A French design concept using the scientific principles of suction created around a wing has received initial design approval as an auxiliary wind propulsion device for large cargo ships. Unlike other designs that are also gaining momentum in the field, the Suction Wing has no high-speed external moving parts and according to its developers provides advantages for ships.
Jointly developed by CRAIN Technologies (Centre de Recherche pour l’Architecture et l’Industrie Nautiques) and its partner REEL (Rationnel Economique Esthétique Léger), the SW270 is a solid thick wing, fitted with a rear flap. Grids located on both sides of the wing section create a suction force that draws the air stream around the wing section from the outside to the inside of the wing. The wing is mounted on a structural foundation that contains the suction fan required to operate the system.
“The suction wing concept appears to be a very promising option to help reduce greenhouse gas emissions from cargo ship operations,” said Laurent Leblanc, Senior Vice President Technical & Operations for Bureau Veritas Marine & Offshore.
BV reports it worked very closely with CRAIN from the earliest stages and recently awarded an Approval in Principle (AiP) for their Suction Wing SW270. The testing and certification group, they conducted a thorough assessment of the conceptual design, risk analysis, wind tunnel report, preliminary stability, loadings, and general arrangement.
During the review, BV considered a suction wing with a span of approximately 88 feet. The companies explained that the design is scalable to all sizes of ships. The concept being presented (shown in the rendering above) is for a 300,000 dwt VLCC tanker that would be fitted with four wind propellers based on the suction wing concept.
“Suction Wing SW270 is an innovative wind-assisted propulsion solution that is suited for a large range of cargo ships,” explains Philippe Pallu De Barriere, CEO of CRAIN. “Developed using technologies already widely used by the naval industry, it delivers great power proportionally to its surface, and is easy to install and use on ships.”
Based on the principle of boundary layer suction, the companies said that the Suction Wing concept delivers a very high lift coefficient, which reduces the size of the device needed to achieve a given pull force. Thanks to the shape of the system, the drag remains moderate. Therefore, the lift-to-drag ratio provides a good performance in upwind conditions and for ships sailing at relatively high speeds, using the wind to propel the ship in combination with the main engine. Furthermore, the wing section can rotate around a vertical axis to adjust to wind direction and optimize performance.
CRAIN reports that studies have been carried out that so far show savings on average fuel consumption of up to 30 percent based on realistic assumptions. Operating conditions of course impact the performance but can be optimized by operating at average speed and employing weather routing.
In the next phase of the development, CRAIN says working with its partner it will pursue the industrialization of the SW270 using the definitions and regulations provided by BV.