Combined biomass gasification, SOFC, IC engine, and waste heat recovery system for power and heat generation: Energy, exergy, exergoeconomic, environmental (4E) evaluations

Abstract

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 unit, is proposed in this work. Based on the modeling, the system is comprehensively evaluated by multiple approaches including energy, exergy, exergoeconomic and environmental analyses. It is found that the overall energy efficiency and exergy efficiency of the hybrid system could reach up to 68% and 51%, both of which are comparable to those of other reported hybrid fuel cell systems. The exergy destruction of the gasifier is the largest whose relative exergy destruction is up to 21.5%. The component of fuel cell contributes to 71% of the total power but with small relative exergy destruction. On the contrary, the HCCI engine contributes to less power but has larger exergy destruction compared to SOFC. The exergoeconomic analysis showed that the fuel cell component has a high exergoeconomic factor of 98.09% due to the large capital investment cost. By comparison, the component engine has much lower exergoeconomic factors of 5.41%. The cost of exergetic product of the hybrid system is 9.7 $/GJ. Besides, the proposed hybrid system presents a low carbon dioxide emission of about 0.119 to 0.139 t/GJ, which indicates few environmental impacts for the system. These results reveal that the proposed biomass-fueled hybrid system is high-efficiency, low-cost and clean for both power and heat generation, which could be promising candidate as advanced energy conversion technology in practical applications.