Return to Tradition: Are Sails Making A Comeback?

It is a common belief that the age of sail” ended in the 19th century with the introduction of the steam engine. This is not quite true: the last engineless sail ship, the German Pamir, only ended her career in 1957, with her sinking 1. These days, sailing ships are mainly relegated to recreational yachts and replicas of historical sail ships, such as the Swedish Götheborg, which occasionally runs tours around Europe and the world 2. However, in recent years, with the shipping industry looking to decarbonise rapidly, there has been a growing interest in sailing ships again, reinvented with the latest technologies for the modern age. The International Windship Association lists 45 wind-powered vessels as of 2024, with the oldest dating from 2010. They range from ferries to cargo carriers to tankers, with the smallest being 48m in length, and the largest 340m3. Perhaps it is worth revisiting sail power, reimagined for the modern era. 

When one thinks of sailing ships, the image that comes to mind is a wooden hull and canvas sails. Certainly, some of the ones operating today are in the traditional design. Commercial cargo sail freighters currently operational include the SV Kwai in the Pacific, Avontuur and Tres Hombres running from the Caribbean, and Apollonia in the Hudson4.

Tres Hombres in Amsterdam in 2010. Credit: S.J. de Waard / CC-BY-SA-4.0 (via Wikimedia Commons). https://commons.wikimedia.org/wiki/File:TRES_HOMBRES_(07).JPG

None of them are particularly large or carry a lot of cargo; traditional sailing ships are best used in small island or river settings where big ports are scarce and fewer resources are required. In the case of the SV Kwai, the high cost of fuel on the Pacific islands makes her sails commercial 5  viable. For larger cargo ships such as those running major shipping routes, sail power does not provide an answer.

One option is to not completely rely on wind power, but rather wind assisted ship propulsion technologies, which work alongside a conventional fuel engine, helping it use less power and thus decrease its emissions. To this end, several technologies have been developed and fitted on ships. These can generally be split into several categories. The first is a vertical aerofoil, which works similar to a plane wing, creating an area of low pressure which pulls the vessel forward. Another is a rotor sail or Flettner rotor, which generates force to propel the ship at the angle of flow.

Maersk Pelican fitted with Flettner (rotor) sails in 2018. They are the largest rotor sails in the world. Credit: Wilsca, CC BY-SA 4.0 via Wikimedia Commons..

https://commons.wikimedia.org/wiki/File:Norsepower_rotor_sails_modern_version_of_flettner_rotor.jpg

There is also a kite sail that works like a giant kite which drags the vessel along 6, with the sail being able to catch the wind as high up as 400 m in the sky 7.

A model of a kite sail in action attached to a cargo ship. Credit: Yves Parlier, CC BY-SA 4.0, via Wikimedia Commons.

https://commons.wikimedia.org/wiki/File:Kite_(1).jpg

Finally, there are proposals to use soft sails, akin to traditional sails but on a larger scale, and wind turbines which can fold up or down depending on if they are required or not 8.

Though the technology may seem experimental, ships, either running on wind power or fitted with such wind assisted propulsion, are already out there. One example is the vertical aerofoils installed on the Cargill company’s chartered cargo ship Pyxis Ocean, that set out on its maiden voyage in 20239. The ro-ro transport ship Canopée, which has been used to transport satellites and components for the European Space Agency since 2022, is powered by a similar technology, alongside a conventional engine10.  can make the transatlantic crossing from France to French Guiana in 10 days 11.

Canopée in Holland, 2022, with sails prominently on display. Credit: kees torn, CC BY-SA 2.0, via Wikimedia Commons.

https://commons.wikimedia.org/wiki/File:Canop%C3%A9e_(ship,_2022).jpg

Rotating sails have been fitted on to ships as varied as tankers, bulk cargo carriers, and even passenger vessels. T first ferry to be fitted with this technology was the Viking Gracein 201812. Kite sails controlled by a computer have been fitted on ships like the MS Beluga (now MS Onego Deusto) in 2008 and could be retrofitted to more13. Only time will tell if more will be added to the list.

Existing ships can have these technologies installed relatively easily, easing the transition from a fully fuel oil powered engine to a more hybrid power system relying on the engine and wind 14. Aerofoils such as WindWings have the benefit of automatically adjusting themselves to the wind and not requiring much maintenance15. Modern meteorology will also help in predicting the weather, specifically wind patterns, to determine the best route. Using less fuel means saving money, helping offset the initial cost of development and outfitting ships. It is estimated that a saving of 8.3% on fuel can be made by retrofitting existing ships with wind assisted propulsion technology16. While this may not seem like much, across the whole sector, this adds up. If combined with an alternative fuel 17, these ships have potential to heavily reduce CO2 emissions. While these fuels are being developed, saving fuel means less greenhouse gases begin pumped into the atmosphere, giving a margin on the targets set for the shipping industry in their goals to reduce emissions. It is likely that fuel price will determine the pace of the adoption of wind assisted technology18.

Despite the promise of wind power, problems still remain with wind powered ships. Fitting sails may not be possible for each and every ship, as depending on the technology used, they may get in the way of shipping cranes at port, or not be able to even fit into certain ports. Sails may also be vulnerable to damage from large cranes, and if damaged and unable to be lowered, this may prevent vessels from being unloaded at all19. Safety is a concern, as such technology is new, bulky, and full of moving parts. It will require extra training to operate, unless significant investment is made into automation 20.  It also goes without saying that vessels which operate in the areas of the world around the equator known as doldrums, where there is little wind, are not suited for sail power21. Scale is also an issue, especially for fully wind-powered cargo vessels: even the largest sailing vessels currently being built can carry 250 tons of cargo, dwarfed by modern super carriers that carry up to 20,00022. Cost is an eternal issue when discussing the adoption of new technology, especially in an industry as conservative and with marginal gains like shipping. Subsidies may be required to increase uptake 23.Though there are examples of sailing ships, or even wind assisted ones, they are yet few and far between, dwarfed by the number of conventional, fuel engine vessels. It will take time, enthusiasm and investment from the industry for this technology to be a solution, though the desire to save money on fuel and meet pollution regulations will likely be the biggest incentive. At the moment, the technology is in the early stage of adoptionand will require growth and development to reach its full potential.

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