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Hybrid ships have recently garnered increasing attention as a promising solution for energy shortages and environmental pollution. However, changes in the navigation environment can greatly affect the energy efficiency of these vessels. Therefore, improving the energy efficiency of hybrid ships continues to be a key issue. Our study examined the energy efficiency of a diesel‐electric series hybrid ship operating on an inland river, and a method to optimise series hybrid ship energy efficiency was proposed. The energy consumption model, power demand model, and decision function with minimum fuel consumption as the evaluation criteria were established according to the ship's characteristics and hybrid system. By analysing the data collected from an actual ship, the operating conditions of the navigation environment were identified using the k‐ means algorithm, and the total distance travelled by the ship was divided into several sub‐ trajectories. Afterwards, the optimised speed of the ship and the optimised output power of each power source were determined using the grasshopper optimization algorithm. The ship's energy efficiency levels before and after using the energy efficiency enhancement method were compared and analysed, and the effects of this optimization method on the ship's energy efficiency in several typical voyages were analysed. Our findings demonstrated that this optimization method can distribute the output of the power source in a better way, thereby optimising the speed of the vessel and maintaining stable sailing. More importantly, the proposed method can reduce fuel consumption by 17.04%. [ABSTRACT FROM AUTHOR]

The reliable performance of the shipboard power system (SPS) is essential for the safe and efficient operation of marine vessels. SPSs are subject to various types of electrical faults that can cause equipment failure, system downtime, and even catastrophic events. One effective way to provide redundancy and fault tolerance in the event of a fault or failure is through the use of zonal configuration. However, the protection of such systems is a challenging task due to their complex topology and the potential for multiple sources of fault. Therefore, it is imperative to protect the SPS with zonal configuration from various types of fault to ensure its continuous operation. This article presents a comprehensive coordinated protection strategy for a hybrid AC/DC SPS with the zonal configuration by using the available protective equipment. The proposed strategy consists of fault current limiting, grounding, fault detection, and faulty section isolation, and provides both primary and backup protections for all SPS equipment, including generator, busbar, line, input and output feeders, loads, propulsion motors, and DC system. Also, it does not require a comprehensive communication infrastructure and training dataset. The selective and reliable performance of the proposed protection strategy is verified through several case studies under various fault scenarios in the ETAP environment. The article provides valuable insights into the selection and implementation of appropriate protection measures for the SPS with ring configuration which are useful for the designers, operators, and maintenance personnel, improving the reliability and safety of these critical and autonomous systems. [ABSTRACT FROM AUTHOR]

Abstract The reliable performance of the shipboard power system (SPS) is essential for the safe and efficient operation of marine vessels. SPSs are subject to various types of electrical faults that can cause equipment failure, system downtime, and even catastrophic events. One effective way to provide redundancy and fault tolerance in the event of a fault or failure is through the use of zonal configuration. However, the protection of such systems is a challenging task due to their complex topology and the potential for multiple sources of fault. Therefore, it is imperative to protect the SPS with zonal configuration from various types of fault to ensure its continuous operation. This article presents a comprehensive coordinated protection strategy for a hybrid AC/DC SPS with the zonal configuration by using the available protective equipment. The proposed strategy consists of fault current limiting, grounding, fault detection, and faulty section isolation, and provides both primary and backup protections for all SPS equipment, including generator, busbar, line, input and output feeders, loads, propulsion motors, and DC system. Also, it does not require a comprehensive communication infrastructure and training dataset. The selective and reliable performance of the proposed protection strategy is verified through several case studies under various fault scenarios in the ETAP environment. The article provides valuable insights into the selection and implementation of appropriate protection measures for the SPS with ring configuration which are useful for the designers, operators, and maintenance personnel, improving the reliability and safety of these critical and autonomous systems.

Abstract Ship motions affect the propulsion system, which causes fluctuations in the power system. Mutually, the power system variations impact the ship velocity by generating speed changes in the propeller. Therefore, interconnecting the ship hydrodynamic and power system has paramount importance in designing and analysing an all‐electric ship (AES). The lack of an integrated model that can be evaluated in various operating conditions, such as manoeuvring, is evident. This paper explores the required perceptions for the power system and hydrodynamic analysis of an AES. Then, an integrated theoretical model comprising both the ship motion and power system is proposed. In addition to providing an accurate model for the ship in varying situations, this study demonstrates that the ship speed estimation during a ship route change differs from when the interconnections are overlooked. In the light of this determination, a straightforward enhancement for the ship speed control system is proposed. The effects of this modification on the ship power system are explored using the proposed model. The developed model is examined in different scenarios, and its advantages are discussed. It is shown that this model is suitable for employing in the model‐based design of AESs.

Ship motions affect the propulsion system, which causes fluctuations in the power system. Mutually, the power system variations impact the ship velocity by generating speed changes in the propeller. Therefore, interconnecting the ship hydrodynamic and power system has paramount importance in designing and analysing an all‐electric ship (AES). The lack of an integrated model that can be evaluated in various operating conditions, such as manoeuvring, is evident. This paper explores the required perceptions for the power system and hydrodynamic analysis of an AES. Then, an integrated theoretical model comprising both the ship motion and power system is proposed. In addition to providing an accurate model for the ship in varying situations, this study demonstrates that the ship speed estimation during a ship route change differs from when the interconnections are overlooked. In the light of this determination, a straightforward enhancement for the ship speed control system is proposed. The effects of this modification on the ship power system are explored using the proposed model. The developed model is examined in different scenarios, and its advantages are discussed. It is shown that this model is suitable for employing in the model‐based design of AESs. [ABSTRACT FROM AUTHOR]

This paper proposes several schemes for optimal scheduling of power producers in a shipboard power system for a typical offshore supply vessel, having a multiple number of possibly varying capacity gensets. The proposed scheduling methods are illustrated using four alternative power system configurations, ranging from a few large gensets to many gensets of smaller ratings. Mixed integer linear programming is used to formulate the optimization problems. Three formulations are presented: one for minimizing online capacity without further objectives, one that includes a redundancy constraint for loosing a group of gensets (to account for a worst-case failure scenario), and one to also balance running hours and minimizing connect/disconnect of the gensets. These different objectives can be combined and weighted based on importance, with or without redundancy constraints. Simulations are carried out to demonstrate the properties of the three different scheduling methods. The first method, minimizing online capacity only, is also used to illustrate the differences between the four genset configurations. This shows, for instance, that using more small gensets ensures generally a lower online available power (the connected capacity matches better the prevailing load) and near optimal loading of each genset around 80% (assuming equal loadsharing), at the same time as resilience to genset failures is preserved. [ABSTRACT FROM AUTHOR]

In the medium voltage direct current (MVDC) shipboard grid, the inherent inertial support from the DC capacitors is too small to resist step changes or fluctuations from the high power pulse load and propulsion load, which results in lower DC voltage quality. This study proposes a decentralised control algorithm for the MVDC shipboard hybrid energy storage system (HESS) to enhance the onboard survivability. This algorithm adjusts the droop control coefficient based on the bus voltage change rate adaptively, meanwhile the voltage differential signal processing and filtering are implemented by the trace differentiator. In addition, the proposed algorithm also has state-of-charge (SOC) balancing and SOC recovery abilities between multiple groups of energy storage devices. The parameter selection principle are analysed, and a variety of working conditions are simulated and verified in PSCAD. Theoretical analysis and simulation show that, HESS can achieve good power distribution and SOC management performance without communication compared to fixed droop coefficient control strategies, and the dynamic characteristics of bus voltage have been significantly improved. [ABSTRACT FROM AUTHOR]

Due to the rapid increase in electrical energy requirements in marine power systems (MPSs), and to reduce the consumption of fossil fuel, there is an emergent need to utilise renewable energy sources (RESs) in MPSs, which has been an attractive field of research. This research aims to present a novel load frequency control (LFC) scheme for a shipboard micro‐grid (SMG) system. Therefore, a MPS with photovoltaic, wind turbine, hybrid energy storage system (ESS), and diesel generator (DG) have been simulated to relate an exact mobile islanded SMG. The system is designed using the transfer function models with the above said generating units and storage systems. Grasshopper optimisation algorithm (GOA) tuned fuzzy‐based proportional–integral–derivative with filter control technique has been proposed to investigate the performance of the LFC scheme for the proposed SMG system. GOA and particle swarm optimisation optimised controllers have been designed and performance evaluation has been carried out on the conventional, adaptive neuro‐fuzzy inference system, and fuzzy cascaded with a conventional controller. The responses obtained from the simulations for different cases are analysed to justify the novelty and superiority of the proposed technique for frequency and power regulation. [ABSTRACT FROM AUTHOR]

Complex energy vessels such as large platforms or drillships require more efficient use of electrical power. As shipboard electrical systems become larger, problems and limits arise with the ac distribution architecture. Hybrid ac/dc onboard distribution systems are today available, which provide higher efficiency and redundancy. IEEE Std. 1662, 1709 and 1826 set technical rules and recommendations for the design of hybrid ac/dc shipboard electrical systems. Among these, zonal electrical distribution systems (ZEDS) are considered a next technological evolution, as they provide optimal power sharing (and energy storage) along with high reliability. [ABSTRACT FROM AUTHOR]

The propulsion system of a medium‐voltage dc (MVDC) ship is subject to large thrust/torque variations due to interactions of the ship and the propeller with sea waves. These variations induce steep power fluctuations on the MVDC bus, adversely impacting the stability, efficiency and power quality. Hybrid energy storage system (HESS) is a promising solution for mitigating these power fluctuations. Dictating the energy that the HESS components must deliver/absorb, the energy management strategy (EMS) impacts the size/capacity of the energy storage system (ESS). Based on this consideration, sizing and EMS of a battery/supercapacitor (SC) HESS are jointly optimised by using a deep reinforcement learning‐based method. The proposed method splits the power between the HESS components such that while the operational constraints are satisfied, energy storage size and losses are minimised. Its features are adaptability to varying sea states, real‐time implementation feasibility, while obviating the requirement for knowledge of the ship propulsion power profile. The efficacy of the joint sizing/EMS on reducing the ESS size is validated by comparing the sizes when battery‐only, SC‐only and HESS are employed in the MVDC shipboard power system. Real‐time implementation feasibility and adaptability to various ship propulsion power profiles is confirmed through real‐time simulations. [ABSTRACT FROM AUTHOR]

The increments of the emission tiers and global warming, as well as the reduction of fossil fuels, have led to a change in the power system of vehicles. Even in maritime transportation, there are more restrictions due to environmental regulations of some ports. In this study, the energy management problem of a marine power system is investigated, such a system includes a diesel generator, solar system, energy storage system (ESS), electrical boiler system, and electrical heat pump. The proposed risk-based strategy for scheduling multiple energy systems of a hybrid cruise ship (HCS) is able to provide the electrical and thermal demands related to the cruise services in a reliable and optimal way. The examined HCS travels daily in the Baltic Sea between Stockholm in Swedish mainland and Mariehamn on the Åland islands and carries hundreds of passengers in various tour programmes, representing an uncertain shipboard loading profile. Therefore, an information gap decision theory-based (IGDT-based) methodology is applied to model the uncertain HCS load. Furthermore, the proposed multiple energy system can adopt various strategies namely risk-averse and risk-seeker to face different consumption patterns. Finally, the numerical results obtained from actual test case validate the applicability and efficiency of the proposed approach. [ABSTRACT FROM AUTHOR]

With the continuous development of pulse load represented by laser weapon and electromagnetic railgun, its application to the naval combat platform becomes a tendency. These pulse loads have the characteristic of high power as well as instantaneous which will impact the volume limited DC ship power system and challenge its stability. For this purpose, the simulation model of a medium voltage DC ship power system is built in PSCAD/EMTDC. Choose electromagnetic railgun which has two-level energy storage system as the representation of the pulse load. The model of the railgun is built through derivation then added to the DC ship power system to study the influence it does to the system voltage stability. The small disturbance method is used to compute the voltage stability of the whole system and the result is compared with the simulation figures. The comparison shows that the two-level energy storage based electromagnetic railgun can works normally in the system thus provides a new method to the way that the pulse load applies to the DC ship power system. [ABSTRACT FROM AUTHOR]

Utilisation of renewable energy sources (RES) is increasing day by day to reduce greenhouse emissions. The toxic emission from ship is the main concern in marine sector. Here, utilisation of renewable energy for propulsion and electrification of accessories in a ship are proposed. Microgrid with AC and DC bus is developed using solar panels, wind mills, fuel cell, diesel generator, and energy storage devices. Energy management system with two fuzzy logic controllers (FLCs) is used to select and manage energy in the microgrid. Selection of source is decided by FLC1 based on the availability of RES. Generation of control pulses for inter‐linking converters is decided by FLC2 based on variation in solar irradiance and wind velocity. The microgrid with RES is simulated using MATLAB/SIMULINK. The results show that uncertainty in RES can be handled by FLCs to provide a continuous power supply for transportation of ship and its accessories. [ABSTRACT FROM AUTHOR]

This study presents a new method to protect the radial feeders on marine vessels. The proposed protection method is effective against phase–phase (PP) faults and is based on evaluation of the ratio between the negative sequence and positive sequence of the fault currents. It is shown that the magnitude of the introduced ratio increases significantly during the PP fault, hence indicating the fault presence in an electric network. Here, the theoretical background of the new method of protection is firstly discussed, based on which the new protection algorithm is described afterwards. The proposed algorithm is implemented in a programmable digital relay embedded in a hardware‐in‐the‐loop (HIL) test set‐up that emulates a typical maritime feeder using a real‐time digital simulator. The HIL set‐up allows testing of the new protection method under a wide range of faults and network conditions and the experimental results demonstrate its effectiveness in all scenarios conducted. The proposed protection method offers a solution to the protection challenges associated with variability of the short‐circuit currents in radial feeders, advancing in this way the traditional mean of protection in maritime feeders, represented by overcurrent relays. [ABSTRACT FROM AUTHOR]

With the continuous development of pulse load represented by laser weapon and electromagnetic railgun, its application to the naval combat platform becomes a tendency. These pulse loads have the characteristic of high power as well as instantaneous which will impact the volume limited DC ship power system and challenge its stability. For this purpose, the simulation model of a medium voltage DC ship power system is built in PSCAD/EMTDC. Choose electromagnetic railgun which has two-level energy storage system as the representation of the pulse load. The model of the railgun is built through derivation then added to the DC ship power system to study the influence it does to the system voltage stability. The small disturbance method is used to compute the voltage stability of the whole system and the result is compared with the simulation figures. The comparison shows that the two-level energy storage based electromagnetic railgun can works normally in the system thus provides a new method to the way that the pulse load applies to the DC ship power system.

We have investigated the behavior of an operating solid oxide fuel cell (SOFC) with supplying a simulated syngas to develop diagnosis method of the SOFC for marine power applications fueled with liquefied natural gas (LNG). We analyze the characteristics of a syngas-fueled intermediate temperature microtubular SOFC at 500 ∘C for accelerated deterioration by carbon deposition as a model case by electrochemical impedance spectroscopy (EIS) to in-situ find parameters useful for the real-time diagnosis. EIS analyses are performed by complex nonlinear least squares (CNLS) curve fitting to measured impedance spectra with an equivalent electric circuit model consisting of several resistances and capacitances attributed to the anode and cathode processes as well as Ohmic resistance of the cell. The characteristic changes of those circuit parameters by internal reforming and anode degradation are extracted, showing that they can be used for the real-time diagnosis of operating SOFCs. [ABSTRACT FROM AUTHOR]

This article examines the selection methodology of class surveys of a shipborne engine room and its impact on the reliability and operation indicators of a marine power plant. We describe the characteristics of four available class survey methods and then carry out a reliability analysis on the basis of four months of activity on six different ships operating on international voyages, taking into account the two most common supervision methods: renewal and continuous survey. Based on this analyses, we conclude that the reliability indices of a marine power plant, classified according to the continuous method, were slightly lower than for the renewal method. However, we identified potential benefits in terms of overall ship maintenance costs, due to a faster and more economical 5-yearly shipyard survey. [ABSTRACT FROM AUTHOR]

Based on an extensive bibliographic synthesis, the present paper presents the state of the art and the characterisitics of the an electric power system onboard shipping vessels and their structure, the criteria to be taken into account during the design phase for the selection of voltage, current and frequency in the bars of the main distribution panel, for the purpose of supplying consumers on-board, and the calculation methods for power requirement analysis to choose the number of on-board synchronous generators and their power. The paper concludes with a case study, which analyzes the functional construction of an electric power system on board an oil tanker, with the presentation of the management system for the synchronous generators and consumers onboard the ship. [ABSTRACT FROM AUTHOR]

The marine energy industry is in its early stages but has a large potential for growth. One of the most significant challenges is the reduction of operation and maintenance costs. Magnetic gears (MGs) offer the potential for long periods between maintenance intervals due to their frictionless torque transmission which could reduce these costs. This study presents a summary of the state of the art in MG technology and then investigates its potential for marine energy applications. A brief overview is given of the state of the marine energy industry and the environment in which marine energy converters (MECs) operate. A short history of MG development over the past century is then presented followed by a discussion of the leading MG technologies and their relative advantages. In order to demonstrate the potential of MGs in marine applications, the current technologies, i.e. mechanically geared and direct drive machines, are examined in terms of sizing, reliability and economic value using previous studies on a similar technology, namely wind. MGs are applied to four types of MECs to demonstrate how the technology can be incorporated. The potential to deploy at scale and potential obstacles to this are then discussed. [ABSTRACT FROM AUTHOR]

The steady and reliable operation of a ship’s diesel engine is important to the ship’s electrical power system and the engine’s performance, and stable control of rotational speed is crucial to a diesel engine’s emission, economy and power performance. A ship’s diesel engine is a nonlinear and time-varying system. A traditional proportional–integral–derivative (PID) controller cannot regulate the speed under different working conditions. In this paper, a nonlinear mathematical model for speed regulation of diesel engines is established according to experiments and a multi-sliding surface variable structure controller for speed regulation of diesel engine is established by sliding mode control. A bulk cargo ship 500-I was analysed as an example. The MATLAB/Simulink simulation took the navigation environment and the effect of the ship propeller on the diesel engine into consideration. A simulation model considering the whole ship–engine–propeller system is built and some conclusions can be drawn from the simulation. The multi-sliding surface control can restrain the overshoot and realize a quick track of the targeted value with high accuracy and strong robustness. In addition, the fuel consumption and CO2 emission of this sliding mode variable structure control is reduced by 4.6% compared with traditional PID control. [ABSTRACT FROM AUTHOR]

The photovoltaic system is widely introduced into ocean-going ships to utilize the abundant solar resources on the ocean, reduce the ship’s fuel consumption and pollutant emission. As the uncertainty of navigation environment, ship’s attitude and climate conditions, the dynamic partial shading or even complex illumination conditions probably occur during the long time voyage. In this paper, a large-scale photovoltaic (PV) system is introduced into the ocean-going green ship to modify the traditional structure of ship’s power grid. Specifically, a novel structure of large-scale PV array based on the ship’s illumination unit (SIU), ship’s photovoltaic group (SPG), operating point controlling device (OPCD) and batteries is proposed, and layout of the array on ocean-going green ship is researched as well. Besides, the MPPT of all the SIUs is modeled as a large-scale global optimization (LSGO) problem, and a meta-heuristic optimization called the DCDE is employed to solve this problem offline. Performance of the DCDE is verified by numerical experiments, and result of simulation also shows that with the application of the proposed structure and its controlling methods, the green ship can make full use of solar resources and achieve its operational safety and efficiency under complex environmental conditions. [ABSTRACT FROM AUTHOR]

This work takes aim at presenting a generic real-time simulation framework for marine power plants with weak power grids, containing transient functionalities such as starting and stopping of arbitrary generators, and phase synchronization. The generator models used in the power plant are hybrid causality models, meaning that they have the ability to switch between causality orientations, between voltage and current. These models facilitate real-time simulations as long as they are solved properly, as will be discussed in this article. Much is devoted to numerical stability, model robustness and power plant control, e.g. rms voltage control, engine speed control, active- and reactive power sharing control and phase synchronization control. Some focus is also given to overall power plant control structure. A case study of a marine power plant including two generators and a fluctuating- and noisy power consumption is presented and analysed, and illustrates the advantages of the proposed framework as well as giving a good foundation for future works. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Machine Construction & Maintenance is the property of Institute for Sustainable Technologies - National Research Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The key market drivers for marine energy are to reduce carbon emissions, and improve the security and sustainability of supply. There are other technologies that also meet these requirements, and therefore the marine energy market is dependent on the technology being cost effective, and competitive. The potential UK wave and tidal stream energy market is assessed using ETI's energy systems modelling environment (ESME) which uses a multi-vector approach including energy generation, demand, heat, transport, and infrastructure. This is used to identify scenarios where wave and tidal energy form part of the least-cost energy system for the UK by 2050, and will assess what Levelised Cost of Energy (LCOE) reductions are required to improve the commercialization rate. The results indicate that an installed capacity of 4.9 GW of wave and 2.5 GW of tidal stream could be deployed by 2050 if the LCOE is within 4.5 and 7 p/kWh for each respective technology. If there is a step reduction to the LCOE of wave energy, however, a similar capacity of 5 GW could be deployed by 2050 at a LCOE of 11 p/kWh. [ABSTRACT FROM AUTHOR]

Between 1 February 2012 and 26 February 2014 using scuba, we surveyed the fishes, invertebrates, and macrophytes living on two energized submarine power cables, an adjacent pipe, and nearby natural habitat in southern California at bottom depths of 10-11 m and 13-14 m. Over the course of the study, average electromagnetic field (EMF) levels at the two cables (A and B) were statistically similar (Cable A = 73.0µT, Cable B = 91.4µT) and were much higher at these two cables than at either the pipe (average = 0.5µT) or sand (0µT). Overall, our study demonstrated that 1) the fish and invertebrate communities on cables, pipe, and natural habitat strongly overlapped and 2) there were no differences between the shallower and deeper fish and invertebrate communities. We saw no evidence that fishes or invertebrates are either preferentially attracted to, or repelled by, the EMF emitted by the cables. Any differences in the fish or invertebrate densities between cables, pipe, and natural habitat taxa were most likely due to the differences in the physical characteristics of these habitats. As with the fishes and invertebrates, macrophytes did not appear to be responding to the EMF emitted by the cables. Rather, it is likely that differences in the plant communities were driven by site depth and habitat type. [ABSTRACT FROM AUTHOR]

In this paper, superheated and saturated vapor ORCs commonly utilized as waste heat recovery systems of a marine power plant are investigated. First, a parametric study with different organic fluids has been carried out by applying conventional exergy and exergoeconomic analyses to the system considered in order to identify the best possible operating conditions and also to evaluate the findings of conventional exergy-based analyses. Then, advanced exergy and exergoeconomic analyses have been performed on ORCs by splitting exergy destruction rates, exergy destruction costs and investment costs of components and overall system to identify avoidable parts of costs and exergy destructions. Finally, decision criteria were suggested on the selection of more appropriate system depending on the results of the analysis. [ABSTRACT FROM AUTHOR]

Copyright of Electrical Engineering & Electromechanics is the property of National Technical University, Kharkiv Polytechnic Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Despite growing interest in advanced marine power systems, knowledge gaps existed as it was uncertain which configuration would be more environmentally friendly. Using a conventional system as a reference, the comparative life cycle assessment (LCA) study aimed to compare and verify the environmental benefits of advanced marine power systems i.e. retrofit and new-build systems which incorporated emerging technologies. To estimate the environmental impact attributable to each system, a bottom-up integrated system approach was applied, i.e. LCA models were developed for individual components using GaBi, optimised operational profiles and input data standardised from various sources. The LCA models were assessed using CML2001, ILCD and Eco-Indicator99 methodologies. The estimates for the advanced systems were compared to those of the reference system. The inventory analysis results showed that both retrofit and new-build systems consumed less fuels (8.28% and 29.7% respectively) and released less emissions (5.2–16.6% and 29.7–55.5% respectively) during operation whilst more resources were consumed during manufacture, dismantling and the end of life. For 14 impact categories relevant to global warming, acidification, eutrophication, photochemical ozone creation and PM/respiratory inorganic health issues, reduction in LCIA results was achieved by retrofit (2.7–6.6%) and new-build systems (35.7–50.7%). The LCIA results of the retrofit system increased in ecotoxicity (1–8%), resource depletion (1–2%) and fossil fuel depletion (17.7–161.9%). Larger magnitude of increase was shown by the new-build system in ecotoxicity (90–93.9%) and fossil fuel depletion (391.3%) as a result of handling additional scrap. Relative contribution of significant components towards environmental impact remained profound for the retrofit system (i.e. more than 84% for all impact categories) and became more prominent for the new-build system (approximately 99% for 18 impacts). For retrofit and new-build systems respectively, changes in fuel consumption quantity by ±10% and ±20% varied (i) ecotoxicity and land use by no means, (ii) fossil fuel depletion by 0.95–1.50 and 4.81–5.01 times assessed by CML2001 (or 0.95–1.50 and 5.12–5.32 times assessed by Eco-Indicator99); and (iii) the remaining impact categories by 0.65–1.37 and 0.34–0.92 times. The new-build system showed the greatest mitigation potential in 18 impact categories. The retrofit system was more environmentally friendly than the reference system. Appropriate life cycle management was warrant to avoid burden shifting whilst alleviating the environmental burdens at the same time. [ABSTRACT FROM AUTHOR]

The impacts of a lightning strike are amplified in an environment with special features such as a ship electric grid, especially within the extended integration of electronic systems. In most marine regulations, lightning protection specifications are inadequate in the cases of metallic vessels, regarding the necessity of installing lightning rods and the method for the definition of their protection zone and subsequently of their height. Therefore, impulse voltage experiments on a scaled‐down ship model were conducted in order to acquire interception probability distributions of its superstructures and to assess the accuracy of various protection zone models, established for isolated rods, on the given complex topology of a ship. The experimental results highlighted the overestimation of the protection zone even by the well‐established rolling sphere model for negative polarity impulses depending on the geometrical conditions and the satisfying performance of statistical models that incorporate proximity effects and lightning interception probability. [ABSTRACT FROM AUTHOR]

The paper presents an improved methodology of analysing the qualitative importance of components in the functional and reliability structures of the system. We present basic importance measures, i.e. the Birnbaum's structural measure, the order of the smallest minimal cut-set, the repetition count of an i-th event in the Fault Tree and the streams measure. A subsystem of circulation pumps and fuel heaters in the main engine fuel supply system of a container vessel illustrates the qualitative importance analysis. We constructed a functional model and a Fault Tree which we analysed using qualitative measures. Additionally, we compared the calculated measures and introduced corrected measures as a tool for improving the analysis. We proposed scaled measures and a common measure taking into account the location of the component in the reliability and functional structures. Finally, we proposed an area where the measures could be applied. [ABSTRACT FROM AUTHOR]

This study presents the multiple energy storage elements usability for ships using a passive hybrid topology. The considered hybridisation is based on a passive parallel topology connecting NiMH batteries and SuperCapacitors to a DC power distribution by a bidirectional DC/DC converter. The overall propulsion architecture is a hybrid series system where an engine–generator group is the main energy source and the multiple energy storage system (ESS) answer the intermittent power demanded by the on‐board loads. First, the multiple ESS is sized using voltages, storage elements' characteristics, and typical power demand profile. Thereafter, a control scheme of this hybridisation is deduced through a cascade of current and voltage linear controllers. The energy management strategy based on the stability of the DC power distribution voltage and the inherent storage elements' characteristics is fully addressed in order to reduce weight and space on‐board, fuel consumption, pollution, and optimise the global efficiency. Experimental results show that the engine–generator fulfil a constant power, meanwhile the multiple ESS stabilises the DC‐link voltage with unknown power demand profile. The effectiveness of the proposed passive hybrid topology with reduced control layer complexity based on the DC‐link voltage stabilisation as an energy management strategy is validated. [ABSTRACT FROM AUTHOR]

This study describes and presents preliminary experimental results from a novel prototype energy scavenging system installed in a model 2 m cylindrical autonomous underwater vehicle (AUV). The system, which is based on control moment gyroscope principles, utilises the gyroscopic response of a gimballed flywheel mounted within an AUV body to generate energy from the wave induced rotational motions of the vehicle. This method, using the reaction of a spinning wheel under an input torque to provide an output torque of greater magnitude, orthogonal to the input torque axis and the spin axis provides a means to harvest energy in‐situ, without external appendages and additional hydrodynamic drag. The system promises to extend AUV mission durations indefinitely and reduce support vessel time currently required for periodical recharging and redeployment. A description of the system operation, design and experimental results from a series of regular wave tests conducted at zero speed in a towing tank are presented in this study. The results show that the system can harvest energy, with the greatest power generation around resonance, tailing off as the frequency increases and typically non‐linear in nature. The system could potentially be applied to any rotationally excited platform e.g. autonomous surface vessels, buoys or boats [ABSTRACT FROM AUTHOR]

Since a pulsed power load (PPL) consumes a huge amount of energy within very short period of time, its deployment might cause large disturbances even instability to a power system that has limited generation, small inertia, and small ramp rate. To mitigate the strike during PPL deployment, energy storage system (ESS) is usually installed in shipboard power system (SPS) to serve as the sole power supply for PPL. To realise fast charging of the ESS and minimise disturbance during charging, generation control and charging control of SPS should be well coordinated. For this important but not well‐studied problem, this study presents an adaptive critic design based control algorithm for a non‐linear model integrating the basic dynamics of synchronous generator and supercapacitor, which is a popular type of ESS for PPL application. Through interactive learning of two neural networks for cost‐to‐go function approximation and optimal control approximation, respectively, near optimal control can be realised even under disturbance and model impreciseness. The algorithm is tested with both detailed single‐ and multiple‐generator SPS models and tested through both real‐time digital and power hardware‐in‐the‐loop simulations. Simulation results demonstrate the effectiveness of the developed model and control algorithm. [ABSTRACT FROM AUTHOR]

Offshore oil and gas vessels operating in deep and ultra-deep waters demand larger and more sophisticated power and control systems. This tendency brings new challenges in integrated power system’s design, especially for platforms/vessels requiring both dynamic positioning and high levels of redundancy. Voltage stability is essential in such systems, being in islanded operation (with related limited power generation) and with continuously changing load demands. In particular, voltage stability issues can arise due to the increasing amount of power electronic converters installed onboard, used to feed variable frequency drives and other electronic loads. Indeed, most of these have a controlled front-end, whose control can affect network voltage with a destabilizing effect named constant power loads (CPLs) instability. Such a behavior deserves special attention in islanded power systems, mostly if the quota of power electronics loads on the total installed power reaches very high values (up to the 85% for new large all electric ships). This paper initially focuses on the CPL voltage instability. Two different models to assess voltage stability in marine systems with high penetration of electronic power conversion are given, focusing on a design-stage assessment. Using the conditions obtained by such models, a practical stability analysis methodology is proposed, to help assessing voltage stability already at design stage, to avoid equipment retrofits during vessel building or commissioning. Finally, some practical case studies are discussed, and solutions to overcome the CPL instability are suggested. [ABSTRACT FROM PUBLISHER]

Previously, life cycle assessment (LCA) focussing on principles or applications has been considerably reviewed. Still, an up-to-date review on LCA methodology development (rather than application) in a chronological order which embraces all life-cycle phases is lacking. The objectives of this article include scrutinising methodology development of conventional LCA phase by phase, providing clarification on goal and scope definition and life cycle inventory (LCI) analysis, discussing recent substantial development on life cycle impact assessment (LCIA) methodology and interpretation, and introducing an LCA framework for marine photovoltaic (PV) systems. For the study presented here, literature on LCA methodology development was categorised into Sample Groups A, B and C, comprising 15 review articles published in the last decade, 95 pieces of other literature types (with 83% journal articles), and 38 additional materials necessary for complementing an in-depth discussion respectively. A threefold analysis was performed to scrutinise and compare the literature in these sample groups. The analysis shows that for Sample Group A, the focus has steered from overarching LCA of all-embracing life cycle phases to single phase and then sole engagement with a specific topic; and for Sample Group B, 44% has reported the scientific endeavour on LCIA compared to other life cycle phases. Following clarification on system boundary, cut-off and existing LCI approaches including attributional, consequential, process based, input–output (IO) based etc., the methodology development of impact categories (covering impacts of water use, noise and working environment), uncertainty and sensitivity analyses are discussed. In addition, classification involving series and parallel mechanisms, LCIA development for space use, odour, non-ionising radiation and thermal pollution, rebound effects, renewability of resources, dynamic of environment and future scenario modelling in LCA context are identified as research needs and areas for future development. In compliance with ISO Standards and based on the findings, an LCA framework for marine PV systems (which exemplify the state-of-the-art development of renewable and sustainable energy in marine industry) is introduced to enhance the practical applicability and usefulness of the findings to LCA researchers. [ABSTRACT FROM AUTHOR]

The potential of marine power to produce electricity has been exploited recently. One of the ways of producing electricity is by using tidal current turbines. In this study, the hydrodynamic performance of a novel type of ducted tidal turbine was investigated. Tidal energy has become a large contender of traditional fossil fuel energy, particularly with the successful operation of multi-megawatt sized tidal turbines. Hence, quality of produced energy becomes an important problem in tidal energy conversion plants. Several control techniques have been applied to improve the quality of power generated from tidal turbines. In this study, the adaptive neuro-fuzzy inference system (ANFIS) is designed and adapted to estimate power coefficient value of the ducted tidal turbines. The back propagation learning algorithm is used for training this network. This intelligent controller is implemented using Matlab/Simulink and the performances are investigated. The simulation results presented in this paper show the effectiveness of the developed method. [ABSTRACT FROM AUTHOR]

The location of individual turbines within a tidal current turbine array – micro-siting – can have a significant impact on the power that the array may extract from the flow. Due to the infancy of the industry and the challenges of exploiting the resource, the economic costs of realising industrial scale tidal current energy projects are significant and should be considered as one of the key drivers of array design. This paper proposes a framework for the automated design of tidal current turbine arrays in which costs over the lifespan of the array may be modelled and considered as part of the design optimisation process. To demonstrate this approach, the cost of sub-sea cabling is incorporated by implementing a cable-routing algorithm alongside an existing gradient-based array optimisation algorithm. Three idealised test scenarios are used to demonstrate the effects of a financial-return optimising design approach as contrasted with a power maximisation approach. [ABSTRACT FROM AUTHOR]

In this study, a control scheme for the stand‐alone generation system based on brushless doubly‐fed machine (BDFM) is presented. The output voltage amplitude and frequency are kept constant under variable rotor speed and load by regulating the amplitude and frequency of the control winding (CW) current of BDFM appropriately. The control scheme utilises a CW current vector controller as the inner loop, and a power winding voltage amplitude controller and a frequency controller as the outer loop. The proposed control scheme has been implemented on a prototype BDFM designed for the variable‐speed stand‐alone ship shaft generation application. Moreover, the satisfactory dynamic performance and low total harmonic distortion of the output voltage in the proposed stand‐alone generation system is verified by experiments with two kinds of typical loads: three‐phase induction motor load and three‐phase RL inductive load. [ABSTRACT FROM AUTHOR]

This article introduces a new fully operative teaching simulator for all kind of marine power stations, both placed on board or on land, allowing to establish an innovative procedure to develop standalone low cost simulators for high level professional instruction of marine engineers, that can be run on conventional computers. This kind of low cost simulators opens a new way not only in the teaching and training of marine engineers, but also in the design and implementation of new power facilities, allowing to train the operators prior to their work in the real installation. [ABSTRACT FROM AUTHOR]

Medium‐voltage direct current (MVDC) power system has been considered the trending technology for future all‐electric ships to produce, convert and distribute electrical power with improved connectivity, reliability and power quality. However, with the substantial employment of high‐frequency power electronics converters in the MVDC system, the corresponding analysis of system stability and especially the accurate assessment of system dynamic behaviours following disturbances have become serious concerns for system studies and control designs. In this study, an analytical time‐domain modelling methodology that leverages average‐value modelling techniques is developed for MVDC shipboard power system to facilitate the system‐level transient analysis. The accuracy of the proposed approach is verified by comparing the simulation results to the equivalent Simulink benchmarks. In contrast with the high‐fidelity model and the conventional modelling approach which only captures the steady‐state characteristics of the system, the proposed method is proven to be effectively and accurately simulate the system behaviour during the transient phase with enough details to verify and refine related system‐level dynamic analysis and control design. [ABSTRACT FROM AUTHOR]

Examines the development of marine vehicle power systems from an historical perspective. from the earliest forms of power systems to the current development of all electric ship technologies. [ABSTRACT FROM PUBLISHER]

In order to retrain chaotic oscillation of marine power systems which are excited by periodic electromagnetism perturbation, two novel model free command-filtered backstepping control methods are designed in this paper. Firstly, the dynamic model of marine power system based on the two parallel nonlinear models is established. Secondly, extended state observer (ESO) and adaptive neural network observer (NNO) are designed to estimate the velocity signal and the unknown dynamic model. Moreover, the uniform form of ESO and NNO is given. Next, the model free command-filtered backstepping controller is put forward based on the uniform observer form. Finally, the simulation results indicate that the two proposed control algorithms can quickly retrain chaotic oscillation and their effectiveness and potential are amply demonstrated. [ABSTRACT FROM AUTHOR]

The reduction of emissions in harbours is of particular importance due to the proximity to human habitation. Vessels normally run onboard generators, typically using diesel fuel, to provide the service loads while berthed. New and upcoming regulations aim to decrease emissions from shipping, and coupled with increased environmental consciousness of ship owners and harbour operators, shore supply is becoming a more popular and feasible option. Cold ironing provides an alternative locally emission-free solution by having berthed ships plug in to the shore electrical network, such that the onboard electrical energy demand is supplied from land. Electrically, a number of different shore network topologies are possible, providing different infrastructural options of supplying power to multiple berths. This paper examines the electrical characteristics of one such installation and the impact on the shoreside electrical network for an existing port using actual visiting ship power profiles. The paper examines how the cold ironing system influences important electrical network characteristics such as bus voltages and power quality, as well as the potential impact on the rest of the utility distribution system. [ABSTRACT FROM AUTHOR]