Hybrid System Test Rig: Start-up and Shutdown Physical Emulation

The University of Genoa (TPG) has designed and developed an innovative test rig for high temperature fuel cell hybrid system physical emulation. It is based on the coupling of a modified commercial 100 kW recuperated micro gas turbine to a modular volume designed for the experimental analysis of the interaction between different dimension fuel cells and turbomachines. This new experimental approach, that generates reliable results as a complete test rig, also allows to investigate high risk situations with more flexibility without serious and expensive consequences to the equipment and at very low cost compared to real hybrid configurations. The rig, developed with the support of the European Integrated Project \u201cFELICITAS\u201d, has been exploited and improved in the framework of the new European Integrated Project \u201cLARGE-SOFC\u201d, started in January 2007. The lay-out of the system (connecting pipes, valves, and instrumentation) has been carefully designed to minimize the pressure loss between compressor outlet and turbine inlet to have the highest plant flexibility. Furthermore, the servocontrolled valves are useful to perform tests at different operative conditions (i.e.: pressures, temperatures, pressure losses), focusing the attention on surge and thermal stress prevention. This work shows the experimental results carried out to study the machine performance, focusing the attention on compressor maps. Then, the preliminary data obtained with the machine connected to the volume regard the test rig safe management to avoid surge or excessive stress, especially during the critical phases (i.e.: start-up and shutdown). Finally, the attention is focused on the valve control system developed to emulate the start-up and shutdown phases for high temperature fuel cell hybrid systems. It is necessary to manage the flows in the connecting pipes, including an apt recuperator bypass, to perform a gradual heating up and cooling down, as requested during these phases. It is an essential requirement to avoid thermal stress for the fuel cell stack. For this reason, during the start-up, the volume is gradually heated by the compressor outlet flow followed by a well managed recuperator outlet flow, and vice versa for the shutdown. Furthermore, operating with a constant rotational speed control system, the machine load is used to reach higher temperature values, typical of these kinds of systems