Peter Vang Hendriksen

Solid oxide fuel cell development at Topsoe Fuel Cell A/S and Risø National Laboratory

The consortium of Topsoe Fuel Cell A/S and Risoe National Laboratory has up-scaled its production capacity. Stacks are based on a compact thin plate multilayer design with metallic interconnects and 12x12 cm{sup 2} or 18x18 cm{sup 2} foot print. Larger (500 cm{sup 2}) cells are currently under evaluation. Stacks have been tested successfully for more than 13000 hours. Several 50 or 75 cell stacks in the 1+ kW power range have been tested successfully at a fuel utilisation of up to 92%. Multi stack modules consisting of four 75 cell stacks have been tested for more than 4000 hours with pre-reformed natural gas and modules consisting of twelve stacks are under development. Our SOFC program comprises development of next generation cells with porous ferritic steel is used as a cheap, ductile, robust cell support and the electrolyte is based on scandia-doped zirconia with improved durability. In collaboration with Waertsilae, a 24-stack prototype based on natural gas is being tested. The range of fuels have further been extended to include ethanol and coal syn-gas by development of a new coke resistant catalyst suitable for future SOFC technology.

Chapter 10 – Testing of Electrodes, Cells and Short Stacks

This chapter discusses the electrochemical testing of individual electrodes and solid oxide fuel cells (SOFC), and the importance of stack testing. One important aspect in electrode testing is to assure a correct geometry in three-electrode set-ups. This is very difficult in practice in case of electrode supported cells with thin electrolytes, probably due to differences in the fabrication of the special cells for electrode characterization and the practical cells. Another important issue is that of gas leakage, which can cause significant errors in performance data. Especially in the case of gas leakage, cells can easily be at a higher temperature than their surrounding environment, causing cells to give better apparent performance than individual electrodes tested under better controlled conditions. Also, the gas composition at the electrodes (usually at the anode) may be different from the intended composition in case of gas leakage. It is recommended that cell test results be reported in a way that makes it easy to derive area specific resistance (ASR) from the i-V curves. Sufficient information should be provided so that the ASR values can be corrected for effects of finite fuel utilization. Also, the choice of fuel composition should preferably reflect real cell operation conditions. The ASR should be derived using the Emf and a cell voltage in the range of 0.5-0.7 V and its corresponding current density.

Status of Development and Manufacture of Solid Oxide Fuel Cell at Topsoe Fuel Cell A/S and Riso̸/DTU

and Risø/DTU DTU Orbit (01/04/2019) Status of Development and Manufacture of Solid Oxide Fuel Cell at Topsoe Fuel Cell A/S and Risø/DTU Fuel Cell (TOFC) provides the SOFC technology platform: Cells, stacks, and integrated stack module for different applications and collaborates with integrator partners to develop, test and demonstrate SOFC applications. The technology development is based on a R&D consortium with Risø National Laboratory (Risø/DTU) which includes material synthesis and cost effective ceramic manufacturing methods for anode and metal supported flat planar cells in addition to multilayer assembling for compact stacks with metallic interconnects. The development is focussing on high electrochemical performance and durability as well as maximal robustness. In 2008 TOFC has constructed a 5 MW/year cell and stack production facility in Denmark featuring all the necessary unit operations from ceramic powder, continuous tape casting, screen printing, spray painting and sintering to complete stack modules. TOFCs engagement in SOFC technology includes system development in collaboration with system partners and development and manufacturing of integrated stack assemblies called PowerCore. ©2009 COPYRIGHT ECS The Electrochemical Society

Passivation and Activation of SOFC Nanostructured Cathodes

For a solid oxide fuel cell, performance is largely determined by the cathode properties, particularly at low operating temperatures (<700°C). Extensive cathode studies have made great strides in reducing the polarization resistance (Rp) in many systems. This has led to reduction of fuel cell operating temperature to allow use of stainless steel as interconnect, and thus reduce cost. However, our studies showed a significant increase of Rp over time when samples were kept at low temperature and open circuit voltage. We have systematically investigated these passivation phenomena in LaSrMnO3, LaSrCoFeO3 and BaSrCoFeO3 systems. On the other hand, Rp was reduced significantly by a high temperature annealing, close to the initial value and sometimes series resistance (Rs) could be recovered completely. Cation diffusion and defect disordering are considered to be the main contributors to passivation and activation.