Abstract
Voyage optimization is a practice to select the optimum route for the ship operators to increase energy efficiency and reduce Green House Gas emission in the shipping industry. An accurate prediction of ship operational performance is the prerequisite to achieve these targets. In this paper, a modified Kwon׳s method was developed to predict the added resistance caused by wave and wind for a specific ship type, and an easy-to-use semi-empirical ship operational performance prediction model is proposed. It can accurately predict the ship׳s operational performance for a specific commercial ship under different drafts, at varying speeds and in varying encounter angles, and then enables the user to investigate the relation between fuel consumption and the various sea states and directions that the ship may encounter during her voyage. Based on the results from the operational performance prediction model and real time climatological information, different options for the ship׳s navigation course can be evaluated according to a number of objectives, including: maximizing safety and minimizing fuel consumption and voyage time. By incorporating this into a decision support tool, the ship׳s crew are able to make an informed decision about what is the best course to navigate.In this study the Energy Efficiency of Operation (EEO) is defined as an indicator to illustrate the ratio of main engine fuel consumption per unit of transport work. Two case studies are carried out to perform the prediction of ship operational performance for Suezmax and Aframax Oil Tankers, and the results indicate that the semi-empirical ship operational performance prediction model provides extremely quick calculation with very reasonable accuracy, particularly considering the uncertainties related to the parameters of interest for the case study data. Within the case studies, the additional fuel consumption caused by the combined hull and propeller fouling and engine degradation is included in the model as a time-dependent correction factor. The factor may assist the ship owner/operator to determine the hull coating selection, and/or the dry-docking and main engine maintenance strategy.
Highlights
Energy efficient shipping is a prerequisite for the reduction of the Green House Gas (GHG) emissions to the levels anticipated within the decades
This paper focuses on the development of an accurate and practical ship operational performance prediction model that can be used to select the optimum routes for minimum fuel consumption, taking into consideration average ship speed, encountering sea states and voyage time
An advantage of using the Efficiency of Operation (EEO) as an indicator is that it contains many of the same elements and could be converted to the Energy Efficiency Operational Index (EEOI), which is recommended within the Ship Energy Efficiency Management Plan (SEEMP) (IMO, 2012)
Summary
Energy efficient shipping is a prerequisite for the reduction of the Green House Gas (GHG) emissions to the levels anticipated within the decades. The performance of each specific ship in various voyage conditions (speed, fouling and propulsion system degradation, and draft) may be quite different, especially under severe weather conditions This highlights the need for real-time, flexible ship-specific modeling in order to provide increased accuracy of ship operational performance prediction for voyage optimization. This paper focuses on the development of an accurate and practical ship operational performance prediction model that can be used to select the optimum routes for minimum fuel consumption, taking into consideration average ship speed, encountering sea states and voyage time. Besides the development of the ship operational performance prediction and the optimum routes selection, a time-dependent fuel consumption increase rate after ship dry-docking has been identified, which may be helpful in monitoring ship fouling and engine degradation condition. The identified fuel consumption rate of increase will further assist shipping companies with planning dry-docking and engine maintenance scheduling
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