Multi-objective optimization using response surface methodology and exergy analysis of a novel integrated biomass gasification, solid oxide fuel cell and high-temperature sodium heat pipe system

A combined system including a biomass gasifier and a solid oxide fuel cell (SOFC) is studied. The heat is transferred from the afterburner to the biomass gasifier reactor by heat pipes. After model verification, response surface methodology (RSM) is utilized in order to investigate and optimize the process. The steam to biomass ratio (STBR), the current density and the inlet temperature of the SOFC are chosen as the input parameters while exergy efficiency and electrical power are considered as the responses. Regression models in order to predict the responses based on the considered input variables are obtained using analysis of variance (ANOVA) tool of the RSM method. The results indicate that the proposed regression models have high accuracy. The exergy efficiency improves by increasing the inlet temperature of the SOFC and decreasing the current density, as the results are illuminating. An optimum point (the current density of 5308 A/m(2), the inlet temperature of SOFC of 1037 K and STBR of 1.6) is anticipated and the outputs and the exergy destruction rate of the combined system components are investigated. The power of 535 kW and the exergy efficiency of 44.22% are obtained in the optimum state.