The world’s first cargo ship to be powered with high altitude kite-like sails tethered on lines 100 metres in the air was “Theseus,” last year.
SkySails cannot power a ship unaided, but it can reduce the amount of power needed by up to 80 percent, without any additional crew or technology.
The “Theseus” is one of three new Rhine class ships being built for Wessels at the Komarno shipyard in Slovakia. It is 90 meters long, has a capacity of some 3,700 dwt and a MaK main engine that produces 1,500 kW of power. A 160 m² SkySails propulsion system works to relieve the main engine of the “Theseus” the same way it does on board the “Michael A.”
The SkySails-System had previously been tested over a period of one and a half years aboard the 133-meter “Beluga SkySails” and the 90-meter “Michael A.” The oil consumption on each ship fell sharply
“We’ve had some extremely promising results from pilot testing,” said Gerd Wessels, the managing partner of the Wessels Shipping Company based in Haren/Ems, “and with a good wind we achieved up to 8 tons of tractive force on the “Michael A.” using SkySails propulsion.” For comparison: The “Theseus” needs approximately 11 tons of thrust for full cruising speed.
SkySails propulsion has been integrated into the ship’s operations; it required no major effort or expense to be installed onto the vessels. And, it has been proven that ships remain fully maneuverable while employing the SkySails-System. What’s more, trials have confirmed that present crew strengths are fully adequate for operating the system and that the operational concept works as intended.
The insights and experience gained by the shipping companies, crews and SkySails engineers during countless launches and recoveries while operating SkySails propulsion on board the ships were fed simultaneously into the SkySails product development effort. “The high seas taught us quite a few lessons,” remarked Stephan Wrage, the founder and managing director of SkySails, “and we were a long way off in terms of operating times during the first phase of pilot testing.” The Wessels Shipping Company summed the situation up by adding that, “The reasons for this can be found mostly in the limited launch opportunities during heavy seas and the degree of resilience and stamina exhibited by some of the components when exposed to harsh conditions at sea.”
SkySails is working on perfecting system performance, and engineering the next larger SkySails propulsion system. Designated the SKS C 320, it will have an approximately 300 m² large towing kite and generate 16 tons of tractive force in good winds – and thus save twice as much fuel as an SKS C 160. Later this year the “Beluga SkySails” will become the first ship to be fitted with an SKS C 320, which of course also incorporates the new module concept.
SkySails is working full steam to expand production at the same time. In early 2009 SkySails, together with the renowned Zeppelin Group, established a joint venture company called “Zeppelin SkySails Sales & Service” to handle the worldwide sales and servicing of SkySails propulsion. The company started operations in March of this year and will use the existing service network of Zeppelin Power Systems, one of the most respected suppliers of marine engines, to ensure that all SkySails-Systems can be rapidly serviced and supplied with replacement parts across the globe.
The questions from Ken seems to be more or less handled by the FAQ and info on the SkySails web pages – there is information about how it’s launched and retracted, plus some information about the controlling panel.
I wrote an email to SkySails with my questions above, and I got a quite long and elaborate reply. Here are some quotes:
Economical acquisition and operating costs for the SkySails-System in combination with the large fuel savings generated by the auxiliary wind propulsion lead to short amortization periods of between 3 and 5 years. Please see our website for a savings calculation of three model ships traveling on four different routes at: https://www.skysails.info/english/products/skysails-for-cargo-ships/business-cases/
Practical experience has shown that (…) hardly any counter rudder needs to be applied when using the SkySails-System. (…) the pivot point of a traveling ship is on its bow. [Also, a counter-acting] force arises from the change in the hydrodynamic flow of the bow caused by the SkySails’ shear force.
Under optimal wind conditions it is theoretically possible to substitute the entire power of the ship’s engine with the SkySails-System.
So in theory, this could be a purely economical decision – there is an investment in buying and installing the device, one will have some maintenance costs with the equipment, there is a fuel saving involved, and not much other side-effects (if one is to believe the hype). I’d be interested in the math – it doesn’t seem to be well-covered on the skysail web page. How long does it take to get the investment paid back?
I really believe in this concept – using high-altitude wind power as auxiliary propulsion, overcoming most of the drawbacks of old-tech sails … in particular I can think of those three:
1) The old sail technology required a lot of manpower, and manpower was more expensive than fuel. This system is (supposedly) fully automatic.
2) Sails have a safety problem in case of sudden increase in wind speed – ship can simply keel over if the sails are not reefed in time. This system has minimal keeling, and at least according to the marketing promises, with one touch of a button, the kite will go into “safe mode” hovering directly above the ship, no matter the wind speeds.
3) there are clear limits for how fast a boat can go and still gain effect from the wind – but since the wind speed is much higher in high altitudes, this concept rocks. (the keeling problem limits the maximum height of traditional masts – the cable weight limits the maximum height of the kites, but it seems like they have managed pretty decent altitudes).
However, I’m having two questions I cannot find answers for … why do they install it in the bow instead of midships? Wouldn’t that cause the ship to constantly turn away from the wind? Adjusting the course with the rudder/engines costs energy, ideally the towing point for a kite should be in the center of the boat. Also, if those sails can yield power while the ship is travelling at ordinary speed – why can’t the system be scaled up to become the primary propulsion system?
I imagine that the weight of a cable that is strong enough to pull with 8 tons of force is substantial – and the longer it is of course the heavier it is. They need fibers made of carbon nanotubes.
I love this idea and hope that it can be provided at a low enough cost to make up for any added inconvenience or the times when the wind isn’t fully cooperating.
I wouldn’t exactly call it “high altitude”, but high enough is all that matters. I wonder if the height could be adjusted if needed, or if it has to be limited to 100 meters for launching or some other reason. It seems that they could slowly let it out further, if conditions warranted.
It doesn’t say how they launch it? I can think of several ways.
An excellent use of low tech to supplement the vast power needs of ships at sea.
Anyone know if the US Navy is/will be jumping on the bandwagon anytime soon? The military is looking into greening up everywhere, and this seems like something that can easily be added to just about any ship.