Investigating the Feedbacks of Large Wind Farms on the Local Weather and Climate

Wind energy is quickly growing in popularity worldwide as a good alternative source of energy to help mitigate global warming. As its use becomes more widespread, however, the feedback between large wind farms and the atmosphere needs to be investigated. Establishing the effects of large wind farms on local meteorology and wind farm efficiency is important to determine any negative and positive impacts on climate and weather. It is also important for site selection and for determining the optimum array efficiency for maximum power performance. In order to determine these effects, flow around turbine blades need to be resolved. A basic aerodynamic model based on the Blade Element Momentum (BEM) theory is used to simulate the forces associated with the spinning turbine blades. Results are verified against turbine blade data. Power curves from the model and the data match very well at low to medium wind speeds (5-13 m/s). Although there is less agreement at high wind speeds, this improves as the power curve is weighted with a Rayleigh distribution function that is typical of a wind site. Since wind speeds at a site are typically mostly in the 7-13 m/s speed range, these results are sufficient for the purpose of characterizing the forces between the turbine blades and the atmosphere. This aerodynamic model is then integrated into a high-resolution atmospheric model to quantify the effects of these forces on the local flow.