Abstract

Recently, tidal stream turbines have become a preferable mode of harvesting tidal energy. The main issue for low utilization of tidal energy is the high levelized cost of energy (LCoE) from tidal stream turbines. A major reason for this is the high operation and maintenance costs for submerged installations. A possible way of minimizing the LCoE and improving the availability is to use a flooded (or a wetgap) generator rather than a conventional airgap generator. Inside flooded generators, the gap between the stator and rotor is filled with the seawater. This architecture has the potential to improve cooling and reduce reliance on ancillary systems (e.g., bilge system), thereby improving reliability. The chapter begins with a brief description of the generator systems used in current tidal stream turbines. The focus of the chapter is, however, to give a basic insight into the design aspects of the flooded generators, and compares it with the currently used sealed airgap generators in tidal turbine systems.

Highlights

  • IntroductionEnergy from tides is predictable over a span of several years, unlike other renewable sources of energy such as solar and wind

  • Tidal stream turbines have become a preferable mode of harvesting tidal energy over tidal range technology

  • We find instances of both metallic as well as non-metallic materials being used for the rotor-can in flooded generators or canned motors [20]

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Summary

Introduction

Energy from tides is predictable over a span of several years, unlike other renewable sources of energy such as solar and wind. Vertical axis tidal turbines and other topologies such as oscillating hydrofoil, enclosed tip turbine and tidal kites are used to harness tidal energy, most of the research and development efforts are focused on HATTs; see Figure 3. This is primarily because of their higher technology readiness level (TRL), and similarity to commercial wind turbines. This chapter gives a qualitative comparison between a conventional airgap and a flooded generator for tidal stream turbines.

Generator types in tidal turbines
Conventional design for tidal generators
Flooded generators
Design choices for flooded generators
Rotor-can materials
Thermal considerations
Findings
Conclusions
Full Text
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