
If left unchecked, shipping could account for almost a fifth of global emissions by 2050. But modern wind propulsion technologies might help the industry decarbonize. Tire manufacturer Michelin has designed giant inflatable sails (pictured here in a rendering) that can be fitted to existing cargo ships, and inflate or deflate at the push of a button -- making it easy for the ship to enter a harbor or pass under a bridge.

So far, Michelin has only tested a miniature version of its design on a 40-foot yacht (pictured), but it hopes to enter full-scale production in 2022. The company says the sails, which work in tandem with the ship's engine, could reduce fuel consumption by 20%.

UK-based BAR Technologies has designed 150-foot-tall rigid sails, to be retrofitted on cargo ships (pictured here in a rendering). The company, which has a deal with US shipping giant Cargill to install its sails on a bulk cargo ship by 2022, says it will increase the vessel's fuel efficiency by more than 25%.

Rigid sails, which look more like aircraft wings than traditional cloth sails, are also being installed on Oceanbird, a transatlantic car carrier (seen here in a rendering) that is due to set sail in 2024. It will rely mostly on wind power, cutting carbon emissions by 90%.