Experimental study of a quadrirotor twin vertical axis tidal turbine behaviour under regular waves

Abstract

The consideration of the environmental conditions on the power output of vertical-axis tidal turbines (VATT) is a key aspect in assessing their in-situ performance and ensuring stable energy production, as well as a satisfactory lifespan. This study presents an experimental analysis of the surface waves effect on the mechanical response (power and torque fluctuations) of a quadrirotor VATT. Tests were conducted in Ifremer's wave-current flume tank on a 1:20 scale model.
The results highlight a significant increase in power fluctuations under regular waves, particularly near the optimal operating point.
Moreover, the phase-averaged modelling of the wave-induced torque variations reveals a strong relationship between wave-induced velocity fluctuations and torque response.
A parametric model, inspired by Morison’s equation to represent the inertial effects of waves on the machine, effectively captures the wave-related torque contribution. The proposed method thus aims to distinguish wave orbital velocity effects to the turbulence-induced fluctuations.