Speed regulated operation for tidal turbines with fixed pitch rotors

A novel method of regulating the power generated by a tidal turbine is presented. The method makes use of the fact that the natural power coefficient curve of a turbine decreases monotonically with tip speed ratios above the maximum power point. Implementation of this method is discussed and results from simulations using GH Tidal Bladed are presented. The results show near-constant power output (with variations of less than 0.6% over the course of a simulation). It is shown that controlling a turbine in this way would allow a fixed pitch rotor to be used which removes the need for a costly and complex pitch system. However, although all rotors exhibit this decrease in power at high tip speed ratios, it is noted that it would not be wise to use this method with certain types of blade for which thrust increases significantly above the design point.