Wind propulsion needs to be integrated into the regulatory process as soon as possible, and declassified from a ‘fuel efficiency measure’ to a ‘propulsive power provider’, according to a recently submitted paper by several member states and the International Windship Association (IWSA).

The document was submitted to the International Maritime Organisation’s (IMO) Marine Environment Protection Committee ahead of its 79th session and the upcoming revision of the Initial IMO Strategy on Reduction of GHG Emissions from Ships as well as the entrance into force of the EEXI and CII in 2023.

The general message of the submission underlies that the potential of wind power technology has been underrated in the reduction of greenhouse gas emissions from ships, especially with regard to the potential of optimizing newbuilding designs and combining the technology with optimisation factors such as weather routing and speed variation to achieve greater efficiency gains.

“Wind propulsion bypasses all energy conversion complexities and, using the wind energy source directly, and mechanically converted to propulsion, presents an efficient energy option, compatible with all other energy sources selected,” the document reads.

The case for wind is being made as the discussion on the decarbonization of the shipping industry continues to center around alternative zero-emission fuels. The production and availability of the so-called e-fuels have become a serious bone of contention having in mind that scaling up the production might take at least one decade, if not longer. What is more, there is also a debate surrounding the huge amount of renewable energy that would be needed for the production of these fuels and whether it should be channeled into the sector in the first place if it could be used more efficiently in decarbonizing other industries.

In practice, wind propulsion technology alone can deliver around 22.3% reduction in carbon intensity when combined with speed reduction measures. However, this figure can reach up to 70% with in voyage optimisation, increasing voyage time by 50%, weather routing, and speed reduction measures, IWSA said citing a voyage optimization with wind-assisted ship propulsion study.

There are seven categories of wind propulsion technologies: rotor sails, kites, hard or rigid sails, soft sails, suction wings, turbines and hull forms. Each of these systems has varied properties and adaptations that can make them suitable to all ship types or selected fleet segments.

Some of the key benefits of wind propulsion technology include the fact that as a direct propulsive energy source it can be used as a partial or main propulsion system. It requires no conversion thus avoiding power loss of up to 90% for alternative fuels based on a well-to-wake calculation. The cost of direct wind energy is zero and tax-free for the lifetime of the ship without competition for supply as wind is abundant and freely available worldwide.

The wind is, however, intermittent and irregular and this variability is route specific with some routes having more wind resources than others. Nevertheless, its predictability can be determined with modern forecasting technologies such as onboard weather stations/sensors, LiDAR etc.

Retrofits with wind-assisted propulsion technology can deliver 5-20% of the propulsive energy requirement depending on motor ship profiles with the potential to optimise these operationally up to 30%. For newbuilds, this can reach 50%+ of propulsive energy requirement (potential for 100%), especially when using wind optimisation techniques.