Interesting question!
The air lubrication technology is not something new.
The concept was first developed in the 1950’s by the US Navy as a radiated noise reduction system. Air bubbles would be injected around the hull and the propeller to distort the acoustic signature of warships. Later on researchers in the US, Russia and Japan started thinking of air lubrication systems as energy saving devices.
In 2018, the IMO officially recognized air lubrication systems as Category B-1 “Innovative Energy Efficient Technology” as (MEPC.1/Circ.815 (2018)).
The operational principle of the air lubrication system is the following: compressed air is injected on the flat bottom of the ship, forming an air layer, hence reducing the direct contact of the ship’s wetted surface with the water flow i.e. reduction of skin friction resistance. The skin friction resistance is the predominant component of the total resistance of conventional hull forms
There are three major categories of air lubrication technology:
According to reported data, a vessel may achieve a net power saving of 4-5%, owed to an air lubrication system.
The installation of an air lubrication system is not simple at all.
Here is an example of the air lubrications system equipment for an LNG carrier.
The installation cost is circa 2 million USD and the yearly maintenance cost is around 25,000 USD (not accounting for the off-hire or extra docking days if it is a retrofit).
The performance of air lubrications systems is strongly affected by weather conditions.
Such systems would not operate efficiently in rough seas.
Higher gains are expected in larger vessels that operate at high speeds.
The installation cost is high. It would make sense to install it in a time chartered vessel where the cost could be shared between the owner and the charterer.