Wind-assisted cargo ships are moving from theory to testable strategy. New modelling work suggests changing both route and speed—using historical Atlantic weather—can cut energy use by about 75%, while experts say hydrogen onboard could bridge weak-wind gaps.
The shipping industry’s emissions sit in plain sight: around 3% of global carbon dioxide output, and still rising. Now, the question being asked in ports and research labs alike is simple but loaded—what if the ocean itself did more of the work?
The push comes as companies explore wind propulsion in multiple forms. Some are designing cargo ships with conventional sails built from the ground up. Others are retrofitting automated sail systems onto existing vessels. The menu of technology is wide. ranging from rigid sails shaped like aircraft wings. to Flettner rotors—rotating cylinders that harness wind—suction sails that pull in air to maximise lift. and giant kites similar to those used in kitesurfing.
Gavin Allwright of the International Windship Association describes the field as a spectrum rather than a single solution. There are “limited wind-assisted vessels” at one end, he says, and ships that get “more than half of their power from wind” at the other.
But one of the biggest shifts isn’t just what’s bolted to a ship. It’s how the voyage is planned. On conventional routes. many wind-assisted ships are still run much like traditional vessels—taking a direct path at a set speed. That approach. according to research led by Thorben Schwedt at the German Aerospace Center and his colleagues. leaves potential on the table.
So the team asked what would happen if the ship’s path and speed were allowed to move. The catch was time. If there were no time constraints, Schwedt says, it would be straightforward to make trips fully wind-powered. The reality is that most cargo has delivery deadlines. When deliveries slip, income slips too. A practical wind strategy has to balance emissions and energy with schedules.
To close another gap—strong winds don’t last—the researchers also assumed ships could generate and store hydrogen. an emerging technology used on only a few ships so far. When winds are very strong. some energy would be used to produce hydrogen. for instance using electricity-generating turbines underneath a ship. That hydrogen could then power engines when the winds drop.
The next step was planning, built directly on weather. The researchers took data on reconstructed historical weather—a hindcast—over one year in the Atlantic Ocean. Using a computer model, they worked out optimal routes and speeds based on that weather.
Schwedt described what the model produced with a mix of disbelief and clarity: “The ships go completely wild routes.” It’s the kind of result that sounds wrong at first—detours that don’t look sane. But, in the calculations, it appeared to be exactly what worked.
On average, the results were striking. The team found that ships taking these optimal routes would have energy consumption 75% lower than those using direct routes. Schwedt presented the findings at a recent meeting of the European Geosciences Union in Vienna.
The most dramatic savings, he said, come only when the route flexibility is real. “The real advantage only comes into play if you are completely open with your route. ” Schwedt said. “sometimes taking really big detours that you couldn’t think work out.” With that freedom. the team reported energy savings ranging from 50 to 100%.
Schwedt and his colleagues are now planning another crucial test: showing the same route optimisation can work with forecasts, not just hindcasts.
Guillaume Le Grand of TOWT, a French company building a fleet of sailing cargo ships, said the modelling expectations match what his company has already been doing. “That is what TOWT’s sailing cargo ships have done,” he said.
Still, not everyone is ready to treat the numbers as automatic. Tristan Smith at University College London points to how route planning already matters in other wind-driven worlds. Yacht racers. he says. can take routes that look circuitous for the same reason—matching winds and performance rather than chasing the shortest line.
Smith also cautioned that the headline savings depend on what speed you’re targeting and why. “Seventy-five to 100 per cent [energy saving] is certainly theoretically possible. ” he said. “but this very much depends on what average voyage speed you are targeting. which is also set by the economics of a ship’s operation and its cargo.”.
In his experience, he said, savings are “significantly lower than this” for most sea-going vessels.
The promise is difficult to ignore: wind-assisted shipping has a clear pathway to cutting the energy ships use—and. with the right design and the right planning. potentially cutting emissions too. But the real test will come in the operational world. where deadlines are non-negotiable and the ocean’s winds don’t schedule themselves.
wind-assisted cargo ships shipping emissions wind propulsion route optimisation Flettner rotors rigid sails suction sails kites hydrogen onboard hindcast European Geosciences Union