Page 94 - Introduction to Transfer Phenomena in PEM Fuel Cells

Charge Transfer Phenomena 83
The main characteristics of a fuel cell can be summed up as a polarization
curve. This curve is a graph representing the voltage at the terminals of the
fuel cell as a function of the current intensity. A curve (I–V) is the most
common method of characterizing or comparing one fuel cell to another. The
polarization curve shows the voltage–current relationship as a function of the
conditions of use such as humidity, temperature, electric charge, the flow
density of the fuel and the oxidant. Polarization phenomena, which lower the
voltage when the current density increases, force the fuel cell outside its
limits (very low or very high current densities).
Finally, several analytical, empirical or semi-empirical models are
presented and compared to give an insight into the work already done on
mathematical models aimed at studying the performances (static or dynamic)
of the PEM fuel cell.