A hull air lubrication system is a technique to reduce the fricional resistance between the ship’s hull and the water using a sheet of air or air bubbles. Reducing a ship’s resistances causes the need for the required driveline power to be decreased. This reduction on the power cuts down on the fuel consumption of the ship and therefore also decreases the operational costs of the vessel. In ideal situations, an air injection system can achieve up to 15% in the reduction of CO2 emissions together with significant fuel savings. A hull air lubrication system would reduce the emissions of Particulate Matter (PM), nitrogen oxides (NO_X), sulpher oxides (SO_X) and carbon dioxide (CO₂).

Compressors are necessary to inject the air to the bottom of the ship’s hull. The amount of air, the ship’s gemeometry and  the pressure needed are important factors that play a roll on the cost of the hull air lubrication system. Ships with flat bottoms have an advantage over V-shaped bottoms since the air on a V-shaped bottom will flow away much more easily than a flat bottom. For a V-shaped bottom ship, it would require more air necessary to have the same effect as the flat bottom, increasing the demand for power. With higher draughts, higher pressure created by the compressor is necessary and therefore requiring more power of the air injection system. To make an air injection system profitable, it is to be considered that the power of the air injection system to be lower the savings in driveline power.

Projects such as Project Energy-saving air-Lubricated Ships (PELS) and the project Sustainable Methods for Optimal design and Operation of ships with air lubricaTed Hulls (SMOOTH) have researched the effects of air lubrication. Project PELS researched air lubrication on a model scale and achieved a 3-10% net effective power reduction in calm waters. Project SMOOTH targeted a 15% reduction of the consumed energy by drag reduction by means of air lubrication techniques.