Fuel Utilization Effects on SOFC-mGT Combined Heat and Power Systems for Smart Grid Applications

Solid oxide fuel cell (SOFC) has been playing an increasingly vital role in the applications of smart grids due to its high efficiency/power level, no/low pollution, wide range of fuel types, etc. Furthermore, the SOFC could operate with a micro gas turbine (mGT), which forms a combined heat and power (CHP) system to further improve the efficiency. As an essential parameter, the fuel utilization factor determines the ratio of output power and heat produced in SOFC-mGT CHP systems. In this paper, a multi-physical power model for the typical SOFC-mGT CHP system is proposed to investigate the effects of the fuel utilization factor on both its power and heat output. The results indicate that when the SOFC stack operates at the rated output current point (100A), the output power of the system slightly increases with the decrease of the fuel utilization factor while the output heat increases significantly. If the output current of the SOFC stack is less than the rated value, there will be situations where the output power of the recuperator and mGT makes it difficult to maintain the normal operation of the system itself.