Technical and Economic Considerations of Solid Oxide Fuel Cell Systems

Abstract

AbstractThe ECLIPSE process simulator has successfully evaluated the technical and economic performance of a number of systems based on a natural gas fed Solid Oxide Fuel Cell (SOFC). These systems differ in their approach to reforming of the natural gas feedstock and in their use of anode gas recycle. The most efficient system is the direct internal reforming SOFC with an efficiency of 48.0% giving C02 emissions of 420 g/kWh. The indirect internal reforming and the external reforming SOFC have efficiencies about 3.5 to 4 percentage points lower. The total energy efficiencies vary between 87.2% and 91.0% and if the useful, high grade heat could be converted into electricity via steam turbines then the electrical efficiency increases by about 10 % points. The effect of anode gas recycle is to improve the electrical efficiency by on average 7.5 % points and to reduce C02 emissions by 15%.Compared to conventional power generation technologies, the efficiency of, and C02 emissions from, a direct internal reforming SOFC are vastly superior to the small scale gas turbine and gas engine systems and slightly better than the large scale gas turbine combined cycle systems. However, from the point of view of cost of electricity, for the SOFC to compete with the small scale systems the SOFC capital cost must be reduced to less than either 500/kWe with a lifetime of greater than 15 years or 600/kWe with a lifetime of greater than 20 years. For SOFC systems to compete with large scale gas turbine combined cycle systems they must be used in a combined heat and power configuration with a similar capital cost as above. Current estimates for SOFC costs are around 1000/kWe with an uncertain lifetime. Therefore, at this stage, the economic viability of SOFC power generation systems depends on cost reduction and lifetime enhancement, probably via materials development and operating temperature reduction.