Advantages in detail

High propulsion power

The technical possibilities resulting from the spatial separation of the ship and the “sail” or towing kite give SkySails an entirely new performance spectrum.

SkySails easily generate five to 25 times more propulsion power per square meter sail area than conventional sail propulsions.

The towing kite of the SkySails propulsion can be navigated “dynamically”. This means that the autopilot can perform flight maneuvers with the towing kite such as the figure of eight (“8”) in front of the ship.

The high airspeed of the towing kite is particularly relevant since the airflow velocity at the kite’s aerodynamic profile is the key to performance.
For the calculation of the tractive force of towing kites the airflow velocity is squared:

F(a) = cl * p/2 * v² * A

If the airflow velocity is doubled, the tractive force of the SkySails-System quadruples. In practice, the towing kite can easily reach speeds three times that of the present true wind and more.

A further significant technological advantage of the SkySails propulsion is that the towing kites can operate at altitudes between 100 and 300 m where stronger and more stable winds prevail.

At an altitude of 150m the average wind speed is approx. 25% higher than at an altitude of 10m, due to the absence of friction with the earth’s and the water surface. As the kinetic energy of an air mass increases to the power of three with the wind speed, more than twice the amount of energy can be available at the operating altitude of the towing kite than at 10m - depending on the weather conditions.

Since the SkySails-System generates a significantly higher propulsion power per square meter sail area than conventional sail propulsions, it is possible to gain significant savings by using comparatively small sail areas.<br><br>For comparison: The 109m long four-mast barque “Sea Cloud” has a sail area of 3,000m² in total. A cargo ship of the same length would be fitted optimally with a towing kite of 300m² in size.

Minimal Heel

Unlike conventional forms of wind propulsion, the heeling caused by the SkySails-System is minimal and virtually negligible in terms of ship safety and operation.

The tractive forces of the SkySails towing kite are transmitted to the ship at deck level. The lever arm which causes the inclined position (heeling) of conventional sailing ships is thus shortened.

Dynamic force control

The position of the SkySails towing kite in relation to the horizon can be varied for the integrated force control of the SkySails propulsion to ensure the ship’s safety. If, for example, sudden, strong winds occur, the autopilot can position the towing kite in the neutral zenith position directly above the ship in max. 30 seconds. In this position the towing kite does not exert any force onto the ship and can thus be safely recovered even in the case of strong winds.

Improved behavior at sea

At sea the SkySails-System damps the waves because the uplifting forces of the towing kite effect a smoother slicing of the ship’s hull into the wave - depending on the ship's size.

Automatic operation

During operation of the system, an autopilot controls the towing kite. The launch and recovery procedure of the towing kite is carried out largely automatically as well. The ship‘s regular crew is adequate for operating the system and no additional personnel costs will arise.

System for retrofitting

Due to the compact and universal design, virtually all seagoing cargo ships can be out- or retrofitted with the SkySails propulsion.

The tractive force of the SkySails-System is directed to the bow area over the force transmission point mounted on the foredeck. Generally the existing ship‘s structures are sufficiently dimensioned, since that is where the anchor windlass is also housed. The power transmitted by the SkySails-System is comparable to that of an ocean-going tug. An appropriate stability computation is made for each vessel prior to the installation of a SkySails propulsion.

Hybrid propulsion

The SkySails-System is used parallel to and for relief of the main engine, if wind conditions allow. The main engine's propulsion power remains fully available if required.

Marginal spacial requirements

Due to the spatial separation of the kite and the ship’s hull, the reduction of the ship’s effective area by the SkySails-System is economically irrelevant.

The textile towing kite is easy to stow when folded and requires very little space on board ship. A folded 160m² SkySails for example is only the size of a telephone booth.

In contrast to conventional sail propulsions the SkySails-System has no superstructures which may obstruct loading and unloading at harbors or navigating under bridges, since the towing kite is recovered when approaching land.

Improved ship safety

SkySails - as an alternative propulsion system - can also minimize the negative economic effects of engine malfunctions.

In the case of a total breakdown of the main engine, the SkySails-System can be used as emergency propulsion to reduce average risk.

SKYSAILS FOR...