Analysis of uncertainties in the prediction of fuel savings from WASP installations

Many ship owners, operators and ship designers tend to put more trust into sophisticated, often CFD based, models for fuel consumption prediction with or without wind-assisted propulsion (WASP). Time consuming and expensive methods are often accurate, but sometimes not required for all parts of a complex system, such as a ship with WASP. Instead, the component imposing the highest uncertainty on the prediction should be modelled with the highest accuracy, while those components causing low uncertainties can be modelled with less sophisticated methods to save computation/analysis time and money. This study analyses the uncertainties from different parts of a WASP ship on the fuel saving prediction. Included components are the sail forces, the sail interaction, the wind speed profile over deck, wind shear, lift to drag and lift coefficients of the hull as well as the rudder forces and the center of lateral resistance of the hull. Further, it is evaluated how the accuracy of the initial power prediction of the ship without sails (including wind and waves) affects the fuel saving prediction. The results of the study provide a guideline on the most important parts of a WASP ship and highlights where sophisti-cated methods are required. Further, the study evaluates the expected accuracy of the empirical/ analytical fuel consumption/fuel saving prediction model ShipCLEAN developed by the lead author