Fixed sails or wings

Fixed installations on the ship in form of a flexible sail, rigid sail, suction sails or turbosail can make use of the wind to replace some of the propulsion power needed. All the possibilities will have pros and cons and must be chosen to best suit the ship type, trade and size. The savings are highly dependent on the wind conditions in which the ship operates.

A variety of concepts and technologies are available on the market today, with several successfully installations on commercial ships. One of the solutions is the Suction Wings/Sails. They are stubby, non-rotating wing sails with vents and an internal fan (or other device) that creates suction which pulls in the boundary layer around the wing generating enhanced effect. Installations to date have been deployed on the bow, stern and as deck containers and flatrack.

The various concepts all have advantages and drawbacks and must be chosen with care based on the appropriate ship type, operational profile and size.

Applicability and assumptions

These initiatives are only applicable for ships with enough deck space, and therefore not container, passenger and offshore service vessels. There is no vessel age restriction for fixed sailed or wings. Stability issues due to the high elevation of additional weight and wind loads are not assumed to be a major obstacle for relevant vessels. Cost estimates are based on ships not needing changes in design to fit the masts. It can be installed on both newbuilds and retrofits.

The effect of each mast will vary with the prevailing wind and therefore will not be effective in great parts of the time. The effect and applicability of this measure is also dependent on operating speed (sails will contribute the most in the lower speed domain).

Cost of implementation

The price per mast (including installation) is expected to decrease dependent on how many masts are installed on board. The cost estimates vary from supplier to supplier and there is great uncertainty around the estimates. A cost of between $500,000 – $700,000 (USD) per sail installed on the ship is estimated.

Additional is the maintenance costs assumed to be 2 % of the installation costs.

Reduction potential

The reduction potential is highly dependent of vessel size, segment, operation profile and trading areas. Based on this trade and operating dependency there are also variations in savings. Some ships have measured savings of up to 30% at full scale. However, it is assumed that the total annual energy saving will be between 3 – 15% depending on the type of ship.

Other References

1. Wallenius Marine, 2021. Oceanbird
2. Atkinson, et al., 2018. Considerations regarding the use of rigid sails on modern powered ships
3. MEPC 81-INF.39 White paper on wind propulsion
4. Hochkirch, K., Bertram, V., 2022. Wind-assisted propulsion: Economic and ecological considerations.
5. Bound4blue
6. BAR technologies’ WindWings
7. FastRig