The determination of EEDIweather during the longitudinal motion of a ship with wing devices in a representative sea condition
Proposed in this paper is the Energy Efficiency Design Index (EEDI) of a container ship on a head sea. Since EEDI is a measure of CO2 emissions of ships in calm waters, which are rarely found in the ocean, IMO has defined EEDI for a “representative marine environment” called EEDIweather. When calculating the EEDIweather, not only a ship but also a ship with wing devices fully or partially propelled through the use of wave energy is calculated. An energy-saving ship with wing devices contributes to the directional influence on its longitudinal motion to reduce motion amplitudes and reduces additional resistance on waves. The longitudinal motion of a ship of given type, geometry, and dimensions on prescribed regular waves are determined to utilize numerical solutions of coupled equations of a ship pitching and heaving. The EEDIweather is dependent on additional resistances on headwinds and waves, so a ship with wing devices has the effect of reducing the EEDIweather in representative sea conditions. Demonstrated in the calculations is the influence upon the EEDIweather of the aspect ratio and reference area of the wings, and also the effect of using simultaneously the bow and stern wings as compared to using just one (bow or stern) wing. EEDIweather reduction results are related to the main goal of the article to the number of harmful emissions into the atmosphere and to ensure the protection of the marine environment through the use of the “Green Ship'' concept.