Op-ed: The digital age of sails

The following article is an op-ed piece authored by Ossi Mettälä, Product Manager for Shipping Solutions, NAPA, who explains that voyage optimization and weather routing are equally important as sails for wind-assisted ships to make a meaningful contribution to the decarbonization of the shipping industry.

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Sails and wind have gone hand in hand for centuries but today, digital technologies are rewriting the playbook. In shipping’s modern age, harnessing wind power is as much about adopting solutions like weather routing and voyage optimisation as it is about the physical wind-assisted propulsion system (WAPS) itself.

From kites to wings and sails, WAPS are gaining in popularity and the International Windship Association estimates that 10-15% of the global fleet will be equipped with wind propulsion systems in 2030. Each new technology brings its own unique criteria and limits on the wind speeds and angles best suited to safely and optimally operate the vessel. This greater emphasis and reliance on wind conditions marks a step change in how ships are operated.

Weather routing and voyage optimisation are able to achieve this granularity in evaluating different routes and speed profiles to make the most of wind patterns, waves and currents. The software assesses (and re-assesses) constantly evolving conditions at sea and calculates the impact of each potential route on the vessel’s fuel consumption, greenhouse gas emissions, safety and stability. These insights can allow crews to take a proactive approach to maximising fuel and emissions savings.

Installing wind propulsion systems without embracing these digital technologies is effectively leaving a lot of potential savings on the table, which is not a viable option at a time of tightening decarbonisation targets.

From the International Maritime Organization’s Carbon Intensity Indicator (CII) to the European Union’s Emissions Trading System (EU ETS) and the upcoming FuelEU Maritime, the industry is under increasing pressure to minimise its carbon emissions and improve its fuel efficiency. WAPS are designed to help the industry meet its decarbonisation targets but, like any new product, installing them is only the first step; understanding how to effectively use them, and ‘hack’ their true potential to gain the maximum savings, is the next step.

This is where digital technologies step in. Recent studies modelling the savings potential of combining weather routing with WAPS demonstrate the untapped potential of these solutions together. A joint simulation project between NAPA, Norsepower and Sumitomo Heavy Industries found that combining WAPS with voyage optimisation can achieve emissions reductions of up to 28% on average on transatlantic journeys between New York and Amsterdam – with the contribution of voyage optimisation estimated at 12%.

Another study in 2023 by the University of Manchester revealed that voyage optimisation can turn some routes from unfavourable to favourable for wind propulsion technology by altering apparent detrimental wind angles. The modelling shows that routes with strong headwinds can still represent good candidates for wind propulsion if combined with weather routing, allowing vessels to catch winds within the range of angles that are suitable for the WAPS. This significantly increases the benefits of WAPS on some routes that would have relatively low savings with rotor sails alone – boosting savings from 7.79% to 19.3% on a route between the UK and the US, for example. This is because, fundamentally, weather routing allows ships to adjust their course to alter detrimental wind angles, a finding that was also validated by recent NAPA simulations.

Given the high CAPEX associated with wind propulsion systems, studies like these strengthen the business case for investing in WAPS by providing greater clarity on tangible fuel savings on the specific route the ship will be operated and the payback period.

Any new technology introduced onboard needs to be evaluated for its impact on vessel stability and safety under all conditions. WAPS are no different.

The heel induced by the WAPS, as well as the added wave resistance and impact of sea currents, can all affect a vessel’s stability. Furthermore, WAPS typically add weight to the upper part of a ship, which also impacts its stability profile.

Digital technologies, such as advanced stability software and electronic logbooks, act as key tools to ensure safety at sea. They can support voyage planning not only by accounting for the higher centre of gravity, but also by validating that other stability criteria that are specific to wind-assisted ships are met. This can include maximum heeling movement from the sail, and the ship’s safety for the levels of beam wind given the wind speed throughout the journey, for example.

All this data is not just reserved for when a WAPS is at sea; digital technologies are informing investments in WAPS as early as the concept and design stage, with the use of 3D models and simulation tools. This enables naval architects and engineers to model the impact of wind propulsion on the ship’s structure, stability, configuration and potential loss of cargo space, providing key insights that help them optimise concepts, both for newbuilds and retrofitting projects.

From considerations around port calls to crew training, maintenance and tonnage, digital simulation tools are removing the guesswork from investing in shipping’s green transition. With a growing number of technologies reaching maturity, decisions around the use of wind propulsion must be grounded in data and based on a holistic approach. This will help teams proactively assess how these systems will impact a wide range of considerations, from vessel designs to operational parameters and safety onboard.

Digital technologies are redefining our understanding of wind-assisted propulsion systems and allowing us to tap into their true potential. Data, simulations and 3D modelling are all important tools to understand how environmental, operational and stability factors impact the performance of WAPS, allowing crews to use this insight to their advantage to minimise emissions, fuel consumption and improve safety. The way forward couldn’t be clearer. To propel the industry towards decarbonisation, we really need both data and wind behind our sails.

• Norsepower, NAPA team up to reap wind propulsion benefits using voyage optimisation 
• NAPA joins International Windship Association
• NAPA rolls out new CII simulation tool to fast-track energy-efficiency measures
• Opinion: Can wind propulsion weather the approaching perfect storm?
• Wind measurements key to improving wind-assisted propulsion