Systematic Characterization of a SOFC Short Stack in Multiple Operation Modes

Abstract

A series of SOC (Solid Oxide Cell) short stacks from identical production batches was operated in 3 different modes for the systematic assessment of performance according to experimental protocols being harmonized across 7 institutes in Europe and Asia. The operation modes were: Solid oxide fuel cell (SOFC) operation under electrical current profiles and thermal cycling conditions for stationary applications (micro-chp and distributed power generation) and mobile application (SOFC-APU). Solid oxide electrolysis (SOEC) operation under dynamic current profiles for H2 production in a power to gas system. Combined SOFC/SOEC operation for electricity storage in a power-to-gas-to-power system. Each of these cases includes both steady state and dynamic operations. The measurements carried out were current-voltage curves, electrochemical impedance spectroscopy and galvanostatic performance, each executed according to agreed and fully developed protocols. These will be established and experimentally validated. The test modules and programs will consider all relevant operating conditions of the complete SOC test system, e.g. input gases, pressure levels, temperatures, current loads, voltage level, mechanical loads, dynamic transients etc. In order to systematically study these effects, a sound understanding of the interaction of the test object with the test bench shall be developed. It needs to include test bench specifications (e.g. temporal resolution of sensor signals or time constants associated to actuators) and the associated limits to the data analysis. Analysis of the short stack response allowed us to map different parameters with the aim to systematically investigate performance dependency in all the operation modes considered, including: Power density versus current density, fuel utilization, gas phase composition; Efficiency versus temperature, inlet pressure, fuel utilization or gas phase composition Degradation versus time The outcome of the campaign is a clearer assessment of SOC performance dependencies as well as a set of harmonized, rigorous, easy-to-understand and user-friendly procedures for univocal testing of SOC stacks in representative application areas of SOC. Preliminary results underline good performance and repeatability of the tested stacks, strong dependence on gas (H2 and air) inlet temperature, strong instability effects in SOEC modes due to high steam contents and imperfect steam supply etc. The test results will lead to recommendations on test procedure execution and instrument specifications for the benefit of reliable characterization of SOC stacks in multiple, application-representative modes.

Improving the durability of cobaltite cathode of solid oxide fuel cells – a review

“… 5 The application of SOFCs, particularly intermediate temperature SOFCs (IT-SOFCs), have potential in both stationary, 6 and mobile areas. 7 For instance, IT-SOFCs can provide advantages such as low noise, 8 and lightweight properties, 9 as well as in military applications 10 when used in unmanned vehicles. 11 Furthermore, the implementation of IT-SOFCs in stationary applications can advance the concept of microgrids.…”