Wind has been the stalwart of shipping for hundreds of years and is now making a return as part of a carefully crafted package to help tanker owners reduce their carbon emissions
Although only 15 commercial vessels are currently fitted with wind-assisted propulsion technologies, the EU is forecasting almost 11,000 installations by 2030. Growth is almost exclusively driven by IMO’s emission reduction targets and the soon-to-be introduced Energy Efficiency Existing Ship Index (EEXI). Forward-thinking owners are realising that a range of eco-measures will be needed to ensure their vessels achieve the required energy targets, and implementing wind assistance to deliver more thrust has become part of that mix. In time, new clean fuels are likely to become the norm and when that day comes, wind-assisted propulsion will be retained to reduce operating costs as well as emissions.
Today’s proven wind-assisted propulsion technology relies on large 20+ m-tall rotor sails installed on the upper deck of a tanker. These cylindrical towers (also known as Flettner Rotors) are driven by a motor to rotate when the prevailing wind is from a favourable direction, generating a phenomenon known as the Magnus Effect. This causes a change in air pressure which creates a thrust perpendicular to the rotor sail to drive the vessel forward. The result is either an increase in vessel speed, or the maintenance of a given speed with reduced fuel consumption.
Anemoi’s wind solution has been fitted to commercial vessels since 2018, delivering significant fuel and emissions savings in that time. The rotor sails – which come in various sizes – are either fixed to the deck or installed on a rail system to allow them to be cleared-away when cargo operations are underway. A foldable option is also available when air-draft is an issue and for vessels carrying potentially hazardous cargo; an ex-rated option can also be installed.
“The EU is forecasting almost 11,000 wind-assisted propulsion installations by 2030”
It is a relatively simple operation to make a tanker ‘wind-ready’. During a scheduled drydocking, the structural and electrical work is completed, including the foundation for the rotor sail and the cabling. Once in place, it only takes a day to fit each rotor sail and this can be done from almost any port. Anemoi reports that rotor sails are designed with a 25-year life and so can easily be removed from an elderly vessel and installed on a replacement.
Tankers are particularly suited to the technology thanks to the large amount of open deck space, which gives greater flexibility on the configuration of rotor sails, along with the ability to install larger sizes and quantities to maximise performance. Anemoi has developed its own app, Fuel Saving Assessment Method (FSAM) which combines rotor sail and vessel performance data with route and wind data. Anemoi says this enables an accurate prediction of vessel fuel and emission savings.
For example, a VLCC sailing a round trip Bonny-Ningbo-Bonny would, on average, save 17.3% on fuel and emissions, according to Anemoi. This equates to 2,197 tonnes of fuel and 7,044 tonnes of carbon saved. Similar calculations show that an Aframax tanker sailing a Houston-Antwerp-Houston round trip would save 24.2% on fuel and reduce emissions; and an MR tanker would save 16.9% on a round trip New York-Rotterdam-New York.
Anemoi says wind-assisted propulsion is easy to deploy and delivers real benefits in terms of fuel and emissions savings. This old – but modernised – means of propulsion is fast becoming a vital element in maintaining an environmentally friendly fleet.
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