Ambitious decarbonization policies and the economics of energy efficiency have nudged ship owners and operators toward a potential watershed moment in the proliferation of wind-assisted propulsion.
According to a recent analysis by Lloyd’s Register, the current wind-assisted propulsion systems market — which primarily includes Flettner rotors, rigid sails, suction wings and kites — “is on the verge of a tipping point” and expected to pass the 100-installation milestone in the next few years. After this benchmark, market forecasts suggest orders will accelerate rapidly, “with analysis of top-end potential identifying nearly 14,000 candidate vessels over the next 26 years,” Lloyd’s said.
The primary benefit of this technology is reduced fuel consumption, which translates into lower operating costs and reduced emissions. Measuring the benefit from wind-assisted technology has thus far proved more art than science. According to Lloyd’s, there is no standard for evaluating the fuel savings claims from these components, with estimates ranging from 5 to 25 percent. There also is uncertainty about the potential hidden costs of these technologies, and concern whether the supply chain can keep up new expected demand.
Still, advocates of this technology are optimistic. They point to the rapid adoption of wind-assisted propulsion in general, and to orders for entire fleets rather than single units — and the orders of multiple units per vessel — as anecdotal indications that industry is moving toward wider adoption. What’s more, wind-assisted propulsion systems are one of many tools in the toolbox: Weather routing, speed reduction and air lubrication systems that similarly offer increased efficiency on oceangoing ships.
“We’ve won the argument that wind is a robust energy source,” said Gavin Allwright, the secretary of the International Windship Association (IWSA), an advocacy group promoting the use of wind propulsion.
Paradigm shifts usually come with fits and starts. Back in 2019, Allwright predicted that by 2030, as much as 15 percent of the world’s commercial fleet could be using some form of wind-assisted propulsion. Allwright also mentioned the 100-installation milestone, where the industry would see “self-sustaining growth develop and production costs starting to drop — and economies of scale starting to be felt.”
Five years later, that projection hasn’t borne out, although Allwright said the Covid-19 pandemic and its aftermath halted what had been budding momentum. “For 18 months, nothing moved. Installations stalled and caused financial pain. The precipice did get pushed back,” he said. “Production flatlined, then went off.”
The Lloyd’s analysis indicates that since 2018, wind-assisted propulsion systems have been or will be installed on 101 ships. “The orderbook for 2024 and beyond highlights the accelerating uptake of (these) systems, with 72 orders compared to the 29 vessels installed between 2018 and 2023.”
The types of vessels installing wind-assisted propulsion varies widely. According to Lloyd’s, bulk carriers are the largest single segment to date, with 10 ships overall and orders for 18 more. “Tankers, passenger and ro-ro (roll-on, roll-off) vessels all have order books similar to the number of installations already performed,” the report noted. “Orders for the first … installations on gas carriers, containerships and car carriers reflect the increasing and broadening uptake of wind power.”
Which type of wind propulsion technology is most popular, or are best suited to certain vessels? “Each one is a slightly different market, and they go through spurts,” Allwright said. “If you take a snapshot right now, it might be another technology a month from now.”
Lloyd’s noted that there are 27 forthcoming installations of suction wings — thick wing sails with built-in mechanical air suction mechanisms — in the general/specialized cargo fleet. Suction wings had previously been utilized by the “core merchant segments of bulk, tanker and container vessels,” Lloyd’s noted, adding that bulk carriers are the most diversified users to date, with installation or orders for all technologies.
The Flettner rotor, which is a cylinder standing up to 115 feet tall by 16 feet wide, creates thrust using the “Magnus effect.” This century-old wind-assist technology is typically utilized by bulk carriers, with gas carriers emerging as a new user base with five planned installations, Lloyd’s said. “Flettner rotors and suction wings are both the widest used technologies overall and the most diversely applied across vessel segments,” the report noted.
The Finnish rotor-sails producer Norsepower is the “market leader in the auxiliary wind propulsion as a whole,” according to CEO Heikki Pöntynen. “Norsepower has installed 29 sails on 15 ships,” and the “installed base will be around 58 within the next 18 months.” The cost of a trademarked Norsepower Rotor Sail is about 1 million euros (about $1.08 million).
“The savings allow shipowners to obtain a return on their investment typically in about three to five years — and the payback period gets shorter as the regulatory costs are on the rise,” Pöntynen added.
A paper written and submitted to the International Maritime Organization (IMO) by the IWSA said past assessments of wind-assist technology had not taken into account other optimization factors, such wind-routing software, which can “double the amount (of fuel) that you’re saving,” Allwright said. The paper also said that on certain vessels, reducing speeds by 20-30 percent can result in further fuel savings and reductions in greenhouse gas emissions. “Bulkers often bring stockpile to stockpile, so you can drop the ETA and speed, and increase the percentage of wind used in the route,” Allwright said, using a shorthand for estimated arrival time.
Air lubrication systems (ALS) are another tool in the hybrid decarbonization toolbox. These systems reduce the frictional resistance of ships by creating a swath of microbubbles on the flat bottom of a vessel’s hull, thus reducing the power needed for propulsion. Allwright said that as far as he is aware, about 100 ALS installations have already taken place on merchant vessels.
Lloyd’s emphasized the perceived savings from wind-assisted propulsion “can vary significantly depending on how they are deployed,” highlighting one of the many challenges of incorporating new technology and meeting environmental goals — to say nothing of supply logistics.
“For technology suppliers to meet existing orders would entail delivering around 2.5 times the number of units they have installed in the past five years,” the Lloyd’s report said, adding that outfitting 15 percent of the global fleet, “as anticipated in the most optimistic forecasts, would require a 75-fold increase, requiring a dramatic increase in production capacity.”