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A novel integrated system based on solid oxide fuel cells (SOFCs), a gas turbine (GT), the steam Rankine cycle (SRC), the Kalina cycle (KC), and the organic Rankine cycle (ORC) is proposed to achieve cascade energy utilization. Mathematical models are introduced and system performance is analyzed using energy and exergy methods. The first and second laws of thermodynamics are used to analyze the system thermodynamically. In addition, exergy destruction and losses of the various integrated subsystems are calculated. The energy and exergy efficiencies of the multigeneration system are estimated to be 60.4% and 57.3%, respectively. In addition, the hot water produced during the waste heat recovery process may also be used for accommodating seafarers on ships. Sequential optimization is developed to optimize the operating conditions of the integrated system to achieve the required power output. A comprehensive parametric study is conducted to investigate the effect of varying the current densities of the fuel cell and working fluid of the ORC on the overall performance of the combined system and subsystems. The working performance of five working fluids for the ORC as candidates—R134a, R600, R601, R152a, and R124—is compared. R152a, which provides 71.23 kW of power output, and energy and exergy efficiencies of 22.49% and 42.76%, respectively, is selected as the best thermodynamic performance for the ORC.

One of the main goals of the shipping industry is to decarbonize the fuels used in maritime transportation. Ammonia is thought to be a potential alternative for hydrogen storage in the future, allowing for CO2-free energy systems. Ammonia’s beneficial characteristics with regard to hydrogen storage include its high volumetric hydrogen density, low storage pressure, and long-term stability. However, ammonia is characterized by toxicity, flammability, and corrosiveness, making safety a challenge compared to other alternative fuels. In specific circumstances, leakage from ammonia bunkering can cause risks, dispersion, and unsafe areas due to its flammability and toxicity. Based on an analysis of 118 research papers and 50 regulations and guidelines, this review report evaluates various aspects of the hazards associated with the ammonia bunkering processes, considering both current and future implications. This report also includes the latest advancements and potential developments related to the safety of ammonia as a marine fuel. Several related regulations and standards for ammonia supply systems are discussed. This paper examines experiments and numerical investigations conducted using different methods of ammonia bunkering, such as terminal-to-ship, ship-to-ship, and truck-to-ship transfers. This review shows that the toxicity of ammonia is more relevant to the topics of vapor cloud dispersion and ammonia bunkering than its flammability. Finally, the main challenges and recommendations for the implementation of ammonia bunkering and further development of ammonia as a marine fuel are proposed. This review suggests new directions to overcome the disadvantages and research gaps associated with the leakage of ammonia during bunkering periods.

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.

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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.

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