Journal - Donghun Yu, Myung-Il Roh, "A Method of Intentional Derating Operation for Rotor Sails to Enhance Overall Energy Efficiency of Ships", accepted for publication in Ocean Engineering, 2026.07.28

Extra Form
Abstract	The IMO’s (International Maritime Organization) strengthening of environmental regulations has driven the adoption of rotor sails. Rotor sails are a wind-assisted propulsion technology that generate aerodynamic thrust and reduce the ME (Main Engine)’s propulsive power demand. This reduction directly lowers the ME’s FOC (Fuel Oil Consumption). However, operating the rotor sails requires additional electrical power. This can force the DGs (Diesel Generators) into inefficient, low-load operation, offsetting the ME-side gains and reducing the ship’s overall energy efficiency. To address this trade-off, this study proposed an IDO (Intentional Derating Operation) method that jointly evaluates the fuel consumption of both the ME and the DGs, rather than evaluating it solely for the DGs. Unlike conventional supply-side approaches, the proposed method adopted a demand-side strategy, modulating rotor sail performance within an NLP (Non-Linear Programming) framework that enforces the available power margin as a hard constraint. A hybrid SLSQP (Sequential Least Squares Programming) and MLP (Multi-Layer Perceptron)-based surrogate model approach solved this in real time, achieving 99.7% accuracy in approximately 1 s. Simulations using real voyage data from a 300K DWT VLCC showed that the conventional method often yields only marginal net fuel savings and, under certain conditions, even negative savings. This result occurred because the SFOC penalty from low-load DG operation exceeded the ME FOC reduction. In contrast, the proposed method suppressed unnecessary DG activation. It eliminated the 13.3% probability of DG overload observed under full rotor sail operation and ensured power system reliability without relying on auxiliary DG activation. It also improved the total FOC and CO2 emission saving rate from 2.6% (conventional) to 3.6%, a relative improvement of approximately 38.4%. These results confirm that intentionally derating the rotor sails’ local performance is essential for achieving the ship’s system-level energy optimum, rather than maximizing individual component performance.
Publication Date	2026-07-28
Role	Corresponding Author
Category	SCIE
Impact Factor	6.3

Abstract

The IMO’s (International Maritime Organization) strengthening of environmental regulations has driven the adoption of rotor sails. Rotor sails are a wind-assisted propulsion technology that generate aerodynamic thrust and reduce the ME (Main Engine)’s propulsive power demand. This reduction directly lowers the ME’s FOC (Fuel Oil Consumption). However, operating the rotor sails requires additional electrical power. This can force the DGs (Diesel Generators) into inefficient, low-load operation, offsetting the ME-side gains and reducing the ship’s overall energy efficiency. To address this trade-off, this study proposed an IDO (Intentional Derating Operation) method that jointly evaluates the fuel consumption of both the ME and the DGs, rather than evaluating it solely for the DGs. Unlike conventional supply-side approaches, the proposed method adopted a demand-side strategy, modulating rotor sail performance within an NLP (Non-Linear Programming) framework that enforces the available power margin as a hard constraint. A hybrid SLSQP (Sequential Least Squares Programming) and MLP (Multi-Layer Perceptron)-based surrogate model approach solved this in real time, achieving 99.7% accuracy in approximately 1 s. Simulations using real voyage data from a 300K DWT VLCC showed that the conventional method often yields only marginal net fuel savings and, under certain conditions, even negative savings. This result occurred because the SFOC penalty from low-load DG operation exceeded the ME FOC reduction. In contrast, the proposed method suppressed unnecessary DG activation. It eliminated the 13.3% probability of DG overload observed under full rotor sail operation and ensured power system reliability without relying on auxiliary DG activation. It also improved the total FOC and CO2 emission saving rate from 2.6% (conventional) to 3.6%, a relative improvement of approximately 38.4%. These results confirm that intentionally derating the rotor sails’ local performance is essential for achieving the ship’s system-level energy optimum, rather than maximizing individual component performance.

Publication Date

2026-07-28

Role

Corresponding Author

Donghun Yu, Myung-Il Roh, "A Method of Intentional Derating Operation for Rotor Sails to Enhance Overall Energy Efficiency of Ships", accepted for publication in Ocean Engineering, 2026.07.28

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