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Critical elements for a successful WAPS business case
New white paper guides through complex WAPS landscape
A new DNV white paper assists shipowners and other stakeholders in understanding the complex wind-assisted propulsion system (WAPS) landscape. It offers crucial guidance and considerations to help determine the most suitable WAPS business case for specific operational and decarbonization needs.
The power of wind
“Wind is an inexhaustible direct source of energy at no cost. So it’s no wonder WAPS look attractive to shipowners who are seeking ways to meet new regulations which are putting a price on emissions and mandating the use of costlier low GHG intensity fuels,” says Hasso Hoffmeister, Senior Principal Engineer / Hull – Passenger & Ro-Ro Ships & Load Line at DNV, and lead author of the paper.
Orderbook shows renewed interest in WAPS technologies
The new paper quantifies WAPS uptake in the global fleet since 2021 across many vessel types but with bulk, tank and general cargo as the main segments. According to Clarksons, the uptake by newbuild is increasing significantly in 2025, and there are already high numbers in the newbuild orderbook for 2026 and 2027. WAPS can be retrofitted on almost any ship with enough deck space and unobstructed airflow. “However, newbuilds offer better optimization by integrating WAPS from the start,” explains Hoffmeister.
Modern WAPS come with innovative new technologies for smarter and more efficient operations
New WAPS technologies include rotor sails, suction sails, wing sails, soft sails, and kites, providing cost-effective and renewable energy solutions. Most modern systems now utilize state-of-the-art intelligent control and automation systems to operate safely and without requiring additional crew. Predictable investment and operational costs enhance their attractiveness as a hybrid propulsion solution.
Assessing the technical feasibility of WAPS systems
When assessing the feasibility of a specific WAPS installation, it is important to identify the design and operational challenges that must be addressed for successful implementation. The characteristics of a specific project highly affect the considerations an owner or operator must address in a feasibility assessment. Assessing feasibility helps bridge the gap between concept and practical execution. The paper provides a detailed overview of the relevant characteristics for a project. For newbuilds, purpose-built hull designs and enhancement of aerodynamics, integrating systems more seamlessly and aligning structural features to fully harness the power of the wind can unlock the full potential of this sustainable propulsion technology.
Possible steps to enhance power-saving potential of WAPS
According to shipowners, operators and technology providers, WAPS have demonstrated fuel savings of 5%–20% annually, translating into proportional reductions in GHG emissions. Under favorable operational conditions, the potential is large, and DNV has verified WAPS reaching peak values of about 30% reduced energy consumption per nautical mile (Kamsarmax B/C Pyxis Ocean). The table shows estimated thrust equivalent power output of WAPS and power savings based on simplified calculations for different ship types. Potential savings depend on multiple factors such as sail area to displacement ratio, wind speed and direction on the route, and vessel speed. An effective ship design may further enhance the overall efficiency of WAPS.
WAPS can help shipowners to comply with IMO and EU regulations
The paper explains how WAPS can help ships meet the Energy Efficiency Design Index (EEDI), Energy Efficiency Existing Ship Index (EEXI) and Carbon Intensity Indicator (CII) carbon dioxide emission requirements by reducing fuel consumption, thus improving vessels’ ratings and compliance. If fitted or retrofitted with WAPS, FuelEU Maritime entitles ships to a “wind reward factor”, reducing the overall GHG intensity of the energy used. Two new DNV case studies in the paper demonstrate how WAPS can help to comply with FuelEU Maritime and EU ETS and can reduce overall annual expenses compared to a non-WAPS equipped vessel.
Case vessels – design and operational assumptions
The two cases present two typically different trades; the short-sea case utilizes a generic general cargo ship of 3,600 DWT, operating purely in European waters and the deep-sea case utilizes a generic Kamsarmax bulk carrier operating on worldwide trades with around 20% of the time in European waters. Real case AIS data from the years 2023/24 has been evaluated to determine the operational modes (time underway at sea, at anchor and moored) and the operational speed profile of both vessels. The wind speed and direction along the routes have been retrieved from historic hindcast weather databases.
Case study results show that WAPS can reduce overall annual expenses
In each case, we examine the reduction in annual expenses for the case vessel with three different WAPS installations compared to the case vessel without WAPS. The annual expense components included in the case studies are the WAPS specific capital and operational expenditures, as well as fuel cost and EU ETS cost. All modelled case configurations obtain a lower annual cost in the years 2026 to 2044 compared to the baseline vessel without WAPS as a result of lower fuel and EU ETS costs. In both cases one modelled installation also generates FuelEU Maritime surplus that could be a potential indirect revenue source in a FuelEU compliance pool or banked as a surplus to offset future GHG intensity compliance deficits. Upcoming IMO regulations in 2027 are expected to further increase the economic benefits of WAPS, especially for the deep-sea case.
Recommendations for shipowners and operators
The paper includes a set of recommendations for shipowners and operators. “The key message is that it makes sense for suitable ships in operation and newbuilds to consider WAPS as an option for regulatory compliance and cost savings,” says Hoffmeister. To identify design and operational challenges to successful WAPS implementation, the decision-making process starts by assessing the technical feasibility early on in the planning stage. Making the business case includes verifying the short- and long-term fuel-saving performance of WAPS at full-scale to provide confidence in achieved savings. Where short-term verification gives information on WAPS performance in certain conditions, long-term performance is affected by diverse conditions across the ship’s full operational and environmental range.
How DNV can support
DNV supports clients with taking WAPS technology from a concept to mainstream use – applying our technical standards and relevant services to provide guidance on compliance with regulatory requirements. The DNV rules and standards provide a framework for the verification and certification of wind-assisted propulsion systems and their onboard integration, whether retrofitted or as part of a newbuild. Our class-independent advisory experts offer a wide range of services to assist the industry in various aspects of the decision making leading up to a WAPS installation and, furthermore, support during operation with, for instance, performance assessments. DNV Recommended Practice DNV-RP-0686 “Performance of wind assisted propulsion systems” is expected to be published in the second quarter of 2025. It aims to set a standard on how to measure, evaluate and verify the power saving of WAPS from long-term in-service measurements by so-called on-off tests.
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