Design and construction of an offshore diffuser augmented wind turbine with a high efficiency alternator

This paper describes the design and the assembly of a new type of a ducted wind turbine with an electric power generator adopting permanent high coercive magnets embedded in the peripheral ring of the rotor. The nominal power is 20 kW, and the maximum diameter of the external duct is 9 meters. The project has been carried out within the Marine Energy Laboratory (MEL) funded by the Italian Ministry for Education, University and Research (MIUR) and collects the most advanced technologies of naval maritime engineering and combines them with energy and turbomachinery technologies. The presence of a divergent duct enables the interception of a greater air mass flow rate, allowing the reduction of the rotor diameter and the deflections of the blades; hence, at constant tip speed ratio, a higher rotational speed compared to conventional turbines and a better efficiency of the permanent magnet power generator.