Individual fuel cell

Design Principles An individual fuel cell will generate an electrical potential of about 1 V or less, as discussed above, and a current that is proportional to the external load demand. For practical apph-cations, the voltage of an individual fuel cell is obviously too small, and cells are therefore stacked up as shown in Fig. 27-61. Anode/ electrolyte/cathode assemblies are electrically connected in series by inserting a bipolar plate between the cathode of one cell and the anode of the next. The bipolar plate must be impervious to the fuel... 

Because each individual fuel cell will operate at 400 mA/cm, we determine the total area required as,... 

As mentioned, there are also models of complete fuel-cell power systems in which the stack is but one component. These models have the benefit of examining true designs and the interconnections between components, but they usually require an even weaker model of an individual fuel cell. In fact, the entire... 

Single Celt. Under load, the voltage of one individual fuel cell element is less than one volt, Therefore, the assembly ol many cells, connected in senes as a stack, is required. Each individual cell contains the elements needed for feeding reactants to the electrode surface, and removal of water front the cell, as shown in Fig. 1 for a hydrogen air-cell with acid electrolyte. 

The core of the Ballard fuel cell consists of a membrane electrode assembly (MEA) that is placed between two flow-field plates. The flow-field plates direct H2 to the anode and Oz (from air) to the cathode. To obtain the desired amount of electric power, individual fuel cells are combined to form fuel cell stacks. Increasing the number of cells in a stack increases the voltage, and... 

An additional component in a fuel cell is the interconnects or bipolar plates. This is a vital component in SOFC development, since it forms the connection between the anode of one cell and the cathode of the next in a stacked arrangement. That is, these components operate as connections between individual fuel cells in a fuel cell stack [128], Then, the interconnects have to be electronically conductive and also possess good impermeability, chemical stability, and good mechanical properties since these components seal the gas chambers for the oxygen and fuel gas feed at either the anode or the cathode [66,137],... 

Figure 2.56 shows a variety of stacked cell designs employed by SOFCs. Since an individual fuel cell produces a low voltage (typically < 1V), a number of cells are connected in series forming a fuel cell stack. An interconnect comprising a high-density material is used between the repeating anode-electrolyte-cathode units of... 

Specify production and distribution pathways for individual fuel-cell fuels. 

SCHEMATIC LAYOUT OF FUEL-CELL UNITS 16.2.1 An Individual Fuel Cell... 

As a rule, any individual fuel cell has a low working voltage of less than 1 V. Most users need a much higher voltage of, for instance, 6, 12, 24 V or more. In a real fuel-cell plant, therefore, the appropriate number of individual cells is connected in series, forming stacks (batteries). 

The heart of any fuel-cell power plant (in Russia, it is called electrochemical generator) or direct energy converter is one or a number of stacks built up from individual fuel cells. Such plants include a number of auxiliary devices needed to secure stable, uninterrupted functioning of the stacks. The number or type of these devices depends on the fuel cell type in the stacks and the intended use of the plant. In the following, we list the basic components and devices. 

A rather dangerous situation arises when individual fuel cells of a multicell fuel-cell stack deviate. Such nonuniformity is most often because of problems in reactant supply. Two systems of gas supply exist parallel and series. In parallel supply, the gas reaches each fuel cell through a narrow channel coming from a common manifold. The pressure in these channels is the same for all elements where they leave the manifold, but on account of differences in gas flow resistance, the amounts of gas (or the pressure) reaching each fuel cell may differ. In series supply, gas is fed to a first individual cell, flows through it, and continues to the next cell, and so on. In each fuel cell in series the amount of gas needed for the... 

Bipolar plates have a number of functions in fuel-cell batteries. Mechanically, they are the backbone of the individual fuel cells and of the battery as a whole. They provide the electrical contact between individual fuel cells in the stack and channel the reactant supply to the entire working surface area of the electrodes. The plates must meet a number of requirements in order to fill all these functions They must (i) be sufficiently sturdy, (ii) be electronically conducting, (iii) have a low surface resistance in contact with other conductors, (iv) be impermeable to gases, (v) be corrosion resistant under the operating conditions of the fuel cells. 

The peripheral equipment needed for direct methanol fuel cells is largely analogous to that of polymer electrolyte membrane fuel cells. The mechanical basis of fuel cells and stacks on the whole consists of bipolar plates between which the sandwiched membrane-electrode assemblies are arranged. For the venting of heat, cooling plates with a circulating heat transfer agent are set up in a particular order between individual fuel cells in the stack. 

The fuel cell components have thicknesses as follows the anode is 0.8-1.5mm thick the cathode, 0.4-1.5 mm, the matrix, 0.5-1 mm. In a fuel cell of the filter-press type, the individual cells are separated by bipolar plates made of nickel-plated stainless steel, contacting the anode with their nickel side, and the cathode with their steel side. All structural parts are made of nickel or nickel-plated steel. In a working fuel cell, the temperature of the outer part of the matrix electrolyte is lower than that of the inner part, so that in the outer part the electrolyte is solidified. This provides for tight sealing around the periphery of the individual fuel cells. 

When assembling a filter-press battery from individual fuel cells of any type, considerable compression must be applied in order to minimize the contact... 

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