The shipping sector is becoming greener, bringing about a return to large sails. China Merchant Energy Shipping (CMES) has commissioned a new supertanker fitted with four large sails. These reduce average fuel consumption by almost 10 per cent.
From sail to diesel ship
Sails were the main drive for large ships for thousands of years. That changed when German inventor Rudolf Diesel got his first engine running in 1897. Six years later, the first diesel-powered ships were already sailing the seas. This was safer and more efficient than steam engines. Slowly, these diesel ships took over the shipping world and became a mainstay of international trade. However, they are polluting: some 50,000 merchant ships account for about 1.7% of global greenhouse gas emissions. Although methanol and ammonia are seen as promising alternatives for cleaner energy, the technology is currently far from crystallised.
Sails, on the other hand, are familiar territory and for at least a decade there have been concepts and plans to bring back big sails in cargo and passenger shipping. Ireland's B9 Shipping came up with the idea of a 100% sail-powered freighter back in 2012, but not much seems to have come of it. Oceanbird, a subsidiary of Wallenius, has pushed back the launch date for its first ship with rigid sails from 2024 to 2026.
And back to diesel/sail ship
But China's Dalian Shipbuilding Industry Co (DSIC) has now taken the plunge. The M/V "New Aden" is a 333-metre-long supertanker. This behemoth, which was launched on 24 September, features a relatively modest but pioneering wind energy system. Four retractable sails are mounted in the middle of the long deck, each protruding 40 m from the deck and covering an area of 1,200 m².
The lightweight, corrosion-resistant carbon fibre composite sheets can be raised or lowered at the touch of a button. An 'Aerofoil Sails Intelligent Control' system is designed to continuously monitor prevailing conditions and navigation data. Based on this, the angle of the sails can be continuously adjusted to make maximum use of the available wind.
As a relatively small implementation of the auto-sail concept, this system is not intended as a primary propulsion system. The ship will still consume a lot of diesel. But on a sample shipping route between the Middle East and Far East, it is expected to reduce average fuel consumption by more than 9.8%. That will save an estimated 2,900 tonnes of carbon dioxide emissions per voyage.
The New Aden is a crude oil supertanker, so despite its green promise, its primary purpose is still to carry around two million barrels of fossil fuel around the world. But whether you see it as greenwashing or not, it clearly proves that these huge sailing systems for large, modern ships make economic sense.
