Numerical analysis and parametric optimization of a direct ammonia solid oxide fuel cell system integrated with organic Rankine cycle

Abstract

In this study, to maximize the electrical efficiency of the direct ammonia solid oxide fuel cell (SOFC) system, anode-off gas is recirculated for enhancing the system fuel utility and the system exhaust heat is utilized for the organic Rankine cycle (ORC) generating additional electricity. To confirm the superiority of the anode-off gas recirculation (AOGR) SOFC–ORC hybrid system, its electrical efficiency has been compared with two reference systems such as the stand-alone SOFC system without AOGR and the stand-alone AOGR SOFC system. A numerical model on three systems has been developed using Aspen Plus® and validated. Parametric analysis of the three systems has been conducted by varying the operating parameters such as the pump pressure, current density, AOGR ratio, condensation ratio, and fuel utilization. The AOGR SOFC-ORC hybrid system has the highest electrical efficiency among the three types of systems, 70.92 % under nominal conditions. The optimal operational range for the AOGR SOFC-ORC hybrid system has been revealed. As an ammonia-fueled distributed power generation, the proposed system can contribute to achieving net zero in countries where renewable energy is not abundant. This study can provide fundamental insights for establishing an optimization of direct ammonia SOFC systems.