Hydrogen Utilization: Fuel Cells - Hydrogen Generation, Storage, and Utilization - page 156

FIGURE 9.2 Schematic of PEMFC and stack. Reproduced with permission from Costamanga and
Srinivasan [19].
Legislations and the U.S. Partnership for a New Generation of Vehicles
program (PNGV), which was initiated in 1993 and sponsored by the U.S.
government and the big three U.S. automobile manufacturers, stimulated its
worldwide renaissance for the transportation application [14]. This renais-
sance, in turn, gave birth to the R&D programs for portable power and power
generation applications [15]. Today, PEMFCs are at the forefront of the dif-
ferent types of fuel cells [16].
Figure 9.2 illustrates the main components of a PEMFC power source: (i)
the single cell containing the porous gas diffusion electrodes (anode and
cathode), the proton conducting electrolyte, anodic and cathodic catalyst
layers, mostly deposited on the electrode (but more recently in some work
on the proton conducting membrane), and current collectors with the reactant
flow fields, (ii) a stack of cells in series, with the current collectors also
serving as the bipolar plates, (iii) cell stacks (modules) connected in series
or parallel, depending on the voltage and current requirements for specific
applications, and (iv) auxiliaries for thermal and water management and for
compression of gases [17]. The unique feature of the PEMFC, as compared
with other types of fuel cells (except for the solid oxide fuel cell), is that it
has a solid proton conducting electrolyte. PEMFCs operate at low tempera-
ture (below 1008 K) and generate a specific power (W·kg −1 ) and power
density (W·cm −2 ) higher than any other type of fuel cell. It is for this reason