Compressed air applications in Marine

Air lubrication is an innovative energy efficiency technology that utilises low-pressure air to reduce a ship’s frictional resistance - the drag or ‘stickiness’ caused by the seawater rubbing against the hull as the ship moves through it. Although being an old technology, it has been further developed in recent times to enhance vessel efficiency and reduce environmental impact, helping ship owners meet stringent international regulations.

Low-pressure air is injected through nozzles or air release units (ARU) that are strategically located along the flat bottom of a wetted hull surface. These nozzles or ARUs then release microbubbles into the boundary layer along the hull, creating a large continuous and uniform ‘air carpet’. The laminar flow in this boundary layer of air and seawater mixture significantly reduces the frictional resistance. Less frictional resistance means less thrust - or power - is required to overcome it, translating into reduced fuel consumption and CO₂ emissions. 

The current air lubrication systems have the potential to create net fuel savings of up to 10% and reduce the carbon footprint of the vessel, while also potentially reducing hull fouling. Besides, studies have also shown that it can reduce underwater radiated noise (URN), which has benefits for the marine life as well as potentially creating a quieter onboard environment. 

There are a number of possible air lubrication methods, however the microbubble method is one of the most typical thanks to its ability to create a stable ‘air carpet’ and to deliver effective friction reduction. These systems may require compressed air or low-pressure air to operate depending on a number of factors. To blow microbubbles under the hull, the corresponding static pressure of 0.5 to 2 bar has to be overcome. In combination with the dynamic pressure, which depends on the air speed and the pipe diameters and lengths, around 1 to 2.5 bar must be applied. In addition, the size and design of the vessel will also impact the compressed air requirement. 

Achieving true energy and emissions savings with air lubrication hinges entirely on the efficiency of the accompanying compressed air system. If the energy consumed by the compressed air system to operate the air lubrication system (ALS) is excessive, the net savings can be diminished. Therefore, the net gain in reduced fuel and emissions must be higher than the power required to operate the compressed air system. A key aspect of this efficiency is the compressed air system’s ability to operate with a low outlet temperature, as this indicates less energy is being wasted as heat during the compression process. Opting for a reliable and energy-efficient compressed air technology that is correctly sized to meet the specific compressed air demands of the ALS’s operating profile, and is correctly controlled and maintained, will all impact its overall efficiency and thereby the final net gains a ship operator can realise from utilising air lubrication to reduce frictional resistance.

KAESER rotary screw blowers present the ideal solution to energy-efficiently meet the low-pressure air requirements of air lubrication systems. Featuring the world-renowned SIGMA PROFILE rotors, these highly efficient blowers ensure maximum air delivery whilst keeping power consumption to an absolute minimum. Savings of up to 35% are possible with KAESER rotary screw blowers in comparison to conventional blower systems.

Thanks to an intelligently designed and exceptionally compact layout, KAESER rotary screw blowers are perfectly at home on a vessel where space is at a premium, offering ease of installation and allowing all maintenance work to be performed conveniently from the front. These “plug-and-play” complete solutions are accepted and approved by all notable vessel classification societies, validating their durability and reliability under the demanding conditions of the high seas.