John Prousalidis

New challenges emerged from the development of more efficient electric energy generation units

The current trends in ship technology are turning ships into more energy efficient ones. Thus, the extensive electrification of ship systems, including propulsion, is a most appealing alternative as, the more electrified a ship, the greener and more efficient it turns. In this paper, a brief overview of novel trends regarding electric energy generator schemes is made, and it is shown that these result in new challenges leading to amendments of the traditional concepts dominating over design and operation standards. The discussion is supported by the results of a model comprising a ship generic power grid with multi-type supply units.

Control system for fuel consumption minimization–gas emission limitation of full electric propulsion ship power systems

Environmental pollution caused by ships’ green house gas emissions and worldwide concern about air quality and oil supplies have led to stricter emissions regulations and fuel economy standards. In this regard, respective limits are set, while efforts to provide general guidelines for the achievement of economic and green ship operation with an urge to ship operators to apply them and return feedback. Also, specific design and operation indicators have been proposed in order to ensure compliance with new emissions regulations and fuel economy standards. Up to now, these indices are limited to ships comprising conventional propulsion systems, while full electric propulsion systems are not examined. In this article, an integrated control system that attains economically optimized and environmentally friendly operation is proposed. Moreover, appropriate reformulation of energy efficiency operation indicator is proposed for real-time assessment of gas emissions. The study is supported with the presentation of results obtained from the simulation of the operation of a ship power system comprising full electric propulsion.

Electric Power Supply Quality in ship systems: an overview

Power Supply Quality (PSQ) has become an important concern for ship electric systems. Thus, deviations of voltage from nominal values and wave-shapes could cause several problems onboard. Considering that ship system electrification eventually dominates according to the All Electric Ship concept, PSQ will be a key-factor of the normal operation, survivability and safety aboard. The paper provides a coherent description and categorisation of the PSQ phenomena (causes, consequences, characteristic parameters etc.) highlighting similarities and differences between terrestrial systems and ship systems in terms of these phenomena. This overview is enriched by cross-references to relevant standards applied in shipboard applications.

PV Systems Installed in Marine Vessels: Technologies and Specifications

Considerations are held about the specificationin whichthe PV plants have to fulfill so that they can be installed on marine vessels. Initially, a brief description of the typical electrical grid of ships is presented, distinguishing the main parts, reporting the typical electrical magnitudes, and choosing the most preferable installation areas. The technical specifications,in whichthe PV plants have to be compatible with, are fully described. They are determined by the special marine environmental conditions, taking into consideration parameters like wind, humidity, shading, corrosion, and limited installation area. The work is carried out with the presentation of the most popular trends in the field of solar cell types and PV system technologies and their ability to keep up with the aforementioned specifications.

Reactive power sharing in ship energy systems with shaft generators

This paper deals with the well-based mathematical formulation of active and reactive load sharing of the synchronised generators of a ship’s electric energy system. Thus, both the first- and second-stage regulation during load sharing is presented via mathematical equations. The novelty introduced in the paper is, on the one hand, that the hybrid parallel operation of shaft and conventional generators is covered, while on the other hand, that the analysis results in solving the combined reactive and real load sharing within the generator rated capacity. Furthermore, the dynamic behaviour of the machines and their controllers during the load sharing problem is also discussed with the aid of simulations in the MATLAB/Simulink environment. The entire analysis, which it is hoped can also be used for educational purposes, is enriched by figurative results obtained from an actual ship case study, in which this work assisted in resolving a series of load sharing problems

A new pattern recognition methodology for classification of load profiles for ships electric consumers

In this paper a new pattern recognition methodology is presented for the classification of the daily chronological load curves of ship electric consumers (equipment) and the determination of the respective typical load curves of each one of them. It is based on pattern recognition methods, such as k-means, adaptive vector quantisation, fuzzy k-means, self-organising maps and hierarchical clustering, which are theoretically described and properly adapted. The parameters of each clustering method are properly selected by an optimisation process, which is separately applied for each one of six adequacy measures: the error function, the mean index adequacy, the clustering dispersion indicator, the similarity matrix indicator, the Davies-Bouldin indicator and the ratio of within cluster sum of squares to between cluster variation. As a study case, this methodology is applied to a set of consumers of Hellenic Navy MEKO type frigates.

Green shipping in Emission Controlled Areas: Combining Smart Grids and Cold Ironing

Worldwide concern about air quality and global warming has led to emission regulations for the shipping industry and Emission Control Areas (ECAs) including the areas around ports. An appealing alternative to reduce the level of pollution from ships when docked in ports is connecting to shore-side electrical power, known as Cold Ironing. Cold Ironing has the potential to make use of zero emissions electrical generation technology from renewable sources to supply clean electrical power to docked ships. Furthermore, the ports can be considered key customers from the National Grid point of view.

Exploiting shaft generators to improve ship efficiency

Shaft generator (SG) systems have been exploited for long due to several appealing advantages they present. This type of generators is installed at the shaft of the main propulsion diesel engine while they are capable of operating as propulsion engine boosting devices if suitable power electronics are used. In this paper an effort is made to provide a comprehensive analysis of shaft generator role in ship power system efficiency improvement in relation with ship operation optimization point of view. Special reference is made to the interdependence of SG with power management system as they alter the operation point of both propulsion engine and the electrical generators affecting the optimal operating point.

On studying the power supply quality problems due to thruster start-ups

The target of this paper is twofold: primarily to highlight the significant effect of certain power supply quality problems on the normal operation of the entire ship grid, namely inrush currents and voltage dips due to manoeuvring thruster motor starting-ups. At a second stage, the paper aims at recommending some amelioration of standardization status. Hence, the authors suggest the exploitation of existing experience on pulsed load standardizing, taking into account the resemblance between the systems. The study is enriched by actual case studies and simulations in PSCAD computer program.

Discussion on adopting intelligent power management and control techniques in integrated power systems of all-electric ships

The development of all electric ship (AES) configurations necessitates the use of multiple power sources to support a wide variety of load profiles. The latter are diverse ranging from propulsion loads to high power pulsed loads while the operational status of the ship varies complicating even further the power and energy management process. The high level of complexity is giving rise to modern sophisticated ship Electrical Power Management and Control Systems (EPMACS) resembling the ones adopted in land-based hybrid systems. This paper discusses the adoption of intelligent control methodologies on an EPMACS which can substantially reduce complexity, increase integrability and improve the overall efficiency and reliability.