Diffusion and Gas Conversion Analysis of Solid Oxide Fuel Cells at Loads via AC Impedance
Table 3
Values for a parallel RC fitted to the low-frequency impedance loops of three cells in a five-cell planar stack operating at 800°C.
(a) The SOFCs were fed with 38.5 ~ 97% H2, 3% H2O, and balance N2, and operated at 1.69 mA cm−2
Physical elements
(Cell 1)
(Cell 3)
(Cell 5)
38.5%
64.6%
97.0%
38.5%
64.6%
97.0%
38.5%
64.6%
97.0%
(Ω cm2)
1.430
1.538
1.373
1.340
1.479
1.263
1.299
1.427
1.301
(F cm−2)
1.185
1.586
1.658
0.9477
1.342
1.465
0.9883
1.238
1.447
Y0 (S cm−2 s1/2)
1.135
1.332
1.441
1.018
1.211
1.397
1.059
1.202
1.338
B (s1/2)
2.025
2.487
2.402
1.727
2.210
2.155
1.743
2.098
2.149
(b) Varying load currents when fed with 97.0% H2 and balance H2O
Physical elements
i (mA cm−2, Cell 1)
i (mA cm−2, Cell 3)
i (mA cm−2, Cell 5)
1.639
52.46
147.5
1.639
52.46
147.5
1.639
52.46
147.5
(Ω cm2)
1.373
0.6570
0.5802
1.263
0.6283
0.4862
1.301
0.6082
0.4373
(F cm−2)
1.659
1.716
1.648
1.465
1.417
1.380
1.447
1.445
1.895
Y0 (S cm−2 s1/2)
1.442
2.051
1.925
1.397
1.857
1.821
1.337
1.907
1.731
B (s1/2)
2.402
1.668
1.554
2.156
1.467
1.376
2.148
1.457
1.259
(c) Varying the anode feed rate j when the SOFCs were operated at 52.46 mA cm−2 and composed of 97.0% H2 and balance H2O, where the total j is assumed to be evenly distributed between the five cells in the stack.
