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.

This study comprehensively reviews the current academic literature concerning the safety and risk assessment associated with the utilization of liquefied natural gas (LNG) in ship-to-ship bunkering scenarios. Simultaneously, it explores the complex system of regulations, standards, and guidelines that oversee the thorough evaluation of risks linked to ship-to-ship LNG bunkering procedures. Special attention is given to the scrutiny of legal frameworks that encompass a range of safety considerations, such as storage facilities, transportation, bunkering processes, and the vessels involved in both bunkering and receiving. The research questions are formulated to provide a clear direction and objectives for this study’s journey. The main hazards and risks related to LNG bunkering are identified and analyzed. The legal framework for LNG bunkering risk assessment is analyzed, and opportunities for improvement in these legal documents are identified. The general methodology and procedure for the safety assessment of the LNG bunkering process are summarized and established. From an extensive compilation of scholarly articles, 210 high-quality research papers have been deliberately selected for thorough examination. The research gaps are identified and analyzed. Through this analysis, the highlighted studies and key points are mentioned and analyzed. The research gaps are also outlined to predict the future directions of research on establishing safety zones during LNG ship-to-ship bunkering. Recommendations are made to propose improvements to the legal documents and suggest further research on the establishment of safety zones during ship-to-ship LNG bunkering to relevant authorities.

This paper presents a systematic investigation that encompasses the safety assessment of a fuel preparation room (FPR) intended for a hydrogen-fueled ship. The primary objective is to determine the appropriate ventilation strategy to mitigate the risks associated with potential hydrogen leakage. The study focuses on a case involving an FPR measuring 10.2 m × 5.3 m × 2.65 m, which is part of a 750 DWT hydrogen-powered fishing vessel. To identify the potential events leading to hydrogen dispersion, an event tree analysis is conducted. Additionally, existing regulations and guidelines related to the safety assessments of hydrogen leakage in enclosed areas are summarized and analyzed. Computational fluid dynamics, FLACS-CFD, are utilized for the consequence analysis in order to evaluate the impact of ventilation on hydrogen dispersion and concentration within the FPR. The research findings indicate significant effects of ventilation on the hazards and safety assessments of FPRs and high-pressure fuel gas supply systems. The study highlights that hydrogen vapor tends to accumulate at the ceiling and in the corners and spaces created by the equipment. The position and size of ventilation openings greatly influence the dispersion of hydrogen leakage. Proper ventilation design, including top inlet ventilation and outlet ventilation on the opposite side, helps to maintain a safe FPR by facilitating the efficient dispersion of hydrogen vapor. Moreover, locating inlet ventilation on the same side as the outlet ventilation is found to hinder dispersion, while the cross-ventilation achieved by placing inlets and outlets on opposite sides enhances airflow and dispersion. Consequently, it is recommended to prioritize the structural design of FPRs and implement enhanced safety measures. Additionally, updating the relevant regulations to address these concerns is strongly advised.

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.

The LNG price is basically determined based on the oil price, but other than that, it is also determined by the influence of the method of LNG transportation; storage; processes; and political, economic, and geographical instability. Liquefied natural gas (LNG) may not reflect its market value if the destination of the purchase is restricted or the purchase contract includes a take-or-pay clause. Furthermore, it is difficult for the buyer to flexibly manage procurement, resulting in the decoupling of oil and natural gas prices. Therefore, as the LNG bunker price is expected to be more volatile than the marine bunker price in the future, shipping companies need to prepare countermeasures based on scientific forecasting techniques. This study aims to be the first to analyze the forecasting of short-term LNG bunker prices using recurrent neural network (RNN) models suitable for highly volatile data such as time series. Predictive analysis was performed using simple RNN, long short-term memory (LSTM), and gated recurrent unit (GRU) models, which effectively forecast time-series data, and the prediction performance of LSTM among the three models was excellent. LSTM had relatively excellent prediction performance of outliers and beyond. In addition, it was possible to effectively manage ship operating costs with improved forecasting in practice. Furthermore, this study contributes to establishing a systematic strategy for supervisors in global shipping companies, port authorities, and LNG bunkering companies.