White paper Wind-Assisted Propulsion Systems (WAPS)

How wind support can help comply with greenhouse gas regulations is outlined in a new report by classification society DNV. DNV’s maritime experts are positive and responding with their offerings.

Wind-assisted propulsion has already delivered annual fuel savings of 5% to 20% for some ships, according to shipowners, operators and technology manufacturers, resulting in a reduction in greenhouse gas emissions in the same proportion. Greater adoption of WAPS by larger cargo ships in the deep-sea segment, which account for about 80% of global shipping emissions, would contribute significantly to meeting IMO’s greenhouse gas reduction targets. […]

Introduction of WAPS in the current fleet

Since 2021, WAPS has been rapidly introduced in the global fleet, with 52 ocean-going vessels in operation and 97 newbuildings with WAPS in the order book (as of January 2025). This includes a wide range of ship types, with bulk carriers, tankers and general cargo ships as the main ship types. Industry developments in recent years have shown that the installation of WAPS is not limited to certain ships or ship types.

Retrofit is always possible

Retrofitting WAPS is technically possible on almost any ship that offers sufficient deck space and unobstructed airflow, even if the ship was not originally designed to accommodate sails (currently, 75% of the WAPS fleet are retrofits). This adaptability allows implementation of WAPS on a wide range of existing ships and ship types. Advancing wind-assisted propulsion WAPS technologies hold great promise as a vital element in hybrid propulsion systems and is a source of propulsion with predictable capital investment and lifetime operating costs.

Modern technology

Modern wind-assisted propulsion systems are built on state-of-the-art technology, with advances in aerodynamics, automation, computer modelling and modern materials. These systems use advanced controls and automation to improve efficiency and operational effectiveness. By reducing fuel consumption, WAPS reduce not only operational costs, but also greenhouse gas and other emissions.

Different operating principles

Although based on the same physical principles, the available WAPS technologies differ in their operating principles and performance-related characteristics. The choice of WAPS technology for a specific vessel is influenced by factors such as the vessel’s average speed, operational route and weather conditions, as well as practical considerations such as available deck space and alignment with cargo operations. […]
Because performance is influenced by many factors, including the hull and structure of the ship, the machinery, the wind environment and the WAPS technology itself, building stakeholder confidence in the performance of wind propulsion systems requires rigorous, standardised verification methods for both short-term and long-term assessments. […]

Emissions trading

From 2024, the EU extended the EU Emissions Trading Scheme (EU ETS) to ships over 5,000 GT carrying cargo or passengers in the EU/EEA, requiring shipping companies to buy and surrender emission allowances for carbon dioxide (CO2) emissions from tank to wak. From 1 January 2025, ships over 5,000 GT carrying cargo or passengers in the EU/EEA must also comply with the FuelEU Maritime Regulation, which sets requirements for greenhouse gas emission intensity for energy used on board. This regulation provides an additional incentive for installing WAPS, as the regulation’s greenhouse gas intensity calculation includes a reward factor of 1%, 3% or 5% for ships equipped with WAPS.

Results of case studies from the EU

Case studies focusing on the impact of EU regulations show that wind-assisted propulsion systems on both coastal and deep-sea vessels can reduce the costs of fuel, EU ETS and FuelEU compliance. In the case of coastal shipping, compared to the base case with coastal shipping without WAPS, annual costs are reduced by about 4% for case 1 (1× suction or rotor sail) in the years 2026-2044, about 8% for case 2 (2× suction or rotor sail) and about 12% for case 3 (3× suction or rotor sail). As the coastal vessel operates full-time in EU waters, the economic benefits of installing WAPS compared to the basic vessels without WAPS are greater than for a vessel operating internationally and for a shorter period in EU waters. […]

Better compliance with regulations

The use of WAPS on ships will help ship owners comply with regulations through lower fuel consumption, and the new regulations may also reward the GHG intensity of ships with WAPS. […] The economic benefits of installing WAPS are expected to increase when the new IMO regulations come into force in 2027. A life cycle analysis that calculates the total cost of ownership is crucial to understand the long-term financial viability of the investment. A holistic evaluation of the cost factors allows ship owners and operators to make informed decisions on the adoption of wind-assisted propulsion, balancing initial costs against long-term operational benefits and meeting regulatory requirements for greenhouse gas emissions.

Taking steps to be ready for WAPS

If WAPS are installed at a later stage, ship owners can prepare the ship and its design for WAPS in the future. This may be relevant if no WAPS is available at the time of construction or at the new construction site. […]
WAPS is one of many possible solutions for decarbonising ships that can be combined with any propulsion system powered by low GHG-intensity fuel or batteries. For ships already in operation and newbuildings, WAPS should be considered as a regulatory compliance and cost-saving option.

Source: Red over Green and DNV’s website.
The full report can be found here.

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