Experimental investigation of the influence of mast proximity on rotor loads for horizontal axis tidal turbines

Abstract

While the world continues to grapple with the increasingly prominent impact on the planet of climate change, a shift towards greater reliance on renewable energy sources is observed. Wind, hydro and solar have seen a rise in uptake, however, tidal energy represents massive untapped potential. For tidal energy to become economically viable, focus must shift towards designing efficient yet structurally sound designs. The current study investigates the influence of the tower distance from the rotor plane on turbine performance, and on rotor loading. A test scale instrumented tidal stream turbine is studied in a water flume tank at the laboratory of IFREMER in Boulogne-sur-Mer, France. Experiments are carried out with 14 different tower positions and the turbine performance coefficients are compared. Both mean Cp and Ct values remain unaffected for these different positions. However, the structural rotor loading is found to fluctuate significantly as the distance between the tower and rotor is reduced. Load measurements are analysed in terms of coefficient of variation, through frequency analysis, in relation with the azimuthal position of the rotor and finally in terms of exceedance. All the experimental measurements associated with this study are available from: https://doi.org/10.17882/81077.