This study presents a framework for designing and optimizing ship energy systems including weather-driven speed variability and navigation safety constraints. Navigation risks including resonance, surf-riding, and successive high-wave impacts, are calculated using five years of hourly weather data. Random speed variations (up to ±5%) are applied to a baseline speed profile to capture operational uncertainty, and safety-based speed reductions (up to 40%) are applied when required. Course changes are excluded. Treating navigation risks as constraints, operating profiles are generated for different weather conditions. For a conceptually retrofitted cargo ship, hydrogen fuel cell and battery capacities, and their power distribution, are optimized for each operating profile to minimize lifetime energy system cost and assess the effects of weather-induced power variation. Results show that speed and weather variability can significantly change power demand, requiring fuel cell capacities between 700 and 1500 kW. The most common configuration is a 1200 kW fuel cell system with 180 kWh of battery capacity, covering 39% of laden profiles, while full power coverage requires 1500 kW. Lifetime cost outcomes exhibit a 5th–95th percentile spread of −10.3% to +11.1% relative to mean cost. The results demonstrate the significant influence of weather variability on system sizing and cost.

Low total lifetime cost is essential for the adoption of zero-emission ship energy systems, which must meet operational power demands while complying with onboard safety regulations. However, many studies rely on a simplified, averaged or insufficiently representative load profile and treat system design, operation, and integration feasibility separately, which can distort lifetime cost assessments and result in practically infeasible retrofit concepts. This study investigates how a hydrogen-based ship energy system can be optimally sized, operated, and arranged onboard to minimize total lifetime cost while satisfying operational constraints and stability requirements for a general cargo vessel retrofit. A representative power profile is synthesized from one year of operational data using a probability-based downsampling method and then used in a mixed-integer nonlinear lifetime cost optimization with discrete placement and ballast decisions, solved using the SCIP solver. The optimal retrofit comprises 1.4 MW of fuel cells, 180 kWh of batteries, and a 146 m³ liquefied hydrogen (LH₂) tank, requires 171 t of ballast to satisfy trim and vertical stability constraints, and is primarily driven by fuel costs, which account for 74% of the total lifetime cost. Overall, the results indicate that the viability of hydrogen-based ship retrofits primarily depends on LH₂ storage integration constraints and hydrogen price assumptions, and that the proposed framework provides a practical basis for lifetime cost assessment of feasible retrofit designs.

In motor drives, the quasi-two-level (Q2L) operation of a multilevel converter introduces a controllable inter-cell delay between level transitions, enabling shaping of the generated output-voltage spectrum and common-mode voltage (CMV). This article quantifies the impact of Q2L on common-mode currents and presents a simplified harmonic approximation that maps any two-level (2L) SPWM spectrum to its Q2L counterpart via a closed-form, delay-dependent scaling factor that also captures finite dv/dt. The model supports rapid benchmarking over key design variables, namely the number of switching cells N , inter-cell delay t_d, and rise/fall time t_rf , and is accurate in practice for (Formula presented), where f_c is the PWM carrier frequency. Experimental validation on a flying-capacitor multi-level inverter operated in Q2L mode, assessed using a DC-side conducted emissions measurement test setup based on the CISPR 25 standard, demonstrates tunable attenuation bands in the low-MHz range and measured reductions of up to 12 dB around 1 MHz when increasing N and appropriately tuning t_d. These results provide simple design rules for targeting frequency bands of concern and indicate that Q2L can materially lower common-mode emissions, and thus required filter size in weight- and volume-constrainedapplications such as in electric transportation.

Fuel cells have the potential to reduce greenhouse gas (GHG) emissions from deep-sea shipping. To fully understand the environmental impacts of integrating fuel cells into deep-sea ships, this study evaluates the life cycle environmental impacts from 2020 to 2050 for two leading fuel cell systems: liquid hydrogen with proton exchange membrane fuel cells (liquid-H₂ PEMFC) and liquid ammonia with solid oxide fuel cells (liquid-NH₃ SOFC). The study covers various factors, including changes in cargo capacity, operation modes, developments in hydrogen production and electricity decarbonization. We examine two energy scenarios developed by the International Energy Agency: the Stated Policies Scenario (STEPS) and the Net Zero Emissions by 2050 Scenario (NZE). Our findings reveal that, under different ranges and speeds, the liquid-H₂ PEMFC results in a 2% increase to a 10% decrease in cargo weight, while the liquid-NH₃ SOFC leads to a 4%–23% decrease. By 2050, under the NZE scenario, liquid-H₂ PEMFC and liquid-NH₃ SOFC can reduce GHG emissions per tonne-nautical mile by 69%–75% and 65%–71%, respectively, compared to traditional ships. The use of fuel cells also introduces environmental trade-offs. This assessment can help policymakers gain a more comprehensive understanding of the role of fuel cells in reducing GHG emissions in deep-sea shipping and underscores the potential environmental challenges associated with their large-scale deployment in the future.

Hydrogen-based fuels are potential candidates to help international shipping achieve net-zero greenhouse gas (GHG) emissions by around 2050. This paper quantifies the environmental impacts of liquid hydrogen, liquid ammonia, and methanol used in a Post-Panamax container ship from 2020 to 2050. It considers cargo capacity changes, electricity decarbonization, and hydrogen production transitions under two International Energy Agency scenarios: the Stated Policies Scenario (STEPS) and the Net Zero Emissions by 2050 Scenario (NZE). Results show that, compared to the existing HFO ship, hydrogen-based propulsion systems can decrease cargo weight capacity by 0.3 % to 25 %. In the NZE scenario, hydrogen-based fuels can reduce GHG emissions per tonne-nautical mile by 48 %–65 % compared to heavy fuel oil by 2050. Even with fully renewable hydrogen-based fuels, 18 %–31 % of GHG emissions would still remain. Using hydrogen-based fuels in internal combustion engines requires attention to minimize environmental trade-offs.

The electrification of shipboard power systems (SPSs), combined with the introduction of heterogeneous power sources and energy storage technologies, is driving a need for more advanced and structured control strategies. This review examines control methods and architectures for DC ships, with a specific interest in power systems integrating energy storage systems and zero-emission power generation. Control methods are categorized based on both their functionality and architecture, evaluating their resilience, adaptability, and scalability. Different hierarchical layers are reviewed, distinguishing local control, coordinated control, and energy management methods. Key challenge in the coordinated control arise due to large load fluctuations, constant-power loads, low inertia, and diverse dynamic capabilities of power sources and storage systems. These characteristics complicate voltage stability, dynamic power sharing, and state-of-charge management. Decentralized, centralized, and distributed control architectures are reviewed with respect to scalability, communication requirements, and fault tolerance. At the high-level layer, energy management strategies are discussed in terms of operational efficiency and resiliency, with predictive and distributed methods forming key trends in shipboard power system control. The review highlights the need for resilient, adaptive, and scalable control solutions tailored to future DC SPSs, particularly those integrating fuel cells and energy storage technologies.

Sustainability regulations urge the maritime sector to implement green technologies. The integration of polymer electrolyte membrane fuel cell (PEMFC) systems is a promising solution to cut emissions. However, their degradation in maritime environments is rarely addressed, while the environment differs significantly from land-based or automotive contexts and can greatly affect the type and extent of damage. Research in this field is especially relevant as ships often operate in isolated areas and require durable and reliable power propulsion systems. This work collects the insights from existing PEMFC durability research and analyzes degradation mechanisms specifically relevant for the maritime field. We consider air and fuel contamination, maritime load profiles, and vessel motions as potential causes. Insightful schematics summarize the content by linking these causes to damage indicators. Moreover, we identify various areas for further research including degradation from interconnected effects of maritime drive cycles, marine air salinity, hydrogen-carriers and their residues, long term maritime vibrations, and dynamic inclination. The overview of existing literature combines insights from electrochemistry and maritime research while the knowledge gaps help to prioritize future research. Together, these elements promote collaboration in this multidisciplinary field, advancing mitigation strategies and improving cell, stack, and ship design and operation. Such improvements encourage PEMFCs application in ships and support the move towards zero-emission shipping.

Batteries have emerged as a promising solution across diverse vessel segments, offering benefits in operational efficiency, cost reduction, and emissions reduction. This study investigates the specific requirements of batteries onboard 7 vessel types, such as tugboats, ferries, cruise ships, yachts, fishing vessel, vessels with cranes, and dynamic positioning vessels, through an in-depth analysis of load profiles and operational needs. By identifying 24 potential operational requirements, ranging from battery electric operation to silent operations and load smoothing, a mixed-integer linear programming model is used to optimize the power and energy allocation for each requirement. This framework enables a generalization of battery requirements for various vessel segments and enables the assessment of three lithium-ion battery chemistries: Lithium Iron Phosphate, Nickel Manganese Cobalt Oxide, and Lithium Titanate Oxide. The results indicate that different vessel types prioritize either high energy density batteries or those capable of delivering high power relative to energy capacity. To guide battery selection, a decision tree is presented that matches battery types with specific vessel needs. Lithium Titanate Oxide batteries are well-suited for applications requiring frequent, high power cycles, especially where fast charging is needed. Lithium Iron Phosphate batteries are best for energy-intensive operations, while Nickel Manganese Cobalt Oxide batteries perform well in both high power and high energy applications. This study offers a practical approach, an inventory of battery requirements, and guidance on selecting the chemistries best suited to various vessel types and operational needs.

This paper presents a desaturation-based technique for short-circuit protection in quasi-two-level converters. The proposed design enables a cost-effective implementation of this protection scheme in a flying capacitor multilevel converter operating as a quasi-two-level converter, requiring only two detection circuits for n series-connected switches. Detailed design guidelines for the protection circuit are provided, along with simulations that illustrate its operational boundaries and experimental verification of the proposed scheme.

Accurate knowledge of the mechanical loads of wind turbine gearboxes has become essential in modern, highly loaded gearbox designs, as maintaining or even improving gearbox reliability with increasing torque density demands is proving to be challenging. Unfortunately, the traditional method of measuring dynamic mechanical torque using strain gauges placed on the outer surface of a rotating shaft and transmitting the resulting signal is unsuitable for serial deployment due to technical and economic constraints. An alternative method based on fiber-optic strain sensors placed on the stationary outer surface of the gearbox ring gear has been proposed. Like shaft torsion, the radial deformation of the ring gear is proportionate to the rotor torque. Placing the sensors on a stationary component is a cost-effective alternative for serial implementation because the need for complex and expensive data transfer via wireless transmission or a slip ring is eliminated. In this paper, we present the results of an extensive field experiment conducted to evaluate the torque measurement accuracy of this novel sensing solution installed on the gearbox of a Gamesa G97 2-MW wind turbine at the National Renewable Energy Laboratory’s Flatirons Campus. Torque measurements derived from fiber-optic strain sensors placed on the ring gear of the planetary stage are compared to conventional torque measurements from strain gauges placed on the main shaft. Two different torque estimation data processing methods were evaluated, with the method based on operational deflection shapes providing the most accurate results with an average normalized root mean square error below 0.7% for a load revolution distribution analysis. The effect of operating conditions on the torque estimate was also investigated, and the third planet-passing operational deflection shape was found to be the least sensitive to nontorque load-related effects. The fiber-optic strain sensors’ successful operation during the complete test campaign has demonstrated a robust and accurate solution for fleet-wide enhanced gearbox remaining useful life estimation.

Hybrid power systems are increasingly adopted onboard. Lithium-ion batteries now serve as a viable energy storage solution that enhances fuel efficiency and reduces the operating hours of main power units, thereby reducing operational expenses. However, integrating batteries onboard requires decision-making that accounts for diverse scenarios, including battery chemistry, variations in vessel operational profiles, and fluctuating fuel prices. To address these challenges, this study investigates whether battery sizing and scheduling of the power and energy management system require a scenario-based stochastic decision framework. Specifically, it examines how energy storage requirements are influenced by varying load profiles, whether the optimal battery size and power management strategy are affected by fuel price fluctuations, and how robust the overall strategy remains under operational uncertainties. A deterministic equivalent of a two-stage stochastic decision framework is introduced to incorporate these uncertainties, offering insights into the required battery technology, capacity, and correlated behavior of onboard energy management. Multiple scenarios are applied to a trailing suction hopper dredger, analyzing three load profiles with distinct variations in power demand. With reserve power constraints enforced, the optimal battery capacity remains fixed. However, when these constraints are relaxed, the optimal battery size becomes more sensitive to fuel price changes. In addition, the results showcase reduction in diesel engine operating hours—thereby lowering both fuel consumption and maintenance costs, demonstrating that these operational benefits depend not only on the battery's size but also on its available throughput, which allows for deeper cycling.