Turbulence analysis and multiscale correlations between synchronized flow velocity and marine turbine power production

• Published in: Renewable energy 2017-11, Vol.112, p.314-327
• Main Authors: Durán Medina, Olmo, Schmitt, François G., Calif, Rudy, Germain, Grégory, Gaurier, Benoît
• Format: Article
• Language: English
• Subjects: Engineering Sciences; High frequency data rate; Intermittency; Marine energy; Multifractal energy cascade; Sciences of the Universe; Turbine power production; Turbulence
• ISSN: 0960-1481; 1879-0682
• DOI: 10.1016/j.renene.2017.05.024

The correlation between the flow turbulence and the performances of a marine current turbine is studied. First, the incoming flow encountered in the flume tank is characterized in the framework of fully developed turbulent cascades in the inertial range. The Reynolds number, the Kolmogorov dissipation scale and the integral scale, are estimated from flow measurements. The intermittency of the turbulence is characterized in the lognormal multifractal framework, and the influence of the turbulent flow on the turbine power is assessed. The rotor speed control unit characteristics used for the turbine regulation induces non-negligible effects on the turbine behavior under fluctuations loads. Even if the power spectrum does not reveal any scale invariance, a multiscale analysis allows us to show the correlations between the turbulence time series and the power produced. The classical Mean Square Coherency function shows that for scales larger than 10 s, the upstream velocity and power have large correlations. In the framework of the Empirical Mode Decomposition method, such correlations are studied using the time-dependence intrinsic correlation analysis method. This method allows to zoom into time-frequency scales where the flow perturbations induced some modifications in power production. •A high sampling rate of a turbulent flow velocity highlights its multiscale properties.•There is no power law in the power production Fourier spectrum.•The intermittency degree of flow velocity increases behind the marine current turbine.•The coherency is higher in the lower frequencies and reach its minimum at 1 Hz.•Local correlation analysis spotted a pattern on the loss of correlation.