Posters

Abstract

Suppression of installation costs of onshore wind turbines contributes to the continuing battle for reducing the levelized cost of wind electricity (LCoE). Under moderate wind conditions, assembly of the full wind turbine system in one shot might not be always feasible, as wind speed often exceeds the safety limits. Then, equipment and people remain idle on site, causing delays and consequently cost increase. A way to overcome the issue is to assemble the turbine in multiple phases, including a two-phase rotor installation. During the first phase, a single or two blades are mounted and left unattended for some period until the second -completion- phase, starts. Then, the question that rises is whether the unfinished turbine is safe against aero-elastic instabilities. In this work we present the methodology and representative results from the aero-elastic analysis performed for single-bladed and two-bladed unattended configurations under moderate to high wind speeds (corresponding to unattended period of less/equal and higher than one week) with the rotor in idling mode and the blades pitched to feather position. Both mechanisms that potentially trigger aero-elastic instabilities are examined; stall induced vibrations (SIV) and vortex induced vibrations (VIV) on all relevant rotor and tower modes. The analysis is performed applying engineering tools that rely on tabulated airfoil data (i.e. polars). The work is concluded by assessing critical design parameters that affect aero-elastic performance.