Table 1 Objective functions, decision variables, and selected flows for the hybrid design (50 kW SOFC system); performance comparison among three designs for a 50 kW SOFC system
From: Scalable modular design of solid oxide fuel cell systems for enhanced large-scale power generation
Objective functions | ||||
|---|---|---|---|---|
Electrical efficiency, % | 66.3 | |||
Global fuel utilization, - | 0.98 | |||
External water flow rate, mol/s | 0.085 | |||
Parameters | Parallel stacks | Series stack 1 | Series stack 2 | Series stack 3 |
|---|---|---|---|---|
Reformer temperature for pre-reformer, °C | 539 | 533 | 518 | 519 |
Reforming ratio for pre-reformer | 0.12 | 0.13 | 0.12 | 0.11 |
Natural gas flow rate, kg/s | 0.0007 | 0.0003 | 0.0003 | 0.0003 |
Natural gas flow rate, mol/s | 0.0409 | 0.0174 | 0.0187 | 0.0186 |
External water flow rate, mol/s | 0.085 | 0 | 0 | 0 |
Fresh air input, mol/s | 2.151 | 0.778 | 0.644 | 0.62 |
COG air input, mol/s | 0 | 0.694 | 0.694 | 0.694 |
Air output O2 mole fraction, - | 0.184 | 0.178 | 0.175 | 0.174 |
Air blower power, kW | 0.74 | 0.64 | ||
Net power from module(s) | 20.88 | 9.89 | 9.95 | 9.79 |
Hybrid | NCNA | NCHA | ||
|---|---|---|---|---|
Natural gas flow rate, kW | 76.67 | 81.98 | 79.77 | |
External water flow rate, mol/s | 0.085 | 0.212 | 0.085 | |
Fresh air flow rate, mol/s | 4.193 | 5.377 | 6.42 | |
Electricity output, kW | 50.51 | 52.79 | 45.9 | |
Electrical efficiency, % | 66.3 | 65.8 | 57.5 | |
Heat available at 600 °C, kW | 4.1 | 7.93 | 5.66 | |
Heat available at 200 °C, kW | 4.47 | 0.92 | 8.87 | |
Cold utility requirement, kW | 30.77 | 37.4 | 40.25 | |
Additional electricity generated by RC, kW | 2.03 | 2.14 | 2 | |
Electrical efficiency with RC, % | 68.5 | 67 | 60 | |
Direct mixing points at high temperature | 8 | 0 | 5 | |
