Setting Sail to Clean Shipping
- Rick Laezman
- Apr 17
- 8 min read
How Wind Power is Reducing the Maritime Industry’s Carbon Emissions
As the fight against global warming intensifies, more industries are joining the fray. In the shipping industry, this means adopting any number of innovations, including wind-aided technologies.
This does not mean modern seafaring vessels will return to the massive sails and giant masts of centuries past.
Instead, it involves a hybrid approach using modern technological advances that harness the power of the wind to complement and improve the efficiency of combustion engines. This is helping maritime vessels significantly reduce fuel consumption and carbon emissions and, when combined with other clean energy improvements, is helping the industry become greener.
Centuries of Sailing Innovation
Humans have used sailing vessels for millennia, but in the late 1800s, ships began converting to combustion engines as the technology became widely used for trains, factories, and later automobiles. Now attention has shifted to reducing carbon emissions, and as shipping looks for new, cleaner forms of power, wind is making a comeback.
Ironically, when combustion engines were revving up, the seeds for wind's return as a clean power source for shipping were being planted.
In 1852, a German experimental scientist at the University of Berlin, Dr. Heinrich Gustav Magnus, described a phenomenon he observed in an experiment using a brass cylinder spinning in a fast-moving current of air. He noted that the interaction between the spinning cylinder and the moving air created a difference in pressure on two sides of the cylinder.
The side of the cylinder that was spinning in the direction into the wind experienced high pressure, and the side of the cylinder that was spinning in the same direction as the wind experienced low pressure. This pressure difference caused the cylinder to move toward the side with the low pressure.
The Magnus effect can most commonly be observed in sports that involve a spinning ball, such as tennis, soccer, baseball, or basketball. For example, when a baseball pitcher puts spin on the ball as he throws it, the Magnus effect causes the ball to curve in the air as it travels to the batter, otherwise known as a “curve ball.” Similarly, when a tennis player hits the ball, the Magnus effect causes it to drop quickly as it travels over the net to the other player, otherwise known as “top spin.”
The benefits of this physical phenomenon are not limited to sports. It can also be used for power and propulsion. In the 1920s, a German engineer and inventor, Anton Flettner, developed a far more effective device than traditional sails for propelling vessels through the ocean. The device, known now as a Flettner Rotor, harnessed the pressure differential generated by the Magnus effect to impart forward motion to ships.
Tall rotating cylinders mounted on the surface of ships create the same pressure difference applied to a traveling tennis ball or a baseball pitch. Instead of causing a ball to curve off its path, the difference in pressure or “lift” causes the ship to propel in a forward direction.
Rotor Sails
Several modern shipping companies are now harnessing and refining the Flettner technology to increase fuel efficiency and reduce emissions. For example, the Finnish shipbuilder Norsepower manufactures rotor sails that can be installed on the decks of shipping vessels, known as the Norsepower Rotor Sail™.
The company prides itself on having "started the whole modern wind propulsion market" and boasts that it coined the term “rotor sail,” which is now used by many other companies. The company reports that it has installed 18 Norsepower Rotor Sails™ on various tankers, cargo ships, and passenger vessels since 2014, and orders for another 35 units will be filled over the next year and a half.
Resembling a tall smokestack—minus the smoke—the Norsepower Rotor Sail™ consists of a large cylinder made of recycled plastic. Mounted on a steel tower, the cylinder measures about 5 meters (15 feet) wide and as high as 30 meters (just under 100 feet). Vessels can have one or more sails mounted on their deck, depending on the size of the ship. The spin of the sail does not come from the wind itself. Instead, the spin is generated by an electric motor.
Norsepower explains that the extra thrust, created by the Magnus effect generated when the rotor sails spin into the wind blowing across the deck, allows the ship to throttle back on its primary motors. This reduces fuel consumption and carbon emissions. Alternatively, the sails can increase the vessel’s speed without increasing fuel consumption.
Norsepower says that its [rotor] sails are 10 times more efficient than traditional sails, allowing ships to realize savings anywhere from 5% to 25% in fuel consumption and emissions.
Norsepower says that its sails are 10 times more efficient than traditional sails, allowing ships to realize savings anywhere from 5% to 25% in fuel consumption and emissions. Norwegian shipping company Sea-Cargo retrofitted one of its Roll-on/Roll-off (RoRo) ships with two 35 meter x 5 meter (114.8 feet by 16.4 feet) Norsepower Rotor Sails™. Norsepower reports that its prediction that the 2021 installation would reduce emissions from the ship by about 25% has proved accurate.
RoRo ships transport automobiles, construction equipment, tractors, and other large-wheeled vehicles. In March 2025, Sea Cargo announced that it was retrofitting two other RoRo vessels, the Misina and Masana, with the technology. Each ship will have three Norsepower Rotor Sails™, which, in conjunction with solar panels and battery storage, will reduce fuel consumption on each ship by 50%.
Regarding rotor sails, Norsepower is not the only shipbuilder using this technology. For example, London-based Anemoi Marine Technologies offers a line of five different rotor sails ranging in height from 21 meters (66 feet) to 35 meters (114 feet). The company boasts that its sails can achieve fuel and emissions savings of up to 30% on shipping vessels. The rotor sail towers can also be folded down and out of the way, moved on rails installed along the deck of a ship, or removed and relocated to another ship owned by the same company, all of which makes the towers more versatile and cost-effective and helps shipping companies maximize space for cargo.
According to Anemoi, the m/v Afros, built in 2018, is the world's first bulk carrier fitted with rotor sails. The massive 64,000 deadweight ton (dwt) ship, owned by Greek shipping company Blue Planet Shipping, has four 16-meter (52-foot) high rotor sails, which can be moved along rails installed on the deck to make room for loading and unloading cargo.
Anemoi Marine Technologies estimates that on one of its recent, routine routes, the rotor sails helped the ship achieve a 12.5% savings, amounting to a reduction of 73 tons of fuel and 235 tons of CO2.
Anemoi estimates that on one of its recent, routine routes, the rotor sails helped the ship achieve a 12.5% savings, amounting to a reduction of 73 tons of fuel and 235 tons of CO2. The route was sailed between November 2019 and January 2020, over approximately 11,800 nautical miles between Nantong, China, and Vancouver, Canada.
WindWings
While rotor sails take advantage of the Magnus effect, other wind technologies are also helping shipping improve its efficiency.
In 2023, a collaboration between American food company Cargill, English maritime engineering company Barr Technologies, Japanese multinational corporation Mitsubishi, and Norwegian green maritime corporation Yara Technologies announced the launch of so-called WindWings, a new technology to harness the wind.
WindWings tap into the same propulsion properties of wind force that enable an airplane to fly. Airplane wings are designed to create a difference in pressure between the top and bottom surfaces of the wing. This creates “lift” that carries the airplane into the sky and keeps it there for as long as the plane is traveling at sufficient speeds.
When WindWings are installed on the surface of a ship, they create a similar lift. But instead of making the ship airborne, they impart forward propulsion to the vessel, which allows it to move faster and power down its fuel-burning motors.
Looking nothing like a traditional sail, the WindWings more closely resemble an airplane wing mounted at a right angle to the ship's deck.
Looking nothing like a traditional sail, the WindWings more closely resemble an airplane wing mounted at a right angle to the ship's deck. Composed of steel and composite construction materials, they measure up to 37.5 meters (123 feet) tall. They have three specially designed sections, each of which can be adjusted to different angles in the wind to achieve maximum lift. Barr Technologies expects the wings to generate average fuel savings of up to 30% on newly built vessels and even higher if used in combination with alternative fuels.
Marine Shipping Transformation
The maritime shipping industry is one of the world's most carbon-intensive sectors. Compared to other industries in 2022, it accounted for a relatively small amount—2% to 3%—of total global emissions. But it is still a significant number, and given the total volume of emissions of about 1,000 million tons annually, the industry faces pressure to decarbonize.
Using 2008 emissions as a baseline, the International Maritime Organization’s new standards call for a reduction of at least 20% by 2030—but striving for 30%.”
In 2023, the International Maritime Organization (IMO), the United Nations Agency responsible for the shipping sector, adopted new standards to reduce emissions. Using 2008 emissions as a baseline, the IMO’s new standards call for a reduction of at least 20% by 2030—but striving for 30%.
The IMO standards further call for a reduction of at least 70%, striving for 80%, by the year 2040, and to “reach net-zero GHG emissions by or around, i.e., close to 2050.”
Decarbonizing shipping is not an easy task. Due to long voyages, heavy cargo, and limited space, the industry has few options to improve its efficiency.
However, efforts are underway [see ‘All the Way to Zero’—Maritime Shipping Charts a Course to Decarbonization The Earth & I, April 2024] to decarbonize the industry, primarily by shifting to alternative fuels, such as liquified natural gas (LNG), liquified petroleum gas (LPG), methanol, hydrogen, ammonia, and biofuel.
The transition to alternative fuels in shipping may take time, “so, we have to throw everything at operational measures on existing ships—like retrofitting vessels with sails, kites, and rotors,” says Dr. Simon Bullock, shipping researcher at the Tyndall Centre at the University of Manchester. “Wind power can make a big difference,” he adds.
One of the greatest benefits of wind technology is the plentiful supply of this natural resource. According to the US Department of the Interior's Bureau of Ocean Energy Management, offshore winds “tend to blow harder and more uniformly than on land.” Seafaring vessels are in an ideal location to capitalize on such a consistent power source.
The drawbacks are that it is a relatively new technology and comes with high upfront costs—although, as the technology advances, costs will come down. Also, like other forms of wind power, sails only work when the wind blows. The technology is also complicated, and ships face tight space constraints to make room for profit-generating cargo.
Finally, shipping companies must consider the comparative cost-benefits of retrofitting existing ships versus installing them on new builds. Retrofits offer more immediate benefits, although they can be costly. Installing wind technology on new builds may take more time to benefit the industry, but it can be more comprehensively and efficiently integrated into a ship's infrastructure.
All Hands on Deck
While initial progress toward wind-aided vessels has been slow, projections envision an industrywide conversion in a relatively short period of time. According to Gavin Allwright, secretary general of the International Windship Association (IWSA), “now is the time for shipping to use wind energy as a fuel for maritime decarbonization.”
The IWSA forecasts around 10,000 ships worldwide to have installed wind (auxiliary) propulsion by 2030 and up to 40,000 ships by 2050.
In the fight against global warming, all hands are on deck.
*Rick Laezman is a freelance writer in Los Angeles, California. He has a passion for energy efficiency and innovation. He has been covering renewable power and other related subjects for more than ten years.
Kommentarer