Fuel cell current/voltage curve

In Figs. 4.15,4.16,4.17, and 4.18 the effect of fuel dilution by nitrogen at fixed temperature is shown with reference to the cell current-voltage curve. 

In Fig. 4.30 the effect of the different direct fuel processing paths is shown at fixed temperature (800°C) on the cell current-voltage curves. In particular, in the case of steam reforming operation the effect of water on a greater decrease in open... 

Fig. 26. Comparison of current voltage curves of membrane fuel cells using impregnated PTFE-bonded eleclrodes (a) prepared from soot activated by 20 wt% Pt and (b) with additional Pt sputtering of ihe contacting surface.

FIGURE 8.16 Schematic fuel cell polarization voltage [V] vs. current density [A/cm2] curve. 

Figure 4. Current-voltage curves for 50 50 mm anode-supported single cells with a YSZ electrolyte applied by sol-gel technique and with an LSCF-type cathode as a function of the temperature (fuel gas H2 (3% H2O) = 1000 ml/min, oxidant air = 1000 ml/min).

Figure 4.5.40. Schematically representation of the corelation between impedance of fuel cell and current/voltage curve, after Wagner [2002].

The proton conductive polymer electrolyte used to separate the anode and cathode compartments of fuel cells. The membrane replaces the liquid electrolytes used in some fuel cells. The voltage produced by a fuel ceU stack at a defined current density. A performance or polarization curve refers to a plot of the cell potential (V) versus current density (1) under specified conditions of pressure, temperature, humidity, and reactant stoichiometry. 

Figure 21.2 shows a typical polarization curve (or current-voltage curve) of PEMFCs. This curve results from both the anodic HOR and the cathodic ORR reactions. The actual celt voltage is much lower than the ideal celt voltage and the theoretical cell voltage. When the current is drawn from a fuel cell, the actual cell voltage will drop from its ideal due to several types of irreversible losses, as shown in Figure 21.2. The drop is mainly caused by mixed potential and fuel crossover, activation overpotential, ohmic overpotential, as well as mass transfer (concentration) overpotential.

Choi et al. (2001) applied plasma etching and plasma palladium sputtering to Nafion membranes. This treatment depressed methanol crossover by about 35%. The current-voltage curves for fuel cells with treated membrane were better than those for fuel cells with an untreated membrane (data concerning the conductivity change were not reported in the paper). 

Figure I.6a displays a selection of fuel cell polarization curves extracted from publications that span a period of 125 years. The ordinate depicts the fuel cell voltage Eceii (jo) as given in Equation 1.21. The abscissa represents, on a logarithmic scale (to the base of 10), the fuel cell current density that has been normalized to the surface area-specific mass loading of Pt, mpf.

The polarization curve represents the fuel cell output voltage as a function of the current density in steady state. Electrical power, in watts, supplied by the fuel cell to the load, can be determined using the following equation ... 

FIGURE 12.19. Current-voltage curve of a tubular solid oxide fuel cell at different temperatures. (From Singhal,... 

FIGURE 13.2. Typical current-voltage curve of a fuel cell obtained by varying the external load. (Reprinted with permission from Debenedetti, RG and Vayenas, C.E., Chem. Eng. Sci., 1983, 38, 1817. Copyright 1983 Elsevier Science Ltd.)... 

Similar current-voltage curves were reported [27] for the hydrogen-oxygen fuel cell with different solid solutions of Ce03—La2 03 as electrolyte. However, the solid electrolytes possessed some electronic conductance. Although the addition of Th02 reduced the electronic conductance, it led to an undesirable decrease in performance. 

In fact, in fuel cell modeling only two levels have been used to date ofif-design operation (based on the current-voltage curve) and dynamic models. Thus far, the design point model of the SOFC is not specific in terms of details, and often instead of any model there are merely assumed constant values of fuel cell efficiency and voltage. 

The typical current-voltage curve is a result of many parameters, which influence fuel cell performance. The parameters can be divided into two groups ... 

Operation of a singular cell is often defined by the current-voltage curve, as with voltaic batteries. Seeing as there are many differences between fuel cells and... 

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