A review of energy efficient methods for all-electric ships

Abstract

With stringent environmental regulations and growing concerns on energy consumption of the marine transport sector, there is a serious effort to make on board energy system more efficient. Improving fuel efficiency is conceived as a sustainable measure in terms of reducing greenhouse gas (GHG) emissions and overall marine energy use. As such, electrification of ship propulsion has been introduced as a solution for operating at higher efficiency and hence more saving fuel. However, energy efficiency in the context of marine transport is to be more stringent over time as required by International Maritime Organization (IMO). The energy performance indicators to evaluate such requirements include Energy Efficiency Design Index (EEDI) and Energy Efficiency Operational Indicator (EEOI). Several energy efficient methods are therefore proposed to further improve fuel efficiency on board electric vessels. These involve integration of energy storage system, implementation of DC distribution, optimal power distribution and scheduling as well as various operational practices that are currently applicable for existing conventional vessels. The paper summaries the concept of ship energy efficiency in terms of the standard indicators and provide a brief review on the energy efficiency improvement strategies published in literature. The aim of the review is to analyze the methods that are potential to incorporate into the autonomous system of all-electric vessels. The results show a significant variation in reported efficiency gain and thus a combination of various methods is suggested to achieve full potential for emissions reduction.