Cell Operation and Performance

A large number of tubular cells have been electrically tested over the years, some for times as long as 8 years. These cells perform satisfactorily for extended periods of time under a variety of operating conditions with less than 0.1% per 1000 h performance degradation. The voltage-current and power-current characteristics of a commercial prototypic 2.2 cm diameter, 150 cm active length cell at 900, 940, and 1000°C with 89% + 11% H2O fuel (85% fuel 

The tubular SOFCs have also shown the ability to be thermally cycled to room temperature from 1000°C over 100 times without any mechanical damage or electrical performance loss. This ability to sustain thermal cycles is essential for any SOFC generator to be commercially viable. 

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The MEA consists of an anodic electrode, PEM, and a cathodic electrode. Because the electrode reactions take place in the MEA, it is the heart of a H2/air PEM fuel cell. The components of an MEA include the anode gas diffusion medium (A-GDM), anode microporous layer (A-MPL), anode catalyst layer (A-CL), PEM, cathode catalyst layer (C-CL), cathode microporous layer (C-MPL), and cathode gas diffusion medium (C-GDM), as shown in Fig. 2.1. A commonly used term is gas diffusion layer (GDL), which actuaUy contains the gas-diffusion-medium layer and the microporous layer. Each component shown in Fig. 2.1 has specific characteristics and functions in fuel cell operation and performance. Therefore, they differ significantly in their design and fabrication. These topics wUl be addressed in the following sections. 

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