A main issue in reducing the cost of electricity produced by an SOFC is the durability of the SOFC stack. Other important aspects are the production cost per unit of cell area and the SOFC stack performance. Published data, and the partners' experience, show that the state-of-the art SOFC degradation rate is too high. It is widely believed that the degradation rate should be below 0.5 % per 1000 h. So far only Westinghouse has reported such results. However, the fabrication method used by Westinghouse is far too expensive.
The objective of the proposed three-year project is the reduction of the cost of SOFC by improving the durability without increasing the production cost or decreasing the stack performance. This will be achieved through a better understanding of the fundamentals of the degradation processes of SOFC components, and through improved fabrication techniques of starting powders and ceramic cells, aiming at appropriate (rather than maximum) purity and quality levels of active components.
In order to test the SOFC-stack durability, it is necessary to undertake accelerated testing. It is believed that many of the causes for the degradation of SOFC-stack performance are due to solid state reactions. This may be either chemical reactions forming deleterious products at the interface between components, undesirable diffusion of elements from one component to another, or growth of the particles of the electrodes resulting in too coarse structures. It is also necessary to study the degradation rates at different temperatures including the operating temperature. As all the mentioned processes are thermally activated it is possible from such data sets to predict the durability with reasonable accuracy. In cases of chemical reactions they may be very sensitive to impurities. Therefore it is important to perform reactivity experiments, thermodynamic measurements and modelling.
Expected Achievements and Exploitation
The measurable objectives are:
A voltage degradation lower than 1 % per 1000 h at steady state operation with 300 mA/cm2, and at reasonable temperature in the range between 800 and 1000 °C. The internal area specific resistance should not be above 1 cm2 in a single stack element (i.e. a cell with interconnects on both sides) tested in simulated reforming gas. Fuel utilisation should be at least 80 %.
A thermal cycling resistance resulting in less than 0.5 % degradation per thermal cycle from operating to room temperature and back to operating conditions.
A further objective of bringing this Consortium together is the positive influence of co-operation and exchange of ideas which may help the European industry to strengthen its competitiveness on the future SOFC-market.
Funding SchemeCSC - Cost-sharing contracts
1755 ZG Petten
SW7 2BP London
DE24 8BJ Derby