Methods To Rate The Operational Energy Efficiency Of Ocean-going Ships Engaged In International Voyages

In a joint effort to address global climate change,the International Maritime Organization(IMO)adopted the Initial Strategy on Reduction of GHG Emissions from Ships in 2018,aiming to phase them out by the end of this century.The Strategy also set out the levels of ambition on the design intensity of ships,carbon intensity of international shipping and marine GHG emissions.As a follow-up action,the IMO has considered imposing a regulatory regime on the operational energy efficiency of ships to complement the existing mandatory mechanism on design efficiency.However,the random and uncertain nature of the operational energy efficiency of ships,in combination with various chartering types and working patterns,poses a significant challenge to performance regulation.Till now,a generally accepted indicator,a common understanding on the fluctuation patterns and a rational method to measure the performance,have all been in absence,which severely hampers the regulatory progress.This research is aimed at contributing to the development of an operational energy efficiency mechanism of international shipping through an in-depth analysis of the potential indicators,the fluctuation patterns of the operational energy efficiency of ships,and a workable rating mechanism.Main contents and achievements are as follows:1)The status and trend of GHG emissions from international shipping are presented,followed by a comprehensive review of the IMO regulatory progress and the main achievements in this area.The unilateral actions of the European Union as well as the industrial initiatives,which are also important drivers of global climate governance,are additionally introduced.Based on an outlook for the regulatory directions,the major technical barriers which hinder the development of an operational energy efficiency mechanism for ships are highlighted.Then,the association between the design and operational energy efficiency of a ship is analyzed,by comparing the two types of efficiency in terms of connotation,metrics and influencing factors.The influencing factors are further explored into with the aid of Random Forest analysis,laying a theoretical and empirical foundation for the thoroughly quantitative research that follows.2)In accordance with the general definition and indicators of energy efficiency,the fundamental principles for constructing an operational energy efficiency indicator are put forward.Accordingly,an alternative metric for operational efficiency,named Energy Efficiency Performance Indicator(EEPI),is proposed based on the unobserved effects model.As demonstrated,EEPI can yield rational metric results without relying on commercially-sensitive data,which overcomes the main shortcomings of the existing options.Having ideally balanced transparency and accuracy,EEPI can promisingly serve as a key benchmarking tool to support the construction of an operational energy efficiency mechanism of international shipping.3)By decomposing the metric of the operational energy efficiency indicator and the pass-on effect of design efficiency,the major drivers of the operational energy efficiency performance of ships are identified.On this basis,a dynamic regression model is developed to measure the contribution of the influencing factors to the fluctuation of the operational energy efficiency of ships,using the key drivers as input variables.Besides,the kernel density estimation is applied to extract the distribution patterns of the full-scale and decoupled fluctuation rates.A scientifically rational approach for performance benchmarking is then demonstrated,taking into account the identified acceptable volatility.4)A quantile regression model,with dummy variables representing the observation calendar years,is applied to quantify the central position,the scale and the skewness of the distribution of the operational carbon intensity performance of international shipping,as well as shifts of these key features between years.A rating mechanism is further constructed on this basis,which is able to regulate the performance of international shipping as a whole in line with the levels of ambition,whilst being robust to certain individual deviations.This rating mechanism is demonstrated using the bulk fleet of China as a sample,which shows its competency as a systematic solution for scientific evaluation of the operational energy efficiency of ships.The novel indicator EEPI,among others,has been listed as a candidate metric of the operational energy efficiency of ships by the IMO.The rating mechanism,in conjunction with the construction methodology,has also been incorporated into China’s submissions to the IMO,proposing draft amendments to MARPOL Annex VI and supporting technical guidelines,subject to further consideration.To complete the operational mechanism,areas that still need technical inputs are put forward,together with potential approaches towards solution.