This document describes the development and application of a simulation tool for vertical and horizontal axis wind turbines called QBlade. QBlade integrates several modules including airfoil analysis using XFOIL, lift and drag polar extrapolation, rotor blade design, and wind turbine performance simulation. It can be used to simulate and compare the performance of different vertical and horizontal axis wind turbine blade designs. The document presents two case studies using QBlade: investigating the effect of vortex generators on a vertical axis wind turbine, and analyzing the impact of helical blades and blade number on loads of a vertical axis wind turbine.