Energy and Exergy Analysis of an Ammonia Fuel Cell Integrated System for Marine Vessels

In this paper, a new integrated system of solid oxide fuel cell (SOFC)–gas turbine (GT)–steam Rankine cycle (SRC)–exhaust gas boiler (EGB) is presented, in which ammonia is introduced as a promising fuel source to meet shipping decarbonization targets. For this purpose, an SOFC is presented as the main power-generation source for a specific marine propulsion plant; the GT and SRC provide auxiliary power for machinery and accommodation lighting, and steam from the waste heat boiler is used for heating seafarer accommodation. The combined system minimizes waste heat and converts it into useful work and power. Energy and exergy analyses are performed based on the first and second laws of thermodynamics. A parametric study of the effects of the variation in the SOFC current density, fuel utilization factor, superheat temperature, and SRC evaporation pressure is conducted to define the optimal operating parameters for the proposed system. In the present study, the energy and exergy efficiencies of the integrated system are 64.49% and 61.10%, respectively. These results serve as strong motivation for employing an EGB and SRC for waste heat recovery and increasing the overall energy-conversion efficiency of the system. The SRC energy and exergy efficiencies are 25.58% and 41.21%, respectively.