The shipping industry is responsible for around 3 per cent of carbon dioxide emissions, and those emissions are growing – but adding high-tech sailing gear to cargo ships and greater use of wind-favourable shipping routes could cut them by more than half. There is growing interest among shipping companies in exploiting wind power, as it can help cut fuel costs. A wide variety of approaches are being explored. Some companies are building ships with conventional sails from scratch. Others are adding various kinds of automated sails to existing vessels. The technologies include rigid sails resembling aircraft wings, Flettner rotors consisting of rotating cylinders, suction sails that suck in air to maximise lift and even giant kites similar to those used by kitesurfers. “There is a whole spectrum of wind propulsion vessels,” says Gavin Allwright of the International Windship Association, ranging from limited wind-assisted vessels through to those that get more than half of their power from wind. Some wind-assisted ships are still operated like conventional ships, taking a direct route at a set speed, so …