Page 91 - Introduction to Transfer Phenomena in PEM Fuel Cells

80 Introduction to Transfer Phenomena in PEM Fuel Cells
Complex models have technical advantages and therefore require more
information about the materials and constituents of the overall PEMFC.
2.7.1. Simple analytical models
These models attempt to represent the phenomena involved in a cell by
simple and short equations describing the reversible voltage and voltage
losses that may exist. Some initial studies, for example, that of Berger
[BER 68], give a theoretical insight into the calculation methodology of the
different voltage losses. Other groups of researchers aim to describe voltage
losses while developing simple and accurate models. The most complete of
these models, based on the study of a Ballard IV fuel cell, was developed by
Amphlett et al. [AMP 95a, AMP 95b] who wanted to generalize the results
of their work by a third approach in [MAN 00].

Other models, including that of Larminie and Dicks [LAR 03], describe
the notion of internal current and include a simplified dynamic performance
model of the fuel cell.

2.7.2. Complex analytical models

Complex analytical models must take into account many of the
phenomena occurring in the fuel cell. In addition, the generation of these
models requires a long period of expertise and observation of battery
behavior under different conditions. The work of Murgia et al. [MUR 02],
Bernardi and Verbrugge [BER 92], Nguyen and White [NGU 93] and
Eikerling et al. [EIK 98] have been the subject of such a modeling category.

2.8. Empirical models

Due to the complexity and interdependence of the variables influencing
the performance of the PEMFC, empirical equations could be used to predict
the polarization curve. The advantage of this approach is that it is relatively
simple to accurately predict the particular polarization curve. The
disadvantage of this approach is that the polarization curve must be
recalculated for any modification of operating conditions (such as humidity
or temperature). An empirical equation (now a reference) was introduced in
1995 by Kim et al. [KIM 95] and gives a more accurate prediction of the