Dynamic Experimental and Numerical Analysis of Loads for a Horizontal Axis Micro Wind Turbine

The optimal use of micro wind energy conversion systems is not only a matter of efficiency, but it also involves a number of issues related to the technology and the dimensions of the system in relation with the environment. The growing request of micro wind energy technology for urban areas is nowadays stimulating the research on several subjects. Structural safety is crucial, in order to prevent damages in case of gusts. Noise and vibration assessment and minimization is another relevant issue too, especially for horizontal axis machines with higher efficiency and larger rotational speed. On these grounds, in this work a horizontal axis wind turbine having 2 m of rotor diameter is studied experimentally and numerically. Experimental tests have been performed with steady and unsteady wind conditions and accelerations have been collected, at meaningful operating conditions of the wind turbine, and consequently analyzed. The analysis of the experimental spectra is compared against numerical simulations performed with the aeroelastic code Fatigue, Aerodynamics, Structures and Turbulence (FAST) and this allows to interpret the complex load structure to which the wind turbine is subjected. In particular, evidence of the bladepassing phenomenon is collected: due to the small size of the system, the tower and blades undergo an interesting mechanical interplay.