The two diagrams to the right show the speed and power for tankers (both oil and chemical). For clarification the definition of design speed is speed at design draught (at aprr. 90% max dwt.) obtained at 90 % MCR with 15 % service margin. According to the attached output from the model that design speed is nearly identical with the reference speed according to EEDI. As there is some doubt about the speed given in the IHS Fairplay database the service speed according to data from RINA´s annual publication ‘Significant Ships’ where the speed is often quoted to be the service speed at 90 % MCR and with 10 % sea margin has been added. Calculations of the consequences of different speed proposals are also included: The speed as it is today, and limit curves imposed on ships in the future as an interim solution to the problem with safe manoeuvring speed. The calculations have been carried out with a generic computer model developed at DTU. Hans Otto Holmegaard Kristensen.
speed comes at a high energy cost. As a result of the EEDI regulations DTU is expecting vessel speeds to reduce, but there may be a twist meeting the EEDI rules can still be achieved through good design. Phase 1 of EEDI will require tankers and
bulk carriers to reduce emissions by 10% compared to the EEDI reference line from 2015 onwards, this can be easily be achieved by simply slowing a 70,000dwt tanker to a little under 15kn. Phase 2 EEDI will require a 20% reduction
on the EEDI reference line between 2020 and 2025 while a 30% reduction will be required aſter 2025. Tese later targets will be harder to meet, but with a 5% elongation of the ship, ducted propeller, reduced steel in building the vessel and a de-rated engine will allow a 70,000dwt tanker to operate at 16kn and still be within the EEDI rules. Speed will inevitably be an issue and
in some instances will be the only way for vessels to achieve their EEDI target emissions. It is with this in mind that the EU has provided €2.6 million (US$3.44 million) in funding for the ULYSSES project that will look at the effect that slow steaming will have on what are already
The Naval Architect March 2012 Slow steaming – adverse conditions Wind and sea margins
IMO RESOLUTION MEPC. 203(62) Adopted 15 July 2011 REGULATION 21.5
For each ship to which this regulation applies, the installed propulsion power shall not be less than the propulsion power needed to maintain the manoeuvrability of the ship under adverse conditions as defined in the guidelines to be developed by the Organisation.
Consequence Normal design conditions have to be changed with more detailed definition of service margins. Wind and sea state have to be defined instead of a general percentage sea margin
Credit: DTU
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