New Wind Propulsion Concepts and Technologies: Enabling Wind-Assisted Commercial Ships and Tankers

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The shipping industry is navigating a critical juncture in its push toward sustainability, driven by the need to cut greenhouse gas emissions and meet stringent international targets. Wind propulsion technologies such as rigid sails, rotor sails, and automated wings are helping the maritime industry take a bold step toward cleaner, more efficient transportation. Among the innovative technologies being developed, wind propulsion has reemerged as a viable solution to assist commercial ships and tankers in reducing fuel consumption and environmental impact. As modern wind propulsion technologies mature, they present a promising way to harness natural wind energy, optimizing engine power and significantly lowering fuel usage. Below, we explore the latest concepts and technologies shaping this new wave of wind-assisted propulsion and their potential to transform the global maritime sector.

Wind-Assisted Propulsion: A Renaissance in Maritime Energy

Wind propulsion has a long history in maritime transportation, but modern innovations take the basic principles to new heights.

For centuries, wind-driven vessels dominated trade routes between nations. Today, while paddles and sails still power smaller boats, most modern ships rely on mechanical propulsion systems, typically involving engines or electric motors turning a propeller. However, wind propulsion is making a comeback in the form of modern, automated wind-assisted technologies, promising to leverage wind power while minimizing fuel consumption.

Unlike traditional sails, modern wind-assisted propulsion systems are more efficient and require smaller windage areas, often utilizing automatic control systems that adapt to wind conditions.  Unlike the sails of old, today’s wind-assisted propulsion technologies are automated, dynamic, and designed to integrate seamlessly with ship engines.  These systems not only optimize wind thrust but also integrate seamlessly with existing vessel structures, reducing retrofitting costs and improving operational efficiency. The goal is not to replace traditional engine power but to complement it, reducing reliance on fuel and cutting emissions.

The latest wind propulsion systems—whether in the form of rigid sails, vertical rotor sails, or automated wings—allow vessels to tap into wind energy as an auxiliary power source. This integration ensures that ships can maintain the same speed with less fuel, making voyages more cost-effective and environmentally friendly. According to the International Maritime Organization (IMO), which aims to have 5% of ships’ energy coming from low-carbon sources by 2030, wind-assisted propulsion could play a pivotal role in achieving this target.

Integration of Wind-Assisted Technologies with Hybrid Systems

While wind propulsion can significantly reduce fuel consumption, its effectiveness depends on wind availability. To maximize efficiency, wind-assisted ships often integrate these technologies with hybrid propulsion systems, where engines and wind power work in tandem. By using wind to reduce engine load during favorable conditions, ships can operate more efficiently, saving fuel and extending the vessel’s range. When wind conditions are not ideal, engines take over, ensuring consistent speed and performance.

Key Wind Propulsion Concepts

Modern commercial vessels incur many times the weight of earlier generation wind-driven ships and require many times the propulsive power. The combination of environmental exhaust emissions regulations and fuel prices have prompted introduction of wind assisted vessel propulsion involving sails, kite sails, bladed horizontal-axis turbines and vertical-axis Magnus rotors. The power requirements of large commercial ships require future innovative breakthroughs in the variation and physical size of wind propulsion technology.

Wing Sail Technology

First studied in the 1980s, the “Wing Sail Concept” involves large, rectangular sails mounted on cylindrical masts. These automated sails require minimal handling and can adjust orientation based on wind direction. Although the concept showed potential for fuel savings, it failed to achieve widespread adoption. Today, modern wing sails offer greater efficiency and automation, making them a promising solution for reducing fuel consumption in commercial vessels.

Kite Sails

These large kites, similar to those used in recreational kiteboarding, harness wind power by flying large kites hundreds of meters above the ship, where wind speeds are stronger and more consistent. The kite sail concept is gaining significant interest due to its low-cost retrofitting capabilities. The kite generates thrust, reducing the load on the ship’s engine. The system can be fully automated, adjusting kite angles and positions to maximize efficiency.  This technology has the potential to reduce fuel consumption by up to 10-35% when used under optimal wind conditions. The system is retractable and can be deployed quickly, making it a flexible option for wind-assisted propulsion. Notable examples include the MS Beluga Skysails, which demonstrated substantial fuel savings and improved overall propulsion.

The 20th century brought significant advancements in fabric technology, with materials like Kevlar, nylon, rayon, glass fiber, and carbon fiber offering lightweight, ultra-strong, and UV-resistant properties. These materials revolutionized sail design, enabling the development of frameless para-cell kites and air-inflated kites that could withstand severe weather. These rugged kites were capable of towing boats in harsh conditions, using energy from strong crosswinds to propel vessels effectively.

Modern freight ships, being longer and wider than traditional wind-powered ships, have the potential to utilize these advanced fabrics to their advantage. With high-tensile strength and greater endurance, modern sails can be designed to cover large areas. Ships that do not need to pass under bridges could use extremely tall, cable-stabilized masts, allowing the deployment of massive sails that could span up to 500 feet in width and rise nearly 660 feet above sea level. These super-sized sails, combined with airborne kite-sails, could harness wind energy when sailing parallel to trade winds, offering a powerful, eco-friendly propulsion solution for modern commercial shipping.

These advancements highlight how the combination of cutting-edge materials and innovative design can help reintroduce wind-assisted propulsion in a way that complements modern shipping demands, improving fuel efficiency and reducing environmental impact.

Soft Sail Systems: Innovations in soft sail systems have gained momentum with advanced automation and route optimization. VPLP’s 121-meter-long RORO vessel design, used to transport Ariane 6 rocket components, employs fully automated wing-sails (Oceanwings), showcasing the integration of wind power in modern shipping. These sails reduce fuel consumption by supplementing propulsion systems, providing a glimpse into the future of wind-assisted shipping.

Rigid Sails: High Performance and Durability

Inspired by aircraft wings, rigid wing sails are fixed or semi-rigid structures that capture wind more efficiently than traditional fabric sails. These sails can automatically adjust their angle to the wind, optimizing performance even in changing conditions. Wing sails are scalable and adaptable, offering significant fuel savings for large cargo ships and tankers, particularly when combined with auxiliary engines.  Rigid sails, such as those used on vessels like EcoClippers and Shofu Maru, are a modern interpretation of traditional sails, built with durable materials and advanced aerodynamics. Unlike fabric sails, rigid sails are constructed from composite materials and maintain their shape in various wind conditions, allowing for more consistent power generation.

Hard sails offer an alternative to soft sails, allowing for aerodynamic structures or photovoltaic coatings. Japan’s Mitsui OSK Lines and Oshima Shipbuilding have designed a bulk carrier with a telescopic hard sail system, claiming up to 8% fuel savings, signaling increasing interest in combining wind technologies with traditional engines.

The Shofu Maru, a Japanese coal carrier, is equipped with a rigid sail known as the “Wind Challenger.” This sail can be raised or lowered depending on weather conditions and cargo needs. The results from the trials on the Shofu Maru indicate a 5-8% reduction in fuel consumption, showcasing the effectiveness of rigid sails in industrial shipping.

Flettner Rotor: A Revolutionary Wind-Propulsion Technology

The Flettner Rotor, an innovative wind-assist propulsion technology, consists of a large, vertically mounted spinning cylinder on a ship’s deck. As the rotor spins, it interacts with the wind, creating a thrust effect known as the Magnus effect, which propels the ship forward.

Rotor sails are large, cylindrical structures that rotate as wind flows over them, generating additional forward thrust that reduces the load on the ship’s engines. This concept, first introduced in the 1920s, has seen limited use over the years but has recently experienced a resurgence in the maritime industry due to its fuel-saving potential and environmental benefits.

The only parameter of the Flettner Rotor requiring control is the speed of the rotor’s rotation, so this method of wind propulsion requires very little operator input. In comparison to kite sails, Flettner rotors often offer considerable efficiency gains when compared to the size of a sail or kite vs. size of the rotor and prevailing wind conditions.

In the 1980s, Canadian physicist Dr. Brad Blackford built a small wind-powered boat using similar principles, which could sail into a headwind at faster speeds than conventional sail-driven boats. He later designed a boat capable of sailing directly into a headwind at 8 knots. Flettner rotors, combined with modern electrical generators and propellers, allow vessels to harness wind power even when facing headwinds, marking a significant advancement in wind-assisted propulsion.

In 2010, a 10,000 dwt cargo ship was equipped with four Flettner rotors to test their fuel efficiency. Since then, multiple cargo ships and even passenger vessels have adopted this technology. Notable examples include the Viking Line’s Viking Grace, which became the world’s first passenger ferry outfitted with a Norsepower rotor sail in 2018. The rotor sail is projected to cut the ship’s fuel consumption and reduce carbon emissions by up to 900 metric tons annually.

Another significant case is the installation of Norsepower’s rotor sails on the Maersk Pelican in 2018, a collaboration between Energy Technologies Institute and Shell. Equipped with two Flettner rotor sails, this vessel demonstrated a 10% reduction in fuel consumption during sea trials. The cylindrical rotors can be deployed on vessels with minimal structural modification, making them a versatile solution for retrofitting existing fleets. These vessels demonstrate that Flettner rotors are part of a growing trend in wind-assisted propulsion, offering a viable solution to meet stringent fuel and emissions reduction targets.

Suction Wing Technology:

Rotor Airfoils: Enhancing Wind-Assisted Propulsion for Ships

Rotor airfoils have emerged as a promising wind propulsion technology for maritime vessels, capable of converting wind energy from crosswinds and diagonally approaching headwinds into thrust. These deck-mounted airfoils work similarly to airplane wings but are enhanced with the integration of transverse-axis Flettner rotors. In aviation, hobbyists have successfully replaced traditional airplane wings with Flettner rotor-based wings, demonstrating their potential in both air and maritime applications.

In maritime settings, the incorporation of Flettner rotors into airfoil sails prevents stalling on the downwind surface by increasing the pressure difference between the upwind and downwind sides. This enhanced pressure differential generates greater propulsive force, making it a highly efficient solution for wind-assisted propulsion. Ships that do not need to pass under bridges can be equipped with taller rotor-airfoil sails, further boosting performance by maximizing wind capture.

Wind Turbines on Ships

Incorporating wind turbines on ships presents another innovative concept. Turbines mounted on vessels can capture wind energy to generate electricity, which can then be used to power auxiliary systems or hybrid engines. This approach combines renewable energy generation with the traditional propulsion system, further reducing fuel usage and emissions.

Mega-Scale Wind Technologies

Commercial ships require massive amounts of power—often between 25,000 to 35,000 horsepower—to operate effectively. Today, the largest 3-bladed wind turbines generate approximately 12,000kW, or just over 16,000 horsepower. However, severe weather and dynamic structural loads, such as ship pitching and rolling, could lead to the collapse of wind turbine towers on ships. Given these risks, the development of mega-scale vertical-axis wind turbines, such as Magnus (Flettner) rotors, on floating platforms may hold promise. These turbines would be designed to withstand the harsh conditions of ocean travel, particularly the stresses imposed by severe waves.

A proposed design involves mounting two mega-sized Magnus rotors on a bi-directional catamaran platform. The twin hulls of the catamaran would be spaced about 100 meters (300 feet) apart, with the Magnus rotors extending up to 200 meters (660 feet) above the platform. These rotors would drive electrical generators, which in turn would power electric motors inside the ship to propel it forward. To mitigate the effects of pitching, torque reaction control arms would secure the catamaran to the ship’s hull. This concept could provide sufficient power to propel ships across challenging routes, such as westbound voyages across the North Atlantic

These technologies leverage wind power at an unprecedented scale, with potential applications in transatlantic shipping and beyond.

Advanced Coupling and Future Research

Future developments could explore the possibility of attaching ultra-tall masts on bi-directional twin-hull catamarans to a ship’s bow at various points and elevations, minimizing pitching movements. These catamarans could be equipped with Flettner rotors or mega-sails, depending on the wind conditions. For instance, while sailing downwind, forward-facing mega-sails could be deployed, and when sailing into headwinds, Flettner rotors mounted on the same catamaran platform could be engaged. To avoid limitations posed by port space and low roadway bridges near ports, such turbine platforms would remain separate from the ship, with detachable couplings designed for easy attachment and removal outside of port areas.

Optiwise Project: The EU-funded Optiwise project, led by MARIN, aims to integrate wind propulsion and hydrodynamic improvements for greater energy savings. The project takes a holistic approach to redesigning ships and their energy management systems to unlock higher savings compared to existing wind-assisted technologies.

Innovations in Floating Wind Turbine Platforms

Another area for future research is the development of mega-scale wind turbines mounted on floating platforms, separate from the ship itself. These platforms would tow alongside or behind the ship, with their turbines generating electric power to sustain the ship’s propulsion system. Mechanical levers attached to the ship’s hull would minimize the pitching of the turbine platform, ensuring stability during rough seas.

Research would also focus on the limits of mobile wind turbine designs, determining the maximum feasible size of both 3-bladed wind turbines and Magnus rotors for maritime use. As ships grow in size, so must the scale of the wind propulsion systems that power them. Advances in lightweight, high-strength materials could be critical to enabling the construction of these mega-scale turbines, which would help ships operate efficiently while minimizing fuel consumption and reducing emissions.

Global Implications: Reducing Costs and Emissions

These wind propulsion technologies offer more than just operational fuel savings—they align with the broader goal of decarbonizing the shipping industry. The IMO’s 2030 greenhouse gas strategy calls for a reduction of carbon intensity by at least 40% by 2030, and wind-assisted propulsion can play a major role in achieving these reductions.

However, the success of these technologies also depends on the maritime logistics network. The trial with Pyxis Ocean highlighted broader challenges, such as the need for port and terminal infrastructure to accommodate vessels with large wind-assisted propulsion units. Cargill, the operator of Pyxis Ocean, is currently in discussions with over 250 ports worldwide to ensure seamless integration of wind propulsion systems into regular operations.

Demonstration Projects Seek to Validate Wind Rotor Technology

In May 2020, a Norsepower Rotor Sail was installed on Scandlines’ ferry, the Copenhagen, which operates between Rostock, Germany, and Gedser, Denmark. This installation marked a significant step towards validating wind-assisted propulsion technology. Weighing 42 tons and measuring 30 meters (98 feet) in height with a 5-meter (16-foot) diameter, the rotor was mounted during a routine overnight stay in Rostock, minimizing service disruptions. The steel foundation for the rotor had been installed during a shipyard visit in November 2019, further streamlining the process.

The rotor’s installation is part of the EU Green Deal’s efforts to reduce pollution and carbon emissions across Europe. As a passenger ferry, the Copenhagen provides a highly visible demonstration of the technology, drawing significant attention from passengers. Already one of the world’s most energy-efficient ferries, the Copenhagen features hydrodynamic hull optimization and a hybrid-electric propulsion system with battery storage. The rotor is expected to reduce fuel consumption by 4-5% on average, with the potential for up to 20% savings in optimal wind conditions.

While positive about the role of wind-assisted propulsion, Lloyd’s Register’s Craddock expressed caution. “Wind technologies are recognized as credible energy-saving solutions that could reduce emissions for certain ship types and routes,” he explained. However, with wind technologies still at a relatively low level of readiness, the market remains cautiously interested. As more pilot projects are successfully completed, confidence in the technology will grow, shortening payback periods and increasing adoption.

UK-based Windship Technology achieved a major milestone in September 2021 when its triple-wing rig received ‘Approval in Principle’ (AiP) from DNV, a leading classification society. Years of design iteration, computational fluid dynamics (CFD), and extensive wind tunnel testing culminated in this approval. Each wing features trailing edge flaps, allowing for optimized power generation from various wind angles. Windship’s rigs are designed to generate enough power to sail an 80,000 dwt vessel on major transoceanic routes, offering the potential for zero-emission shipping through its integrated carbon capture system, which drastically reduces fossil fuel consumption.

French company CRAIN Technologies has also secured AiP for its suction wing technology, the SW270, which enhances propulsion efficiency using a solid thick wing with rear flaps. The system creates a suction force, improving lift-to-drag ratios and enabling better performance in upwind conditions. CRAIN’s solution, developed in collaboration with Bureau Veritas (BV), is adaptable for various ship sizes and is expected to move towards industrialization soon.

Furthermore, the Optiwise project, funded by the Horizon Europe research program, aims to improve efficiency gains by integrating wind propulsion and hydrodynamic optimizations. Led by the Maritime Research Institute Netherlands (MARIN), the €5.3 million initiative seeks to develop methods that can deliver energy savings of 30-50% compared to conventional ships. The project will focus on bulk carriers, tankers, and passenger vessels using different wind propulsion technologies, combining extensive simulation and testing to deliver an integrated vessel optimization system.

WindWings: A Case Study of Real-World Application

One of the most compelling examples of wind-assisted propulsion in action is the Pyxis Ocean, a Kamsarmax-sized bulk carrier retrofitted with BAR Technologies’ WindWings. These solid wind sails, each standing at 37.5 meters, are designed to harness wind power to reduce the vessel’s fuel consumption.

Since August 2023, the Pyxis Ocean has been engaged in a six-month trial that spans some of the world’s busiest maritime routes, including the Indian Ocean, Pacific Ocean, and both the North and South Atlantic. The vessel, equipped with two WindWings, delivered remarkable results, achieving an average fuel saving of 3 tonnes per day in normal conditions, with fuel savings soaring to 11 tonnes per day in optimal conditions.

WindWings operate autonomously once deployed, with sensors continuously measuring wind conditions and adjusting the wings for maximum efficiency. A simple traffic light system tells the crew when to raise or lower the sails, and from there, the technology manages itself. The insights gained from these early trials have been instrumental, shedding light on both the performance of the sails and the logistical challenges of integrating such systems at ports and terminals around the world.

BAR Technologies’ CEO, John Cooper, highlighted that while Pyxis Ocean operates with two WindWings, future Kamsarmax vessels could carry three, potentially boosting fuel savings by 50%. As this technology rolls out globally, the scalability and adaptability of WindWings promise to revolutionize fuel consumption for commercial vessels.

In summary, these wind propulsion demonstration projects represent a significant step forward in reducing greenhouse gas emissions in the maritime industry. They not only demonstrate the viability of wind-assisted propulsion but also pave the way for broader adoption across various ship types and routes, contributing to the IMO’s ambitious decarbonization targets.

Challenges to Widespread Adoption

While numerous innovative wind propulsion technologies have been developed for commercial shipping, none have yet reached full market maturity.

1. Initial Investment Costs

The upfront costs for retrofitting existing ships or installing wind propulsion systems on new builds can be significant. Although the long-term fuel savings may offset these costs, the initial investment may deter some operators, especially those with smaller fleets.

2. Operational Constraints

Wind propulsion is inherently dependent on weather conditions, which may limit its effectiveness in certain regions or during specific seasons. Ships may need to plan routes that maximize wind availability, which could impact scheduling and cargo delivery times.

3. Infrastructure and Maintenance

The installation of wind propulsion systems requires specialized infrastructure and ongoing maintenance to ensure optimal performance. This could add complexity to ship operations and require training for crews to manage and maintain these systems effectively.

While wind-assisted propulsion technologies hold great promise, there are still challenges to their widespread adoption. A study commissioned by DG Climate Action focused on the direct use of wind for the propulsion of commercial vessels through wind-assisted shipping technologies. The study identified multiple barriers to the widespread adoption of these technologies, with three primary obstacles standing out.

First, there is a lack of trusted information on the performance, operability, safety, durability, and economic implications of wind propulsion technologies. Second, access to capital for developing and scaling wind propulsion systems remains limited, particularly when it comes to building and testing full-scale demonstrators. Third, there are insufficient incentives for improving energy efficiency and reducing CO2 emissions in the shipping industry. These barriers are closely intertwined, particularly through a “chicken-and-egg” dilemma between the need for reliable performance data and the lack of investment for scaling up the technologies. Overcoming these challenges will require the development of standardized methods to assess wind propulsion systems, alongside pilot projects to refine these assessments.

Assessing Savings Potential

Models have been developed to determine the potential energy savings offered by various wind propulsion technologies. These models have been applied to six different types of ships, analyzing their power savings across real-world voyage profiles and routes. The study differentiates between two speed regimes and finds that significant savings could be achieved, depending on the technology and ship type.

Flettner rotors and wingsails, for instance, show savings of 5-18% in high-speed scenarios, with larger ships like bulk carriers benefiting the most. In contrast, towing kites deliver relative savings of 1-9%, performing better on smaller vessels than on larger ones. Wind turbines, while showing the lowest relative savings (1-2%), still offer some advantages. Notably, both wingsails and Flettner rotors show greater absolute savings at higher voyage speeds, making them attractive for faster vessels.

Market Potential and Environmental Impact

If wind propulsion technologies reach marketability by 2020, their adoption across bulk carriers, tankers, and container ships could be substantial. The study estimates that by 2030, between 3,700 to 10,700 systems could be installed, depending on factors such as fuel prices, vessel speed, and the discount rate applied. This includes both retrofits on existing ships and installations on newbuilds. The adoption of these systems could lead to CO2 savings of approximately 3.5 to 7.5 million metric tons by 2030, contributing to global efforts to reduce emissions in the shipping industry. The wind propulsion sector could also create between 6,500 to 8,000 direct jobs and 8,500 to 10,000 indirect jobs.

The Future of Wind-Assisted Propulsion

The potential of wind-assisted propulsion to transform the shipping industry is undeniable. As more real-world trials validate these technologies, the path to widespread adoption becomes clearer. With solutions like WindWings, rotor sails, and rigid sails proving their efficacy in reducing fuel consumption and emissions, the future of commercial maritime transport looks greener and more cost-efficient.

Furthermore, innovations in automation and sensor technology are making wind propulsion more accessible, even for crew members without specialized training. Fully automated systems, like those seen in the WindWings technology, allow ships to harness wind power efficiently without adding complexity to operations.

As global regulations on emissions tighten and fuel prices remain volatile, wind-assisted propulsion technologies are emerging as a viable solution to maritime shipping’s most pressing challenges. The success of projects like Pyxis Ocean points to a new era where wind, one of the oldest sources of maritime power, returns to help guide the industry toward a sustainable future.

By embracing wind-assisted propulsion technologies, commercial ships and tankers can drastically reduce their environmental impact while maintaining operational efficiency. The integration of these systems—whether through rotor sails, rigid sails, or WindWings—offers a clear pathway to a more sustainable shipping industry, where cleaner skies and cost savings go hand in hand.

Looking ahead, the combination of wind propulsion with other green technologies, such as hydrogen fuel cells and biofuels, could revolutionize the maritime industry, leading to a new era of eco-friendly shipping. As the industry works toward decarbonization, wind-assisted propulsion offers a clear, viable path to a cleaner, more sustainable future on the high seas.

Conclusion

The resurgence of wind propulsion concepts, supported by modern technologies, offers the maritime industry a viable solution to reduce emissions, cut fuel costs, and meet global sustainability targets. From Flettner rotors and rigid wing sails to high-flying kites and suction wings, these innovations are reshaping the future of commercial shipping. As the industry embraces these new technologies, wind-assisted propulsion has the potential to redefine how tankers and commercial ships navigate the seas, making them cleaner, more efficient, and better aligned with the global push for sustainability.

References and Resources also include:

http://www.motorship.com/news101/engines-and-propulsion/wind-as-a-viable-future-propulsion-technology

https://www.maritime-executive.com/article/demonstration-projects-seeks-to-validate-wind-rotor-technology

https://www.maritime-executive.com/article/project-unites-wind-propulsion-and-hydrogen-generation-to-create-fuel

https://www.theengineer.co.uk/wind-ships-marine-propulsion/

https://shipinsight.com/articles/windship-technology-gets-dnv-aip-for-wind-propulsion-system/

https://www.seatrade-maritime.com/sustainability-green-technology/53m-wind-propulsion-optimisation-project-gets-underway

https://splash247.com/french-wind-propulsion-tech-makes-headway/