A new paper that was released recently, addresses the impact of periodic hull cleaning on oil tankers’ energy efficiency using real 2012 – 2016 fleet performance and weather data extracted from 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.
[smlsubform prepend=”GET THE SAFETY4SEA IN YOUR INBOX!” showname=false emailtxt=”” emailholder=”Enter your email address” showsubmit=true submittxt=”Submit” jsthanks=false thankyou=”Thank you for subscribing to our mailing list”]
The main results of the research show the following:
- Periodic hull cleaning leads to a significant reduction in the daily fuel consumption;
- Dry-docking leads to greater and significantly different reductions in fuel consumption than underwater hull cleaning, approximately 17% versus – 9%;
- Hull cleaning energy efficiency effect is greater when the vessel is sailing laden rather than in the ballast condition.
Cleaning the hull can reduce emissions and improve the energy efficiency of the world’s fleet. Hull fouling contributes greatly in increased emissions, and is the only main driver over which the ship owner has a large degree of control. Specifically, while the rate of marine growth on the hull is not on the ship owner’s hands, the frequency and quality of periodic maintenance on the underwater hull is decided by the ship owner.
Moreover, the study shows that it is possible to reduce GHG emissions by 50 – 60% per freight unit transported with current technologies within 2050. However, only a few such measures are used by shipowners.
Out of the 30 technologies for energy efficiency and CO2 reduction reviewed by the authors, the most common initiatives include bulbous bow designs, pre/post swirl devices to improve propeller efficiency, and the tuning, derating and waste-heat recovery of ship engines.
A reason for this, as Poulsen and Johnson (2016) noted, is the lack of reliable data on energy efficiency measures or a distrust on fuel consumption reports.
You can see the full report in the following PDF