3D modelling of the generator for OpenHydro´s tidal energy system

OpenHydro is developing open centred submerged turbines for the extraction of energy from ocean tides. Power take off is via a surface-mounted, radial-flux, permanent-magnet generator mounted to the rim of the turbine blades. A number of full scale devices have been deployed globally, upto 2MW and 16m diameter. The aspect ratio of the machines mean that end effects are likely to be significant and hence 3D modelling is required to fully capture them. In this paper, alternative methods for modelling the existing machine design is discussed and compared. It is demonstrated that, although a full scale detailed FEA approach yields the best results, simplified FEA and even analytical approximations are best for the purpose of designing the machines.