Modeling of a novel SOFC-PEMFC hybrid system coupled with thermal swing adsorption for H₂ purification : parametric and exergy analyses

Abstract

A novel hybrid system fueled with natural gas (NG), consisting of solid oxide fuel cell (SOFC), proton exchange membrane fuel cell (PEMFC) and gas processing (GP) subsystem for H2 production and purification, is proposed and modeled in this paper. The combination of water gas shift (WGS) and thermal swing adsorption (TSA) methods is adopted to convert the syngas from the SOFC into H2 with high purity for subsequent use as a fuel in PEMFC for additional power generation. The parametric and exergy analyses show that the proposed hybrid system can achieve high energy conversion efficiency of approximately 64% and exergy efficiency of 61%, which are higher than some other fuel cell systems, such as reformer-PEMFC, standalone SOFC, SOFC-engine/gas turbine and SOFC-chemical looping hydrogen production. The waste heat recovery for driving the TSA reaction and the H2 recirculation for the PEMFC are found to improve the net electricity efficiency by 3.24% and 6.33%, respectively. In addition, using TSA method instead of the traditional pressure swing adsorption (PSA) could improve the efficiency of the SOFC-PEMFC hybrid system without increasing the exergy destruction. These results reveal that the novel hybrid system is a promising energy conversion system with high efficiency.