Rotor Sails: The Compelling Decarbonization Solution

Global supplier of wind propulsion, Anemoi Marine, believes Rotor Sails - which are unique, tall cylindrical sails that can be installed on the deck of commercial vessels - offer an immediate and compelling solution for shipowners working to reduce vessel emissions.

Anemoi estimates that a VLCC with six Rotor Sails would reduce fuel and emissions by approximately 14.9% (c.1,889 tonnes fuel and c.6,058 tonnes of carbon) per year, based on a Bonny-Ningbo round trip.

When considering fuel savings for bulk carriers, Anemoi’s research suggests a VLOC fitted with six Rotor Sails could achieve an annual 15.5% fuel and emission reduction based on a Qingdao-Tubarao round trip. This equates to c.1,437 tonnes of fuel and c.4,607 tonnes of carbon per year.
The International Maritime Organization (IMO) wants considerable cuts in ship emissions as part of its 2030 and 2050 targets. The goal is to reduce Greenhouse Gas (GHG) emissions from vessels by at least 40% before the end of this decade and by at least 50% by 2050 (compared with 2008 baseline figures). The long-term target is full decarbonisation, although this will likely require a range of solutions.

The Energy Efficiency Design Index (EEDI) is already in place and has been created to ensure newbuild vessels meet requisite levels of efficiency. The Energy Efficiency Existing Ship Index (EEXI) is due to come into force by January 2023. Carbon Intensity Indicators (CII) are also on the cards. These measures mean shipowners already have to carefully weigh up the options available to achieve compliance. Debate still surrounds the realistic timeline, availability and eco nature of alternative fuels.

As a result, many shipowners are ready to take the plunge and invest in future proof technologies. Installing wind technologies as retrofit or newbuild could be the ideal answer for the maritime community, particularly as using Rotor Sails would lower the consumption and cost of expensive clean fuels.  

Photo courtesy Anemoi

Simplicity in mind

Installing Anemoi technology can be a straightforward process because wholesale changes to the vessel structure, or dry docking, is not necessary. Rotor Sails and all associated equipment are delivered to the dockside, ready for installation. Our specialist and highly trained team then supervise the full equipment installation. Each Rotor is installed in a single crane lift and connected to the foundation on the ship’s deck once the vessel integration work is complete.

Prior to this taking place, a feasibility study - which is unique to each vessel - will have been conducted to determine the optimal Rotor Sail positioning. This is to maximise performance within the vessel constraints and the required Deployment System for the vessel.

The vessel integration stage is crucial to the process and we constantly support clients at every stage, including the design and installation of the structural foundations and the electrical cabling from the vessel main switchboard to each Rotor Sail. The vessel integration can be completed during the construction phase of a newbuild vessel, or during a survey at a shipyard for a retrofit vessel. Once the Rotor Sails are installed and all cables are connected, we complete final commissioning of the system prior to handover. This crucial stage ensures safe operation and compliance with Class requirements through rigorous testing.

Ease of use and monitoring

The Anemoi Rotor Sail System is comprised of the Rotor Sail itself, the Foundation, Deployment System (if required), wind sensors and Electrical, Control, and Automation systems. The main components of our Rotor Sails are the “Rotor” (the cylindrical, rotating part), the support Tower, upper and lower bearings, and the electrical drive system.

The Rotor is built from advanced lightweight composite material and the Tower is a steel column structure. We use these materials to ensure maximum performance of our Rotor Sails and to withstand all weather conditions.

The Rotor Sails have a control station located on the bridge. This automatically controls the speed and direction of the Rotor Sails, as well as monitoring the performance and status of the system. Our control system is designed to maximise performance and minimise crew input with automated speed and direction setting, equipment monitoring, safety features and performance reporting to stakeholders using a ship to shore data transmission.

Technology reimagined

Rotor Sails were first fitted to a vessel over 100 years ago. They make use of the aerodynamic phenomenon known as the ‘Magnus Effect’. As the cylinder rotates within an airflow, a forward thrust force perpendicular to the apparent wind direction is created, which delivers additional thrust to the vessel. The thrust generated can either provide additional vessel speed or maintain vessel speed by reducing power from the main engine.
But with sustainability now a key focus for the entire maritime community, Anemoi has successfully reimagined the concept as a modern-day solution that can help facilitate the push towards industry-wide decarbonisation.

The Author: Nick Contopoulos, COO, Anemoi. Photo courtesy Anemoi