Fuel cells basic elements

A fuel cell has two basic elements a fuel delivery system and an electro-chemical cell that converts the delivered fuel into useful electricity. It is this unique combination that enables fuel cells to potentially offer the best features of both heat engines and batteries. Like batteries, the cell generates a dc electric output and is quiet, clean, and shape-flexible, and may be manufactured using similar plate and filmrolling processes. By contrast, the fuel delivery system ensures that fuel cells, like heat engines, can be... 

The PEM cell is the cleanest fuel cell since the fuel is hydrogen, the oxidant oxygen and the product water. Although it clearly falls outside the scope of a text focused on electroceramics there are good reasons for prefacing the present discussion with a brief outline of those elements of the science and technology basic to it and common to the ceramics-based fuel cells. Also, for an intelligent... 

Elementary Na/S battery science The basic science of the Na/S cell is identical to that of the fuel cell. In both cases the essential is an electrolyte. On one side of the electrolyte membrane there is a source of sodium ions at a particular chemical potential, and on the other side a sink for the ions at a relatively lower chemical potential. The elements of the process are illustrated in Fig. 4.28. 

This chapter has provided basic electrical fundamentals, including concepts and definitions for circuit elements, and their relationships within electric circuits. Various basic AC electric circuits were also presented. Following upon primary circuit theories, the concept of electrochemical impedance spectroscopy and basic information about EIS was introduced. This chapter lays a foundation for readers to expand their study of EIS and its applications in PEM fuel cell research and development. 

In summary, simple combinations of elements and basic equivalent circuits for electrochemical systems have been introduced in this section. Although these models are relatively simple, they are commonly employed in the investigation of electrochemical systems, including fuel cells. A real electrochemical system may be much more complicated. However, complicated electrochemical systems can still be constructed from these basic equivalent circuits. 

The basic elements of a SOFC are (1) a cathode, typically a rare earth transition metal perovskite oxide, where oxygen from air is reduced to oxide ions, which then migrate through a solid electrolyte (2) into the anode, (3) where they combine electrochemically with to produce water if hydrogen is the fuel or water and carbon dioxide if methane is used. Carbon monoxide may also be used as a fuel. The solid electrolyte is typically a yttrium or calcium stabilized zirconia fast oxide ion conductor. However, in order to achieve acceptable anion mobility, the cell must be operated at about 1000 °C. This requirement is the main drawback to SOFCs. The standard anode is a Nickel-Zirconia cermet. 

Colloidal Pt/RuO c- (C5 0.4nm) stabilized by a surfactant was prepared by co-hydrolysis of PtCU and RuCls under basic conditions. The Pt Ru ratio in the colloids can be between 1 4 and 4 1 by variation of the stoichiometry of the transition metal salts. The corresponding zerovalent metal colloids are obtained by the subsequent application of H2 to the colloidal Pt/Ru oxides (optionally in the immobilized form). Additional metals have been included in the metal oxide concept [Eq. (10)] in order to prepare binary and ternary mixed metal oxides in the colloidal form. Pt/Ru/WO c is regarded as a good precatalyst especially for the application in DMECs. Main-group elements such as A1 have been included in multimetallic alloy systems in order to improve the durability of fuel-cell catalysts. PtsAlCo.s alloyed with Cr, Mo, or W particles of 4—7-nm size has been prepared by sequential precipitation on conductant carbon supports such as highly disperse Vulcan XC72 [70]. Alternatively, colloidal precursors composed of Pt/Ru/Al allow... 

Fuel cells are composed of galvanic elements in which the reactants and the products are continuously supplied and removed. The basic idea dates back to Schonbein and Grove [11, yet enthusiasm and research activity was never as intense as today. 

In active fuel-cell hybrid systems, the coupling between fuel cell and energy storage system is done via power electronic devices. The main elements are DC-DC converters. The following basic types exist [26] ... 

In Figure 36.13, four elements A, B, C, and D are also marked. These are the basic combination elements used to make a fuel-cell hybrid system out of a pure fuel-cell system. In the next step, these elements are combined with the basic types in Figure 36.13 to obtain a second stage of fuel-cell hybrid systems. 

An overview of possible fuel-cell hybrids is presented in Table 36.4, indicating which initial concept is combined with which combination element. The resulting final concepts are enumerated according to the matrix in Figure 36.14. The basic types in Figure 36.13 result from the first combination step. For concept 1.2, only combination elements A and C are possible. Using combination element B will lead to a concept with two DC-DC converters in a row. They could be combined to make a single DC-DC converter. Combination element D is also not possible, as this would result in four DC-DC converters. Table 36.4 also indicates whether the final concept is a passive or an active hybrid or a mixture of both. 

Table 4.2 shows the values of enthalpy of formation and absolute entropy of the basic elements of a hydrogen-oxygen fuel cell with reference state considered as 298 K and 0.1 MPa for the enthalpy and 0 K and 0.1 MPa for the absolute entropy. This is reproduced from Table C.7. 

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