An initial test of a hotbox stack module being developed in the SOFC20 project has been completed successfully.
The SOFC20 project partners are working on a natural gas fuelled stationary system demonstrator that will have an electrical efficiency in excess of 50% at over 5 kW output. The initial test of the newly developed hotbox was done in March 2012, during which the stack module achieved a power output of 5.5 kW. Following a further test using simulated natural gas reformate, the stack module will be installed in a specially developed system test environment at AVL.
The insights derived from the tests and characterisation of the stack are fed into the development and optimisation of individual components. The target high power density of the cells and the cyclic stability required for the application can only be achieved if the components are perfectly harmonised.
The project partners are the Fraunhofer Institute for Ceramic Technologies and Systems (IKTS), PLANSEE, AVL List, SCHOTT and the Jülich Research Center.
Fraunhofer IKTS designed the hotbox with eight fuel cell stacks in series. These stacks use interconnects from PLANSEE, the world's largest at 130 x 150 mm, with an integrated protective coating manufactured using powder metallurgy (below). These components connect the individual fuel cells and distribute fuel gas and air in the system. The MK351 interconnect is made from a CFY alloy (chromium, iron and yttrium), intended specially for use in combination with electrolyte-supported cells made from fully stabilised zirconia: the coefficient of expansion of this chromium-based interconnect is perfectly matched to that of the electrolyte. (The MK351 interconnect is available to all potential stack manufacturers.)
SCHOTT specialises in glass technology, including complex glass-to-metal seals; with Fraunhofer IKTS it is developing new joining materials that are fully compatible with the CFY interconnects in terms of their thermomechanical properties. Optimum, long-term sealing using suitable sealing glasses is a prerequisite for achieving high levels of efficiency with the fuel cell stack.
As well as coordinating the overall project, Fraunhofer IKTS is responsible for the construction, sealing and characterisation of the stacks (bottom). AVL is developing the fuel cell system from gas conditioning right up to the AC inverter and is responsible for integrating the stack module. The company has developed a large number of peripheral components especially for this project, such as the ignition boiler or the residual anode gas recycling blower. The Jülich Research Center provides support for system design, particularly desulphurisation materials.
SOFC20 is sponsored by the German Federal Ministry of Economics and Technology.
Source: FuelCellToday