The wind may be free, but it’s not easy to catch

Shipping is rediscovering sail power thanks to innovative projects reaping promising results on the high seas. Selwyn Parker sets sail to find out how, and when, ships may once again be powered by the wind.

Within the next few months, one of Japan’s biggest shipowners, Mitsui OSK, will send a giant wind-assisted coal carrier to sea in an experiment that is being closely watched by the entire maritime sector.

The vessel of 88 900 deadweight tonnes will fly a 52-metre high “hard sail”, retractable to less than half the height, that is designed to convert the wind into, in effect, free propulsion.

Mitsui’s Wind Challenger shows impressive early results

Called the Wind Challenger project, Mitsui has been quietly working on the technology for 13 years and will put it to the test in the Southern Hemisphere autumn. In terms of fuel saved, the shipping group estimates the additional power provided by the sail will enable it to cut the vessel’s greenhouse gas emissions by between five and eight per cent.

If the technology operates to expectations, Mitsui says it may install sails on other big vessels in what would mark another step forward in the belated effort to harness the wind for commercial shipping.

The wind is free. Yet shipping has largely ignored it since sail-powered cargo vessels all but disappeared from the world’s oceans. Until the last three or four years, that is.

Quite suddenly, wind-powered technology is evolving rapidly. Currently, shipowners have a choice of seven different systems, including rotor sails, hard or rigid sails (like Mitsui’s), soft sails, kites, suction wings and turbines.

And the penny is dropping. Gavin Allwright, the secretary of the International Windship Association, tells me: “The industry is waking up to the fact that wind-assist (and primary wind) propulsion systems are needed in the toolbox of decarbonisation solutions. Perception has shifted, especially in Europe but increasingly in Asia too.”

While it’s early stages in the rediscovery of wind, he estimates that the number of installations globally will double over the next 12 months to about 40. And that’s just on larger ships like tankers, roll-on/roll-offs, large bulkers and general cargo, among others. 

About 20 smaller vessels, including cruise ships, already use soft-sail rigs, with more on order.

Largely unnoticed outside the industry, wind-assisted technology is moving rapidly from an experimental process to everyday use. One of several shipping groups to take the plunge, German ferry group Scandlines will in May 2022 install a second Norsepower-built rotor sail on its hybrid-powered Berlin, following successful trials on a sister ship sailing across the Baltic Sea to Denmark where prevailing winds are favourable.

Rotor wind power: German’s Scandlines hybrid ferry in operation

According to chief operating officer Michael Guldmann Petersen, the retractable, chimney-like sail achieved the targeted reductions in CO2 emissions of four to five per cent, quite enough to make the trial permanent. Other shipping groups report similar or better results. The Maersk shipping giant, for instance, calculates an average improvement of 8.2 per cent in fuel efficiency after 12 months of sea trials on a tanker.

Many of the wind-power projects have the backing of emissions-conscious governments. Mitsui’s Wind Challenger programme is funded from Tokyo, while Scandlines’ rotor sail is one of the beneficiaries of the Wind Assisted Ship Propulsion (WASP) project supported by a EUR 4.5m grant from the European Regional Development Fund.

Governments have high hopes for wind-powered ships. A five-year-old EU report estimated up to 10 700 installations by 2030, while UK’s Clean Maritime plan is even more hopeful, anticipating about 40 000 vessels – or up to 45 per cent of the fleet – will be sail-driven to some extent by 2050.

So far, shipping groups plying coastal routes have led the charge and most of them have gone for hard sails, notably from the factories of Netherlands eConowind and Finland’s Norsepower. The latter specialises in rotors, a modernised version of a 100-year-old technology that can deliver fuel savings of up to 25 per cent in the right conditions.

Here, due recognition is appropriate. Anton Flettner was a German aviation engineer who devised what some still call the Flettner rotor. Long before his time, he saw that a spinning cylinder, using the Magnus effect, could harness and boost energy from the wind. A rotor-powered ship crossed the Atlantic as long ago as 1925. However, the shipping industry was looking the other way and Flettner’s rotor was forgotten for the best part of a century.

But Anton Flettner’s day has finally come. Another coastal trader, Netherlands’ Boomsma Shipping, has opted for eConowind’s foldable VentiFoil. Not dissimilar to rotors, it operates on a principle known as boundary layer-suction created by ventilators mounted inside the aerofoils. Boomsma hopes for savings of ten per cent.

A demo of the Ventifoil in action

The wind may be free, but there have been teething troubles in harnessing it. Some shipping groups tell me it’s been a steep learning curve for the crew of some vessels, for instance, in maintaining and deploying sails. And some manufacturers have had to send their sails back to the workshop after storm battering.

While all this technology is about adding power, one shipping group prides itself on deriving all its propulsion from the wind, save for a small engine to be used in port. In mid-February, Brittany-based Grain de Sail placed an approximately EUR 10m order for the construction of an aluminium cargo schooner that will transport fine products, mainly coffee, chocolates and wines, across the Atlantic and sail back with raw materials. The yacht will have a payload capacity of 35 tonnes, seven times more than its predecessor currently plying the oceans, plus bulk liquid tanks. Each crossing should take about two weeks.

The first of the fleet: Brittany’s Gain de Sail’s first sailing cargo ship is already in operation

Being driven 99 per cent by the air flowing across its 1 170 square metres of sails, the vessel’s crew costs are cut to the bone. Although the schooner will carry a crew of about nine, just two will be able to handle it at any one time.


Selwyn Parker is an independent journalist and author of Chasing the Chimney Sweep about the first Tour de France of 1903.


The International Transport Forum’s report on Navigating Towards Cleaner Maritime Shipping shares lessons from the Nordic Region’s work to meet energy and environmental policy goals, including energy diversification, cutting air pollution and reducing greenhouse gas emissions. Get the report

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