Design, Modelling, and Thermodynamic Analysis of a Novel Marine Power System Based on Methanol Solid Oxide Fuel Cells, Integrated Proton Exchange Membrane Fuel Cells, and Combined Heat and Power Production

Abstract

A novel maritime power system that uses methanol solid oxide fuel cells (SOFCs) to power marine vessels in an eco-friendly manner is proposed. The SOFCs, gas turbine (GT), steam Rankine cycle (SRC), proton exchange membrane fuel cells (PEMFCs), and organic Rankine cycle (ORC) were integrated together to generate useful energy and harvest wasted heat. The system supplies the exhaust heat from the SOFCs to the methanol dissociation unit for hydrogen production, whereas the heat exchangers and SRC recover the remaining waste heat to produce useful electricity. Mathematical models were established, and the thermodynamic efficiencies of the system were evaluated. The first and second laws of thermodynamics were used to construct the dynamic behavior of the system. Furthermore, the exergy destruction of all the subsystems was estimated. The thermodynamic performances of the main subsystem and entire system were evaluated to be 77.75% and 44.71% for the energy and exergy efficiencies, respectively. With a hydrogen distribution ratio of β = 0.12, the PEMFCs can generate 432.893 kW for the propulsion plant of the target vessel. This is also important for the rapid adaptation of the vessel’s needs for power generation, especially during start-up and maneuvering. A comprehensive parametric analysis was performed to examine the influence of changing current densities in the SOFCs, as well as the influence of the hydrogen distribution ratio and hydrogen storage ratio on the operational performance of the proposed systems. Increasing the hydrogen storage ratio (φ = 0–0.5) reduces the PEMFCs power output, but the energy efficiency and exergy efficiency of the PEMFC-ORC subsystem increased by 2.29% and 1.39%, respectively.