Cars, trucks and planes get plenty of blame for helping drive the climate crisis, but shipping produces a large portion of the world’s greenhouse gases, as well as nitrogen oxides and sulphur pollution because ships largely use cheap heavy fuel oil. It’s been a struggle to clean up the shipping industry but one solution is to use wind-powered ships. That may seem like going back to the days of the Cutty Sark, but new hi-tech wind-propulsion can be fitted to existing ships to cut fuel use, supplying between 10% and 90% of a ship’s power needs, depending on where on the ocean they are and which weather patterns they harness. Wind is free, blows harder at sea than on land and weather-routing software uses sophisticated algorithms to plot the fastest and most fuel-efficient voyage. A wide range of wind-powered devices for ships have been designed, using sails, kites or rotors that look like vertical cylinders. These are mounted on a ship’s deck and many can be retrofitted to existing vessels. Already more than 20 commercial cargo ships use wind power to cut their fuel use, and more are being launched, but it is taking a long time for wind power to become widely accepted in the industry.