Partial-Load Analysis of a Temperature-Controlled Solid-Oxide Fuel Cell-Gas Turbine (SOFC-GT) Hybrid Power Plant

Due to high conversion efficiency and low environmental impact, solid-oxide fuel cells coupled with a gas turbine (SOFC-GT) have received much attention. A proper stack temperature control strategy ensures safety and enhances performance. A heat management subsystem capable of adjusting the stack temperature is critical for the hybrid plant. Most present SOFC-GT plants deliver the full volume of the GT's exhaust to heat up the stack. Stack cooling is realized by blowing extra air, which consumes more parasitic energy and impacts the plant's conversion efficiency. In this study, a heat management subsystem has been added into the SOFC-GT plant. The stack average temperature can be adjusted by controlling the volume of the GT's exhaust and additional fuel. In this way, the parasitic energy owing to the air compressor is reduced. To investigate the proposed plant's performance, a corresponding model has been established. Simulation results of the specific operating point show that the heat management subsystem can maintain the stack average temperature at its proper value. Furthermore, based on the different air/additional fuel supply patterns, the partial-load performance of the proposed plant has been compared, and an optimal partial-load strategy is proposed. The proposed SOFC-GT plant shows a wide output range (370.0-1540.7kW) with remarkable efficiency (56.8%-75.0%).