Ever seen a massive tanker ship...with wind sails? You might soon. That's because the Sohar Max, a 400,000-deadweight-ton vessel, was just retrofitted with five 35-meter rotor sails at China's COSCO Zhoushan shipyard, according to Bloomberg. The purpose is to reduce fuel use by 6% and cut annual carbon emissions by 3,000 tons. Bloomberg reported that the shipping industry already faces regulatory pressure to reduce emissions. Rotor sails remain uncommon, and the adoption of wind technologies hinges on cost savings. Their appeal may grow as…