Journal of Power Sources 171 (2007) 155–168 Experimental evaluation of the sensitivity to fuel utilization and air management on a 100 kW SOFC system M. Santarelli a,∗ , P. Leone a , M. Cal` ı a , G. Orsello b a Dipartimento di Energetica, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino, Italy b Gas Turbine Technologies, Corso Romania 661, 10156 Torino, Italy Received 14 September 2006; received in revised form 1 December 2006; accepted 11 December 2006 Available online 28 December 2006 Abstract The tubular SOFC generator CHP-100, built by Siemens Power Generation (SPG) Stationary Fuel Cells (SFC), is running at the Gas Turbine Technologies (GTT) in Torino (Italy), in the framework of the EOS Project. The nominal load of the generator ensures a produced electric power of around 105 kW e ac and around 60 kW t of thermal power at 250 ◦ C to be used for the custom tailored HVAC system. Several experimental sessions have been scheduled on the generator; the aim is to characterize the operation through the analysis of some global performance index and the detailed control of the operation of the different bundles of the whole stack. All the scheduled tests have been performed by applying the methodology of design of experiment; the main obtained results show the effect of the change of the analysed operating factors in terms of distribution of voltage and temperature over the stack. Fuel consumption tests give information about the sensitivity of the voltage and temperature distribution along the single bundles. On the other hand, since the generator is an air cooled system, the results of the tests on the air stoichs have been used to analyze the generator thermal management (temperature distribution and profiles) and its effect on the polarization. The sensitivity analysis of the local voltage to the overall fuel consumption modifications can be used as a powerful procedure to deduce the local distribution of fuel utilization (FU) along the single bundles: in fact, through a model obtained by deriving the polarization curve respect to FU, it is possible to link the distribution of voltage sensitivities to FC to the distribution of the local FU. The FU distribution will be shown as non-uniform, and this affects the local voltage and temperatures, causing a high warming effect in some rows of the generator. Therefore, a discussion around the effectiveness of the thermal regulation made by the air stoichs, in order to reduce the non-uniform distribution of temperature and the overheating (increasing therefore the voltage behavior along the generator) has been performed. It is demonstrated that the utilization of one air plenum is not effective in the thermal regulation of the whole generator, in particular in the reduction of the temperature gradients linked to the non-uniform fuel distribution. © 2006 Elsevier B.V. All rights reserved. Keywords: Tubular SOFC generator; Experimental session; Fuel consumption; Air stoichiometry; Local fuel utilization; Temperature distribution 1. Introduction Gas Turbine Technologies (GTT) and Politecnico di Torino, both located in Torino (Italy), have installed a SOFC laboratory in order to analyze the operation, in cogenerative configuration, of the CHP-100 SOFC Field Unit built by Siemens Power Gen- eration (SPG) Stationary Fuel Cells (SFC). The generator was commissioned on June 19, 2005, and to date has shown the ∗ Corresponding author. Tel.: +39 011 564 4489; fax: +39 011 564 4499. E-mail addresses: massimo.santarelli@polito.it (M. Santarelli), pierluigi.leone@polito.it (P. Leone), michele.cali@polito.it (M. Cal` ı), gianmichele.orsello@siemens.com (G. Orsello). record availability of 99.8%, showing more than 30,000 operat- ing hours at this scale. The demonstration of this generator is the first phase of the EOS project (2004–2009), that has the follow- ing aims: (i) to establish a research group that, joining university and industry, will allow the growth of the scientific knowledge about SOFC technologies; (ii) to provide GTT with installation and operational know-how with SOFC; (iii) to extend life testing of SOFCs of varying pedigrees; (iv) to perform experimental and modeling activity to characterize the generator behavior. At present, approximately 100 kW e of ac electrical energy are delivered to the grid, and 55 kW t of thermal energy provides heating and cooling for the facility’s buildings upon integration with a district HVAC. Politecnico di Torino has developed sev- 0378-7753/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jpowsour.2006.12.032