Spanish wind-propulsion pioneer bound4blue has secured a DNV Type Approval Design Certificate for its high-capacity Model 3-24 eSAIL®, validating its largest and most powerful installed suction sail system to date. First deployed on Klaveness Combination Carriers’ MV Baltazar, this independent class certification provides shipowners with a risk-mitigated, future-ready solution to lower fuel burn and manage compliance under tightening EU ETS and FuelEU Maritime regulations.
Barcelona | June 9, 2026 – In a major boost for the commercial viability of Wind-Assisted Propulsion Systems (WAPS), Spanish wind-propulsion pioneer bound4blue has secured a Type Approval Design Certificate (TADC) from classification society DNV for its new Model 3-24 eSAIL®.
The certification, formally handed over at the Posidonia exhibition in Athens, marks a critical milestone for bound4blue’s largest and most powerful installed suction sail to date. The structural and aerodynamic validation establishes a clear pathway for shipowners looking to deploy high-capacity wind propulsion to mitigate rising compliance costs under EU ETS and FuelEU Maritime frameworks.
Scale and Deployment: The Model 3 Platform
The Model 3 range represents bound4blue’s shift toward larger tonnage, offering suction sails ranging from 24 meters to 36 meters in height. The newly certified Model 3-24 features an expanded chord length and optimized aerodynamic surface area compared to the company’s established Model 2 platform, designed specifically to generate higher lift coefficients without adding prohibitive mechanical complexity.
The commercial debut of the Model 3-24 occurred in April 2026, when two units were retrofitted onto the Klaveness Combination Carriers (KCC) newbuild, the DNV-classed CABUIII combination carrier MV Baltazar.
- Airflow Capture & Intake
- Boundary Layer Airflow: Bound-layer drag and surface air are continuously captured from the sail’s aerodynamic boundary.
- Suction Fan: Power-driven internal micro-fans generate active negative pressure to draw the boundary layer airflow inward.
- Internal Distribution
- Internal Ducting: The captured airflow is channeled through integrated, low-friction internal routing lines directly into the core matrix.
- Performance Optimization & Outputs
- [eSAIL®] Core System: The localized mass-balance accounting of the airflow matrix processes the boundary layer dynamics to yield dual aerodynamic benefits:
- Aerodynamic Lift Force: Re-establishes laminar flow over the sail surface, multiplying total aerodynamic thrust.
- Reduced Engine Load: Offsets mechanical propulsion requirements, yielding immediate fuel savings and lower carbon intensity.
- [eSAIL®] Core System: The localized mass-balance accounting of the airflow matrix processes the boundary layer dynamics to yield dual aerodynamic benefits:
How Suction Sail Technology Generates Propulsive Force:
Unlike traditional rigid wings, the eSAIL® utilizes boundary layer suction technology. A heavy-duty internal fan draws in the boundary layer of air across the sail’s trailing edge, preventing airflow separation. This aerodynamic control allows the cylindrical sail to generate up to seven times more lift than a conventional airplane wing, delivering substantial forward thrust to relieve the main engine load.
Compliance and Fleet Performance Metrics
As the maritime sector faces tightening regional and global decarbonization penalties, the financial business case for WAPS has evolved from experimental efficiency to regulatory defense. bound4blue’s autonomous system feeds directly into multiple compliance metrics:
- EEXI & CII: Immediate reduction in fuel consumption improves a vessel’s attained Energy Efficiency Existing Ship Index (EEXI) and protects Carbon Intensity Indicator (CII) ratings from annual tightening curves.
- EU ETS & FuelEU Maritime: By lowering overall fuel burn, the technology reduces a fleet’s exposure to carbon allowance purchasing and compliance penalties associated with energy well-to-wake intensity.
- Fuel Agnostics: The system operates independently of the main engine, meaning the fuel savings scale commercially if a vessel switches to expensive future fuels like green methanol or ammonia.
Industry Validation: Bridging the Confidence Gap
For shipowners, charterers, and marine underwriters, the lack of standardized technical data has historically been a barrier to widespread wind retrofit adoption. Independent class validation aims to bridge that gap.
José Miguel Bermúdez, CEO and co-founder of bound4blue, noted during the handover:
“Independent validation from a leading classification society like DNV confirms that the technology meets relevant standards for reliability and performance. Such class developments are essential for accelerating uptake across the industry. They reduce uncertainty, support acceptance by regulators, insurers and charterers, and give shipowners the basis they need to invest in proven, future-ready solutions.”
Cristina Saenz de Santa Maria, CEO of DNV Maritime, highlighted that the industry is entering a mature phase of alternative propulsion deployment:
“We’re now beginning to see the next generation of WAPS units. One of the key enablers of these developments is the parallel evolution of technical standards, which have been a vital part of building acceptance in the market. This means working closely with technology providers to assess new solutions against independent technical standards.“
Technical Overview: bound4blue eSAIL® Product Portfolio
The Model 3-24 approval solidifies bound4blue’s position in a competitive wind-assist landscape alongside providers like Norsepower and Anemoi. The current eSAIL® lineup scales across various vessel segments:
| Model Series | Height Range | Primary Vessel Targets | Key Features |
| Model 1 | Up to 18 meters | Coasters, Gen Cargo, Fishing Vessels | Compact footprint, plug-and-play installation. |
| Model 2 | 18 – 22 meters | Handysize Bulkbuilt, Medium Range (MR) Tankers | Tilting capability options for cargo gear clearance. |
| Model 3 | 24 – 36 meters | Panamax/Capesize, VLCCs, LNGCs, Large Ro-Ro | Wide chord, boundary layer optimization, high-output lift. |
The Model 3-24’s design avoids complex tilting mechanisms where possible, favoring structural simplicity to keep maintenance overhead low while optimizing the aerodynamic profile for large-deck vessels.
Expanding Orderbook
The DNV Type Approval comes amid a period of rapid commercial scaling for bound4blue. The technology provider has secured high-profile installation contracts with major shipping players, including Maersk Tankers, Eastern Pacific Shipping, Odfjell, Amasus, and the Louis Dreyfus Company.
With validated performance data from the MV Baltazar and a formal DNV Type Approval in hand, bound4blue is well-positioned to convert trial installations into multi-vessel fleet agreements as the industry moves closer to the IMO’s 2030 decarbonization checkpoints.
About bound4blue
Leading the Wind Revolution Founded in 2014, bound4blue is a pioneer in automated wind-assisted propulsion. Its eSAIL® system is a turnkey, low-maintenance solution designed to slash fuel costs and emissions. With headquarters in Cantabria and offices in Barcelona and Singapore, the company has deployed its technology on 11 ships to date, with an order book exceeding 50 eSAILs®.
Source: bound4blue