Energy, exergy, and economic (3E) evaluation of a CCHP system with biomass gasifier, solid oxide fuel cells, micro-gas turbine, and absorption chiller

The aim of this work is to investigate a novel integrated cooling, heating, and power (CCHP) system with biomass gasification, solid oxide fuel cells (SOFC), micro-gas turbine, and absorption chiller. The performance of this system is analyzed by mathematical models consisting of lumped models of SOFC and absorption chiller and one-dimensional model of a downdraft biomass gasifier. Effects of main operating parameters such as moisture content of biomass, air flow rate in the gasifier, and temperature of fuel gas on the overall energy and exergy performance of CCHP system are evaluated. The net present value (NPV) method is used to analyze the economic prospects of this system. The results show that higher flow rate of air for the gasifier with lower moisture content of biomass are beneficial for the improvement of the output of cooling, heating, and power of CCHP, and, accordingly, the electrical efficiency as well as overall energy and exergy efficiency of CCHP rises. Increasing mass flow rate of air for the gasifier can increase exergy efficiency by 10%. Moisture content less than 0.2 could result in exergy efficiency greater than 45% and CCHP efficiency over 65%.The decrease of the exhaust gas temperature further boosts the production of cooling and heating of the CCHP system. Specifically, a 10% improvement of overall efficiency of CCHP is obtained when the exhaust gas temperature is reduced to 90 degrees C. In this work, an electrical efficiency over 50%, exergy efficiency more than 40%, and CCHP efficiency up to 80% can be achieved. Economic assessment shows that the initial investment of SOFC is above 50%-60% of the total investment of the CCHP and the payback period is about 7-8 years.