integration of solid oxide fuel cells and ... - Ea Energianalyse

5.3. Partial optimization of standard parameters
Figure 5.15: A Blower Power and Air Utilization in the SOFC. B Nernst potential, cell voltage
and Area Specific Resistance.
Figure 5.15A+B shows why the electrical efficiency changes - three
things occur when the outlet temperature of the cell increases:
1. The blower power consumption (black curve) decreases because of
a smaller air flow (green line: big air utilization = small air flow).
2. The Nernst potential (grey curve) decreases which in itself reduces
the cell voltage.
3. But at the same time the Area Specific Resistance (blue curve)
decreases. From figure 5.15B it can be seen that the ASR decrease
is more dominant than the Nernst potential drop, so as a total, the
cell voltage increases (brown curve).
Changing T SOFC ,in
Now the inlet temperature of the SOFC is examined. ∆T SOFC is kept
constant, so when the inlet temperature is increased x degrees, so is the
outlet temperature. Again, it is hard to get the inlet temperature much
lower than 650 ◦ C if the chemical reactions are to take place.
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