Biomass fueled SOFC-Engine combined heat and power system: energy, exergy and thermo-economic evaluations

A novel hybrid system using biomass as fuel for both power and heat generation, which consists of biomass gasification unit, solid oxide fuel cell, homogeneous charge compression ignition engine and waste heat recovery subsystems, is proposed in this work. Based on the thermodynamic modeling, the system is comprehensively evaluated by energy, exergy and thermo-economic analyses. The results show that the proposed hybrid system has an energy conversion efficiency of approximately 68% and the exergy efficiency of 51%, both of which are comparable to other biomass fueled hybrid fuel cell systems reported in literature. The exergy destruction of the gasifier is the largest, whose relative exergy destruction is up to 21.5%. The fuel cell component contributes to 71% of the total power but with small relative exergy destruction. Besides, the specific electric energy cost of the proposed hybrid system is calculated to be 0.054 $/kWh. The payback period and annual return on investment can reach 2.4 year and about 9.83%. These results reveal that the proposed conversion technology of biomass to power is efficient and economical, which could be a promising way for biomass utilization.