Assessment of Ships’ Speed-Power Relationship at Lower Sailing Speeds

This study assesses the relationship between speed and power of ships, and is based on operational data derived from more than 50,000 noon reports retrieved from 88 tankers. The analysis is made with a data-driven model based on principles from naval architecture and an econometric framework. The model facilitates the determination of a draught- and speed-dependent exponent. It is shown that the exponent is significantly lower than 3 at speed intervals below the design speed. The finding of a (much) smaller exponent, relative to 3, at low speed intervals is important in the slow steaming debate, since slow steaming will not be as good as often stated when the cubic speed-power relationship does not hold. On a practical level, the developed method can be used to set a more reliable benchmark in the performance monitoring of ships.