Viking Grace operates in the archipelago between Turku, Finland and Stockholm, Sweden (Image: Viking Line)
Independent tests have shown that Viking Line’s Viking Grace could save up to 300 tonnes of LNG fuel per year in the long term by using Norsepower’s Rotor Sail technology.
Viking Grace, which operates in the Åland archipelago between Finland and Sweden, was retrofitted with one medium-sized Norsepower Rotor Sail Unit in April 2018, making her the first-ever cruise ferry to be powered by LNG fuel and wind-generated electricity. Developed as a modernised version of the Flettner rotor, the fully automated solution senses when the wind is strong enough to deliver fuel savings and automatically starts the rotors.
According to analysis carried out by software and data analyst NAPA and technology provider ABB, there was an “evident change” in the propulsion power breakdown of Viking Grace, caused by the Rotor Sail. The same conclusion was confirmed with a strain gauge analysis, where forward thrust of the Rotor Sail was measured and converted into propulsion power.
Conclusions showed that the expected long-term change in Viking Grace’s annual fuel consumption due to the Rotor Sail would be between 231 and 315 tonnes on annual basis. This equates to an average propulsion power between 207 and 282 kilowatts.
“We are pleased to see that independent testing from respected, independent companies NAPA and ABB has shown impressive fuel savings potential on Viking Grace,” said Tuomas Riski, CEO of Norsepower. “This project has confirmed, that our technology works also with high-speed cruise ferries and that favourable results can be achieved with a service speed of 21 knots.”
According to NAPA’s analysis, Norsepower’s Rotor Sail delivers more forward thrust when Viking Grace is on the open sea, but as she mainly sails in the archipelago, the annual fuel savings potential is on the same level within both route areas.
“In the actual navigational conditions there is always variation in the environment, which has an important effect on the fuel consumption,” said Jaakko Talonen, data scientist at NAPA. “This is why a statistical regression model was applied, to overcome the variations in the comparison conditions and to disclose the effect of the Rotor Sail. The long history of NAPA on ship performance modelling gave a really good basis for the study.”
Viking Grace’s Rotor Sail is now fully operational and Viking Line and Norsepower have agreed to continue working together to optimise the technology.
“As an Åland shipping company, we rely on the sea for our livelihood so it’s of prime importance for us to promote the well-being of the marine sea,” said Jan Hanses, CEO of Viking Line. “We want to pioneer the use of solutions that reduce the environmental load. Viking Line has been testing the Rotor Sail on Viking Grace for a year now, and together with Norsepower we will continue testing and optimising the sail for its current route.”
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