“Cargo Sail” is an innovative design concept addressing maritime transport systems and their energy balance. Across the world there are more than 100,000 cargo ships, which use from 200 to 370 million tons of heavy oil and cause double the quantity of CO2 emissions to that produced by global aviation. Meanwhile, the wind is an abundant and free resource at sea, which can be directly converted into marine propulsion without any energy loss. Starting out by analysing traditional sailing navigation, an innovative and ecological hybrid concept (wind energy + stored energy) was produced for the emission-free transport of cargo.