The aim of this study is to estimate the wind power that can be extracted by an horizontal-axis wind turbine (HAWT) as a function of upstream wind. The incompressible Navier-Stokes equations are solved on a fixed cartesian mesh via a second-order accurate scheme in space and time. The turning blades and the mast are modeled by a penalization term in the governing equations within a collocated Chorin-Temam fractional time integration algorithm. The turbulence model is based on a large-eddy simulation model initially fitted on experimental data. This numerical procedure allows massive parallelization by using existing distributed linear-algebra libraries. The test case under consideration is the two blades NREL ametest wind turbine that has been intensively studied in wind tunnel.