Spanish wind propulsion specialist bound4blue has carried out the first installation under its agreement with Maersk Tankers, fitting four 24-metre eSAIL units on the medium-range tanker Maersk Trieste.

The project forms part of a wider contract covering 20 suction sails to be deployed across five MR tankers. The agreement, concluded in December 2024, is the largest single order bound4blue has secured to date.

The installation was finalised on 26 January at EDR Shipyard in Belgium, following earlier preparatory work completed at Yiu Lian Shipyard in Shenzhen, China. That initial phase included structural and electrical modifications to prepare the vessel for wind-assisted propulsion.

Once in Belgium, the four units were lifted into place, fixed to pre-installed foundations and connected to onboard power and data systems. The installation approach was designed to limit vessel downtime by separating preparatory work from final fitting.

Bound4blue CEO and co-founder José Miguel Bermúdez described the development as "a watershed moment" in the acceptance and adoption of wind power for the maritime industry.

Bound4blue’s eSAIL technology generates thrust by drawing airflow across an aerodynamically optimised surface. The company says this method can produce significantly higher lift than conventional rigid sail designs of comparable size.

According to bound4blue, the system can deliver double-digit reductions in fuel consumption and CO₂ emissions, while also improving a vessel’s Carbon Intensity Indicator performance. The technology may also support compliance with regulatory frameworks such as FuelEU Maritime and EEDI/EEXI.

The eSAIL configuration used on Maersk Trieste has been developed with tanker operations in mind. The company said the design avoids tilting mechanisms, maintains a standard operational air draft and does not require ATEX-rated systems, simplifying integration on tankers.

"Our system was designed from day one to deliver maximum performance with minimum complexity," Bermúdez commented, "and that's especially important for scaling up installations within segments that present specific integration challenges, such as tankers."

He added that the size and efficiency of eSAILs enable tankers to benefit from wind propulsion "safely and cost-effectively, without altering operational profiles, avoiding tilting systems and retaining a normal operational air draft, and all with the simplicity of a non-ATEX solution."

Claus Grønborg, chief investment officer at Maersk Tankers, said, "For the tanker industry, progress on emissions reduction requires concrete investments and implementation. At Maersk Tankers, we focus on deploying advanced energy-efficient technologies to reduce fuel consumption and CO₂ emissions. Implementing wind-assisted propulsion systems at scale enables more energy-efficient voyages for our customers, while supporting compliance with FuelEU Maritime and the EU Emissions Trading System."

The eSAIL system is DNV type-approved and can be installed on both newbuildings and existing vessels. bound4blue said installations can be completed in under a day, where scheduling allows.

The Maersk Tankers project follows earlier eSAIL deployments with shipowners including Louis Dreyfus Company, Eastern Pacific Shipping, Odfjell, Klaveness Combination Carriers and BW Epic Kosan.

Founded in 2014, bound4blue is headquartered in Cantabria, Spain, with offices in Barcelona and Singapore. Since completing its first installation in 2021, the company has deployed its eSAIL system on eight ships, with 11 more in its order book, representing more than 50 eSAILs.