Search Results (108)

This study proposes an improved super-twisting sliding mode (STSM) control method for a brushless doubly fed induction generator (BDFIG) used in standalone ship shaft power generation systems. Focusing on the problem of the low tracking accuracy of the power winding (PW) voltages caused by the parameter perturbation of BDFIG systems, a mismatched uncertain model of the BDFIG is constructed. Additionally, an improved STSM control method is proposed to address the power load variation and compensate for the mismatched uncertainty through virtual control technology. Based on the direct vector control of the control winding (CW), the proposed method ensured that the voltage amplitude error of the power winding could converge to the equilibrium point rather than the neighborhood. Finally, in the experimental investigation of the BDFIG-based ship shaft independent power system, the dynamic performance in the startup and power load changing conditions were analyzed. The experimental results show that the proposed improved STSM controller has a faster dynamic response and higher steady-state accuracy than the proportional integral control and the linear sliding mode control, with strong robustness to the mismatched uncertainties caused by parameter perturbations. Full article

With the natural evolution of the Arctic route and advancements in related technologies, the development of new green ice-class ships is becoming a key technological breakthrough for the global shipbuilding industry. As a special vessel form that must perform icebreaking operations and undertake long-distance ocean voyages, an ice-class ship requires sufficient icebreaking capacity to navigate ice-covered water areas. However, since such ships operate for most of their time under open water conditions, it is also crucial to consider their resistance characteristics in these environments. Firstly, this paper employs linear interpolation to extract wind, wave, and sea ice data along the route and calculates the proportion of ice-covered and open water area in the overall voyage. This provides data support for hull form optimization based on real sea state conditions. Then, a resistance optimization platform for ice-class ships is established by integrating hull surface mixed deformation control within a scenario analysis framework. Based on the optimization results, comparative analysis is conducted between the parent hull and the optimized hull under various environmental resistance scenarios. Finally, the optimization results are evaluated in terms of energy consumption using a fuel consumption model of the ship’s main engine. The optimized hull achieves a 16.921% reduction in total resistance, with calm water resistance and wave-added resistance reduced by 5.92% and 27.6%, respectively. Additionally, the optimized hull shows significant resistance reductions under multiple wave and floating ice conditions. At the design speed, calm water power and hourly fuel consumption are reduced by 7.1% and 7.02%, respectively. The experimental results show that the hull form optimization process in this paper can take into account both ice-region navigation and ice-free navigation. The design ideas and solution methods can provide a reference for the design of ice-class ships. Full article

This study presents a multi-objective predictive energy management system (EMS) for optimizing hybrid renewable energy systems (HRES) in autonomous marine vessels. The objective is to minimize fuel consumption and emissions while maximizing renewable energy usage and pure-electric sailing durations. The EMS combines nonlinear model predictive control (NMPC) with metaheuristic optimizers—Grey Wolf Optimization (GWO) and Genetic Algorithm (GA)—and is benchmarked against a conventional rule-based (RB) method. The HRES architecture comprises photovoltaic arrays, vertical-axis wind turbines (VAWTs), diesel engines, generators, and a battery storage system. A ship dynamics model was used to represent propulsion power under realistic sea conditions. Simulations were conducted using real-world operational and environmental datasets, with state prediction enhanced by an Extended Kalman Filter (EKF). Performance is evaluated using marine-relevant indicators—fuel consumption; emissions; battery state of charge (SOC); and emission cost—and validated using standard regression metrics. The NMPC-GWO algorithm consistently outperformed both NMPC-GA and RB approaches, achieving high prediction accuracy and greater energy efficiency. These results confirm the reliability and optimization capability of predictive EMS frameworks in reducing emissions and operational costs in autonomous maritime operations. Full article

With the increasingly stringent regulation of ship carbon emissions by the International Maritime Organization (IMO), improving ship energy efficiency has become a key research direction in the current shipping industry. This paper proposes and evaluates a comprehensive energy-saving solution that integrates a wind-assisted propulsion system (WAPS) and an organic Rankine cycle (ORC) waste heat power generation system. By establishing an energy efficiency simulation model of a typical ocean-going cargo ship, the appropriate optimal system configuration parameters and working fluids are determined based on minimizing the total fuel consumption, and the impact of these two energy-saving technologies on fuel consumption is systematically analyzed. The simulation results show that the simultaneous use of these two energy-saving technologies can achieve the highest energy efficiency, with the maximum fuel savings of approximately 21%. This study provides a theoretical basis and engineering reference for the design of ship energy-saving systems. Full article

This paper presents a robust optimization-based approach for voyage and power generation scheduling to enhance the economic efficiency and reliability of electric propulsion ships powered by polymer electrolyte membrane fuel cells (PEMFCs) and battery energy storage systems (BESSs). The scheduling method is formulated considering generation cost curves of PEMFCs with mixed-integer linear programming (MILP) and is extended to a robust optimization framework that accounts for marine environmental uncertainties. The robust optimization approach, implemented via the column-and-constraint generation (C&CG) method, ensures stable operation under various uncertainty scenarios, such as wave speed and direction influenced by wind and tidal currents. To validate the proposed method, a simulation was conducted under realistic operational conditions, followed by a case study comparing the MILP and robust optimization approaches in terms of economic efficiency and reliability. Additionally, the optimization model incorporated degradation costs associated with PEMFCs and BESSs to account for long-term operational efficiency. The case study assessed the performance of both methods under load variation scenarios across different marine environmental uncertainties. Full article

22MnCrNiMo steel, a high-strength low-alloy material, is primarily used in the production of mooring chains for offshore oil platforms, offshore wind turbines, and ships. The application of additive manufacturing technology allows for the direct fabrication of seamless mooring chains. This paper investigates the selective laser melting (SLM) process parameters for 22MnCrNiMo mooring chain steel, analyzing the effects of different process parameters on the microstructure, phase composition, and mechanical properties of the steel. The experimental results demonstrate that under the laser parameters of 200 W laser power, 800 mm/s scanning speed, 30 μm layer thickness, and 110 μm scanning spacing, the SLM-formed parts exhibit the best comprehensive mechanical properties, with a microhardness of 513.2 HV0.5, a tensile strength of 1223 MPa, a yield strength of 1114 MPa, an elongation of 8.5%, and an impact energy of 127 J. This study reveals the microstructure evolution and the mechanism of enhanced mechanical properties in SLM-fabricated 22MnCrNiMo steel, providing a new approach for the preparation of high-performance mooring chains using 22MnCrNiMo steel. Full article

Offshore wind energy is increasingly considered a vital resource to contribute to the renewable energy future. This renewable energy can be converted to clean energy alternatives such as hydrogen and ammonia via power-to-x technologies, enabling storage, energy security, and decarbonization of hard-to-abate sectors. This study assesses the techno-economic feasibility of integrating offshore wind energy with hydrogen and ammonia production as sustainable energy carriers and their transportation via pipelines or shipping. The methodology incorporates Proton Exchange Membrane (PEM) electrolysis for hydrogen production, seawater desalination, and the Haber–Bosch process for ammonia production. Offshore transport scenarios are compared to evaluate their cost-effectiveness based on distance and electrolyzer capacity. Results show the levelized cost of hydrogen (LCOH₂) ranges from EUR 6.7 to 9.8/kg (EUR 0.20–0.29/kWh), and the levelized cost of ammonia (LCOA) ranges from EUR 1.9 to 2.8/kg (EUR 0.37–0.55/kWh). Transportation costs vary significantly with distance and electrolyzer capacity, with levelized cost of transport (LCOT) between EUR 0.2 and 15/kg for pipelines and EUR 0.3 and 10.2/kg for shipping. Also, for distances up to 500 km, pipeline transport is the most cost-effective option for both hydrogen and ammonia. Despite high production costs, economies of scale and technological improvements can make offshore hydrogen and ammonia a promising means for a sustainable energy future. Full article

Offshore cranes are widely used in important fields such as wind power construction and ship replenishment. However, large payloads such as wind turbine blades are hoisted by multiple steel wire ropes, which makes it difficult to directly control their movements; that is, the number of input degrees of freedom is less than that of the output degrees of freedom. In addition, compared with land cranes, offshore cranes are inevitably affected by waves, wind, etc. The transition from a fixed base to a dynamic base brings severe challenges to their oscillation suppression and precise positioning. At the same time, to improve operational efficiency, the hoisting operation of offshore cranes usually adopts velocity input control patterns that fit the habits of manual operation, and most of them are in the form of dual-axis linkage for pitch and hoisting. Therefore, this paper proposes a fast terminal sliding mode control method for double-pendulum offshore cranes with distributed-mass payloads (DMPs). First, a nonlinear dynamic model of offshore cranes considering DMPs is established, and a dynamic model based on acceleration input control patterns is acquired. Based on this, considering the variation in hoisting rope lengths, a novel adaptive control method is proposed. Finally, simulation results verify the effectiveness of the proposed method, and the robustness of the proposed method to DMP mass parameter uncertainty and disturbances is demonstrated. Full article

This study introduces an innovative Emotional Artificial Neural Network (EANN) model to predict ship fuel consumption with high accuracy, addressing the challenges posed by complex environmental conditions and operational variability. This research examines the impact of climate change on maritime operations and fuel efficiency by analyzing climatic variables such as wave period, wind speed, and sea-level rise. The model’s performance is assessed using two ship types (bulk carrier and container ship with max 60,000 dead weight tonnage (DWT)) under various climate scenarios. A comparative analysis demonstrates that the EANN model significantly outperforms the conventional Feedforward Neural Network (FFNN) in predictive accuracy. For bulk carriers, the EANN achieved a Root Mean Squared Error (RMSE) of 5.71 tons/day during testing, compared to 9.91 tons/day for the FFNN model. Similarly, for container ships, the EANN model achieved an RMSE of 5.97 tons/day, significantly better than the FFNN model’s 10.18 tons/day. A sensitivity analysis identified vessel speed as the most critical factor, contributing 33% to the variance in fuel consumption, followed by engine power and current speed. Climate-change simulations showed that fuel consumption increases by an average of 22% for bulk carriers and 19% for container ships, highlighting the importance of operational optimizations. This study emphasizes the efficacy of the EANN model in predicting fuel consumption and optimizing ship performance. The proposed model provides a framework for improving energy efficiency and supporting compliance with International Maritime Organization Standards (IMO) environmental standards. Meanwhile, the Carbon Intensity Indicator (CII) evaluation results emphasize the urgent need for measures to reduce carbon emissions to meet the IMO’s 2030 standards. Full article

This study presents a methodological framework for integrating LCA principles into the preliminary design phase of an offshore vessel. The framework is based on the case of a wind farm installation vessel (WTIV). The proposed approach diverges from traditional ship design by treating environmental impact as an important criterion and integrates the LCA into the early design stages, which is a novelty of the sustainability-driven ship design. On the basis of steps usually conducted in the preliminary ship design, a parametric study was conducted to evaluate the life cycle emissions associated with the shipbuilding, maintenance, operation, and dismantling phases. Ship characteristics such as displacement, lightship weight, and main dimensions were correlated with LCA factors, enabling the quantification of emissions at an early design stage with the use of the developed database and statistical regression models. Power demand estimation for different operational scenarios—free-running transit, dynamic positioning, and stationary installation—highlighted the significant contribution of offshore-specific vessel activities to life cycle emissions. The results demonstrate that the operational phases remain the most important contributors to overall emissions, mostly through CO₂ and NO_x production. However, emissions from shipbuilding, maintenance, and dismantling also play a critical role, justifying the need for early design interventions. Our findings highlight the need to integrate LCA into the design spiral for balanced sustainability, efficiency, and feasibility. This study provides a foundation for future research into multi-objective optimization models that incorporate LCA into offshore vessel design. Full article

This study investigates the seakeeping performance of a wind power generation ship (WPG ship). This type of vessel uses rigid sails for propulsion and submerged turbines in the form of either two or four booms to generate energy. The research includes both tank tests and simulations using Ansys AQWA, validated with the new strip method (NSM). The vessel used in this study is the container ship KCS. Overall, the power generator increases the ship’s stability and reduces roll but has almost no impact on pitch. The findings show that the 4-boom configuration offers better stability and seakeeping than the 2-boom configuration. The ship’s speed has a significant impact on the ship’s RAO, especially roll and pitch, both for the bare hull and the hull with power generation equipment. When the ship’s speed increases slightly, the roll RAO tends to decrease, but as the speed becomes higher, the RAO tends to increase. Wind conditions notably increase the roll RAO peak, reducing stability, while pitch changes are minimal. The KCS model maintains operational capability in winds up to Beaufort scale 11. Full article

The maritime industry is going through a technology transition, aiming to have carbon-neutral propulsion systems. A significant trend of orders for ships with alternative propulsion has been observed. A favorable means to meet the decarbonization requirements imposed by IMO (International Maritime Organization) is to operate vessels with sustainable energy. Harvesting wind power and its conversion into ship propulsion are gaining popularity due to emission reductions and expected reductions in fuel consumption. This paper reviews recent studies on wind-assisted propulsion systems (WAPSs), the different aspects of using sail applications in the maritime industry, and the types of wind-assisted propulsion systems. The study also presents the latest developments in WAPS systems offered by leading maritime market manufacturers and their applications on existing vessels. The article is based on a literature review (peer-reviewed articles), the information provided by wind propulsion systems manufacturers and internet research. Full article

In order to solve the problem of large-scale offshore wind power consumption, the development of an offshore wind power hydrogen supply chain has become one of the trends. In this study, 10 feasible options are proposed to investigate the economics of an offshore wind hydrogen supply chain for offshore hydrogen refueling station consumption from three aspects: offshore wind hydrogen production, storage and transportation, and application. The study adopts a levelized cost analysis method to measure the current and future costs of the hydrogen supply chain. It analyses the suitable transport modes for delivering hydrogen to offshore hydrogen refueling stations at different scales and distances, as well as the profitability of offshore hydrogen refueling stations. The study draws the following key conclusions: (1) the current centralised wind power hydrogen production method is economically superior to the distributed method; (2) gas-hydrogen storage and transportation is still the most economical method at the current time, with a cost of CNY 32.14/kg, which decreases to CNY 13.52/kg in 2037, on a par with the cost of coal-based hydrogen production using carbon capture technology; and (3) at the boundaries of an operating load factor of 70% and a selling price of CNY 25/kg, the offshore hydrogen refueling station. The internal rate of return (IRR) is 21%, showing good profitability; (4) In terms of the choice of transport mode for supplying hydrogen to the offshore hydrogen refueling station, gas-hydrogen ships and pipeline transport will mainly be used in the near future, while liquid organic hydrogen carriers and synthetic ammonia ships can be considered in the medium to long term. Full article

Many modern electric drives for cars, trucks, ships, etc., use permanent magnet synchronous motors because of their compact size. At the same time, permanent magnets are expensive, and their uncontrolled flux is a problem when it is necessary to provide a wide constant power speed range in the field weakening region. An alternative to permanent magnet motors is synchronous motors with field windings. This article presents a novel design of a traction brushless synchronous motor with a field winding and a two-phase harmonic exciter winding on the rotor and zero-sequence signal injection. The two-phase harmonic exciter winding increases the electromotive force on the field winding compared to a single-phase one and makes it possible to start the motor at any rotor position. This article discusses the advantages of the proposed design over conventional solutions. A simplified mathematical model based on the finite element method for steady state simulation is presented. The machine performance of a hysteresis current controller and a field-oriented PI current controller are compared using the model. Full article

To attain a low Energy Efficiency Design Index (EEDI), large ships possibly lack the necessary propulsion power to avoid stranding in case of strong adverse wind and wave conditions. To estimate this danger, here, the longitudinal and transverse drift force and the yaw drift moment caused by regular waves of arbitrary frequency and direction are computed using a 3-dimensional Rankine panel method. In many cases, drift forces are larger in shallow than in deep water. Therefore, the theory for computing drift force and moment is extended to shallow water. As published results for shallow water are lacking, the method is verified only for deep water by comparisons with results of model experiments and CFD computations for three ships. For one of them, the dependence of non-dimensional coefficients of longitudinal and transverse drift force and of the drift yaw moment on wave frequency, wave angle, water depth and ship speed is shown. The source files of the programs used for these computations may be obtained from the author if an adequate fee is donated to the Medecins Sans Frontieres or to the author. Full article