Rig Performance Evaluation for Wind Powered Pure Car Carrier

Abstract: Carrying around 80-90% of world volume of goods, the shipping industry has a considerable environmental impact. The International Maritime Organization (IMO) fixed a 50% greenhouse gases emission reduction target by 2050 with respect to 2008 levels. Toward the objective of sustainable shipping, Wallenius Marine, together with KTH Royal Institute of Technology and SSPA Sweden, launched the project to develop a wind powered pure car carrier ship. The 200 meters long vessel is powered by four 360 degrees rotating upright wings that allow sailing in all conceivable wind conditions. The implementation of such concept strongly depends on the aerodynamic properties of the multi-wings system. However, its assessment is challenging due to flow interactions between the wings.The main goal of the study is to investigate and find a suitable wing design and configuration to propel the ship only using wind power, ie when the installed engine power is off. The first task of this study was to determine the reliability and limitations of the aero-modelling tools developed by KTH including a 2D wing trimming optimizer and a vortex lattice method code. Flapped-wing and symmetrical wing (NACA-4 digits profiles) rig designs have been investigated. The flapped wing profile enhances by 30% the thrust power of the multi-rig system compared to a symmetrical wing profile for same arrangement on deck and total sails area. The “rectangle” disposition of the rigs on deck appeared to be more performant than the in-line arrangement. Indeed, this configuration allows to sail with a larger range of incident wind angles (closer to the wind) and with higher vessel’s speed than the base design one. Further numerical testing using more accurate tools that can take turbulence effects into account, such as CFD and model testing in wind tunnel or real conditions may be done to validate the conclusions raised by this study.