Components of a Fuel Cell

In accordance with thermodynamic laws, only the Gibbs free energy, AG °, of the overall fuel cell reaction can be converted into the equivalent electric cell potential, AE° these two quantities are linked via 

The thermodynamic efficiency of a fuel cell is defined as the ratio between AG° and the enthalpy of reaction, AH°, p = AG°IAH°, and is not, unlike thermal external or internal combustion engines, limited by the ideal Carnot cycle. 

hydrogen gas (red), comes in contact with a catalytically active electrode (the anode), on the surface of which the hydrogen molecule splits into protons and electrons in the hydrogen-oxygen reaction (HOR) according to 

The protons travel across the ion-conducting (liquid) electrolyte to the opposite electrode (the cathode), where they recombine with the oxidant, here oxygen (blue), 

A second class of fuel cells employs hydroxide-conducting (alkaline) electrolytes, again either in form of a solid membrane (alkaline membrane fuel cells) or a liquid electrolyte (alkaline fuel cells). While the modem era of fuel cells began with the latter type, the former type is under intense research today because a stable, highly conducting alkaline membrane with good C02 tolerance has remained elusive to date. 

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Figure 13.12. Shares of added value of the individual components of a fuel cell (by the target costing method) and a combustion engine drive system (Schirrmeister et al., 2002).

It is important to note that Vie and Kjelstrup [250] designed a method of measuring fhe fhermal conductivities of different components of a fuel cell while fhe cell was rurming (i.e., in situ tests). They added four thermocouples inside an MEA (i.e., an invasive method) one on each side of the membrane and one on each diffusion layer (on the surface facing the FF channels). The temperature values from the thermocouples near the membrane and in the DL were used to calculate the average thermal conductivity of the DL and CL using Fourier s law. Unfortunately, the thermal conductivity values presented in their work were given for both the DL and CL combined. Therefore, these values are useful for mathematical models but not to determine the exact thermal characteristics of different DLs. 

This introduction illustrates that the membrane is one key material component of a fuel cell whose properties limit the achievable performance. The ideal fuel cell membrane should... 

PVDF/graphite composites can lend themselves as the best materials for both molded and coated plates. A key component of a fuel cell stack is the bipolar plate. Also referred to as a water transport plate or a separator... 

A fuel cell is an electrochemical device that converts the chemical energy of a fuel and oxidant directly into low-voltage, direct cnrrent electricity. Unlike batteries, the fuel and oxidant are stored externally and are fed to the electrodes as needed. For most terrestrial fuel cells, the oxidant is atmospheric oxygen, whereas the fuel can be H2 or a low-molecular-weight hydrogen-containing compound such as methanol. For H2 and O2 reactants, operation and components of a fuel cell are illustrated in Figure 26.39. 

The components of a fuel cell that act as the current collector for the positive electrode in one cell and for the negative electrode in the adjacent cell and also serve to join the cells electrically. The cells in a stack are series-connected and so allow the voltage to be built up. 

A component of a fuel cell that consists of a polymer membrane electrolyte coated with (or sandwiched between) positive and negative electrodes and then placed between bipolar plates. 

In last few years there has been considerable amount of activity in using ink-jet technology for printing different components of a fuel cell particularly those for polymer electrolyte membrane fuel cell (PEMFC) and direct methanol fuel cell (DMFC). The various components reported to have been printed using ink-jet are as follows ... 

Main Components of a Fuel Cell System Powertrain 4.5.1 Fuel Cell Stack... 

The final component of a fuel cell to be discussed in this chapter is the current collector plates (CCP) or more commonly called the bipolar plates (BP) or flow field plate (FFP). As observed in Fig. 7.1 the fuel cell stack is composed by a number of BP, each of which will separate a pair of MEA and with two end plates completing the stack. At either side of the BP, an arrange of channels provide the flow paths for the fuel and oxygen. One of those faces is in contact with the anode of one MEA and the other face with the cathode of the other MEA, hence, the name bipolar plate. The end plates have channels only on one face, and the stack is typically completed by two metal plates with a series of bolts that holds the stack... 

A breadboard system is often a necessary step in evaluating the major components of a fuel cell system together, and it is easier to rearrange the parts during the evaluation process. Figure 5.23 shows a breadboard system with most of the major parts laid on a table, and some parts placed beside and underneath the table. Figure 5.24 shows the V-I and W-I curves of the stack obtained from this system. It should be noted that the performance of a stack tested in a system can be quite different from that tested on a test stand, because the system may not be able to offer the best conditions for the stack. 

Major components of a fuel cell system developed by Shanghai Shenli High Tech. Company. Courtesy of Shanghai Shenli High Tech. Company. 

As has been defined, a fuel-ceU hybrid consists of a fuel cell with an energy storage system and optionally a DC-DC converter for power control. The fuel-cell system with aU peripheral components such as pumps and blowers is controlled, in addition to the power distribution via the DC-DC converter. In the following, the main components of a fuel-cell hybrid system are described. 

A solid polymer thin film that is proton conducting and functions as the central component of a fuel cell. 

BoP Balance of plant - summary term for all components of a fuel cell... 

The roughness factor is an important parameter in describing the dispersion and porous structure of the active components of a fuel cell catalyst. It is defined as ... 

Furthermore, the fuel cell itself is generating nniegulated DC. The electric energy thus needs to be converted into a form that is compatible for the application intended. Figure 4.13 shows the general components of a fuel cell system. The integration of fuel cells into an application thns constitntes a system challenge. 

At the moment, the fuel cell technology is under extensive development and is considered as one of the viable options for high-efficiency power generation. As shown in Figure 8.1, four main components of a fuel cell are (1) electrolyte, (2) electrodes (anode and cathode), (3) gas diffusion layers, and (4) chemicals (fuel and oxidizer). The electrolyte [e.g., KOH(aq)] is needed to conduct OH (aq) ions from the cathode to the anode. The electrodes are needed to speed up electrochemical reactions and reduce the charge transfer overpotentials. The gas diffusion layers are needed to provide the desirable mass transport of chemicals to (from) the electrodes, reduce... 

Four main components of a fuel cell are (1) electrolyte, (2) electrodes, (3) gas diffusion layers, and (4) chemicals (fuel and oxidizer). Different kinds of fuel cells have different materials of the components. 

The main components of a fuel cell stack are the membrane electrode assemblies or MEAs (membranes with electrodes on each side with a catalyst layer between them), gaskets at the perimeter of the MEAs, bipolar plates, bus plates (one at each end of the active part of the stack) with electrical connections, and the end plates (one at each end of the stack), with... 

The individual components of a fuel cell stack, namely MEAs, gas diffusion layers, and bipolar plates, must be somehow held together with sufficient contact pressure to (1) prevent leaking of the reactants between the layers and (2) to minimize the contact resistance between those layers. This is typically accomplished by sandwiching the stacked components between the two end plates connected with several tie-rods around the perimeter (Figure 6-30) or in some cases through the middle. Other compression and fastening mechanisms may be employed too, such as snap-in shrouds or straps. 

While the fuel cell stacks are the main functional component of a fuel cell power system, there are many other ancillary components that are needed for a complete system. Because the ancillary components tend to be off-the-shelf or at least minor modifications of commercial/industrial products, a much higher level of cost estimation can be to arrive at cost estimates. The magnitude of the price discount varies depending on purchase quantity and the specific component. 

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