New microtube concepts

Micro-tubular solid oxide fuel cells (SOFCs) have been developed over the past decade to provide four features which were not thought to be possible in the early 1990s: small SOFC systems from 1 We to 1 kWe; rapid heating systems with start-up in under 1 min; high power densities near 1 kWe l−1; direct running on a variety of fuels. The main drive for this research emerged as a result of studying extrusion methods for effective fabrication of high quality ceramic membranes, to reveal increased performance combined with extra economy. A further impetus was given by the observation that small tubes of yttria-stabilized zirconia (YSZ) could resist thermal shocks almost a million times better than flat plate designs. Rapid start-up of SOFCs thus appeared as a remarkable and new possibility. Such micro-tubular SOFCs could be used to drive combined heat and power devices to run electronic equipment. Then it became apparent that micro-tubular cells could run directly on a wide range of fuels, varying from hydrogen, through methane to alcohols to jet fuel and diesel oil. This chapter explains the background and progress of these developments and assesses the potential for further penetration both in technical and application terms. Keywords: micro-tubular; SOFCs; rapid heating; multi-fuel; yttria-stabilized zirconia; small SOFC systems