In connection with the (SOFC, Solid Oxide Fuel Cell) (SOFC) one thinks primarily of a system for stationary electricity and heat production. The largest SOFC system in operation was built by the Siemens Westinghouse Power Corporation and has been designed as a natural-gas-fuelled 100 kW generator. This system contains tubular cells of 
materials normally used today . Due to the tubular design, the operating temperature of the system is 950 °C (1742 °F). This temperature implies considerable restrictions with respect to the materials used for plant design and makes it difficult to achieve a cost target of 1000 $/kW of installed power for an SOFC system.
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One possible way to cost reduction is to lower the operating temperature by the use of thin electrolyte films. By using the anode as the substrate, the mechanical stability of the cells is transferred from the electrolyte to the anode. This enables a reduction of the electrode thickness from ~ 150 µm to ~ 5 µm. This leads to a decrease in resistance by more than one order of magnitude across the electrolyte. If electrodes with optimized microstructure are used, it is possible to lower the operating temperature of these cells below 800 °C (1472 °F). Electrochemical experiments experiments show that at these temperatures it is easy to meet a minimum requirement of 0,2 W/cm2 at an operating voltage of 0.7 V. Moreover, it is endeavoured to lower the operating temperature still further. However, in addition to the development of of new materials, this also requires a study of the electrochemical fundamentals.
Research Centre Jülich works on the construction of SOFC stacks using the substrate cell technique. The design of these stacks is optimized with the aid of model calculations calculations of temperature distribution, gas stream and mechanical load. The thermomechanical data required for these calculations are determined experimentally. Since a stack does not only consist of single cells but also of other components such as interconnect foils, contact layers and glass ceramic sealings, materials research *) plays an essential role. Another priority is stack construction.
A medium-term goal at Research Centre Jülich is the design and construction of a 25 kW system for combined heat and power generation with natural gas in order to demonstrate the feasibility of an anode-substrate-based SOFC. For this purpose, investigations are carried out on the balance of plant of an SOFC system. However, these investigations extend to the whole range of power plants and are not restricted to the above 25 kW system. The use of natural gas requires the investigation of fuel gas processing, for example of hydrocarbon reforming. Further investigations at Research Centre Jülich are concerned with the socio-economic and environmental impacts of electricity production with fuel cells.
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last change 13.07.2003 | ief3 info | Print