Novelties in the international policy towards mitigation of greenhouse gas emissions from ships and necessary measures in marine industry Part 2. Efficiency analysis of power-saving measures intended to reduce greenhouse gas emissions

Object and purpose of research. This work was intended to analyse technical solutions that could contribute to power efficiency of in-service fleet in the light of new IMO policy aimed at the mitigation of greenhouse gas emissions from international marine traffic. This is the second publication in the series of articles discussing various aspects of this new IMO policy, as well as shipbuilding challenges that have to be faced in order to meet relevant requirements. Subject matter and methods. This work is an analytical review of available publications on above-mentioned topic. It relies on Krylov State Research Centre experience in the optimization of ship fuel consumption, as well as on the results of IMO correspondence group discussions on power efficiency with participation of Krylov State Research Centre and RS experts. Main results. This paper discusses the efficiency of measures taken all over the world to improve fuel efficiency of ships taking into account the experience of their implementation at the early stage of IMO regulations for greenhouse gas emissions. It is shown that each of these measures might reduce the emissions from global marine traffic by ~5%, which is not enough to achieve the final goal, i.e. 70% reduction in emissions by the year 2050 as compared to 2008. Besides, these measures cannot be implemented in full due to certain limitations. For example, in Russia the main obstacle is that practically all its ships must have an ice class, so they cannot use a whole number of various power-saving devices because of their vulnerability to ice impact. Still, provided that power-saving devices are robust enough, they might prove to be a useful (and sometimes the only possible) way to reduce gas emissions of a ship after several years of service. It is incorporated to the system rating the ships in terms of their emission score assigned as per the new provisions of MARPOL Annex VI adopted in 2021, see Part I of this series. Conclusion. Analysis of power saving measures (along with assessment of their efficiency and applicability to ice-class ships) enables a justified selection of power efficiency enhancement tools for a ship in case its annual Carbon Intensity Indicator (CII) goes beyond IMO thresholds that gradually become more and more stringent in accordance with new provisions of MARPOL Annex VI. Still, these measures will not be sufficient to achieve target levels of emission reduction prescribed by IMO. These levels could only be achieved through radical changes in marine power systems, like the transition to alternative fuels with low or zero carbon footprint. This matter will be discussed in the third article of this series.