|dc.description.abstract||Increasing focus on reduction of CO2 emissions, and the possibility of future severe shortage of oil have sparked renewed interest in wind as supplementary propulsion of merchant ships. Several alternative solutions are considered, like kites, conventional soft sails, rigid sails, Flettner rotors, and wind turbines. A tempting aspect of wind turbine propulsion is that it can provide propulsive force when sailing directly upwind, something that is impossible with the other mentioned forms of wind-assisted propulsion.
A method based on axial momentum theory has been outlined, in order to predict the steady-state speed of a wind turbine powered boat. This method is applied to a notional wind turbine powered catamaran. The predicted boat speed to wind speed ratio when the boat is sailing upwind is in good agreement with results from testing of a similar, but smaller, full-scale wind turbine boat.
A related topic to wind turbine propulsion is the reversed configuration, where a water turbine is driving an air propeller. This configuration allows for the theoretical possibility of sailing faster than the wind, directly downwind. Based on a similar approach to the method of velocity prediction of wind turbine powered boats, design criteria with respect to water turbine efficiency and hydrofoil chord length, are set for a given hydrofoil boat in order to sail faster than the wind, directly downwind.
The design of optimal wind turbine blades for wind turbine powered vessels is studied. A 326 m LWLVLCC is equipped with a Vestas V90 wind turbine for auxiliary propulsion, and set to sail a route across the North Sea. By employing the wind turbine, 3.6% of the fuel is saved when the ship is sailing at 15 kn. If the ship speed is reduced to 10 kn, the fuel saving increases to 21.1%. The optimal blade design theory is applied to the wind turbine ship, keeping the wind turbine diameter fixed at 90 m. The optimal blade design increases the fuel saving by a few percentage points. The main drawbacks for a wind turbine powered ship are shown to be the low ship speed to wind speed ratio in order for wind turbine propulsion to be the preferred form of wind-assisted propulsion, as well as the height of such a ship.
Attached is a CD-ROM containing Matlab files used for creating various of the results in this thesis, as well as an electronic version of the thesis.||nb_NO