Wind-assisted propulsion company Anemoi Marine Technologies has announced independently verified results of its rotor sail system following nearly a year of rigorous testing.
In a statement of fact, Lloyd’s Register (LR) Advisory confirmed the methodology Anemoi used for calculating fuel and emissions savings from the three 24m high rotor sails installed on TR Lady – a Kamsarmax bulk carrier owned in funds managed by Tufton Investment Management and chartered by Cargill. The extensive dataset is considered to establish 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. The average net savings across this period calculated from the verified performance model were 1.9t of fuel per day and 7.0t CO2e per day (well-to-wake). This is estimated to equate to an average of 9.1% net propulsion fuel and emissions savings.
The achieved average savings align closely with Anemoi’s predicted 10% savings, making this a positive result. 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, Anemoi considers it especially important 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.
LR 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”.
Dr Dogan Uzun, LR Advisory Ship Performance Consultant and project manager of the assessment, said: “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. 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, an 82,000 dwt Kamsarmax bulk carrier, was installed in June 2023 with three Anemoi Rotor Sails, 5m in diameter and 24m in height – a shorter height and a lower aspect ratio compared to Anemoi’s standard products to suit air draught requirements. Anemoi has confirmed that testing is currently underway on several vessel installations featuring its larger rotor sails, measuring 35m in height, which, thanks to their higher aspect ratios, are expected to achieve higher performance results.
Clare Urmston, CEO Anemoi Marine Technologies, said: “This independent verification is a crucial step in building trust across the industry. Lloyd’s Register Advisory’s rigorous and transparent approach gives shipowners and operators the confidence that our technology delivers measured fuel savings and emissions reductions in line with expectations. At Anemoi, we believe that credibility is earned through data, openness and accountability, and this verification underpins our commitment to setting a new standard as emerging technologies like wind propulsion pave the way in clean maritime innovation.”
Nicolas Tirogalas, Tufton Chief Investment Officer and President, added: “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.”
Chris Hughes, Decarbonisation Specialist, Cargill, 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.”
Image: ‘TR Lady’ with three 24m Anemoi rotor sails (source: Anemoi/Wake Media)
