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Wednesday, February 12, 2020 

Classification society DNV GL is working with two French companies in using aerospace technology to double the potential power of wind-assisted ship propulsion.

VPLP Design, together with engineering firm CNIM, have developed a new wing sail concept called OceanWings. In most wing sails, the propulsion principle of traditional sailing boats is combined with the aerodynamic efficiency of an aeroplane wing with the trailing edge flap extended for starting or landing. “There is a slot between the two elements of the wing, and the air going through the slot accelerates the flow and pushes the turbulence towards the trailing edge”, said Marc Van Peteghem, naval architect and co-founder of VPLP Design.

Transferring the two-part concept of the plane wing and flap to a sailing boat results in a wing sail, which consists of two vertical, more or less symmetric, parallel 'wings' with a narrow gap between them. The gap splits and redirects the airflow again, reinforcing the aerodynamic effect and producing an additional thrust. The OceanWings design takes a slightly different approach: each of the two straight blades has a mast of its own and consists of several horizontal segments, the 'body' of each segment formed by a flexible fabric. Raising or lowering these segments along the mast allows the surface of the sail to be increased or reduced, and lowering all segments to the lowermost position furls the sail entirely. The angle between the two parts of the sail can be adjusted as desired; each blade can rotate 360 degrees around its mast.

In the OceanWings concept the entire wing sail is fully computer controlled. All the operator needs to do is choose the heading, and the computer will position the two parts of the sail to achieve optimum thrust, adjusting the camber and twist as required.

“It is time to transfer the technology we have developed in the yachting industry to the shipping industry”, said Van Peteghem.  According to Van Peteghem, trials on small vessels suggest OceanWings sails could reduce fuel consumption by 18 to 42%, depending on ship type, route and sail arrangement. His company offers its OceanWings wind propulsion technology as an auxiliary source of propulsion power for merchant ships to help achieve the desired EEDI. Looking further into the future, hybrid vessels combining an eco-friendly engine fuel with wing sails and solar panels on board could one day be an option for GHG-neutral, sustainable shipping.

DNV GL points out that projects like the recent successful rotor sail installations by the MariGreen consortium and Norsepower, both with DNV GL certification, as well as OceanWings and other sail types have delivered encouraging results. To support these efforts DNV GL has published its new class notation 'Wind assisted propulsion systems'. DNV GL's independent maritime advisory network has expertise in calculating the amount of auxiliary propulsion power or fuel savings specific wind systems will generate on a specific ship on a given route, while its EEDI calculation for a given hybrid propulsion configuration includes wind assistance, expressly permissible under IMO statutes. The third service is a new class notation involving technical certification and approval of the safety, structural stability and resilience under extreme conditions of a ship using auxiliary sails.

“The technology is there, and we offer the necessary independent advisory and approval services,” said Hasso Hoffmeister, Senior Principal Engineer, DNV GL. “It is up to the shipping industry to seize these opportunities.”

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