Modeling of atmospheric wind speed sequence using a lognormal continuous stochastic equation: Fid-Bau Portal

Modeling of atmospheric wind speed sequence using a lognormal continuous stochastic equation

Calif, R. / Schmitt, F.G.

Abstract In this paper, we have presented a spectral and a multifractal analysis performed on 412 time series of wind speed data each of duration of 350s and sampled at 20Hz. The average spectrum for the wind speed displays a scaling behavior, in the inertial range, over two decades, with $β = 1.68$ close to the Kolmogorov value −5/3. A multifractal analysis has been motivated by the presence of scaling invariance in data set. Then we have considered their scaling properties in the framework of fully developed turbulence and multifractal cascades. The results obtained for wind speed confirm that the exponent scaling function $ζ_{V} (q)$ is nonlinear and concave. This exponent characterizes the scaling functions in the inertial range indicating that the wind speed is intermittent and multifractal. Moreover the theoretical quadratic relation for lognormal multifractals is well fitted. We investigate the consequence for wind energy production: we generate stochastic simulations of a multifractal random walk, and using a power curve derived from experimental data, we generate the associated power time series. We show that, due to the saturation of the power curve for large speed values, when the input time series (turbulent wind speed) is multifractal, the output can be almost monofractal.

Highlights ► The scaling statistics of wind speed data is studied in the framework of Kolmogorov's theory. ► We show that the wind speed is intermittent and multifractal. ► We propose a lognormal stochastic equation to simulate a multifractal random walk. ► We generate the associated output power time series using a power curve of a wind turbine.