ABSTRACT

Hull roughness, caused by biofouling and aging of a ship hull, significantly increases GHG emissions. Studies (GloFouling, 2022) suggest that a mere 0.5mm slime covering half the underwater hull can intensify the GHG emissions by 25%. This paper presents a methodology using a time-dependent roughness function to predict fuel demands, aligning with (MEPC.378 (80), 2023). Integrating the famous empirical method (Holtrop, 1982) the approach which will help the stakeholders to identify the rising power demands on the basis of ship's idle time and help in prioritizing cleaning efforts based on drag impact. This methodology aims to enhance biofouling management strategies, promoting sustainable maritime practices and reducing GHG emissions.

INTRODUCTION

Most of a ship's energy is used for propulsion, though some vessels like cruise ships and offshore support vessels also have significant onboard power demands. Overcoming water resistance is essential for movement, with key resistance components being:

Skin Friction Drag: Friction between the ship and water.

Wave-Making Drag: Energy dispersed by ship creating waves on water surface.

Form Drag: Drag from pressure differences around hull.

Air Drag: Resistance from motion due to wind.

Resistance increases with speed, especially wave-making resistance, which grows roughly as the cube of speed. Slowing down reduces energy demands significantly, although it also decreases operational productivity.

Energy-efficiency measures include:

• Smooth Surfaces: To reduce skin friction.

• Streamlined Hull Forms: To lower wave-making and form drag.

• Bulbous Bows: To create wave patterns that reduce wave-making resistance.

• Stern Appendages: To decrease drag and improve propeller performance.

Hull roughness significantly contributes to increased frictional drag on ships. The roughness intensifies because of biofouling (Figure. 1), weld distortion, waviness of hull plates, corrosion, and damage, potentially causing higher skin friction. Marine biofouling is a growing issue from both economic and ecological perspectives, leading to increased resistance, fuel consumption, GHG emissions, and the transfer of harmful aquatic organisms. Biofouling is a continuous process (Davidson I, 2013) that accelerates within a few days (Bressy, 2014), impacting hull and propeller smoothness post dry-docking. Antifouling coatings (AF) can prevent marine organism adhesion, potentially saving $60 billion and reducing CO2 emissions by nearly 400 million tons, and SO2 emissions by 3 million tons annually (GloFouling, 2022). A quick assessment of increased power due to biofouling is critical for timely decision-making regarding in-water cleaning. Despite antifouling coatings and regular maintenance, biofouling persists, leading to significant increases in frictional resistance and power demands.

This content is only available via PDF.
You can access this article if you purchase or spend a download.