Experimental Analysis of the Voltage and Temperature Behavior of a Solid Oxide Fuel Cell Generator

A solid oxide fuel cell (SOFC) laboratory has been installed in Torino, Italy, in order to analyze the operation, in a cogenerative configuration, of the CHP-100 SOFC Field Unit built by Siemens Power Corporation (SPG) Stationary Fuel Cells (SFC), within the framework of the EOS Project. An experimental session was performed, varying the setpoint temperature $TGEN$ and the fuel consumption (FC), with the aim of characterizing the behaviour of the local voltages and temperatures. A design of experiments procedure was applied to obtain first (simple $22$⁠) and second-order (spherical central composite design (CCD)) regression models, which were then used in subsequent constrained optimization procedures. A sensitivity analysis was also performed: FC revealed as the prevailing control factor of the operation, and it was shown that the analysis of the local voltage and temperature sensitivity to FC can be used as a diagnostic tool for the fuel distribution within a SOFC generator (the homogeneity of the sensitivity of the various cells was $∼10%$⁠, depending strongly on the cell bundle arrangement in the stack). Finally, the effect of any changes in the control factors on the tube temperature profile was evaluated and discussed; a link between a high terminal voltage and a more uniform temperature along the cell tube has been pointed out.