Energy harvesting efficiency analysis of counter-rotating horizontal-axis tidal turbines

In this paper, a new design scheme for counter-rotating horizontal-axis tidal turbines (CRHATTs) is introduced using blade element momentum (BEM) theory. The coordinated working performance between rotor and generator of the CRHATT are analysed by experimental and CFD methods. The effects of the key parameters on the energy harvesting efficiency of the CRHATT are studied in detail. The study indicates the existence of the optimal rotor solidity (sigma) combination and blade installation angle (gamma) combination for dual rotors to reduce the power coefficient (C-p) deviation of the dual rotors. The distance between dual rotors (L) is suggested to be set as about 0.225D, which can maximise the C-p of the CRHATT. Finally, the hydrodynamic performance of the flow field is carried out to verify the reliability of the CRHATT design. The results presented in this paper may serve as a reference in the design of CRHATTs in practical engineering.