Start-up approach based on hybrid system emulator with a re-compression system for a pressurized Solid Oxide Fuel Cell Gas Turbine

This paper presents a novel machine start-up technique for SOFC hybrid system based on a re-compression approach. This approach shows the reality of operating the system without the manufacturer’s usual technique of using the standard control system. A hybrid system emulator rig located at Savona, Italy will be used for these research activities. The experimental test rig consists of an emulator that is based on a 100 kW microturbine connected to a modular vessel designed for fuel cell emulation. The microturbine pipes were carefully insulated and connected to a high temperature modular vessel necessary to emulate the dimension of an SOFC stack and lastly, for the purpose of re-compression, the test rig was modified to accommodate a turbocharger capable of increasing the fuel cell pressure (using part of recuperator outlet flow). This is necessary for operating at high efficiency conditions hybrid systems based on a cathodic recirculation driven by an ejector. For both economic reasons and to avoid system abnormal operations during the plant start-up conditions, a theoretical activity is very vital. A dynamic model of the solid oxide fuel cell gas turbine system was developed in Matlab®-Simulink® environment to investigate the transient behaviour during start-up phase. The results obtained shows reasonable values for several parameters, such as surge margin, turbine outlet temperature, and rotational speed. The results demonstrated the feasibility of this machine coupling (the microturbine with a turbocharger) avoiding risk operations during the start-up phase.