LR confirms performance of Anemoi rotor sails after 167 on-off tests on Kamsarmax bulker

May 20, 2025, by Naida Hakirevic Prevljak

Classification society Lloyd’s Register has verified the performance of Anemoi Marine Technologies’ rotor sails on a Kamsarmax bulker, confirming the latter’s method for calculating rotor sail technology performance.

In a statement of fact, Lloyd’s Register Advisory confirmed the methodology Anemoi used for calculating fuel and emissions savings from the three 24-meter-high rotor sails installed on TR Lady – the 82,000 dwt bulk carrier owned in funds managed by Tufton and chartered by Cargill.

As explained, the extensive dataset establishes “a reliable and repeatable benchmark” for wind-assisted propulsion performance under a broad range of real-world conditions.

During the testing period, TR Lady sailed the Indian Ocean, South Atlantic, North and South Pacific, Southern Ocean and rounded both the Cape of Good Hope and Cape Horn, along with some of the busiest shipping routes, including the Strait of Malacca. Data from eight consecutive laden and ballast legs were analysed to provide a long-term average of the fuel and emissions savings.

A chart below shows five of the 167 on-off tests performed on the TR Lady. The graph clearly demonstrates that when rotor sails are switched on, the vessel’s SOG increases and the main engine power usage is reduced.

The average net savings across this period calculated from the verified performance model were 1.9 tonnes of fuel per day and 7 tonnes of CO2 per day (well-to-wake). This equates to an average of 9.1% net propulsion fuel and emissions savings.

The achieved average savings are said to align closely with Anemoi’s predicted 10% savings. Additionally, since TR Lady does not follow a fixed route, the results varied from voyage to voyage depending on the route taken and the wind conditions encountered. For example, on a 22-day voyage across the North Pacific, average route savings of 21% net propulsion fuel reduction were calculated from the verified performance model. That said, it is especially important for Anemoi to share the full, transparent picture in the first instance, rather than focusing solely on one particularly favourable route, to provide a more relevant measure of long-term performance.

Lloyd’s Register Advisory confirmed that the findings of this study validate Anemoi’s approach as a reliable method for calculating rotor sail performance. The statement of fact concluded that “there is close agreement between the predicted thrust coefficient trends and the measured values”.

“We have independently verified Anemoi’s methodology to calculate thrust power and predict fuel consumption, confirming its accuracy when ship-specific coefficients are correctly applied and kept up to date. Our assessment, drawing on high-frequency operational data and CFD analyses for rotor sail-equipped vessels, highlights the value of detailed, vessel-specific modelling,” Dogan Uzun, Ship Performance Consultant at Lloyd’s Register Advisory and project manager of the assessment, commented.

“The findings show that wind-assisted propulsion, when supported by robust data and transparent methods, can significantly reduce uncertainty and contribute meaningfully to emissions reduction in commercial shipping.”

TR Lady was installed in June 2023 with three Anemoi rotor sails, 5 meters in diameter and 24 meters in height – a shorter height and a lower aspect ratio compared to Anemoi’s standard products to suit air draft requirements.

Anemoi has also confirmed that testing is currently underway on several vessel installations featuring its larger rotor sails, measuring 35 meters in height, which, thanks to their higher aspect ratios, are expected to achieve even higher performance results.

Clare Urmston, CEO of Anemoi Marine Technologies, emphasized that the verification underpins the company’s commitment to setting a new standard as emerging technologies like wind propulsion pave the way in clean maritime innovation.

“Verifying the performance of Rotor Sails has been a key objective of this project for Tufton. The latest fuel consumption calculations, following the methodology independently verified by Lloyd’s Register Advisory, closely match our original expectations. We are excited by the results, which not only confirm the technology’s effectiveness but also the strong operational and environmental benefits we anticipated,” Nicolas Tirogalas, Chief Investment Officer and President of Tufton, said.

“Building up an accurate understanding of the real-world, on-ship performance of technologies is a key piece in the wind assist propulsion puzzle. By combining the data from more than 167 rotor on/off tests that were conducted by the TR Lady, together with the independent verification from LR, Anemoi installed confidence in the accuracy of their analysis. We have already used the results of this study to fine-tune our weather routing digital twins for TR Lady; and it will also help inform future decisions on deploying wind assist across our fleet,” Chris Hughes, Decarbonisation Specialist of Cargill, noted.

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In related news, Anemoi recently launched a collaboration with Hafnia, Guangzhou Shipyard International (GSI) and DNV to develop the integration design of rotor sails suitable for installation on 50,000 dwt medium-range (MR) tankers.

The companies also signed a joint development project (JDP) to develop a new generation of environmentally friendly rotor sail vessel designs to increase the efficiency of MR tankers within the wider global fleet.