The energy efficiency effects of periodic ship hull cleaning

International audienceThis paper investigates the impact of periodic hull cleaning on oil tankers' energy efficiency using real 2012–2016 fleet performance and weather data extracted from noon reports for a fleet of eight identical Aframax-size crude oil tankers. The impact of changes in fuel consumption is estimated around the discontinuity when a vessel is cleaned and rely on both before-after and difference-in-differences estimators. The main results show that (i) periodic hull cleaning leads to a significant reduction in the daily fuel consumption; (ii) dry-docking leads to greater and significantly different reductions in fuel consumption than underwater hull cleaning, approximately −17% versus −9%; (iii) hull cleaning energy efficiency effect is greater when the vessel is sailing laden rather than in the ballast condition. These findings represent a key building block for the optimization of maintenance intervals