Suction wings are wing sails with very large thickness and an in-built mechanical air suction mechanism.
Suction wing sails are currently installed on a number of general cargo vessels, bulk carriers and oil/chemical tankers.
Econowind Ventifoils on MV Ankie / Image courtesy of Econowind
Suction wing sails are comprised of the below main components:
- Vertically installed wing incorporating the ventilator fan
- Ventilator system for the fan
- Folding mechanism (for folded systems)
- Hydraulic system & powerpack
- Control Panel and Electrical system
To control the airflow around the ‘thick’ foil-shape, a boundary layer suction is applied for which one or more Ventilators needs to be installed inside the suction wing profile. At the leading edge (the ‘nose’ of the egg-shaped cross section) the airflow is accelerated leading to very low pressure on the top-left side of the profile and all along the suction-side.
It is an artificial way to reduce the drag coefficient of the wing profile while keeping the lift coefficient high, even as high as up to 7-8 depending on the angle of attack and the suction efficiency. The sizes can vary between 10 and 36 m tall.
The suction wing sail can develop quite high lift forces without any self-rotation mechanism, with relatively compact dimensions. They are fully automated and can be foldable in case of unfavourable wind conditions or during cargo operations.
Suction wing sails can be installed either in a containerized form or with a flat-rack or fixed on the deck. When a containerized system is considered then it can be installed as a simple container unit by fixing the system with straps to the hatch cover and plug the system to a 400V/32A plug.
It is expected that certain maintenance will be needed on the main bearing, the ventilator fan, the flap motor and the hydraulics, with most components being familiar/similar to other usual ship equipment.
– Information courtesy of Konstantinos Fakiolas’ book ‘Wind Propulsion Principles’, Edition 1 –