Regulating the safe navigation of energy-efficient ships: A critical review of the finalized IMO guidelines for assessing the minimum propulsion power of ships in adverse conditions

Abstract

This study first reviews the various stages of development of recent International Maritime Organisation (IMO) guidelines for the assessment of the minimum propulsion power for safe navigation of ships in adverse conditions, while complying with the requirements of energy efficiency in the frame of the IMO strategy for Green House Gas (GHG) emission reduction from ship operations. It summarizes the underwent key revisions of the guidelines after their original introduction in 2010 (MEPC 61) referring to key elements in the assessment method, such as the definition of the adversity of the operational conditions and ship's navigation speed, to the variety of methods for the prediction of the added resistance in waves, to the recommended thrust deduction fraction and wake fraction, etc., as outlined in the latest version of the guidelines adopted at IMO-MEPC76 (June 2021). An inconsistency in the recommended alternative methods for the added resistance prediction is demonstrated by the analysis of a series of typical tanker and bulk carrier designs. A minimum propulsion power assessment is conducted for the KVLCC2 standard tanker ship to show the impact of the recommended new guidelines on the ship powering requirement. Lastly, the uncertainties involved in the assessment procedure are discussed.