon-like hydrophobic polymer backbone with sulfonated hydrophilic side chains." Nafion and related sulfonic-add based polymers have the disadvantage that the polymer-conductivity is based on the presence of water and, thus, the operating temperature is limited to a temperature range of 80-100 °C. This constraint makes the water (and temperature) management of the fuel cell critical for its performance. Many computational studies and reviews have recently been pubhshed," and new types of polymers are proposed at any time, e.g. sulfonated aromatic polyarylenes," to meet these drawbacks. 

The acronym for fuel cell (FC) is used in the terminology denoting the different technological approaches. This chapter deals exclusively with hydrogen fuel cells and focuses on two types of cells Proton Exchange Membrane Fuel Cells (PEMFCs) and Solid Oxide Fuel Cells (SOFCs). 

Hydrogen is not the only energy source for fuel cells. There are many different types of fuel cells (e.g., solid oxide fuel cells and direct ethanol fuel cells) which do not use hydrogen. 

The major types of fuel for solid-oxide fuel cells (as the reactants being oxidized) are hydrogen and carbon monoxide. An important difference exists between these fuel cells and other types of fuel cells, in that various natural fuels or products of relatively simple processing of such fuels may also be utilized directly. 

In conclusion, despite some attractive properties for these embedded Pd Ce02/Al203 catalysts, they are not ideal for WGS. Still, there are clear indications that core-shell-type materials have very different properties from conventional catalysts. The easily reducible, ceria shell in this new type of material could allow these catalysts to find applications in other areas. Indeed, we will show later in this chapter how these materials exhibit superior stability in solid oxide fuel cell (SOFC) anodes (see Section 7.3.3). 

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