Wind propulsion can be a long-term solution in the battle to reduce carbon intensity, writes Anemoi mechanical engineer Joe Baker
Everyone in the maritime world is fully aware of the need to comply with IMO’s ambitious greenhouse gas (GHG) reduction targets for 2030 and 2050. IMO is committed to reducing CO2 emissions as an average across international shipping by at least 40% by 2030. This first target needs to be met as a matter of urgency according to IMO and there are already steps in motion to help achieve this.
Newbuildings, for example, must already achieve compliance with the Energy Efficiency Design Index (EEDI). This initiative is designed to ensure newbuildings meet the requisite levels of efficiency. The Energy Efficiency Existing Ship Index (EEXI), meanwhile, will also be with us soon. The EEXI will impact all existing commercial vessels and is currently expected to come into force by January 2023. Once in place, ships already in operation will need to achieve specific energy efficiency requirements, which is intended to follow the EEDI phasing.
For hundreds of years, ships sailed without any fossil fuel-backed propulsion. At Anemoi, a global provider of proven wind technology, we believe the power of the wind can, and is, once again being harnessed as shipping looks towards a more sustainable future. Rotor sails offer an immediate and long-term solution to support decarbonisation. These unique tall, cylindrical sails can be installed on the upper deck of vessels. An electric motor is used to rotate the sails in order to harness the renewable power of the wind and propel the ship.
The ’Magnus Effect’ – named after the German physicist Heinrich Gustav Magnus – is the key to our technology. As the cylinder rotates within an airflow, a force perpendicular to the apparent wind direction is created, which delivers additional forward thrust to the vessel when the wind direction is favourable. The thrust generated can either provide additional vessel speed or maintain vessel speed with reduced power output from the main engine. The obvious benefit from this is less fuel burned and reduced emissions. Depending on the vessel type and trading pattern, Anemoi’s rotor sail technology has the potential to reduce fuel use and associated emissions by as much as 30% – this is no mean feat.
The process of installing Anemoi technology on a ship can be straightforward, as wholesale changes to the vessel structure, or drydocking of the vessel are not required. Rotor sails and all associated equipment are delivered to the dockside, ready for installation. Our highly trained team supervise full equipment installation and each rotor is installed in a single crane lift and connected to the foundation on the ship’s deck. A typical installation of rotor sails can be completed in a day, once the vessel integration work is complete.
Prior to this taking place, a case-by-case feasibility study will have been conducted to determine the optimal rotor sail positioning to maximise performance within the vessel constraints and the required deployment system for the vessel. Key considerations will include cargo operations, available deck space, proximity to existing structures that may affect aerodynamic performance and the structural arrangement of the vessel’s deck for the development of the foundation structure. Safety and regulatory considerations that must also be addressed include compliance checks related to stability, navigation (visibility, navigation lights and radar), helicopter operations and safe access on deck.
The vessel integration stage is key, and we can support clients at every stage, including the design and installation of the structural foundations and the electrical cabling from the vessel’s 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.
Rotor sails are comparatively simple mechanically. They are built to last 25 years and have low maintenance costs. Regular maintenance would ordinarily include periodic visual inspection of components and primary structural items, bearing lubrication replenishment and greasing of mechanical components.
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 lightweight materials used also mean that our systems are typically less than 0.2% of vessel deadweight.
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.
Minimal crew input is required to use Anemoi rotor sails due to the automated control unit. But to ensure the maximum benefit is extracted – and the equipment is well understood – we provide full training for the crew and onshore technical departments. Full lifecycle support, data analysis and periodic reporting is provided as standard and we can provide further training services if necessary.
Typically, a few hours are all crew members need to understand the system and we are very aware that crews change periodically. Crew members are able to confidently hand over to their counterparts once they have been trained.
Beyond 2030 and moving forward to 2050
Rotor sails are designed to complement existing and future technologies. They can reduce the consumption and storage requirements of alternative fuels and compliment air lubrication systems, to name a few. Meeting the challenging IMO targets will necessitate the integration of multiple technologies together. As other eco-technologies, energy-saving devices and future fuels emerge, these can be used in conjunction with auxiliary wind propulsion to achieve enhanced environmental benefits and will help validate the economic case for other new and emerging technologies.
With a design life of 25 years, our rotor sails can also be redeployed between vessels. Decarbonisation will not happen overnight, but rotor sails have a crucial role to play as shipowners and operators look for innovative solutions to help them meet compliance targets.
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