A review of ship energy efficiency research and directions towards emission reduction in the maritime industry

To improve energy efficiency of ships, initiatives have been taken by the international and regional regulatory bodies, ship owners, shipping lines, and other involved stakeholders. While existing literature has investigated ship energy efficiency from different perspectives, a comprehensive review on measures, practices, policies, feasibility, and alternatives remains absent. This study presents a retrospective review of ship energy efficiency literature by utilizing a hybrid review method that combines bibliometric and content analysis approaches. For bibliometric analysis, the bibliometrix package in the R software was used in combination with the VOSviewer software. The outcomes of bibliometric analysis are the most ranked articles, journals, authors, and institutions related to ship energy efficiency research. The bibliographic coupling analysis identified five research clusters: (1) decarbonization and emission reduction measures, (2) speed management, (3) policy and regulations, (4) economic and organizational factors, and (5) alternative energy sources. Future research directions are proposed for each cluster.