Elevating gas turbine system efficiency by integration with super-high-temperature solid oxide fuel cells

The solid oxide fuel cell-gas turbine (SOFC-GT) hybrid system is among the most efficient power generation technologies. However, the development of SOFCs has focused on lower operating temperatures, which is much lower than the turbine inlet temperature (TIT) of the advanced hundred-MW-class gas turbines (GTs) (＞1400oC), hindering their integration. Therefore, current large-scale GTs still primarily enhance power generation efficiency by increasing TIT, which approach has suffered from prominent marginal effects, leading to the bottleneck in efficiency enhancement. To address this, we propose a super-high-temperature SOFC operating at above 1200°C, which can be integrated with a commercial hundred-MW-class gas turbine to break the efficiency bottleneck. In our laboratory, a single tubular SOFC achieved a peak output power of 4.67 W at 1200°C, which is 5.5 times higher than that at 700°C. We simulated a hundred-MW-class hybrid system to demonstrate the necessity of the elevation of SOFCs temperature, analyzing it thermodynamically based on a T-s indicator diagram. When the SOFC operating temperature increases from 800°C to 1200°C, the temperature mismatch degree between the SOFC and the F-class gas turbine decreases significantly from 68.16% to 0%. This improvement is accompanied by an increase in fuel cell combustor (FCC) exergy efficiency from 76.52% to 85.93%, and an increase in system efficiency from 58.60% to 74.12%. Further elevating the SOFC operating temperature to approximately 1300°C could potentially yield a system efficiency of 80.31%. Considering these substantial thermodynamic advantages, we propose a new development route for SOFCs towards a super-high operating temperature of over 1200oC.