Plant Characteristics af a Multi-Fuel Sofc-Stirling Hybrid Configuration

A novel hybrid system ( kWe) for an average family house including heating is proposed. The system investigated, contains of a Solid Oxide Fuel Cell (SOFC) on top of a Stirling engine. The off-gases produced in the SOFC cycle is fed to the bottoming Stirling engine wherein additional power is generated.

Simulations for the proposed system were conducted using different fuels which facilitate use of variety of fuels depending on availability. Here, results for Natural Gas (NG), ammonia, Di-Methyl Ether (DME), methanol and ethanol are presented and analysed. System behaviour is further investigated by comparing the effects of key factors such as: utilisation factor, operating conditions, Oxygen-to-Carbon (O/C) ratios and fuel preheating effects on these fuels.

Moreover, effect of Methanator on plant efficiency is also studied. The combined system improves the overall electrical conversion efficiency compared with the stand alone Stirling engine or SOFC plant. For the SOFC and Stirling combined configuration, the overall power production has increased by about 10% compared to the stand alone SOFC plant.

System efficiencies of about 60% are achieved which is remarkable for such small plant sizes. Additionally, heat is also produced for heating the family house whenever it is needed.