Energy saving, fuel economy of 15%, by reducing frictional drag on the immersed hull by means of injected streams of air bubbles has been proven effective by recently concluded practical tests. Two years of trials of a technology known as ‘Air Chamber Energy Saving’ (ACES) installed in a working Dutch inland waterway tanker back up this claim.

ACES

Damen Shipyards in Holland commissioned the exercise in the Dutch inland waterway tanker Till Deymann provided by subsidiary company Bodewes Binnenvaart back in 2009 on the heels of detailed analysis of tank-testing and computer modelling (at the Dutch Institute MARIN in Wageningen and DST laboratories in Duisberg, Germany), that indicated the time was right for putting ACES to the test under operational conditions.

Till Deymann, chosen for conversion in order to test out the ACES system, was a standard 'River Liner' type 11.45e product from the Damen yard, of 2858 dwt, with a LOA of 110 m, moulded breadth of 11.45 m, and a design draft of 3.55 m. The main engine produces 1307 kW to provide a service speed of 11.4 kts

As a result of extended sea trials of the ACES system, average frictional water resistance was found to be reduced between 10% and 20% depending upon ship’s speed. Damen also advised that ACES would deliver similar benefits to general cargo and bulk carriers, adding that classification society Bureau Veritas,  one of the many participants in the whole project, would append the notation ‘Air Lubrication Vessel’ to such ships.

Damen River Liner type 11.45e: Photo courtesy of Damen Shipyards

ACES and MALS

In an article in these columns last October this writer focussed attention on Mitsubishi Heavy Industries’ concept design container ship  ‘MALS-14000’, where the acronym ‘MALS’ signified the Mitsubishi Air Lubrication System (claimed to deliver similar  benefits) that was to be integrated in the design of the proposed 14000 TEU box carrier. Perhaps due to contraction in the market, no further news of the project has yet been announced .

What distinguishes the ACES system from MALS is that while ACES targets the injection of air-bubbles mainly to formed chambers in the after part of the ship, and also downstream of the forward tunnel thruster openings) MALS is understood to provide for an ad hoc supply over most of the submerged hull form

On the evidence it seems on the cards that the hand holding the ACES may prevail.