Analysis of Operational Strategies of a SOFC/Micro Gas Turbine Hybrid Power Plant

The present work deals with the analysis of operational concepts for a solid oxide fuel cell/micro gas turbine (SOFC/MGT) hybrid power plant based on a test rig at the DLR, Institute of Combustion Technology. Here, a Turbec T100 MGT and a fuel cell emulator are used. The emulator is composed of two pressure vessels. The first represents the cathode volume of the fuel cell to simulate the residence time and pressure loss. The second is equipped with a natural gas combustor to emulate the varying heat input of the fuel cell. The MGT and the SOFC are connected via different piping paths. The procedures start-up, load change, and shutdown are analyzed in matters of temperature gradients, pressure gradients, and fluctuations, as well as the air mass flow provided at the interconnections to the coupling elements. To achieve the required inlet conditions of the SOFC, transient operations, using the different piping paths, are investigated. Concepts for heating up and cooling the SOFC using hot air from the recuperator and relatively cold air from the compressor outlet are experimentally tested and characterized. Selected critical situations and their effect on the SOFC are investigated. An emergency operation and its impact on both subsystems and limitations are shown. Further operational limits of the MGT control system and power electronic were observed and analyzed. Based on the experimental results, the applicability of the used MGT procedures in a hybrid power plant was reconsidered. Finally, adaptions and strategies for the operational concept are derived and discussed.