Spanish maritime startup bound4blue on Monday declared that it had fitted four eSail units on the Trieste (IMO: 9708617), a medium-sized vessel from Maersk Tankers, in what is its largest order till date.
This is part of a five-vessel contract inked in December 2024 for 20 eSail units—four per ship, with each measuring 24m in height.
The turnkey suction sails, which are large, mast-like structures installed on the deck of the ships, utilise the company's flagship wind-assisted propulsion system (WAPS) to cut down emissions, improve fuel efficiency, and boost ships' Carbon Intensity Indicator (CII) ratings.
The use of suction sails can also unlock regulatory and cost benefits under frameworks such as FuelEU Maritime (via the Wind Reward Factor) and the EEDI/EEXI.
bound4blue’s autonomous eSAILs work by drawing air across an aerodynamically optimised surface to generate lift—said to be up to seven times more than that generated by conventional rigid sails of a comparable size.
They are also capable of adjusting to prevailing wind conditions to ensure optimal performance, are tailored to the needs of individual vessels, and can either be retrofitted (fitted onto existing ships) or built into a vessel during its construction.
“Our system was designed from day one to deliver maximum performance with minimum complexity,” explained José Miguel Bermudez, CEO and Founder of bound4blue.
“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," he added.
The deal with Maersk Tankers is the latest in the Spanish startup's growing portfolio, with 18 eSails already fitted across 7 vessels, and 36 more to be fitted for 12 vessels.
The company is also working to optimise not just its own WAPS technology, but also the efficiency of the eSail installation process (by minimising downtime) for both newbuild and retrofit projects.
This is said to be a major push towards making sustainable wind propulsion systems a core part of mainstream maritime decarbonisation strategies.
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