Study of a novel rotational speed amplified dual turbine wheel wave energy converter

Abstract

In this study, a novel wave energy converter is proposed, which features a dual turbine wheel to provide an amplified rotational speed to the generator. The design novelty of the system is that the counter-rotational turbine wheels are connected to the generator stator and rotor respectively through a belt-drive transmission system for amplification of the rotational speed of the generator. This arrangement enables the power take-off system to be placed inside the buoy which is above the waterline. Furthermore, the belt-drive transmission system can effectively absorb the load fluctuations or vibrations caused by sea waves. A lumped parameter analytical model of the system has been developed where the Lagrange principle is applied to analyze the motion of the system and the computational fluid dynamics simulation is employed to determine the drag coefficients of the system. The results obtained from the lumped parameter analytical model have been verified by experimental test results. The developed lumped parameter analytical model allows accurate performance prediction without the high computational cost of the detailed simulations. The proposed research method could be applied as an effective tool to explore the science of wave energy conversion and to optimize the power absorption capacity and the efficiency of the power take-off system, which is the originality of this paper and contributes to the new knowledge in this area. For this prototype of the dual turbine wheel wave energy converter with an overall underwater volume of 0.002 m3, the maximum harvested efficiency and harvested power at the wave excitation condition of 80 mm in amplitude and 0.3 Hz in frequency are 11.57%, and 26.4mW, respectively.