International shipping carries much of the world’s trade and accounts for approximately 3% of global human-caused greenhouse gas (GHG) emissions. As international and regional regulations place increasingly stringent limits on GHG emissions, the maritime industry needs technologies that can reduce fuel.

Wind-assisted propulsion systems (WAPSs), offer one possible near-term solution. Rather than converting wind into electricity, they use aerodynamic forces to produce thrust directly. They operate alongside a ship’s main propulsion system, reducing engine load and fuel consumption when wind conditions are favorable.

A team led by Wenzhe Zhang from the Universidad Politécnica de Madrid has now published a comprehensive techno-economic review of WAPSs in Ocean. The researchers examined scientific studies, industrial developments, classification-society guidance and lifecycle assessment methods to determine how wind-assisted propulsion can be integrated into commercial shipping safely, efficiently and economically.

The review classifies modern WAPS into four main categories. Rotor sails use electrically driven rotating cylinders to generate force through the Magnus effect. Boundary-layer control sails use active suction or air injection to prevent airflow separation and increase lift. Wing sails rely on aerodynamic profiles and adjustable angles or flaps, while kite sails fly at altitude and can follow dynamic crosswind trajectories to generate towing force.

“Wind-assisted propulsion is not simply a return to traditional sailing. Modern systems combine aerodynamic design, automation and ship-level control with conventional propulsion, allowing vessels to use wind energy without sacrificing operational reliability,” Zhang said.

The authors screened more than 400 records and selected 212 highly relevant publications for detailed analysis. Their assessment shows that research activity has risen rapidly, particularly since 2020. Wing sails have received the greatest academic attention, whereas rotor sails and boundary-layer control sails currently attract stronger commercial interest.

Rotor sails, boundary-layer control sails and wing sails have reached full commercial maturity in some applications. Kite sails remain at a lower and more variable level of technological readiness because reliable automated launching, recovery and flight control remain challenging.

The review emphasizes that aerodynamic efficiency alone does not determine whether a system will succeed. Wind-assisted devices can affect vessel stability, visibility, maneuverability, deck operations and interactions with the main engine and propeller. Their design must therefore balance three objectives: safety, propulsion efficiency and lifecycle cost.

Real-world performance is another major issue. Numerical simulations and scaled experiments sometimes indicate fuel savings of around 20%, but operational measurements summarized in the review generally report savings below 10%. Complex marine environments, differences among routes and ships, system-control strategies and ship–sail interactions can all contribute to this gap.

“Shipowners need credible estimates of fuel savings and investment returns under realistic operating conditions. Standardized sea-trial procedures, full-scale operational datasets and digital twins could help connect theoretical predictions with actual performance,” Zhang said.

The researchers propose evaluating the technology across its full lifecycle. Such assessments should include emissions and costs associated with manufacturing, transportation, installation, dry-docking, maintenance, additional electricity use, possible cargo-space losses, decommissioning and recycling. Fuel savings, avoided emissions and reductions in carbon-related expenses should be considered alongside those costs.

The review identifies nine priorities for future research: optimizing high-lift and kite technologies; improving multi-device layouts; developing dedicated design standards; integrating WAPS with ship-level predictive control; introducing structural health monitoring and digital twins; assessing maneuverability and collision avoidance; building data-driven performance models; conducting comprehensive lifecycle assessments; and quantifying the effects of carbon pricing and other policy incentives.

The ultimate goal is to move from controlling individual sails for maximum thrust to optimizing the vessel as a complete system. By jointly managing weather routing, engine load, vessel speed and wind-assisted devices, ships could capture more wind energy while maintaining safety and schedule reliability.

“Wind-assisted propulsion will not be a universal or stand-alone solution to shipping emissions, but it can become an important part of an integrated decarbonization strategy—particularly for existing ships that need practical reductions in the near term,” Zhang said.

This research has been funded by the Ministry of Science, Innovation and Universities (MCIU) of Spain under the project FOWTDAMP2 (Grant No. PID2021-123437OB-C21), and project RENEWFLOAT (Grant No. PID2024-161775OB-C21).

DOI Link:

https://doi.org/10.26599/OCEAN.2026.9470019

About Ocean

Ocean is an international peer-reviewed journal that offers open access and serves as a multidisciplinary platform for the state-of-the-art research and practice in the domains of ocean science, technology, and engineering. The journal is dedicated to publishing articles, reviews and perspectives in these areas, with the goal of promptly disseminating and promoting theoretical, numerical, site-based, and experimental advancements in the context of global sustainability.