A white paper published by DNV highlights that wind-assisted propulsion systems (WAPS) could play an important role in helping shipowners meet current and upcoming GHG regulations, and describes the technology as an ‘enabler’ for the transition to new fuels.
The report asserts that WAPS, such as rotor, suction, wing and soft sails and kites, ‘can be a cost-effective means’ of meeting current EEDI, EEXI and CII requirements, set by the International Maritime Organization (IMO), as well as the EU’s new Emissions Trading System (EU ETS) and FuelEU Maritime regulations.
With shipowners, operators and technology providers reporting annual fuel savings between 5% and 20%, Hasso Hoffmeister, Senior Principal Engineer at DNV and lead author of the white paper, believes that the potential of wind propulsion as a means to comply with IMO and EU regulation is ‘definitely worth exploring’.
The classification society ran simulations on two model ships: a 3,600 DTW general cargo ship operated only in Europe; and a 81,000 DWT deep-sea Kamsarmax bulk carrier operated in EU waters 20% of the time. The exercise found that the use of a WAPS would reduce annual costs for the years 2026 to 2044 in both cases, as a result of lower fuel consumption, as well as EU ETS and FuelEU compliance costs.
Each theoretical vessel was ‘virtually equipped’ with three different types of installations, testing different numbers of suction, rotor or wing sails, Hoffmeister explained. AIS data was used to determine operational modes, and wind speeds and direction were retrieved from historical weather databases.
The reduction in annual expenses ranged between 4% and 12% for the short-sea vessel and 1% to 11% for the deep-sea ship, compared to the same vessels without wind propulsion systems. These calculations encompassed the WAPS specific capital and operational expenditures, as well as fuel costs and EU ETS costs.
However, Hoffmeister emphasised that while the simulations are precise for the specific ships modelled, the results might be different for other vessels. This is because there are wide variations in the fuel savings delivered by wind-assisted propulsion depending on the system selected, the ship’s type and service speed, and the routes where it is operated, he underscored.
‘The savings are probably in the range between low single digits and maybe up to 20% in some cases,’ he explained. ‘It’s very much depending on a lot of input parameters.’
The business case for wind propulsion
Hoffmeister expects the upcoming IMO regulations on a global pricing mechanism for shipping’s GHG emissions, which are currently under discussion and may enter into force from 2027, to further boost the economic case for wind propulsion.
‘We do see a return on investment that is not excessively long,’ he said. ‘The outlook to the future, with the tightening regulations and perhaps also rising and uncertain oil prices and sourcing of these products, may be giving us even more restrictions or even a higher cost if you look at the alternatives.’
A key advantage of wind technology compared to new fuels, Hoffmeister highlighted, is the predictability of costs related to purchasing the system, its installation and maintenance. ‘It is quite a high capex, but I think one of the attractive characteristics of wind propulsion is the fact that the capex is known,’ he said.
He further noted that operational costs are relatively well-established and stable, unlike alternative fuels, where future costs over one, five or ten years remain uncertain. ‘The wide range of fuel options adds an additional challenge, as availability cannot always be guaranteed,’ he added.
The report also found that wind propulsion systems ‘could play a central role’ in the transition to alternative fuels. ‘As low GHG intensity fuels are more costly than traditional fuels, reducing fuel consumption becomes vital for improving the business case for these fuels,’ the authors stated.
Accelerated uptake
The white paper reports a rapid uptake of wind propulsion systems in the global fleet since 2021, with 52 wind-equipped seagoing vessels now in operation and 97 more newbuilds in the orderbooks as of January 2025. More than half of those vessels are tankers or general cargo ships.
‘We are at a stage where the industry realises that [wind propulsion] might be a feasible option, because it has proven to work,’ Hoffmeister commented. ‘It has proven to deliver savings.’
DNV expects the uptake to accelerate rapidly in response to new international and regional regulations, and the use of more expensive low-carbon fuels.
But the report also calls for a standardised methodology for measuring the fuel savings achieved by wind propulsion systems.
‘In the last years, it was more about the trust being gained from the stakeholders in getting these systems in operation at all. Can they operate reliably? Is it practical to have something like that, or is that putting hurdles on operations?’ Hoffmeister illustrated.
‘Now that people see that it seems a workable solution, they take the next step and ask, “what are the savings that can be achieved?” And that is a very simple question, but the answer can be very difficult to give, because people might have different perceptions of what they mean with the term fuel savings.’
The report emphasises that standards for short- and long-term verification will be key to reduce bias and ensure fair competition.
The full white paper is available to download here.
Photo: Hasso Hoffmeister, Senior Principal Engineer at DNV and lead author of the white paper (credit: DNV)