PBZ

 IWV

 ZCH

 ZEL

 ZAT

In charge: Dr. R. Steinberger-Wilckens, PBZ, r.steinberger@fz-juelich.de

Aims and Objectives

Cells, components, stacks and systems for high temperature fuel cells with ceramic electrolyte (SOFC) and low temperature fuel cells with polymer electrolyte (DMFC and PEFC) are being developed within the framework of this programme sub-topic. The primary goals are enhancing the power density, reducing degradation (improvement of durability), reducing materials and manufacturing costs, improving stack design and optimising system technology. This includes the development of new and improved materials for cells and stacks as well as low-cost processing that is suitable for mass-production (for instance roll coating, screen printing, tape casting, sputtering etc.). Modelling of mechanical and thermal strain of components, development of practical life cycle and performance predictions for single components and complete fuel cell systems constitute a further important activities that are in part also coupled with the assessment of technical developments within the process and system analysis group.

Significant Results in 2003

• The current density of SOFC cells manufactured at FZJ could be increased to above 1,5 A/cm² (at 800°C, 0.7 V, 5x5 cm² cells) thanks to new cathode materials. This enabled lowering the operation temperature by 100°C (to 700°C) whilst maintaining the overall power of stacks. The lower temperature allows a longer life-time due to reduced corrosion.
• The steel material developed together with Krupp VDM (JS-3) was made commercially available by VDM under the trade name CroFer 22 APU. This large scale manufactured material, though, showed some deviations in properties from the pre-series batches of JS-3. Accelerated corrosion was observed which led to untimely failure of stacks. A detailed analysis revealed that the presence of hydrogen in combination with the BaSi-glass sealing were a prerequisite for this process. Meanwhile new steel batches are available and the glass materials are being re-developed so that this corrosion type can be avoided.
• In order to analyse the corrosion process testing arrangements were designed that allowed an insight into single possible influences and boundary conditions on a very short time scale. This equipment decisively contributed to the understanding of the phenomenon.
• Within the ZeuS-project (terminated July 2003) a new stack design on the basis of metal sheet stamping (G-Design) was developed. Funding for further work on these extremely light-weight stacks could be secured (ZeuS II project, duration 2004-2006).
• Modelling of a stack configuration with 60 planes (cells) was successfully implemented. Owing to a novel aggregation within the model a high level of detail could be achieved whilst at the same time reducing the computing time dramatically. A patent application was filed for the methodology used.
• The implementation of the 20 kW system further progressed. The test rigs for afterburner and pre-reformer were taken into operation. The thermal insulation and integration concept of all 'hot' components was completed and a patent applied for.
• Finally, the contract for the EU-funded project Real-SOFC was signed. The project is aimed at a substantial increase in SOFC stack material durability. It will terminate in January 2008 and comprises 25 further European partners with FZJ acting as a co-ordinator.

• In the area of Direct Methanol Fuel Cells (DMFC) the consumption of noble metals could be reduced by half whilst maintaining the original power output by using carbon-supported electro catalysts and optimising the membrane electrode assembly. At the same time the production of gas diffusion electrodes, also used for PEFC, was switched to continuous automatic manufacturing (desk coater). This became especially possible due to the development of finely dispersed, stable catalyst suspensions.
• A DMFC short stack with a single electrode area of 310 cm² and bipolar plates made of extruded graphite was tested successfully and displayed a considerably increased power and energy density.
• Progress was also achieved in the development of PEFC stacks in the areas of flow distribution, sealing, and water and heat management and further contributed to the design of a 5 kW stack.

• A fuel processing system for diesel in the range of 1 - 5 kWel was designed and built (autothermal reformer, steam shift reactor, reactor for partial CO-oxidation and catalytic afterburner). The autothermal reformer already produces 95% of the required hydrogen at 350°C after 1 minute from a warm start. The power density is 2 kWel/Litre.
• Various catalysts were tested for use in the shift reactor. The most active displayed a conversion rate of 85% (product concentration 0.9%) at 280°C and volume flow of 12.000 1/h. Two of these catalysts were integrated into a shift reactor of the 3 kW class at a volumetric power density of 1 kWel/Litre.

• Attaining the set cost targets is one of the main concerns with fuel cells, besides issues of durability, efficiency and environmental performance. As an assessment tool a techno-economic cost model was established for PEFC stack materials on the basis of a newly developed benchmarking methodology.
• The future application of fuel cells in vehicles is closely linked to the supply of non-conventional fuels. International studies on this topic were evaluated and ethanol as well as Fischer-Tropsch-Diesel and methanol further analysed. Process analyses were performed in the field of dynamic simulation of SOFC-based auxiliary power units (APU) and the application of SOFC and MCFC for hydrogen-rich "waste gases " from the chemical industry.