Designing a new vessel is a complex multi-objective design process. It involves knowledge from different fields, like naval architecture and mechanical engineering. Assessment of an optimal design for more complex topologies than a conventional Diesel powertrain becomes more difficult due to the increased number of powertrain components and feasible combinations. The purpose of this work is to present a system-level design methodology, which speeds up the component sizing and control for a powertrain topology. This system-level design problem is formulated into the minimization of a cost function. The cost function consists of the costs of the different powertrain components together with the operational costs over a specified operational profile. For the sizing of the battery and control parameters, the use of a convex optimization algorithm ensures a global optimum is found very quickly in the search space at relatively low-computational effort. For the ON/OFF switching of the Diesel engine and the Diesel generator set, an iterative scheme using convex and mixed-integer optimization is proposed. Here, without loss of generality, the optimization case study is presented for a hybrid tug.

Saving fuel and reducing emissions are major drivers in the marine industry, with a large number of potential modifications and machinery options available to enable the greening of shipping. Assessing which technology and what combination of solutions gives favourable economic results needs careful consideration of the vessel's operational profile. Electrification of shipboard systems introduces operational flexibility, offering the potential for fuel savings arid emission reductions. Auxiliary drives, energy storage and onshore power supply are three approaches which address the issues of ship fuel consumption/emissions, specifically during in-harbour operation of vessels. In this paper, the impact of these three technologies on ship environmental performance and energy consuffiption is assessed by considering a real case RoRo vessel sailing a real operational profile. Models of the resultant system are built such that the machinery configurations can be analysed separately or in conjunction with each other. The results stress the importance of the operational profile of the vessel, showing significant fuel and emissions reductions during in -harbour operations but relatively small savings when considering operation through a complete return voyage. The sensitivity of the results to fuel and utility costs are also considered and shown to have a large impact on the economic feasibility (or otherwise) of different solutions. (C) 2016 Published by Elsevier Ltd.

The efficient utilization of energy is of high importance for shipboard applications, for environmental and economic reasons as well as maximized vessel operation. The electrification of marine systems facilitates the storage and generation of energy from multiple sources, offering the potential for energy savings, due to the flexibility associated with electric systems. In this paper, an energy management system (EMS) based on bond graph system models used in conjunction with a stochastic search algorithm is proposed and developed. The EMS optimizes the configuration of the vessel’s onboard machinery system based on the current operating condition. The approach is universal, with the system model and optimization routine being separate and distinct. The effectiveness of the proposed EMS is demonstrated using a real operating profile of a roll-on/roll-off vessel fitted with a hybrid machinery configuration including energy storage, onshore power supply, and photovoltaic generation. The results show fuel savings of around 23% compared with current fuel consumption levels.

Auxiliary drives can provide an alternative propulsion system for marine vessels giving the potential to achieve improved environmental performance during low-speed sailing. In this work, two case vessels were considered for analysis, a Roll-On-Roll-Off ship and a harbour tug boat. Actual sailing operational profiles were used as the basis for energy considerations to assess the potential for lower emissions. An energy-centric simulation model was built to estimate the emission of various pollutants, considering different machinery set-ups. Results have shown that savings are possible, especially for vessels which run on residual fuels, where auxiliary drives provide a way of exploiting the advantages of cleaner sources for manoeuvring instances.

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. (C) 2015 Elsevier Ltd. All rights reserved.

Insulated-gate bipolar transistor (IGBT) power modules find widespread use in numerous power conversion applications where their reliability is of significant concern. Standard IGBT modules are fabricated for general-purpose applications while little has been designed for bespoke applications. However, conventional design of IGBTs can be improved by the multiobjective optimization technique. This paper proposes a novel design method to consider die-attachment solder failures induced by short power cycling and baseplate solder fatigue induced by the thermal cycling which are among major failure mechanisms of IGBTs. Thermal resistance is calculated analytically and the plastic work design is obtained with a high-fidelity finite-element model, which has been validated experimentally. The objective of minimizing the plastic work and constrain functions is formulated by the surrogate model. The nondominated sorting genetic algorithm-II is used to search for the Pareto-optimal solutions and the best design. The result of this combination generates an effective approach to optimize the physical structure of power electronic modules, taking account of historical environmental and operational conditions in the field.

Cold ironing (or onshore power supply) addresses airborne emissions while ships are berthed in port. By providing the electrical power demands from shoreside electricity, the onboard auxiliary generators can be switched off for a locally emission-free solution. The net emissions will of course be dependent on the actual shoreside electricity mix, but reductions can be realised in most cases. This study looks at the various electrical configurations available for cold ironing of berthed vessels. Shoreside generation using liquefied natural gas as an alternative fuel is also considered as a complement to cold ironing. This provides the possibility of hybridised solutions combining power supply from the grid or from clean, onsite generators. Using real data from an operational European port, the various cold ironing configurations are modelled and optimal trade-off solutions were identified. This is achieved by considering the reduction in emissions and minimisation of component costs as a multi-objective non-linear optimisation problem. The results show that CO2 emissions can be reduced by up to 40% by using cold ironing, while the use of liquefied natural gas shore generation can reduce the sulphur and particulate emissions in port to extremely low levels.

Ships require continuous onboard electrical power to supply essential loads as well as hotelling demand. This extends to the period of time spent berthed, where the onboard power is typically provided by running of the vessel’s diesel generators. Cold ironing eliminates these in-harbour emissions by connecting the ship’s electrical network to the shoreside grid. This paper looks at various shoreside network topologies which can provide the required power when berthed from the local supply. Each topology presents different flexibility and efficiency attributes which can be best matched to the expected load by considering the harbour’s visiting ships’ electrical profile. Use is made of a multi-objective particle swarm optimisation algorithm to identify optimal configurations based on berth powers, with a view to reduce installation cost as well as shoreside emissions. These resultant emissions depend not only on the shoreside network but also on the local generation mix which therefore must be taken into account in order to provide a sensible comparison with onboard generation.

Conventional propulsion systems are matched to meet power demand at designed operating points. Off-design conditions result in sub-optimal operation of prime movers since these are sized to cater for the peak power requirement. Hybridisation of power sources enables the advantages of separate sources to be exploited to best match actual operating conditions. In this work, permanent magnet machines are considered as auxiliary drives, providing propulsion at low ship speeds, complementing their use as shaft generators. Various topologies of auxiliary drive layout were analysed, considering different machine torque and speed ratings according to installation choice. As part of this study, the examination of auxiliary electrical drives was performed on a RoRo and tug with a view to assess reductions in exhaust gas emissions and fuel consumption. The two vessels were considered under typical operating scenarios. By means of simulation, the emissions and fuel consumption under auxiliary propulsion were quantified and compared to the contribution from the main engine. Significant emission savings were observed for the RoRo case particularly due to the use of cleaner fuel as a source. In the tug case, emission reductions could not be observed for this particular setup since the auxiliary drive system only adds additional inefficiencies in the propulsion system. Capital costs are significant, and the use of diesel fuel represents an increased cost. Yet if emission reductions are incentivised, auxiliary drives using permanent magnet machines are an attractive solution.

Hybrid vehicles offer the advantages of both conventional and electric vehicles. Improved fuel consumption is generally the main driver for these systems with the option of silent, emission-free operation also being a big advantage. Marine hybrid vehicles however, do not experience significant recovery of energy via regeneration, because of their operating profiles. Fuel savings can be realised by optimal component operation rather than free-energy recovery, yet this requires correct component sizing considering the typical usage over a scenario. In this study, a model is built to calculate the fuel consumption of a hybrid motoryacht over a given day-cruise scenario. A genetic algorithm is then applied to optimise the component sizing of this hybrid system with respect to minimisation of fuel consumption and total installation weight.

Powertrain hybridization permits the benefits of more than one power source to be integrated and exploited for a beneficial effect on an objective, such as reduction of fuel consumption or emissions. Due to their operating profiles however, marine hybrid vessels do not exhibit much opportunity for free energy recuperation. Fuel savings can be realized by bettering component operating points, yet this requires correct sizing matched to the expected usage. In this paper, a multi-objective genetic algorithm is used to optimally size propulsion components in order to minimize fuel consumption as well as installation weight for a hybrid motoryacht operating on a day cruise scenario.

An auxiliary drive is an electric machine and power electronic converter mounted in parallel with the main ship propulsion system. With a bidirectional electric drive system, Power Take In and Power Take Off are both possible, enabling hybrid operational modes. This gives the opportunity for slow speed motoring periods with improved prime mover operation and potentially lower emissions. Permanent magnet and induction machines are the two likely electrical machine choices. This paper presents an evaluation of the relative efficiencies of the two machine types when implemented on a shipboard auxiliary drive system. Depending on the operational strategy and the adopted propulsion system, the auxiliary drive is required to operate at various points in its operating envelope. By using a detailed computer model of an auxiliary drive system, the efficiencies at various operating conditions are calculated, showing how knowledge of the ship’s operational profile is essential in order to identify the configuration with the best efficiency.