Small fuel cells seals

With respect to fuel-cell technology itself, the small portable units use commercially available membrane electrode assemblies (MEA) and gas diffusion layers (GDL). As the operating temperature of small fuel-cell stacks usually lies below 50 °C, the requirements with respect to material stability of MEA and GDL, but also of sealing gaskets and bipolar plates are comparable lower than for other applications. For example, it is well known that metallic bipolar plates show significantly lower corrosion below 50 °C than at typical operation temperature of 80 °C [6,7], so that a sufficient lifetime for portable applications can be achieved with stainless steel. 

Sealing means must be provided at the edges of the cells to prevent reactants from escaping to the atmosphere from porous elements of the electrodes. Also, since reactant manifolding is usually internal to the stack in small fuel cells (for the sake of compactness), sealing around manifold holes is required to prevent the mixing of reactants between manifolds and electrodes the considerations are the same for internal tie-bolt holes. 

Since X-rays are strongly attenuated by metals and other components used in fuel cells, slight design adaptations are necessary to allow for sufficient beam transmission. Small sealed holes are drilled into the metallic end plates while all other components remain unchanged. The cross-section of a fuel cell prepared for studies in through-plane perspective is sketched in Figure 18.5. Realistic conditions for heat and mass transfer can be retained because the cell design modification is kept to a minimum. 

Ceramic Fuel Cell Ltd. (CFCL) from Australia pursued a 10-kW class design in the 1990s [11]. This was abandoned, and all activities were directed toward small CHP units for residential application. CFCL is now heavily and successfully active in building 1-2 kWei units for residential CHP based on planar stack technology in which each repeatable unit consists of four relatively small (7x7 cm ) anode-supported cells sealed in a stainless steel window frame. For these small units, they... 

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