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

5.3. Partial optimization of standard parameters
Figure 5.18: Triangular markers (Case 1) is when all the fuel is sent through the cell (and U f
varies). Round markers (Case 2) is when some of the fuel is by passed the SOFC and fed directly
to the burner (U f remains constant).
is an endothermic reaction. But the exothermic electrochemical reaction
only occurs at a rate corresponding the current draw, and the exothermic
water gas shift is not enough to make up for the heat consumption of the
endothermic reforming. Furthermore the heat generation due to ASR
loss decreases when the current draw is minimized. So when i d goes
below 2100A/m 2 , the fuel cell will lack heat, and its inlet temperature has
to be higher than the outlet temperature now that the chemical reactions
sum up to be endothermic
It can, however be seen from figure 5.18 that for current densities
over 2100A/m 2 , sending all the fuel through the Fuel cell gives the best
η sys,el ,net (while COP ABS,f uel is almost identical). But for current densities
below 2100A/m 2 it is necessary to bypass some of the fuel directly to the
burner.
Method 1 is more efficient, but only method 2 can be used for lower
current densities. Both these ways of increasing cooling power at the
expense of electrical power will now be examined:
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