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| In
order to achieve appreciable
output voltages several
individual fuel cells must
be combined to a unit called
a fuel cell stack. |
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 The
diagram on the transparency shows a fuel cell
stack consisting of three individual fuel
cells. These are represented as yellow and
blue units where the electrolyte (or PEM)
is shown in yellow and the electrodes in blue.
Adjacent cells are connected by a separator
plate (gray with horizontal and vertical grooves)
which has a number of task: 1) to provide
the electrical connections between the cells,
2) to facilitate gas transport to and away
from the cells, 3) to dissipate the heat produced
in the cells, and 4) to seal off adjacent
cells and prevent fuel and oxidant leakage.
In the figure the electrical connections are
not shown explicitly, the gas transport channels
are represented by horizontal (hydrogen) and
vertical (oxygen supply and water exhaust)
grooves. Special end plates are attached to
the end members of the stack (left and right
side, grey). The end plates have electrical
connectors for the external circuit as well
as hook-ups for gas supply and possibly coolant.
Depending on the stack's total output power
and the heat generation associated with it
stacks are either air- or water-cooled.
Simply by varying the number of individual
cells, stacks can be designed for any desirable
output voltage. Since the cells are electrically
connected in series adding a cell will increase
the output voltage. The total output voltage
of stack is given by the sum of all individual
voltage of cell.
Source: h-tec GmbH © h-tec GmbH
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