Designs of SOFC

Winkler, W., Cost effective design of SOFC-GT, in Proceedings 6th International Symposium on SolidOxideFuel Cells, Honolulu, USA, S.C. Singhal, M. Dokiya(Eds.), The Electrochemical Society, Pennington, NJ, 1999, pp. 1150-1159. 

Fig. 10.1 Pictures for the different designs of SOFCs and the related cross-sectional diagrams (a) electrolyte-supporting planar cell, (b) anode-supported planar cell, (c) tubular cell, (d) segmented cell in-series design.

The designers of SOFCs have to face the new developments posed by the circulators of Figures A.l and A.2. The letters SOFC denote a vigorous, diverse and expanding family of fuel cells based on the idea that at high temperature the thermal oscillations of the ions at the electrolyte/reactant/product interfaces lead to vigorous exchange... 

SOFC system-level models provide valuable insight into the overall operation and design of SOFC power systems. They provide a means to investigate an SOFC... 

The performance of a stack, reflected in its cell voltage and current density, is an important operating parameter in the design of SOFC power systems. System efficiency is obviously a strong function of cell voltage/current Figure 33.10 shows the effect of voltage and current density on the net system efficiency (defined as... 

There are two basic designs of SOFC units. In the planar design, components are assembled in flat stacks where the air and hydrogen traditionally flow though the unit via channels built into the anode and cathode. In the tubular design, air is supplied to the inside of an extended solid oxide tube (which is sealed at one end), whilst fuel flows round the outside of the tube. The tube itself forms the cathode, and the cell components are constructed in layers around the tube. 

Figure 8.7 Flat-plate design of SOFCs. (From Yamamoto, 2000, with permission from Elsevier.)...

Application of new electrolytes for design of SOFC requires in turn development of suitable anode and cathode materials to provide a good cell performance at decreased temperatures. Thus, the cathode must possess a high electrical conductivity, thermal... 

Inside the planar design of SOFC cells, the development of new materials and techniques of production allowed an evolution of the configurations of planar cells. 

Each design may have variants, but the seal-less tubular designs, microtubular designs, and bipolar flat-plate (planar) designs have received wide attention. Hence, the discussion in the present section is limited to tubular (seal-less), microtubular, and planar designs only. The design of SOFC usually depends on three criteria as follows. 

Tubular design of SOFC was initially made by Siemens Westinghouse, USA. Each tube in the mbular stack is made of a large test tube closed at one end which eliminates seal requirement. The tubular SOFC consists of two tubes, i.e. an outer tube and an iimer tube (Fig. 4.13a). The outer mbe (cell tube) consists of an inner surface and outer surface. The outer surface of the ceU tube is regarded as the anode side of the ceU and the iimer surface is considered to be the cathode side of the cell tube. The solid electrolyte is fabricated within the inner and outer surface of the cell tube. The inner tube is also known as the injection/guidance mbe. The injection tube is made up of alumina through which preheated air is injected towards the bottom of the ceU mbe. This preheated air then Uows over the cathode surface of the cell through the gap between the cell and injection mbes. 

Planar SOFC also uses the same common materials for component fabrication as used for other designs of SOFC YSZ is used as an electrolyte, NiA"SZ cermet as an anode, and lanthanum strontium manganite as the cathode. If the electrolyte thickness is 5-20 pm instead of 100 pm then the cell can operate at reduced temperatures, which allows a wide choice of materials along with the reduction in thermal stress. Anyhow, the planar geometries offer some drawbacks including ... 

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