A scenario-based assessment of the energy efficiency existing ship index (EEXI) and carbon intensity indicator (CII) regulations

International Maritime Organization has entered into force several regulations to lessen the carbon footprint of maritime transport. EEXI is utilized to sustain continuously increased energy efficiency and CII is utilized to measure carbon emissions and rating boundary of ships. In this paper, five different ship types, which are the bulk carrier, gas carrier, tanker, general cargo, and container ship, are examined in seven scenarios. Meeting EEXI and CII requirements is extremely challenging for marine vessels where conventional fuels such as MDO and HFO are utilized and without having an engine power limitation application based on the outcomes of the scenarios. Engine power limitation provides a significant advantage, and the usage of alternative fuels such as LNG and methanol is effective to avoid falling below the threshold of EEXI and CII. The specifications of primary fuel and the usage rate of the alternative fuel are the prominent criteria for dual-fuel engines utilizing LNG to meet the requirements. The EEXI values and CII ratings can be significantly reduced by converting a conventional engine to a methanol engine. The proper selection of the engine size and the speed optimization of the vessel is the key factor for this application.s.