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

D.3. Water consumption
Hence it is likely to be between 735 ◦ C and 780 ◦ C (15 ◦ C < ∆T SOFC ,av
< 60 ◦ C))
• η W B,Tower is typically around 0,75 according to [14]. Since 0 equals
no evaporation at all and 1 equals the best possible theoretical
situation, it must be reasonable to assume that the value would not
be outside the interval 0,6 to 0,9.
• FR and FW: These values have been set so the change of the
flow (partial pressure) for the different species in the pre reformer
reassembles the TOFC data. Hence the standard configuration
values must be quite close to reality. FR (0,14) is assumed to be
within [0,1 to 0,2] whereas FW (0,6) is assumed to be within [0,45 to
0,75]
• i d The current density is controlled by the operator, so this can be
set exactly as desired - it is just a matter of buying the right amount
of cells for the desired current draw. As was shown in figure 5.19B
page 132 the current density can not go below 2100Ωm 2 if the fuel
input remains at the 100kW for the given number of cells since
the heat generated in the electrochemical reaction is not enough to
make up for the energy used in the endothermic reforming process.
The current density can not go above 3300Ωm 2 either, since the
voltage falls below 0,7V (0=>Nickel Oxidation).
• The efficiency of the FAN (for the cooling tower) can vary quite
a lot depending on the size of the system (and hence FAN), so
depending on the system size, it is assumed that it can range from
0,3 to 0,6.
• The isentropic efficiency of the blower in the SOFC system should
be relatively exact for the given size (100kW of fuel), since the
blower power consumption fits very well with being 10% of the
net electricity [25]. But it does depend a lot on the size, so it can
be suspected to range from 0,4 to 0,8 if the system is scaled up or
down.
D.3 Water consumption
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