Let’s be clear, these are sailing ships, not sailboats. Before we used fossil fuels for powering transportation, businesses around the world used sails to capture wind to move cargo. The ease, convenience, and reliability of burning fuel to turn wheels and propellers took over, but possibly only for a while. Cargo vessels are again being designed to travel by wind, about the most direct application of renewable energy possible. They’ll move slower (about 12 days to cross the Atlantic instead of 7 days); but they’ll be able to carry 7,000 cars, or their equivalent. The ships will require some motors for maneuvering in traffic, especially in harbors; and backups are handy when things break. That’s why the emissions will be down 90%, not 100%. Old tech returning as new tech also means the new tech will begin a new ear of innovation, so the vessel scheduled to operate in 2024 will probably be superseded with designs that learn from it. Until then, noisy, smelly, and massive ships will be the norm – for a while.