Tidal energy is one of form through which renewable energy can be extracted from oceans which covers more than 70% of the earth surface. Tides are a periodic function and can be predicted for a long period this makes tidal energy more favorable than other ocean energy. To prevent the sealing problems associated with the tidal generators the stator-rotor gap is flooded with seawater. Insulating sleeves are used to overcome issues of corrosion of the permanent magnets and the electrical insulation which arises due to the flooding of the stator-rotor gap. The aim of the thesis is to suggest a suitable material that can be used for the insulating sleeve based on the eddy current loss and temperature of the generator. Magnetohydrodynamics is other phenomena that will arise due to flooding of the stator-rotor gap of the tidal generator. Losses associated with Magnetohydrodynamics are also evaluated.

The geometrical parameters of the generator are calculated based on the required power rating and the average velocity of the tides. The eddy current losses in the insulating sleeves are evaluated analytically by calculating the magnetic flux density in the insulating sleeves. A thermal model of the
machine is developed to investigate the temperature distribution inside the generator due to different materials of the insulating sleeves to derive at the suggestion for the material to be used.

It is observed that the Magnetohydrodynamics losses are not significant as compared to the other losses. It is also found that the steel is a suitable material which can be used on the rotor while for stator non-metallic material will be most suitable.

Wave power is a large untapped source of renewable energy. There is a wide variety of wave energy converters and one of them is the Symphony Wave Power device. The aim of this thesis is to find the best generator design for the Symphony. There is some research available on generator designs for wave energy converters but the Symphony is a unique case, so a new research needed to be conducted. Several generator types can be used in the Symphony. Compared to an induction and switched reluctance generator, the iron-cored permanent magnet synchronous generator (PMSG) seems a good choice because it is efficient and reliable. A disadvantage, however, is that, in the case of the Symphony, the iron losses are relatively high at partial loads. An air-cored PMSG does not have this problem since it has no iron losses at all. A drawback of the air-cored PMSG is that it needs more permanent magnetic material, which is expensive. Finally, it was decided to test and compare the iron-cored radial flux PMSG and the air-cored axial flux PMSG on both performance and costs. For both generator types, an analytical model was built which puts out the efficiency and material cost. To find the best generator geometries for the case of the Symphony, an optimization procedure was created which minimizes both material costs and losses. It was found that an axial flux air-cored PMSG is both cheaper and more efficient than a radial flux iron-cored PMSG. The iron losses of an iron-cored generator are relatively high at partial loads while the Symphony operates at partial loads most of the time.