Wind-Assisted Propulsion: Sails, Kites, and Flettner Rotors in Modern Ships

Discover how sails, kites, and Flettner rotors are powering modern ships with wind-assisted propulsion. Explore technologies, case studies, and future trends.

Introduction

Imagine a massive bulk carrier sliding through the ocean without burning a drop of fuel, its sails—or giant rotating cylinders—capturing the wind to help push it forward. Or picture a cargo ship subtly using a kite high above the deck to reduce engine load and fuel consumption. Sounds like a return to the age of sail? In truth, it’s the future of maritime decarbonization.

Wind-assisted propulsion technologies—like rigid wingsails, kite sails, and Flettner rotors—are breathing new life into an old principle: harnessing the wind. For an industry under pressure to cut emissions under IMO’s net-zero roadmap and tightening regulations, these systems offer immediate, fuel-saving, and low-carbon gains without waiting for new fuels or engine technologies to mature.

In this guide, we’ll explore why wind-assisted propulsion matters for modern shipping, walk through the leading technologies, spotlight real-world applications, unpack challenges and solutions, and gaze toward a future where wind does more than just fill our sails.

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Why Wind-Assisted Propulsion Matters in Modern Maritime Operations

Greenhouse gas emissions from shipping account for around 3% of global totals, potentially rising to 5–8% by 2050 without meaningful intervention. Wind-assisted systems (WAPS) offer a practical means to shave that number—some estimates suggest a reduction of 500–1,000 million tonnes CO₂e by 2030 when combined with other technologies (CE Delft report, cited in IOM3)

Regulatory drivers are powerful. IMO’s Energy Efficiency Design Index (EEDI), Efficiency Existing Ship Index (EEXI), and upcoming Carbon Intensity Indicator (CII) create financial and operational incentives for fuel reduction. According to DNV, retrofits can achieve 4.5–9% fuel savings, with potential up to 25% in optimized newbuilds

Wind isn’t just free; it’s scalable and mature. The CE Delft study projects 3,700–10,700 WAPS installations by 2030 in sectors like bulk carriers and tankers . The market is booming—with a predicted CAGR of 73%, growing from US $71 million in 2023 to over US $40 billion by 2034.

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Key Technologies and Developments Driving Change

Wing Sails (Rigid or Inflatable)

Wing sails are rigid, airplane-wing-style sails that use aerodynamic lift. The Oceanbird concept employs 40-meter wingsails mounted on car carriers, aiming for up to 90% emissions cut, potentially even 100% under optimal routing and speeds. A land-based prototype was constructed in 2023, with deployment on the ship Wallenius Tirranna expected soon.

These systems benefit from automation, ease of control, and no need for sails to be furled during heavy weather—a modern take on sail.

Flettner Rotors (Rotor Sails)

Rotor sails, or Flettner rotors, are spinning cylinders that leverage the Magnus effect—creating force perpendicular to wind direction. These vertical rotors are rapidly gaining adoption. The E‑Ship 1, launched in 2010, has four Flettner rotors and achieves measurable fuel efficiency .

More recent installations include:

• Maersk Pelican (tanker)—reporting 8.2% fuel savings.

• MV Afros (bulk carrier)—eventual multiple rotor installations.

• Scandlines ferries (M/F Copenhagen and Berlin) .
  By early 2025, ~75% of WAPS installations were retrofits, with rotors dominating for tankers and bulk carriers (54% share) .

Kite Sails

Kite sails fly hundreds of meters above the water, where winds are stronger and more stable. MS Onego Deusto (Beluga SkySails), outfitted with a 160 m² controllable kite, showed 15–20% fuel savings on average and up to 10–12% on transoceanic routes . SkySails estimates global adoption could cut 146 million tonnes CO₂ annually.

Emerging Hybrids and Modularity

Manufacturers like bound4blue are delivering modular, automated systems—like the DNV Type Approved eSAIL®—that blend features of rigid wings and rotors, requiring no crew interaction.Modular WAPS can be installed during maintenance, then moved between ships, improving flexibility and ROI.

Racing Tech Makes Waves

State-of-the-art raceboat technologies influence commercial design. WindWings, derived from America’s Cup sailing, have been deployed by Berge Bulk and Cargill, delivering up to 20% fuel savings, and up to 37% CO₂ reduction in ideal conditions .

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Challenges and Practical Solutions

Retrofit Complexity and Capital Costs

WAPS retrofit involves structural preparation, automated control integration, and crew training—all with initial costs. Shipping lenders are cautious, redeploying capital sparsely .

Solution: Modular systems and leasing models help mitigate risk. Shared ROI, fuel savings, and carbon trading benefits strengthen the business case.

Variable Wind and Operational Dependence

Wind isn’t constant, and fuel savings can fluctuate. Precision weather routing and integration with ship management systems reduce operational uncertainty and maximize savings .

Regulatory Gaps and Standardization

Standards for WAPS performance (fuel savings claims, safety, design) remain nascent. The Wind‑Power and Wind‑Assisted Ships Committee (ITTC) and IMO are advancing guidelines, but harmonization is pending.

Solution: Classification societies (like DNV) already offer advisory services. Early adopters should engage with regulators to shape future standards DNV.

Crew Training and Safety

Adding wind systems requires personnel training around emergency procedures, rotor pitch, or kite control. However, modern systems are highly automated, minimizing operator input .

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Case Studies / Real-World Applications

Oceanbird / Orcelle Wind

A visionary concept featuring wingsails to cut emissions by up to 90%, with full-scale prototype wing installed ashore and ship launch planned for 2026. A bold statement that wind propulsion is not just an assist—it can be central .

Maersk Pelican

A successful retrofit of rotor sails delivering 8.2% fuel savings and leading the way for corporate adoption of WAPS .

Beluga SkySails (MS Onego Deusto)

Early kite-sail experimentation delivering 10–15% savings on long ocean routes, showing high-altitude wind’s real value despite earlier economic setbacks .

E-Ship 1

Launched in 2010, this cargo ship demonstrates long-term viability of rotor technology, serving Enercon’s nacelles with consistent energy savings .

Grain de Sail II and Modern Sail Cargo

Sailboats like Grain de Sail II are leading a niche—but growing—revival of wind-only shipping, reflecting both environmental values and regulatory momentum.

Cargill’s Pyxis Ocean Test

A rigid sail retrofit led to 15% diesel savings, capturing sails 89% of the time and potentially saving 11 tonnes daily in ideal conditions .

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Future Outlook & Trends

Market Growth and Adoption

WAPS demand is surging, with expectations to exceed 100 installations in coming years.The market value could reach US $40 billion by 2034 .

Policy Alignment

EU and IMO regulations—like FuelEU Maritime and CII/EEDI/EEXI—will increasingly favor wind-assisted systems by offering correction factors for compliance and economic incentives.

Hybridization with Alternative Fuels

Wind systems are likely to complement low-carbon fuels like green ammonia and e-methanol—creating climate-resilient, efficient, and flexible fleets .

Future Designs

Autonomous ships with adaptive rotor sails, automated kite deployments, and fully integrated wingsail rigs—like the Oceanbird—may become mainstream for newbuild designs by 2030.

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FAQ – Brief Answers to Common Questions

1. How much fuel can wind-assisted technology save?
Savings typically range from 5% to 25% depending on system and vessel; some reports show up to 37% CO₂ reduction under ideal conditions .

2. What is the difference between wingsails, rotor sails, and kites?

• Wingsails resemble airplane wings, generating lift like modern sails.

• Rotor sails use spinning cylinders and the Magnus effect to create thrust.

• Kite sails fly high to capture stronger winds, pulling the ship via tether.

3. Can wind-assisted systems work on existing ships?
Yes—around 75% of WAPS are retrofits, especially feasible for tankers and bulkers with deck space and automation .

4. Are these systems automated?
Most modern systems (eSAIL®, rotor controls, kite operations) require minimal crew via advanced automation .

5. What are the main barriers to uptake?
High upfront cost, uncertain savings depending on wind access, lack of standard regulation, and capital availability .

6. How quickly can wind propulsion reduce emissions?
Many systems offer immediate gains, compared to future fuel transitions. With modular retrofits, savings can begin quickly upon installation.

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Conclusion

Wind-assisted propulsion brings the elegance of centuries-old sailing into the modern age. Sails, kites, and rotors—combined with digital controls and renewed regulatory incentives—offer practical, scalable, and impactful solutions for maritime decarbonization. These technologies don’t replace engines; they enhance them, offering immediate fuel and emission savings while new fuels and marine engines mature.

As pressures grow around carbon regulation, fuel costs, and sustainability expectations, wind-assisted systems stand ready to capture not just wind—but opportunity. Whether you’re a student, shipowner, or port planner—embracing this wind-powered wave may just chart your most sustainable voyage yet.

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References

• DNV. (2025). Rapid WAPS uptake driven by stricter emission regulations. 

• Kolodziejski, M. (2025). Review of Wind-Assisted Propulsion Systems in Maritime. Energies, 18(4), 897.

• CE Delft via IOM3. (2024). Wind propulsion technologies make waves in shipping.

• BIS Research. (2025). Wind-Assisted Propulsion Market projection.

• EMSA. (2023). Potential of Wind-Assisted Propulsion for Shipping.

• Bound4Blue. (2024). A guide to Wind Assisted Propulsion Systems.

• Wikipedia. (2025). Wind-assisted propulsion.

• DNV. (2023). Wind assisted propulsion overview.

• Wikipedia. (2025). Oceanbird concept.

• Wall Street Journal. (2024). America’s Cup charts a course.

• AP News. (2024). Sails make a comeback.

• The Times. (2023). Pyxis Ocean sail-powered cargo ship.

• Reuters. (2025). Shipping industry net-zero drive & Wind-assisted propulsion savings.

• Wired. (2023). Oceanbird wingsail innovation.