The complex, unsteady aerodynamics of vertical-axis wind turbines pose significant challenges for performance prediction, particularly for Darrieus rotors intended for urban or low-speed wind environments. This study develops a numerical framework based on the Actuator Line Method to simulate the aerodynamic response of a small-scale commercial VAWT. The turbine geometry was generated form a 3D scanned model, and the aerodynamic properties of the blade section were characterized through a series of 2D RANS simulations over a wide range of angles of attack. The resulting lift and drag coefficients, obtained at different Reynolds numbers, are integrated into the ALM formulation, where blade forces are projected onto the flow field using a Gaussian kernel with optimized smoothing lengths to balance accuracy and numerical stability. Simulations were performed for multiple tip-speed ratios, and each correspondent power coefficient was obtained. The predicted Cp-TSR is compared with available wind tunnel measurements for moderate and high TSR and the model’s reliability at low TSR regime is analysed. Results indicate that the adapted ALM reproduces the main performance trend and captures the mean power production while reducing the computational cost by several orders of magnitude relative to blade-solved CFD. The methodology provides a robust and efficient tool for performance assessment and design optimization of VAWTs operating in urban and turbulent flow conditions.