An investigation into the factors influencing EEDI's contribution to wing sail-assisted technology

Wing sail-assisted technology is an option for the cargo ship retrofitted or designed to meet the requirement of EEXI or EEDI. In this paper, the factors influencing the EEDI contribution of wing sails for a VLCC have been carried out based on the wind tunnel and tank model test results, including the arrangements of sails, the total area of sails, the sailing speeds of the ship, and wind probabilities along the main global routes. Investigation of the influence of the side force induced by the sails into the net EEDI contribution was also provided considering drift and rudder angle variation of the ship. The conclusions obtained in this study show that wind probability is a sensitive factor, and when following the method in MEPC.1/Circ.896, the EEDI contribution of four sails for the VLCC can reach almost 6%. The EEDI contribution of the sails tends to increase as the ship speed decreases. The total area of the sails has a greater effect on the EEDI contribution than the sail arrangement. Wing sails' contribution to EEDI will be overestimated by the method described in MEPC.1/Circ.896, which ignores variations in the drift and rudder angle of the ship, compared to MMG-based model results.