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The cruise ferry M/S Viking Grace, operated by Åland-based shipping company Viking Line, made its first voyage equipped with the rotor sail in April 2018, travelling between Turku, Finland and Stockholm, Sweden – a route on which the wind-propulsion system is set to slash the ferry’s carbon emissions by up to 900 metric tonnes per year.
Developed by Finnish engineering company Norsepower, the M/S Viking Grace’s 24-metre-high cylindrical rotor sail is a modernised, lightweight and highly efficient version of a Flettner rotor, invented by German engineer Anton Flettner a century ago.
The technology makes use of the Magnus effect, whereby wind passing a spinning cylinder moves air faster on one side than the other resulting in thrust at 90 degrees to the wind direction.
This allows a ship’s engines to be throttled back, cutting fuel consumption by as much as 30 % and reducing carbon emissions and pollution. Furthermore, the patented turnkey solution offers auxiliary wind propulsion for freight vessels, requires no additional crew to operate the rotor sails, and is suitable for retrofitting over 20 000 vessels in the global merchant fleet.
Norsepower’s patented rotor-sail solution is fully automated and senses when the wind is strong enough to deliver fuel savings, at which point the rotor starts automatically without requiring any crew intervention. The system, which uses a relatively small amount of power to operate, will shut itself down in response to any disadvantageous changes in wind speed or direction, ensuring energy efficiency and reducing emissions and pollution.
Thanks to the EU-funded RotorDEMO project, the installation on the M/S Viking Grace will demonstrate the rotor sail’s performance and benefits for the global commercial maritime industry, including operators of tankers, bulk carriers, ro-ro vessels and ferries. M/S Viking Grace is a liquid natural gas-powered ferry that was already one of the most environmentally friendly in the world when it launched in 2013.
The first practical auxiliary wind propulsion solution on the market, the Norsepower rotor sail is designed to be an affordable off-the-shelf product that can be retrofitted into existing vessels or installed into new-build ships with an estimated long-term return on investment of around 20 %.
It is therefore set to offer a commercially viable solution for passenger and cargo-shipping lines to reduce carbon emissions, save fuel and meet increasingly stringent EU and international environmental standards.