The passenger vessel Viking Grace has completed a trial of the rotor sail technology developed by the clean tech company Norsepower. The Viking Grace was the first passenger ship in the world to be equipped with a rotor sail which is 24m in height and 4m in diameter. It was also the first passenger ship to run on LNG. 

Rotor sails like this one generate thrust using the "Magnus" effect, the same phenomenon that explains commonly observed deviations in sport where a spinning ball deviates from its typical trajectory.  This reduces the need for propulsion force, thus reducing fuel consumption. 

The sail is fully automated and detects situations in which wind conditions are favourable for operation and then starts up automatically, requiring no input from the crew. 

Norsepower have said that the potential fuel savings for new vessels could be up to 20 per cent with a rotor sail in use. This is a significant saving and is likely to excite interest amongst shipowners as it will not only save money in the long term, after initial investment, it will also assist with the ongoing decarbonisation of the shipping industry. 

The system has already been installed on the tanker Maersk Pelican showing that the technology can be applied outside of the passenger industry. Concerns will obviously be present with regards to height clearance and also maintenance of the system is likely to require specialist engineers to come on board. All of these factors would need to be balanced by any owners considering taking this step towards green energy.