Search Results (388)

The accelerated global transition toward eco-friendly mobility has necessitated robust decarbonization measures across the maritime sector, with battery-powered electric propulsion ships emerging as a promising alternative. Accordingly, the applicability of silicon carbide (SiC)-based technology to propulsion inverters, a key component of such vessels, is currently under investigation. Although life cycle assessment (LCA) studies comparing conventional silicon (Si)-based and SiC-based inverters have been conducted previously, these analyses neglect realistic operating profiles and load fluctuations, limiting their applicability. Furthermore, life cycle cost assessment (LCCA) integrating real-world operating conditions has rarely been addressed. To address these gaps, this study conducted a comparative LCA and LCCA of Si IGBT and SiC MOSFET inverters for marine electric propulsion systems across three vessel types: a cruise ship, a passenger and car ship, and a recreational boat, incorporating real-world load profiles to evaluate global warming potential (GWP), fossil depletion (FD), and cumulative energy demand (CED). The static LCA results showed negligible differences between inverter types, contributing less than 1% to total impacts. The dynamic LCA demonstrated that SiC MOSFET inverters reduced environmental impacts by approximately 57%, 52%, and 34% for cruise ships, passenger and car ships, and recreational boats, respectively. Despite a 40% higher initial investment cost, SiC inverters achieved payback periods well within vessel lifetimes across all vessel types. These findings support SiC inverters as a sustainable and economically viable solution for ship electrification. Full article

The maritime sector accounts for approximately 3% of global greenhouse gas (GHG) emissions and faces binding decarbonization obligations under the International Maritime Organization’s (IMO) Net-Zero Framework and the FuelEU Maritime Regulation. Conventional marine fuels, including very low sulphur fuel oil (VLSFO) and liquefied natural gas (LNG), are insufficient to meet long-term regulatory intensity targets on a well-to-wake (WtW) lifecycle basis, creating an urgent need for credible fuel alternatives. This study investigates ethanol as a primary fuel for marine dual-fuel propulsion systems, assessed across four distinct production pathways, sugar beet, corn, sugarcane, and wheat straw, to determine its full decarbonization potential relative to VLSFO and LNG benchmarks. A simulation-based multi-dimensional evaluation framework is developed and applied, integrating dynamic operational simulation, energy analysis, environmental lifecycle modelling, and regulatory compliance assessment. The framework is calibrated against a high-resolution dataset from an active container ship, with scenario-specific engine data. While ethanol requires 39.1% more fuel mass than VLSFO due to its lower energy density, all four ethanol pathways deliver substantially superior WtW GHG reductions: from 50.2% (corn) to 76.9% (wheat straw), compared with 20.6% for LNG. All ethanol scenarios satisfy FuelEU compliance limits across the 2026–2045 horizon, with wheat straw ethanol achieving a GFI of 22.52 gCO₂e/MJ, compliant marginally with the 2040 IMO target. These findings demonstrate that bio-based ethanol, particularly from lignocellulosic feedstocks, is a technically viable and regulatorily superior alternative to LNG for maritime decarbonization, warranting accelerated research into production scale-up and bunkering infrastructure development. Full article

Layered Li-rich manganese-based Li_1.2Ni_0.13Co_0.13Mn_0.54O₂ (LNCMO) is regarded as a promising high-capacity cathode material. However, its commercial application is severely hindered by rapid capacity fading, serious voltage decay and poor cycling stability. Herein, a facile non-sintering electrostatic adsorption strategy employing PDDA is proposed to fabricate a uniform and dense graphene oxide (GO) coating on LNCMO particles. Structural and morphological characterizations confirm the successful decoration of GO on the surface of LNCMO. The optimized 0.5@LNCMO sample delivers a discharge capacity of 330 mAh g⁻¹ at 0.1C, and maintains a capacity retention of 86.5% after 200 cycles at 1C and 83.3% after 400 cycles at 5C, showing much better electrochemical performance than pristine LNCMO. This study proves that the proposed strategy is an effective modification method for constructing high-performance Li-rich cathode materials. Full article

This paper presents a robust fault-tolerant control (FTC) strategy for a multiphase PMSM-based propulsion system. The proposed approach combines an innovative super-twisting sliding mode controller (IST SMC) with a fault-tolerant model of the machine when an open-circuit fault occurs. The electrical propulsion system mainly has a two-line structure with a single DC source, a five-leg inverter and a Five-Phase Permanent Magnet Synchronous Motors (5-Φ PMSM), suitable for marine propulsion applications. Two main scenarios are investigated in this work. Firstly, if an open-phase fault occurs in one of the two 5-Φ PMSMs, a reconfiguration step of the machine control is applied in order to improve the performance of the propulsion system and to ensure the continuity of operation. Then, if the fault occurs in one of the two inverters, the faulty one is removed and the electrical series connection is made between the two machines, where they are powered by a single five-arm inverter, thus ensuring the continuity of operation of the system. Considering these two scenarios, a comparative analysis is made between the IST SMC and the classical PI controllers in terms of robustness to uncertainties, external disturbances and tracking accuracy for healthy and faulty operation modes, and during transient states. Full article

The dilution of lubricating oil with diesel oil (DO) is a significant operational problem in piston combustion engines, as it degrades lubrication conditions and may accelerate the wear of interacting components. This study aimed to evaluate the usefulness of selected thermophysical and electrical properties of lubricating oil for determining the degree of its dilution with diesel oil. The tests were conducted on mixtures of SAE 30 or SAE 40 lubricating oil with diesel oil over a concentration range of 0–100% m/m of the latter material. Changes in thermal conductivity, thermal effusivity, and breakdown voltage were examined as a function of the mixture’s fuel content. The thermal conductivity and effusivity of the tested oils were measured using the MTPS (Modified Transient Plane Source) transient method, while the breakdown voltage of the tested oils was measured at mains frequency using an apparatus in which the oil sample was exposed to an increasing electric field by gradually increasing the alternating voltage at a constant frequency until electrical breakdown occurred. An increase in the proportion of diesel oil caused a systematic linear decrease in thermal conductivity and thermal effusivity. A decreasing trend was also observed for breakdown voltage; however, this parameter exhibited significantly greater variation in results. The results indicate that thermal conductivity and thermal effusivity are more useful for assessing the degree of dilution of lubricating oil with DO than breakdown voltage. Full article

This paper presents a complete analysis and simulation of the operation of a zero-emission marine vessel with electric propulsion. A hypothetical passenger ferry operating in the Aegean Sea, Greece, is considered, which is powered by a hydrogen fuel cell, a battery energy storage system (BESS) and photovoltaic (PV) energy. Wind-assisted ship propulsion (WASP) is employed to reduce the energy consumption of the ship. A complete analysis is performed, which includes optimal energy management, dynamic analysis and emerging stability concerns due to the high integration of power electronic converters in the shipboard microgrid. The energy management system (EMS) applies multi-objective optimization based on the corona virus optimization (CVO) algorithm and the teaching–learning-based optimization algorithm (TLBO). The dynamic behavior of the microgrid is tested using real-time digital simulations. Converter-driven stability issues are investigated, which may arise due to interactions among the various converter controllers and passive components of the microgrid. Full article

Additive manufacturing (AM), also known as three-dimensional (3D) printing, has emerged as a revolutionary digital near-net-shape manufacturing technology, offering innovative solutions for the design and fabrication of complex, high-performance structures and equipment. This paper reviews the recent advancements and applications of metal AM technologies in the marine sector. Firstly, the principles and characteristics of three most widely adopted metal AM processes in this field are introduced: laser powder bed fusion (L-PBF), directed energy deposition (DED), and wire arc additive manufacturing (WAAM). Subsequently, the application status of metal AM is summarized in four key marine sectors: propulsion systems, underwater vehicle housings and structures, hull structures and shipboard equipment and components, as well as marine equipment repair and emergency support. Building on this, the major challenges for metal AM applications in the marine environment are further discussed, including the fabrication of large-scale components, standardization of materials and processes, integration of smart manufacturing and digital technologies, and sustainability and circular manufacturing. Finally, future trends are projected toward higher efficiency, intelligence, and environmental sustainability. It is indicated that metal AM will fundamentally reshape the manufacturing mode of marine equipment and support its high-performance, low-cost, intelligent and rapid-response development. Full article

In this work, the underwater acoustic signatures of marine vessels are investigated, with a focus on the impacts of methanol-based high-temperature proton exchange membrane fuel cell (HT-PEM FC) propulsion systems and their coupling with structural dynamics. The acoustic field is modeled through a monopole–dipole representation directly linked to the vibration and dynamic response of the vessel structure and propulsion units. The model is validated against experimental sound pressure level (SPL) data as a function of depth, showing excellent agreement: the SPL decreases from about 140 dB at 5 m to approximately 120 dB at 50 m, where the model prediction (119 dB) closely matches the experimental value (121 dB). Representative numerical results indicate the suppression of the monopole component for the HT-PEM FC and a reduction in the dipole pressure amplitude by approximately a factor of 19 relative to the diesel engine (DE) configuration. In the 20–100 Hz band, at $r=10$ m, the acoustic pressure amplitudes range from $\mathcal{O}({10}^1-{10}^2)$ Pa for the diesel engine (DE) to $\mathcal{O}({10}^0-{10}^1)$ Pa for the HT-PEM FC, while, at $r={10}^5$ m, they decrease to $\mathcal{O}({10}^0-{10}^1)$ Pa and $\mathcal{O}({10}^{-1}-{10}^{-2})$ Pa, respectively. The absolute levels depend on the assumed structural excitation and vibro-acoustic coupling and are mainly used here to quantify the relative reduction achieved by the HT-PEM FC with respect to the DE. A distance-normalized formulation is introduced to account for geometric spreading, enabling a consistent comparison despite differences in source characteristics. Overall, the proposed framework establishes a direct link between structural vibrations and underwater radiated noise and provides a physically consistent and quantitatively validated approach for the design of low-signature marine propulsion systems. Full article

With the development of shipping to harsh marine environment, it is very important to understand the transient behavior of a marine diesel engine in high sea conditions. Wave-induced hull motion will lead to severe load fluctuations and air-fuel ratio imbalance. In this study, an integrated simulation platform coupled with environmental loads, hull dynamics, propeller characteristics and a high-fidelity thermodynamic engine model was constructed to explore the response characteristics of the propulsion system. The model integrates a zero-dimensional multi-zone combustion method, turbocharger dynamic characteristics and an incremental PID governor, and has been verified based on the bench test data of TBD234V12 diesel engine and the 20 m Wigley standard ship. The simulation results under the sea conditions from level 7 to 9 show that the transient load has a nonlinear amplification effect. Specifically, from sea state 7 to sea state 9, the engine load fluctuation range expands by 2.0 times, while the main peak amplitude of speed fluctuation increases by 3.7 times. Furthermore, the peak exhaust pressure rises by 1.8 times, and the exhaust temperature fluctuation amplitude broadens by 35%. Frequency domain analysis further identified the low-frequency energy concentration phenomenon in the exhaust pressure spectrum and the precursor characteristics of compressor surge. The research results quantify the deterioration law of thermodynamic stability and mechanical stress under wave disturbance, and provide an important reference for the formulation of an engine robust control strategy and fatigue life assessment under high sea conditions. Full article

Ocean monitoring is essential for understanding climate change and marine ecosystem dynamics, yet achieving comprehensive global coverage remains a challenge in oceanography. Current technologies face limitations in cost, power, hardware, and depth capacity that restrict widespread monitoring capabilities. Here we show that biohybrid robotic jellyfish (Aurelia aurita) can serve as autonomous vertical ocean profilers by integrating microcontrollers with positively buoyant sensor payloads, achieving controlled vertical-profiling capabilities. Laboratory experiments demonstrated repeatable up–down trajectories, quantified force balance limits, and identified predictable, size-dependent descent swimming speeds. Field deployments in Massachusetts coastal waters and the open ocean off the Florida Keys demonstrated field operation to ocean depths >25 m with successful in situ temperature and depth measurements. To our knowledge, this represents the first biohybrid jellyfish platform to combine autonomous, pressure-triggered vertical profiling with onboard oceanographic sensing in natural marine environments. This approach leverages the global distribution and remarkable swimming efficiency of living jellyfish while eliminating propulsion power requirements by utilizing the animal’s natural swimming capabilities. While further development is required for long-term ocean deployment, this study lays the groundwork for a new class of biohybrid ocean-sensing platforms with advantages in cost, power, and mission flexibility, providing a pathway toward dense sensor networks and increased ocean monitoring observations. Full article

The exhaust gas temperature (EGT) of the gas generator is a critical indicator for the health management system of a marine gas turbine engine. Therefore, EGT prediction can not only support predictive maintenance decision-making but also serves as a reliable virtual sensor for EGT measurement. However, the engine EGT exhibits strongly nonlinear coupling relationships with other gas path variables, which causes challenges for data-driven prediction. Graph neural networks (GNNs) are particularly effective in capturing the coupling relationships among gas path sensor variables. However, conventional static graph structures fail to characterize the varying coupling strengths under different operating conditions. In this study, a thermodynamic knowledge-driven graph attention network (TKD-GAT) method is proposed for accurate and robust EGT prediction. First, a physics-guided graph topology is constructed based on the gas turbine thermodynamic equations. Subsequently, a multi-head attention mechanism is introduced to generate edge weights that capture the varying thermodynamic coupling strengths under different operation conditions. The proposed model is evaluated on a real-world LM2500 gas turbine, which is widely used in modern propulsion systems of commercial and military ships. The ablation study confirms that the thermodynamic knowledge-driven graph topology and the attention mechanism-based edge weights are both necessary to enhance the EGT prediction performance. The TKD-GAT model shows the best performance with an RMSE of 0.446% and an R² of 0.971 compared with state-of-the-art models. The paired t-test and effect size measurement (Cohen’s d) statistically confirm the significance of performance improvements. The statistical results from multiple independent experiments prove the stability of the TKD-GAT model. Additionally, the model achieves a competitive computational cost despite the integration of a physics-guided graph topology and attention mechanisms. Crucially, an interpretability analysis confirms that the learned attention weights adhere to thermodynamic principles under different operation conditions. The proposed TKD-GAT model provides an effective solution for EGT prediction in health management systems. Full article

The in-service assessment of marine propulsion engines requires more than nominal rating comparison because operating severity is shaped by propeller demand, resistance growth, air-path response, and thermal state. This study develops a quantitative benchmarking method for the regime-dependent performance assessment of a low-speed two-stroke Wärtsilä 6RT-flex58T-D engine installed on a 31,000 DWT multi-purpose container vessel. The method integrates certified sea-trial measurements, endurance-test records, manufacturer load-diagram constraints, and a 15% service-margin projection within one reference framework. Three representative regimes are evaluated: a measured light-running baseline (SR1), a measured thermally stabilised sustained regime (SR2), and a projected heavy-running regime derived from the baseline using a 15% sea-margin assumption (R2). Comparison is performed using indicators of operating-point position, shaft torque, propeller-law consistency, selected air-path and thermal variables, load-diagram proximity, and corrected specific fuel oil consumption where available. The SR1 baseline followed the fitted propeller law with deviations not exceeding 1.18%, confirming a coherent light-running reference. In SR2, corrected SFOC decreased from 174.4 to 172.0 g/kWh, while the exhaust temperature before turbine increased from 359 °C to 435 °C, and the corresponding thermal margin decreased from 156 °C to 80 °C. Under the +15% service-margin projection, the required shaft power at the 100% trial point increased from 12,046.0 to 13,852.9 kW, exceeding the 13,560 kW installation MCR by 2.2%, with corresponding 15% increases in torque and BMEP. These results demonstrate that measured baseline operation, sustained-load severity, and projected heavy-running demand can be distinguished quantitatively within one installation-specific load-diagram-based benchmarking framework. Full article

Ship propulsion electrification is an important enabler towards a sustainable shipping industry. Ship power systems are turning into modern microgrids integrating different generation/storage resources, converter technologies and electric propulsion, utilizing different control levels and communication systems. The definition of comprehensive test requirements, set-ups and procedures is critical to ensure that the equipment will behave as expected in the ship system context. Comprehensive testing is becoming increasingly challenging due to complex interactions at the system level, attributed to electrical, mechanical/hydrodynamic, control, protection, and information and communication systems present in modern and future ships. Standardization has addressed the testing of several individual components, as well as specific system tests for marine applications; however, a holistic testing approach is missing. This paper reviews the generic and maritime standards for testing ship electric power propulsion systems and equipment, focusing on generators/motors, power electronic drives and onshore power supply systems. A review of the scientific literature is performed, classifying the publications according to the testing method, such as pure hardware tests, co-simulation and hardware in the loop simulation (HIL). The need for holistic testing of shipboard microgrids is explained. A holistic HIL testing approach is proposed, which integrates hardware controllers and power equipment of different manufacturers and functions, in order to reduce the complexity and cost of sea trials. The proposed approach is accompanied by example implementation and application guidelines. Full article

This article presents a proposed a new method for estimating the degree of dilution of lubricating oil with diesel oil, which can be applied to systems for ongoing monitoring of lubricating oil quality in an internal combustion engine. The test is performed for reference blends based on two commonly used single-season lubricating oils for marine and industrial engines. SAE 30 and SAE 40 viscosity grade base oils and ISO-F-DMX category diesel oil are used. For each base oil, reference blends are prepared with diesel oil content in the lubricating oil mixture equal to 0, 1, 2, 5, 10, 20, 30, 40, 50, 75, and 100% m/m. Concentration estimates are made for each mixture based on measured kinematic viscosity at different temperatures. Measurements are made for 40, 50, 60, 70, 80, 90, and 100 °C. The results are evaluated by determining the model’s fit to the empirical data and the maximum percentage absolute error in estimating the degree of dilution of the lubricating oil with diesel fuel. The results are contrasted with a previously used model based on the inverse Arrhenius equation for determining the viscosity of binary mixtures. The proposed new model for both base oils, for all tested reference concentrations and for all tested temperatures shows a much better fit to empirical data (R² > 0.999). Moreover, the maximum absolute error of the SATUFER estimation did not exceed the value of 1.5% m/m and, relative to the model based on the inverse Arrhenius equation, it is ~8.9 times higher for mixtures of SAE 30 grade base oil and ~10.3 for mixtures of SAE 40 grade base oil. Full article